HIGH INTENSITY SUPPLEMENTARY LIGHTING 0F POT CHRYSANTHEMUMS IN THE GREENHOUSE Déssertation fer the Degree of Ph. D. MICHIGAN STATE UNIVERSITY GARY ALLEN ANBERSON 19' 73 “H.945 MichEgm State University ABSTRACT HIGH INTENSITY SUPPLEMENTARY LIGHTING OF POT CHRYSANTHEMUMS IN THE GREENHOUSE By Gary Allen Anderson Continuous supplementary lighting of pot cultivars of Chrysanthemum morifolium Ramat. with Lucalox (#00 W) sodium vapor and Multivapor (400 W) mercury lamps at 58 to 116 W/mz improved plant quality from Sept. to Apr. The benefits were measured during vegetative growth and at flowering from lighting stock plants, lighting during propagation, or lighting after transplanting. Maximum benefits from lighting determined by the increases in plant height, fresh and dry weight, flowering branch num- ber and floral display diameter resulted from lighting during the 3 weeks after transplanting. Smaller benefits were found from lighting stock plants or during propaga- tion. Chrysanthemum stock plants lighted continuously with Multivapor and Lucalox lamps (100 W/mz) produced larger numbers of cuttings with greater fresh and dry weight and Gary Allen Anderson stem diameter than those receiving only seasonal daylight and photoperiodic lighting. Cuttings from plants receiv- ing high intensity supplementary lighting rooted in fewer days, had greater root fresh and dry weights, and greater top fresh weight than plants lighted photoperiodically. After transplanting these cuttings became established more rapidly and developed into flowering plants of higher quality. Continuous high intensity supplementary lighting of Chrysanthemum vegetative cuttings during propagation from Oct. to Mar. at 116 W/m2 reduced the number of days to rooting and increased root number, length and fresh weight over non-lighted cuttings. Lighting benefits were lost at 17h W/m2 when foliar chlorosis developed which delayed rooting and reduced root growth. Benefits were similar from supplemental lighting at 116 W/m2 with combined Lucalox and Multivapor lamps and 58 W/m2 with Lucalox lamps. Increasing light intensity by adding the Multivapor lamp to the Lucalox did not signifi- cantly improve Chrysanthemum growth and quality over bene- fits from Lucalox lamps. High intensity supplementary lighting: (1) increased the plant display diameter because more flowering branches developed from the pinch, (2) increased branch diameter Gary Allen Anderson resulting in a sturdier plant with less need for support and better shipping quality and (3) slightly increased plant height with significance depending on the cultivar. The prospect of greatly improving pot mum quality during the winter months by using a highly efficient light source snould make installation of a Lucalox lighting system attractive to commercial growers. HIGH INTENSITY SUPPLEMENTARY LIGHTING OF POT CHRYSANTHEMUMS IN THE GREENHOUSE By Gary Allen Anderson A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1973 Qua no... .l To Cheryl ii ACKNOWLEDGMENTS The author is indebted to Dr. William J. Carpenter for his valuable guidance and assistance during the com- pletion of the degree requirements. The cooperation and helpfulness of Drs. Lee Taylor, Harold Davidson, Irving Knobloch and John Beaman is gratefully acknow— ledged. Special thanks is given to the General Electric Foundation for their support of the study and to Yoder Brothers, Inc. for the cuttings. iii TABLE OF CONTENTS Page LIST OF TABLES ...... . .................................. vi LIST OF FIGURES.... .............. . .................... vii INTRODUCTION ...... . ................. . ................... 1 SECTION ONE High Intensity Supplementary Lighting of Chrysanthemum Stock Plants.....,.......... ...... 5 SECTION TWO REVIEW OF LITERATURE .............................. 16 Advancements in horticultural lighting ....... 16 Photomorphogenesis in Chrysanthemum ........ ..25 Light and photosynthesis............. ..... ...33 I. EVALUATING SUPPLEMENTARY LIGHTING DURING AND AFTER PROPAGATION.............. ........ 41 Materials and Methods................ ........ “2 Results.OIOOIOOOOIOOOIIIOIIOOIO. 0000000000000 [+6 Discussion....... ........... ....... ........ ..62 II. SHORT-TERM SUPPLEMENTARY LIGHTING OF POT CHRYSANTHEMUMS AFTER TRANSPLANTING............68 Materials and Methods........................69 Results...‘ ....... 0......OOOOIIOCIIOOOOOOOIIO7O Discussion...................................7’~I III. INTERACTION OF STOCK PLANT LIGHTING AND SUPPLEMENTARY LIGHTING OF POT CHRYSANTHEMUMS AFTER TRANSPLANTING ..... ...........77 Materials and Me thOdS O O O O O I O O C O O O I O I O I O O O O O O O 77 Results.OIOOCIOIIOOOOIOO0.0.0000...I00000000081 Discussion.................................. IV. BENEFITS AT FLOWERING FROM LIGHTING AFTER TRANSPLANTING...............................85 Materials and Methods........................86 ResultSOOIOOCOOOCIOCOOIOOOOOOOII0.0.0.000000088 Discussion............... ............ .......106 iv Page SUNHVIARY ...... 0000000000000 ....... 00000000000000 000000 0113 APPEF‘IDIX A. I I I 0 I I I I I I I I 0 I I I I 0 0 I I I I I I I I I I I I I I I I I 0 I I I I I I116 APPENDIX BI I I I I I I I 0 I I I I I I I I I I 0 I I I I I I I I I I I I I 0 I I I I 0 I I I I 0119 APPENDIX C0 0 0 I I 0 0 I I I I I I I I 0 I I 0 I I 0 I I 0 I I I I I 0 I I I I I I I I I I 0 I 0120 BIBLIOGRAPHY IIIIIIIII IIIIIIIIIIIIIIIIIII IIIIIIIIIIIIII 122 Table LIST OF TABLES Page Quality of 8 cm terminal cuttings from plots of Chrysanthemum stock plants under various light regimes............................10 Comparison of Chrysanthemum plants propa- gated and grown under normal light condi- tions but ori inating from stock plants lighted 100 W m2 with combined Lucalox and Multivapor lamps.... ........ .......... ..... ..11 The influence of supplementary light in- tensity on the vegetative propagation of Chrysanthemum, cv. Bright Golden Anne, comparing 0. 116, and 174 W/m2 of light from combined Lucalox and Multivapor lamps (1# days after cuttings were placed in the propagation bench)........................47 The influence of supplementary light from Lucalox lamps on the vegetative propaga- tion of chrysanthemums...........................b8 Mean light intensities in late December in non-lighted and lighted greenhouses at night and cloudy and sunny days..................53 Supplementary lighting (116 W/m2) effects on Chrysanthemum vegetative growth from lighting during propagation, or from trans- planting to SD treatment, or during both periods..........................................55 Supplementary lighting (116 W/m2) effects at bud development from lighting during propagation, or lighting from transplanting to SD treatment, or during both periods on Chrysanthemums................................56,57 vi Table Page 8. Supplementary lighting (116 W/m2) effects at flowering comparing plants lighted only during propagation, or from planting to SD treatment, or lighting during both periods on chrysanthemums..................................58 9. Weekly evaluation of Chrysanthemum plants, cv. Bright Golden Anne, comparing plants lighted 24 hours daily after transplanting with Lucalox and Multivapor lamps (116 W/m2), only Lucalox (58 w/m2) and unlighted ..... . ...... 71,72 10. Evaluation of Chrysanthemum plants, cv. Bright Golden Anne, comparing plants lighted 100 W/mZ as stock and after trans— planting, lighted 100 W/mZ after trans- planting only, lighted 100 W/m2 as stock and unlighted ....... . ......... .............. ........... 79 11. Evaluation of flowering Chrysanthemum plants, cv. Goldstar, which had been lighted continuously for O, 7, and 14 days after potting with a Lucalox lamp (58 W/mz)...........89,90 12. Evaluation of flowering Chrysanthemum plants, cv. Torch, which had been lighted continuously for O, 7, 1N, and 21 days after potting with a Lucalox lamp (58 W/mZ).....91,92 13. Evaluation of flowering Chrysanthemum plants, cv. Deep Cristal, which had been lighted continuously for O, 7. 14, and 21 days after potting with a Lucalox lamp (58 w/m2).......................................93,9u vii Figure 1. LIST OF FIGURES Page Mean monthly no. of 8 cm terminal stem cuttings per Chrysanthemum stock plant comparing treatments lighted continuously (100 W/mé from Lucalox and Multivapor lamps) with unlighted (only photoperiodic lighting).........................................12 Fresh root wt of Chrysanthemum cuttings propagated under 0. 116. 17G W/m2 of supplementary light from combined Lucalox and Multivapor lamps..............................49 Top length of Chrysanthemum cuttings propagated under 0 and 58 W/m2 of supple- mentary light from Lucalox lamps..................49 Chrysanthemum leaf temperatures during propagation under intermittent misting comparing those receiving no supplementary light during a sunny day with 116 and 174 w/m2 in late December.............................52 Supplementary lighting (116 W/mZ) effects on dry root wt at SD treatment from light- ing during propagation, or lighting from transplanting to SD treatment, or during both periods......................................59 Supplementary lighting (116 W/m2) effects on dry top wt at bud development from light- ing during propagation, or lighting from transplanting to SD treatment, or during both periods......................................59 No. of flowers per plant comparing those receiving supplementary light (116 W/mZ) 24 hrs. daily during propagation, or from potting to SD treatment, or during both periods...........................................6O viii Figure Page 8. Fresh top wt at flowering comparing plants receiving supplementary light (116 W/m2) 24 hrs. daily during propagation, or from pot- _ ting to SD treatment, or during both periods ...... 60 9. Weekly evaluation of Chrysanthemum fresh root wt comparing plants lighted 24 hrs. daily after transplanting with Lucalox and Multivapor lamps (116 W/m2), only Lucalox (58 w/m2) and unlighted.................... ....... 73 10. Weekly evaluation of Chrysanthemum top length comparing plants lighted 24 hrs. daily after transplanting with Lucalox and Multivapor lamps (116 W/m2), only Lucalox (58 W/m ) and unlighted...........................73 11. Fresh root wt of Chrysanthemum plants, 3 weeks after transplanting, lighted with HID lamps for various combinations of time as stock plants and 3 weeks after transplanting ...... 8O 12. No. of flowering branches per Chrysanthemum plant lighted various combinations of time as stock plants and 3 weeks after trans- planting..........................................8O 13. No. of flowering branches per pot for cv. Goldstar comparing plants lighted 58 W/m2 with Lucalox lamps for O, 7, and 14 days after transplanting...............................95 14. No. of flowering branches per pot for cv. Torch comparing plants lighted 58 W/m2 with Lucalox lamps for O. 7. 14, and 21 days after transplanting...............................96 15. No. of flowering branches per pot for cv. Deep Cristal comparing plants lighted 58 W/m2 with Lucalox lamps for O. 7. 14, and 21 days after transplanting...............................97 16. Display diameter of cv. Goldstar comparing plants lighted 58 W/m2 with Lucalox lamps for O, 7, and 14 days after transplanting.........98 ix Figure Page 17. Display diameter of cv. Torch comparing plants lighted 58 W/m2 with Lucalox lamps for O. 7. 14, and 21 days after trans- planting.........................................99 18. Display diameter of cv. Deep Cristal comparing plants lighted 58 W/m with Lucalox lamps for O. 7. 14, and 21 days after transplanting.............................1OO 19. Fr. wt of individual plants at flowering for cv. Goldstar comparing plants lighted 58 W/m2 with Lucalox lamps for O, 7, and 14 days after transplanting.....................101 20. Fr. wt of individual plants at flowering for cv. Torch comparing plants lighted 58 W/m2 with Lucalox lamps for O, 7, 14, and 21 days after transplanting.................102 21. Fr. wt of individual plants at flowering for cv. Deep Cristal comparing plants lighted 58 W/m2 with Lucalox lamps for O, 7, 14, and 21 days after transplanting.......103 22. Cv. Deep Cristal at bud develo ment showing a plant lighted 58 W/m for 3 weeks after transplanting (left) and an unlighted control (right)............108,109 23. Calculated daily natural light inputs outside the greenhouse for clear and typically cloudy days at East Lansing, Michigan, and natural and supplemental daily light inputs inside the greenhouse........111 A1. Spectral distribution for typical 400-watt Lucalox lampSIIIIIIIIIIIII.IIIIIIIIIIIIIIIIIIIII116 A2. Spectral distribution for typical 400-watt Multivapor lamps................................116 A3. HID luminaire showing mounting arrangement, ballast, and faceted reflector..............117.118 B1. Weekly mean solar radiation values for East Lansing, Michigan from Oct. 1971 to Mar. 19730IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII0119 INTRODUCTION During short winter days natural greenhouse light in— tensities are low and the growth of many greenhouse crops is slowed. In Michigan, winter days are frequently cloudy and often less than one-half the potential sunlight is re- «ceived. Artificial lighting has been used to control day- length (photoperiodic lighting) and to a lesser extent to promote growth rate and plant quality (photosynthetic lighting). In the greenhouse, photosynthetic lighting most frequently is used to supplement natural daylight but in some cases plants have been successfully grown entirely under artificial light. The widespread use of photosynthetic lighting has been retarded by the lack of a highly efficient lamp source which could provide high light intensities at an economical cost. The advent of high intensity discharge lamps (HID) is making commercialization of horticultural lighting more promising. Lucalox sodium vapor and Multi- vapor lamps (HID) have the highest light producing effi- ciency of any commercial source of white light. The HID lamp is about 30% efficient in its use of electrical in- put, compared with about 20% for fluorescent lamps and only 8% to 10% for incandescent lamps. The Lucalox (400 W) sodium vapor lamp produces 105 lumens per watt compared with 80 lumens per watt for a Multivapor (400 W) mercury lamp. For Lucalox lamps a sodium/mercury amalgam in a ceramic arc tube is vaporized to emit "golden white" light. For Multivapor lamps mer— cury and metallic iodides are vaporized in a quartz arc tube. The Multivapor lamp emits more blue light and less orange—red light than the Lucalox lamp (Figures Al and A2). The elliptical bulb shape for both lamps is very com- pact and permits optimum control of the direction of light. Long lamp lives and lumen maintenance character- istics contribute to significantly reduced costs of light- ing maintenance. Their high efficacies make for low elec- tric energy costs. The Duraglow luminaire used with HID lamps is well suited for greenhouse applications (Figure A3). The faceted reflector design of the luminaire provides uni— form, diverging light with no photometric crossovers or hot spots. The design also eliminates the redirection of radiant energy through the arc tube of the lamp and thus insures long lamp life. The reflector is lightweight and coated with a special glass finish to make it impervious to plant nutrients, insecticides and moisture. This study was initiated to determine the possible benefits of supplemental lighting of pot Chrysanthemums with HID lamps. Pot mums are an important greenhouse crop grown in quantity throughout the year. In northern lati- tudes, winter pot mum quality declines due to slower growth, less branching and weaker stem and foliage develop- ment. It was the aim of this study to determine the ex- tent to which normal winter pot mum quality could be im- proved using Lucalox and Multivapor lamps. NOTE TO COMMITTEE This dissertation has been prepared in two sections. Section One, 'High Intensity Supplementary Lighting of Chrysanthemum Stock Plants,‘ is a paper in journal format that has been submitted for publication in HortScience. Section Two is in the traditional thesis form. The body is divided into four parts for clarity and conven- ience in future publication. SEC TION ONE High Intensity Supplementary Lighting of Chrysanthemum Stock Plants1 G. A. Anderson and W. J. Carpenterz'3 Michigan State University, East Lansing Abstract. Stock plants of Chrysanthemum morifolium Ramat. cv. Bright Golden Anne lighted continuously from Sept. 30 to May 15 with Multivapor and Lucalox lamps (100 W/mz) produced larger nos. of cuttings than those receiving only seasonal daylight and photo- period lighting. Supplementary high intensity lighting improved cutting quality by increased fresh and dry wt and stem diameter. Cuttings from plants receiving high intensity lighting rooted in fewer days, had greater root fresh and dry wts, and greater top fresh wt than 1Journal Article No. 6456 from the Michigan Agri- cultural Experiment Station. 2Graduate student and professor, Department of Horticulture. 3The authors wish to acknowledge the financial support and equipment from the General Electric Foundation and cuttings from Yoder Bros. Inc. 6 plants lighted photoperiodically. After transplanting these cuttings became estab- lished more rapidly and developed into flowering plants of higher quality. Low greenhouse light intensities in winter limit the growth rate and quality of plants. Supplementary artifi- cial radiation has been successfully used in northern Cli- mates to improve the growth rate and quality of green- house crops (6). Supplemental photoperiodic lighting of carnations with 75W and 150W incandescent reflector lamps allows the earlier flowering of shoots and increases flower yield (7). Supplementary high intensity green- house lighting using combinations of mercury vapor and incandescent lamps has increased plant top heights and dry wt and reduced the no. of days to flowering for peas, beans, tobacco, and snapdragon (2). Sodium vapor lamps are more efficient than others, producing larger plant tissue dry wt from equal energy in the visible region (1). Flint reported geranium and Chrysanthemum stock plants lighted 10 hrs nightly with color-corrected mercury vapor lamps produced 56% and 20% respectively more out- tings than photoperiodically lighted controls during Nov. and Dec. Benefits from high intensity lighting of chry- santhemum decline more rapidly in the spring than for geranium (3). Swain found that 4 cultivars of 7 Chrysanthemum stock plants lighted from Sept. 29 to Jan. 3 with mercury vapor lamps (300-600 ft-c at plant level) produced significantly more and heavier cuttings than photoperiodically lighted controls (6). Our study determined Chrysanthemum stock plant bene- fits from continuous high intensity supplementary lighting with Lucalox and Multivapor lamps and the later influence on cutting prOpagation and plant development. These high intensity discharge lamps are of particular interest be- cause they have the highest light producing efficiency of any commercial sources of white light. Their compactness eliminates any significant shading from the lighting sys- tem and allows for good control of the direction of light. Long lamp life, lumen maintenance and high efficacies make for reduced costs of lighting maintenance. Rooted cuttings (210) of Chrysanthemum cv. Bright Golden Anne were planted in each of 2 adjacent north-south 4.5m by 1m raised benches Oct. 1. Above one bench 2 Luca- lox (400W) sodium vapor lamps and a Multivapor (400W) mer- cury vapor lamp with reflectors were alternated, providing 100W/m2 22 cm above the bench surface. High intensity lighting 24 hrs daily began Oct. 20 and continued to May 15. Light (50 ft-c) from incandescent lamps (60W) 4 hrs nightly kept plants in the adjoining bench vegetative. A black sateen cloth was hung vertically between the two benches. Cultural practices were followed as recommended for Chrysanthemums (4), and a 1200—1500 ppm 002 level was maintained in the greenhouse air. Twelve plots were established in each bench to com- pare cutting no. and quality beneath and between each lamp with plants lighted only photoperiodically. Records in- cluded cutting no. harvested monthly from each plot and cutting measurements of node no., basal diameter, and fresh and dry wt. The rootability and subsequent development of cut- tings from lighted stock plants was determined by propa- gations in Nov. and Jan. Terminal cuttings (8 cm) from each plot were propagated in a medium of coarse sand with bottom heat (24°C) and intermittent misting 10 sec. each 10 min. Incandescent lighting 4 hrs nightly during prop- agation prevented flower bud initiation. Rooted cuttings from each plot were harvested Dec. 14 and Jan. 20 and the no. of days for rooting, root no., root fresh and dry wt, and top length, fresh wt, and node no. were determined. Other rooted cuttings from each treatment were potted 3 to a 6 inch clay pot in a medium of equal parts of soil, peat moss, and Turface and given recommended cultural prac- tices (4). Plants were harvested 5, 10, 15, and 20 days after transplanting and at flowering to determine the lasting extent of the benefits found at propagation. Cutting yield. Chrysanthemum stock plants receiving 100W/m2 continuously from Lucalox and Multivapor lamps produced a larger no. of cuttings than those lighted photo- periodically during each of the 7 monthly periods (Fig. 1). Lighted stock plants yielded 43% more terminal cuttings in Nov.-Dec. than photoperiodic lighting, 102% in Jan.-Feb. and 33% in Mar.-Apr. Cutting quality. Improved cutting quality resulted from high intensity lighting of stock plants. Cuttings from high intensity lighted plants had larger and thicker leaves and greater basal stem diameter than cuttings from photoperiodic lighting. In Jan. terminal stem cuttings (8 cm) from high intensity lighted stock plants had 64% greater fresh wt and 108% more dry wt with a 58% larger basal stem diameter. Similar differences in cutting size and wt were found during Nov. and Mar. (Table 1). The node no. per 8 cm terminal cutting was slightly greater from high intensity light than photoperiodic lighting of stock plants. No significant difference was found among cuttings from the various lighted plots. Propaggtion. Cuttings from high intensity lighted (100W/m2) stock plants developed roots 2 days earlier in Nov. and Dec. with thicker roots having 45% greater root fresh wt, and slightly larger top fresh wt and node no. (Table 2). Growth after transplanting. TOp and root measure- ments, 20 days after transplanting, showed plants derived from high intensity lighted stock plants had larger fresh 10 Table l. Quality of 8 cm terminal cuttings from plots of Chrysanthemum stock plants under various light regimes. Trial Lucalox Multivapor Luca./Mult. Control Node no./cutting Nov. 4.26xa 4.67x 4.12x 3.69y Jan. 4.17x 4.88x 3.75x 3.78x Mar. 4.58x 4.58x 4.00x 3.33y Cutting base diam. (cm) Nov. 0.52x 0.49x 0.51x 0.37y Jan. 0.49x 0.49x 0.50x 0.31y Mar. 0.53x 0.51x 0.47x 0.30y Fresh wt (g) Nov. 4.26x 4.67x 4.12x 3.69y Jan. 3.22x 3.58x 3.72x 2.21y Mar. 4.64x 4.49x 3.68y 2.70z Dry wt (g) Nov. 0.54x 0.56x 0.51x 0.27y Jan. 0.52x 0.53x 0.51x 0.25y Mar. 0.61x 0.63x 0.52x 0.21y aFigures based on 4 replications of 6 cuttings each. Figures on a given line followed by the same letter are not significantly different at the 5% level. 11 Table 2. Comparison of Chrysanthemum plants propagated and grown under normal light conditions but originating from stock plants lighted 1OOW/m2 with combined Lucalox and Multivapor lamps.a Nov./Dec. Jan./Feb. Lighted Unlighted Lighted Unlighted Stock Stock Stock Stock End of Propagation Days to root 11.50x 13.90y 11.80x 14.30y No. of roots 32.56x 34.31x 27.91x 25.77x Fr. root wt (g) 1.49x 1.03y 1.37x 1.19y Dry root wt (g) 0.27x 0.19y 0.22x 0.15y Top length (cm) 8.81x 8.47x 8.75x 8.86x No. of nodes 4.32x 3.67y 3.92x 3.82x Fr. top wt (g) 4.19x 3.57y 4.02x 2.97y Day 10 Fr. root wt (g) 3.56x 2.83y 3. 3x 2.15y Dry root wt (g) 0.52x 0.46y O. 49x 0.39y Top length (cm) 10.94x 8.85y 9. 94x 9.32y No. of nodes 5.32x 4.39y 4. 69x 4.41x Fr. top wt (g) 5.95x 3.75y 4.92x 4.06y Day 20 Fr. root wt (g) 6.44x 5.47y 5.94x 4.82y Dry root wt (g) 0.79x 0.71y 0.75x 0.64y Top length (cm) 14.69x 12.02y 12.92x 11.93x No. of nodes 7.44x 6.38y 6.21x 5.95y Fr. top wt (g) 8.00x 6.32y 6.75x 6.04y At Flowering Plant ht. (cm) 68.32x 62.49y 65.32x 61.77x No. of fl. branches 3.24x 2.63y 3.12x 2.54y Fr. top wt (g) 75.12x 70.41y 74.01x 69.36y Dry top wt (g) 10.29x 9.90y 9.97x 8.65y Flower diam. (cm) 9.76x 9.57x 9.52x 9.35x aFigures based on 4 replications of 3 plants each. Figures on a given line followed by the same letter are not sig- nificantly different from the other value within the trial at the 5% level. CUTTINGS/ PLANT 12 12 .— _ UGHTED 10 __ ......... unuemeo 8 .— 6 I— 4 _ 2 _ l I L I l l N D J F In A MONTH Mean monthly no. of 8 cm terminal stem cuttings per chrysanthemum stock plant comparing treat- ments lighted continuously (100 W/m2 from Lucalox and Multivapor lamps) with unlighted (only photo— periodic lighting). 13 wt, greater plant height, top fresh wt, and stem node no. (Table 2). At flowering, treatment differences were visi- ble, and measurements showed these plants had 23% more flowering branches and were slightly taller and heavier than those from photoperiodically lighted stock (Table 2). Terminal stem cutting numbers yielded by chrysanthe- mum stock plants from Oct. through May were increased greatly by continuous lighting with Multivapor and Lucalox lamps at 100W/m2. The increased cutting no. reflected a 4.7 day decrease (from 16.3 to 11.6 days during Dec. and Jan.) in the no. of days from cut-to-cut for high inten- sity lighted versus photoperiodic lighted plants. The no. of branches/m2 in high intensity lighted plots was in- creased 110% and 68% in Jan. and Mar. respectively. High intensity lighting allows a greater density of branches while the limited photosynthesis at normal winter green- house daylight intensities is inadequate to support large nos. of branches. High intensity supplemental lighting has been repor- ted to increase the total reducing sugar level in rose leaves.“ Chrysanthemum leaves probably also contain higher carbohydrate reserves after exposure to nAnderson, G. A. 1970. The Effect of High Intensity Supplemental Lighting of Roses in the Greenhouse. Master's Thesis. Michigan State University, East Lansing. 14 supplementary high light energy levels. Since chemical synthesis and plant growth are dependent on the amount of available photosynthate, this could explain the stockier cuttings with greater fresh wt from the high intensity lighting of stock plants. The greater carbohydrate re- serve probably also accounts for the faster rooting and heavier root system. The benefits in plant quality after propagation were found to continue through the first 20 days of growth after transplanting and provided for a slightly higher quality plant at flowering. Our results indicate that supplementary lighting of stock plants with high intensity discharge lamps during the winter months in northern lati- tudes increases cutting no. and improves chrysanthemum plant growth and development to flowering, and should have commercial application. 15 Literature Cited Arthur, J. M. and E. K. Harvill. 1937. Plant growth under continuous illumination from sodium vapor lamps supplemented by mercury arc lamps. Contrib. Boyce Thompson Inst. 8:433-443. Craig, D. L. 1959. Response of greenhouse crops to supplementary illumination during the winter months in Nova Scotia. Can. J. Plant Sci. 39:135-140. Flint, H. 1957. Lighting of geranium and mum stock plants for more cuttings. N. 1. State Flower Growers' Bul. 39:1-2. Laurie, A., D. C. Kiplinger, and K. S. Nelson. 1968. Commercial Flower Forcing. McGraw-Hill Book Company, New York. Payne, R. N., R. E. Moon and R. D. Morrison. 1972. Fluorescent lighting studies with chrysanthemum, poinsettia, and hydrangea pot plants. Oklahoma State University Agricultural Experiment Station Bulletig B-701. Swain, G. S. 1964. The effect of supplementary illumination by mercury vapor lamps during periods of low natural light intensity on the production of chrysanthemum cuttings. Proc. Amer. §Q£. Hort. Sci. 85:568-573- White, H. E. 1961. The effect of supplementary light on growth and flowering of carnations (Dianthus caryophyllus). Pro. Amer. Soc. Hort. Sci. 76:594-598. SECTION TWO REVIEW OF LITERATURE Advancements in horticultural lighting Many possible methods of supplementing greenhouse daylight during the winter months have been investigated since L.H. Bailey in 1893 used artificial light on growing plants. Enclosing a carbon arc lamp in glass to absorb the damaging ultraviolet radiation, he showed that elec- tric light could benefit plant growth. Bailey called the new technique electro-horticulture (42). Although scientists recognized that an increased light intensity increased assimilation in plants, its use in reg- ulating plant growth received limited attention until Garner and Allard discovered the controlling influence of daylength on the flowering of plants (12, 32). Following this discovery, artificial lighting to control daylength was used in biological research and for commercial plant production. During the 1920's and 1930's research was be- gun to make qualitative measurements of light's effect on photosynthesis and subsequent plant growth (4, 14, 61. 64, 68). Researchers reported that carbohydrate levels in plant tissue could be changed by the light intensity or daylength (23, 26). Went (84) reported in 1941 that 16 17 although qualitatively a number of effects were known, understanding of the quantitative relationship between wavelength, light intensity, and total energy and their physiological effects was still shockingly deficient. Lighting equipment has two general uses in horticul- ture, photoperiodic and photosynthetic lighting. Photo— periodic control of chrysanthemum flowering is well known. The development of practical applications of daylength to chrysanthemum production was made by Laurie and his co- workers in 1930 (46). Photoperiodic lighting is accomplished with relatively low intensities (10 foot—candles of incandescent light) at critical periods to produce desired responses. Incandes- cent lamps are superior to other types because they emit more orange-red radiation (600-700 nm) than most other lamps, and the orange-red rays are more effective in con- trolling the photoperiodic phenomena (46). Most fluores- cent lamps emit lower intensities of orange-red radiation than incandescent lamps and therefore must operate for longer periods to achieve the same photoperiodic result. However, pink fluorescent lamps, which emit considerable orange-red radiation, can produce a desired photoperiodic response with half the duration of lighting each night than incandescent lamps (46). Over the last forty years much information has been acquired regarding the specific ratios of light to dark 18 periods that are required to manipulate the bloom of floriculture crops. The eXplanation of this phenomenon is intimately related to the action of the light-absorbing pigment, phytochrome. The chrysanthemum is perhaps the most extensive commercial greenhouse crop controlled in this way. High intensity lighting for increased photosynthesis, while used by growers in Europe, has had less application by U.S. growers (10). Photosynthetic lighting of horticul- tural crops requires irradiation levels from ten to over a hundred times that needed for photoperiodic control of flowering. The need for photosynthetic lighting in the greenhouse is greatest at northern latitudes during the winter months when normal greenhouse light intensities are low. For maximum benefit, artificial lighting is used to supplement natural daylight with higher day temperatures and supplemental carbon dioxide throughout the lighting period~(77). I Bickford stated that horticultural applications of lighting would be grossly impractical if it were necessary to duplicate the radiant intensity of natural spring or summer daylight (10). Fortunately much lower levels of light are sufficient to induce many plant photo-responses, including photosynthesis. It is upon this premise that horticultural lighting is based. 19 Canham summarized the desirable properties of a lamp to supplement daylight and accelerate plant vegetative growth as: (1) The spectral flux distribution must give the maximum increase in the rate of plant growth per unit of incident flux; (2) It should permit the plant to grow and develop normally, e.g. does not cause excessive elon- gation or soft growth; (3) The intensity of incident flux per unit area should be as high as possible for a given input; (4) The capital and running costs per plant irra- diated should be as low as possible; (5) The lamp life should be as long as possible; (6) The lamp and fitting should be as compact as possible to reduce shading of natural daylight; (7) The fitting should stand greenhouse conditions without deterioration; (8) The distribution of radiant flux over the bench area should be as uniform as possible (16). Basic and applied research and practical applications indicate that those lamps most efficient in radiating energy in the 580 to 800 nm spectral region are most effective and most widely used in horticulture. The spectral distribution of energy is just as impor- tant as the total energy emitted. Studies of the effect of different spectral regions on various plant responses show red and blue light control most plant processes (26, 74). Therefore, a greater percentage of energy should be in the 600—700 nm region with lesser percentages in the 700-800 nm and 400-500 nm regions. 20 Lamps in horticultural use today include incandescent lamps, standard "white" and plant growth fluorescent lamps and mercury vapor lamps. The suitability of lamps for lighting plants has been studied in many research projects. Seasonal and geographic variations in natural daylight and differences among species and varieties in response to lighting treatments have made comparisons of supplemental lighting studies difficult. Incandescent lamps have wider use because of a lower initial cost and simplicity. Unfortunately they have a low energy conversion and a short lamp life, about one- tenth that of a standard fluorescent lamp (10). However, a larger part of the visible energy emitted by these lamps is in the red region. There is also a substantial portion of energy emitted in the far-red region which has been shown by Roodenburg to cause undesirable formative effects with many plants (67). The fluorescent lamp is a diffuse light source with a relatively high energy conversion efficiency, long life and spectral flexibility. The ultra-violet part of the radiant energy is absorbed by a fluorescent powder on the inside of the glass envelope, where it is converted to vis- ible radiation. The spectral emission depends upon the particular fluorescent powder which coats the inside of the lamp (81). Plant growth lamps are used when high emission in the 600-700 nm region is desired. W.S. Gro—Lux 21 lamps emit more energy in the far—red 700—800 nm than any other fluorescent lamp (16). Although fluorescent lamps may provide a more ideal distribution of light for green- house benches, the acceptance of fluorescent lamps for greenhouse lighting has been hindered by equipment and installation costs and by the form and bulk of available industrial fixtures that produce excess shading of plants (10). Plants lighted with high intensity discharge lamps have been shown to produce normal growth (65). However there have been reports of excessive ultra-violet emission from clear mercury lamps (16). The uniform distribution of light energy over a growing area is a problem in green- house lighting. Mercury fixtures or mercury reflector lamps manufactured for commercial use may not provide a suitable light distribution for greenhouses where low mounting heights exist (10). Bickford and Dunn (10) list four general applications of photosynthetic lighting for greenhouses: (1) overbench and overbed lighting, (2) inter-plant lighting, (3) under bench lighting, and (4) growth (propagation) room light- ing. Overbench and overbed lighting with incandescent, fluorescent or mercury lamps is the most widely used method. Perhaps the first commercial all fluorescent photo- synthetic lighting system was installed in a greenhouse in 22 Alaska (10). The very short Alaskan daylight period (only about four hours in winter) was extended to fifteen hours to promote the growth of salad crops (tomatoes, lettuce, cucumbers, radishes, and peppers). Since Alaskan green— houses normally close down during winter because of low natural light intensities and extremely low temperatures, this became the first continuously productive commercial greenhouse operation. The lighting system consisting of W.S. Gro-Lux lamps mounted at twelve inch spacing in socket strips with ballasts remotely mounted provided 20 W/ftz. Lamps were at fixed mounting 6% feet above beds and 3% feet above the propagation benches. Canham (16) describes another technique for providing photosynthetic lighting that involves mounting the light- ing equipment on movable runners so that it can be easily moved from one area to another. This efficient use of equipment, called "double batching" permits lighting of two groups of plants for twelve hours each during a single day. Inter-plant lighting is efficient from the standpoint that shaded leaves are exposed to radiation levels much higher than would be possible with overhead lighting. Plants responding well to this treatment include tall- growing plants which require high intensity light at all leaf levels. Carpenter and Anderson have shown that inter- plant lighting of roses with W.S. Gro-Lux lamps improved flower yields by increasing bottom breaks, stimulating 23 axillary shoot development after flower removal, and slightly reducing the days from cut—to-cut (17). Plant contact with 800-1000F W.S. Gro-Lux lamp surfaces results in little or no tissue burn. Underbench lighting utilizes greenhouse space more efficiently. Total growing area can be doubled or tripled when fluorescent lamps are mounted beneath benches. Plants with short growing habits as African violet, foliage plants, gloxinias, geraniums, and chrysanthemums are possibilities for underbench areas. Growth (propagation) room lighting is of intereSt because it permits lighting of a small area yet can affect the later growth of most plants. Lighting during seed germination, seedling growth, rooting and growth of cut- tings, and bulb forcing for a relatively short time has the potential to improve plant quality and hasten plant development (81). Little work has been done on the effects of photo- synthetic lighting on the growth and cutting yield from chrysanthemum stock plants and on the subsequent rooting of cuttings. In 1964, Swain used clear mercury lamps at 27 W/ft2 to provide light each day (8 a.m. to 8 p.m.) from September to April for growing chrysanthemum stock plants in Nova Scotia. He found lighted plants grown from Sep- tember to January produced 22% more cuttings of greater fresh weight than plants grown in the unlighted plots. 24 Lighted plants grown from January to April produced heavier cuttings but not a greater number than from the unlighted controls (7?). Flint (30) using mercury lamps nightly (10 hours) for chrysanthemum stock plants found a 20% increase in cutting yield over unlighted controls in November and December. Lindstrom found that chrysanthemum cv. Shoesmith pro- duced significant increases in height, fresh weight, dry weight, stem diameter, and flower diameter when exposed to higher supplemental light and carbon dioxide levels in the greenhouse during the pre-flower induction period. He com- pared cool white and W.S. Gro-Lux fluorescent lamps in- stalled at about 20 W/ft2 to provide an 18 hour photo- period with daylength extension lighting to midnight for the first four weeks of growth. He compared light sources with supplemental carbon dioxide (2000 ppm), without supplemental carbon dioxide, and with the usual incandes- cent control treatment used for chrysanthemums. The re- sults show that the combination of supplemental light and carbon dioxide is better than either applied alone. With- out supplemental carbon dioxide, plants under W.S. Gro-Lux lamps produced greater growth than those under cool white and the incandescent control. With supplemental carbon dioxide the same relationship was evident except that plants under the cool white treatment were taller than those under Gro-Lux (50). 25 Payne and others (56) studied fluorescent lighting of chrysanthemums in Oklahoma and found that greenhouse grown plants receiving supplementary lighting from Standard Gro— Lux and W.S. Gro-Lux lamps in the spring were signifi- cantly heavier in dry weight of flowers and vegetation than the control plants. Other differences were not sig- nificant. During the summer trial the number of breaks and the dry weight of flowers were significantly higher with a daytime supplementary lighting treatment than for control plants in the greenhouse. Since there were few easily observed quality differences among plants in the various lighting treatments, it was concluded that day- time supplementary fluorescent lighting of chrysanthemums in Oklahoma appears to be of questionable value. Reports from growers in areas of low winter green- house light intensity differ from those of Payne. Kenneth Maekowa, pot-mum specialist of Seattle, Washington, re- ported they now use 600 foot—candles from 1 a.m. to 6 p.m. daily for the first 19 days after potting. They found the improved quality of their dark-weather crop justified the expense (8). Photomorphogenesis in chrysanthemum The ability of light intensity, duration and quality-If to influence plant growth, development, differentiation, and reproduction has been recognized for some time (48). 26 Stem elongation is of major importance when considering the morphological manifestation of plant growth resulting from variation in environmental factors. It is well known that excessive plant stem elongation occurs in continuous darkness. Light depresses this internode extension and far-red radiation in the 700~800 nm range as well as visi- ble light in the red and olue regions can elicit this response. Supression of stem elongation is not, however, di- rectly correlated with an increased light intensity. Inadequate light intensities limit the development of many species, particularly of high light requiring plants as chrysanthemums. This is evident in the reduced vegetative growth of greenhouse crops during the winter months in northern latitudes compared with growth during spring and autumn when natural light intensities are higher (46). In 1872 Sachs recognized light inhibition of growth when he observed that many plant species are inhibited in stem elongation during daylight hours (48). A high light intensity inhibits cell elongation and limits growth in most higher plants. Yet in spite of such inhibition, overall maximum growth, as determined by shoot elongation and leaf expansion, is made by most high light requiring plants in full sunlight of 10,000 foot-candles or more (80). At these high light intensities sufficient light of perhaps 2,000 to 3,000 foot-candles is available to the 27 inner, shaded parts of the plants. Treshow reports that sun-loving plants grown in full sunlight have thicker stems, with well developed xylem and supporting tissues and internodes relatively shorter than when grown in the shade (80). In summer's high light in- tensities, stems of greenhouse grown roses and carnations may be shorter than desired. If the light intensity is reduced to some extent, leaves may become quite dark green, the stems somewhat longer, and the leaves thinner (46). Craig (22) found that several greenhouse crops, in; cluding peas, beans, tobacco, snapdragon, and strawberry responded well to mercury vapor, mercury fluorescent and incandescent supplementary illumination during the winter months in Nova Scotia. Plant height and plant top dry weights were greater for lighted than unlighted plants. I Swain reported that four cultivars of chrysanthemum stock plants lighted from September to January with mercury vapor lamps (300-600 foot-candles at plant level) pro- duced significantly more and heavier cuttings than un- lighted controls (77). No information was given as to whether the increased cutting production was attributed to more rapid vegetative growth or increased branching of stock plants. Carpenter and Anderson found that roses lighted 20 hours with 31.3 lamp watts/ft2 with W.S. Gro— Lux lamps to supplement natural daylight responded with improved flower yields by increasing bottom breaks, 28 stimulating axillary shoot development after flower remo— val, and slightly reducing the days from cut-to-cut. De- velopment of additional axillary buds was the principal factor in the improved branching of lighted plants (17). Stimulation of chrysanthemum axillary bud develop— ment has the potential of increasing cutting production from stock plants as well as improving the floral show of pot mums at flowering. Vegetative growth and branching of chrysanthemums grown under normal greenhouse light con- ditions is much improved after April 1. when solar radia- tion levels are higher than during the winter months (62). Another morphological response to light is the devel- opment and ultimate expansion of the leaves. Smaller but denser and heavier leaves are often produced in full sun- light, while shading results in much larger, thinner leaves with thinner epidermis, less palisade, more inter- cellular space and spongy parenchyma, and more numerous“; stomata (80). When shading reduces the light intensity to 2,000 foot-candles, the ultimate leaf area may be in- creased 15% to 55% while the plant weight is reduced nearly in half (53). The palisade cells, which contain the principal supply of chloroplasts, are formed in larger numbers with increasing light intensity during leaf devel- opment (48). The morphological response to bright light seems to offer a basis for the physiological adaptation of leaves to high light intensity. It is commonly observed 29 in the greenhouse during winter that plants easily wilt on a sunny day which has been preceeded by several cloudy days (46). This is evidence that plants can rapidly adapt to changing light intensity levels. Individual cells of the leaf blade are usually smal- ler at high light intensities than in subdued light or shade. The result is smaller but thicker leaf blades, denser but smaller stomata, and more conducting and mechan- ical tissue. The cuticle and cell walls are generally thicker, intercellular spaces smaller, and blades of a harder texture. From an evolutionary viewpoint, these morphological modifications help make the plant more re- sistant to temperature and drought stress and infection by fungus and bacterial parasites (80). Plants grown at lower light intensities are characterized by more weakly developed spongy parenchyma and a better-developed pali- sade layer. . Light quality may also influence leaf expansion. The effect of different wavelengths on size and shape of ex- panded leaves varies considerably among species. While the situation regarding chrysanthemum is not well docu- mented, cells in the under surface of tomato leaves ex- pand irregularly and incompletely in red light, so that ,the mature leaves are curled (80). Leaf color can also be influenced by light quality and duration. Prolonged daily exposure to light can 3O prevent chlorophyll formation. The result is chlorosis due to the revealing of more of the yellow caratenoid. Wolf has shown that in seedlings the biosynthesis of carote- noid pigments is greatly stimulated in light compared with that of seedlings in darkness (90). Anthocyanin is known to be formed only in the presence of light and may be ex— cessive in unshaded plants grown for their green foliage color. Anthocyanin synthesis in many plants requires pro- longed irradiation at moderately high intensities (10). Shirley's controlled studies with ultraviolet light showed that plant growth was inhibited by high light in- tensities, but once light intensity was reduced, normal growth was resumed and there was no permanent damage to the plants (68). High intensity of radiation in the far ultraviolet and shorter wavelengths is usually negligible in sunlight, since it is absorbed by ozone in the atmos- phere. When sunlight passes through glass most of the ultraviolet rays are removed (46). Therefore the action of ultraviolet on plants in the greenhouse becomes impor- tant only if radiations of very short wavelength are pro- duced artificially. Although such radiations could have an injurious effect on lighted plants, they are not pro- duced to any significant extent by lamps used in horti- cultural lighting (10). Furthermore plant tissue is quite insensitive to the near ultraviolet spectral region of wavelengths (those longer than 290 nm). Radiation is 31 active only to the extent it can be absorbed and ultra- ViOlet cannot penetrate to the interior of the plant, like the visible and near-infra-red (78). Since the greatest part of the ultraviolet radiation which strikes plant sur- faces is absorbed by the directly exposed cells, the immediate reaction may be only superficial. However, it is possible that significant repercussions may ultimately develop from such exposure (78). In some plants continuous lighting has been found to produce considerable morphological alterations (3, 26). Continuous illumination of tomato produces a very poorly developed plant which does not bear fruit. However, many plants, including begonia, cotton, and geranium, show ex- cellent leaf color and normal development and flowering (3, 62). There is no evidence in the literature of un- favorable effects on chrysanthemum as a result of lighting 24 hours daily. Light affects root initiation and growth of leafy cuttings. Light intensity and duration must be great enough so that carbohydrates will accumulate in excess of those used in respiration. Stoutemyer and Close have shown that light intensities of 150 to 200 foot-candles 18 hours daily provided by white fluorescent lamps were sufficient for satisfactory rooting in some species of greenwood cuttings (75). These intensities are low com- pared with 10,000 foot-candles in full sunlight, but 32 woody cuttings are much more dependent upon stored carbo- hydrates than herbaceous cuttings. Stoutemyer and Close have shown that radiation in the orange-red portion of the spectrum favors rooting of cut- tings more than the blue region (76). However, when stock plants of Gordonia axillaris were exposed for six weeks to p» light sources of different quality before taking the cut- tings, best rooting resulted for cuttings taken from plants exposed to blue light (76). “ Waxman and Nitsch reported that long days increased and short days decreased the rooting quality for a number of species of cuttings (83). It is likely that in some cases long light periods may have contributed to photo- synthate production rather than to any direct photoperi- odic effect. Chrysanthemums must be given long days dur- ing propagation to keep the cuttings vegetative (46). This is commonly accomplished with 60 W or 100 W incandes- cent lamps lighted four hours nightly to break the dark period. In chrysanthemum the formation of adventitious roots takes place after the cutting is made (36). The origin of these roots is a group of cells in the interfascicular re- gion which are capable of becoming meristematic. The small groups of cells, the root initials, divide forming groups of many small cells which develop into root primordia. As cell division continues a vascular system develops in the 33 new root primordium and becomes connected to the adjacent vascular bundle (29). The root tip grows outward, through the cortex, emerging from the epidermis of the stem. Be- cause the roots originate within the stem tissue and grow outward, they are said to arise endogenously. Root ini- tials were observed microscopically in terminal stem cut— Fl tings of chrysanthemum after three days in the propagation bench (72). At least ten days is normally required for visible roots to emerge. After chrysanthemum stem cuttings are placed in the propagation bench, callus will develop at the basal end of the cutting. The callus is an irregular mass of paren— chyma cells which arises from the region of the vascular cambium and adjacent phloem. Formation of callus and formation of roots are independent of each other, however they often occur simultaneously due to their dependence upon similar internal and environmental conditions (36). Light and photosynthesis A number of environmental factors, including light, temperature, carbon dioxide, water and nutrients can affect the rate of photosynthesis and the amount of photosynthate subsequently produced. A deficiency of any one of these factors can limit growth and reduce plant vigor. Light is of great importance to the plant because it provides the energy necessary for the conversion of carbon dioxide and 34 water by chlorophyll-containing plants into carbohydrates in the photosynthetic process. Seventy-five percent of the total photosynthate may be incorporated in poly- saccharide, much of which is used to build cell walls; fifteen to twenty percent may be consumed in respiration; and.'Uu3 remaining serves as substrate for carbohydrate, fat, and protein metabolism (80). Thus all chemical syn- thesis, energy and plant growth depend on adequate photo- synthesis to provide the needed photosynthate. Many plants are structurally organized to receive the greatest amount of light possible. Maximum light absorp— tion is facilitated by the large surface/volume ratio of the leaf, coupled with the large intercellular surface area and lamellar chloroplast structure (80). According to estimates made by Brown and Escombe, about seventy percent of the sunlight striking a leaf sur— face is absorbed, the remaining thirty percent being transmitted or reflected. Twenty percent of the light energy may be transformed into heat and re-emitted by radiation while nearly fifty percent may be used for evap- oration. Only about one percent of the light energy is used for photosynthesis (78). I There are several methods available for determining quantitatively the amount of photosynthesis that has taken place. The dry weight method is commonly used. Increase in the dry weight of test plants in comparison with 35 appropriate control plants is often used as an overall measure of photosynthetic efficiency. Another method is standard analytic determination of carbohydrate present in leaves at the start and at the end of a photosynthetic period. Anderson has shown that high intensity supple- mental lighting of rose leaves (31.3 W/ft2 with W.S. Gro- Lux lamps) increases the total reducing sugar level com- pared with leaves exposed to winter's normal greenhouse light intensities. The amount of photosynthesis, as de- termined by the total sugar content of the tissue, may in turn be correlated with morpho-physiologic changes in the plant (1). - Light quality, intensity, and duration are all vital to normal plant development, but the intensity is the most critical variable influencing photosynthesis (80). Photo- synthesis increases with increasing light intensity in a linear manner, up to a certain level with sufficiently high temperatures and carbon dioxide supply. Beyond that point there is no further increase and the curve flattens into a plateau with greater intensities of light. However, most of the work relating light intensity to photosynthe- sis has been done using lower plants. Therefore the measurement of the saturation effect of light intensity on higher plants is at best rather empirical (10). The intensity required for light saturation is different for different kinds of plants and varies with 36 the age of the same plant. Shading of lower leaves by upper ones accounts for large differences in light re- quirements. Increasing light intensity usually results in greater photosynthesis in plants which have many shaded leaves. Since many leaves on chrysanthemums are shaded by adjoining foliage because of close planting, as much sun— PM light as possible should be admitted to permit maximum photosynthesis without damaging the plants from excessive intensities (46). Insufficient light limits the radiant energy available for photosynthesis, causing food reserves to be depleted faster than they can be stored. Gerhold showed that the photosynthetic rate of Scotch pine de- creased in direct proportion to decreasing light intensity from 6,400 to 1,800 foot-candles. Below 1.800 foot-can- dles the photosynthetic rate dropped still more steeply (34). Competition for light as a result of shading or crowding can substantially reduce the growth rate of plants. Shiroya and others attributed poor root growth of shaded pine seedlings to limited photosynthate trans- located to the roots (69). The effect of low light in- tensities in reducing root growth helps explain the diffi- culty unadapted species have competing for nutrients and water in a low light intensity situation. Too high a light intensity may reduce photosynthesis by rapidly photo-oxidizing chlorophyll, so that the 37 remaining supply is inadequate to absorb sufficient light energy. Leaf color fades as the old chlorophyll is des- troyed in the upper palisade cells. A pale green or yellowish cast results because chlorophyll breakdown by intense illumination is faster than chlorophyll synthesis (80). Chlorophyll synthesis may also be inhibited by high light intensities. Leaves have a limited protective mechanism against chlorophyll loss. Chloroplasts may migrate to the center of the cell under conditions of light stress (80). High light intensities may also affect photosynthesis by the oxidizing of the enzymes partici- pating in photosynthesis. These explanations are some— what theoretical because plants vary so greatly in their response to light and ‘Uue optimum light requirements are unknown for most plant species. Gerhold found that photo— synthetic activity in Scotch pine was inhibited only when the light intensity reached 9,300 foot-candles (34). Shirley found that maximum dry weight increase of red pine seedlings occurred at 98 percent of full sunlight, although maximum growth was reached at half this light in- tensity (68). Leaves adapted to winter's low light intensities may respond quite differently to increase in light intensity than summer grown plants. Barua studied the photosynthe- tic rates of detached tea leaves as influenced by various light intensities (9). He found significantly different 38 assimilation rates for the various light intensities which could not be explained by the thickness of the leaf lamina or the chlorophyll concentration of the leaves. Shade adapted leaves had significantly higher rates of photo- synthesis in the weakest light and lower rates in the higher intensities than the corresponding sun adapted leaves. Therefore it is likely that tissues adapt to specific conditions and their response at any particular time is influenced by their previous conditioning. The effect of various wavelengths of light on photo— synthesis has been difficult to determine precisely. Many observers find that the red and blue portions of the spectrum are most effective in photosynthesis with red light causing 13m; best yield under intensities of equal energy (38, 52). In 1970 Balegh and Biddulph measured the photosynthetic action spectrum for bean leaf (7). Their graph shows a peak in the blue region about 440 nm and two peaks (at about 670 and 630 nm) in the region of longer wavelengths. Dunn and Went have plotted micrograms of photosyn- thetic yield of tomato seedlings per foot-candle of light from various portions of the spectrum as emitted by colored fluorescent lamps. The contours of this graph are very similar to the action spectrum of chlorophyll (26). 39 Light intensity, temperature and rate of photosynthe- sis are inter-related. Plants differ considerably in the range of temperatures in which photosynthesis can pro- ceed. Emerson and Green used Barcroft-Warburg manometers to measure rate of Gigartina photosynthesis under various light intensity and temperature regimes. Banks of incan- descent lamps of unspecified intensity were shielded with filters to produce lower light intensities. At low light intensities and high carbon dioxide photosynthesis is in- dependent of temperature. With strong light and abundant. carbon dioxide, photosynthesis increases with higher tem- peratures (27). As temperature increases so do respira- tion rates. Increased respiration reduces carbohydrate reserves resulting from photosynthesis. Too high tem- perature (above 32°C) can cause stretching of chrysanthe- mum plants and delayed development of flower buds. Too low temperatures (below 160C) can retard or cause uneven development of chrysanthemum flowers. Chrysanthemums are usually grown at a night temperature of not less than 18°C (46). The carbon dioxide content of the air is approxi- mately 0.03 percent, and during periods of high light in- tensity and warm temperatures when plants are well sup- plied with water, it may be a limiting factor in photosyn- thesis (46). In general, the rate of photosynthesis in- creases in proportion to increase in carbon dioxide 40 content of the air, up to a point where some other factors become limiting. It is a common greenhouse practice to enrich the air with carbon dioxide (1200-1500 ppm) to help increase photosynthesis. Higher intensities from supplemental lighting would increase the utilization of carbon dioxide added to the greenhouse atmosphere. I EVALUATING SUPPLEMENTARY LIGHTING DURING AND AFTER PROPAGATION The regulatory effect of lighting for photoperiodic control has shown long days (LD) cause earlier and better rooting for many species (25, 45, 70), but delay the root- ing of others (40). Leshem and Schwartz (49) found LD reduced chrysanthemum rooting, but this response was pre- vented by exogenously applied IBA. Stoutemyer and Close (76) propagated various plant species under equal inten- sities (150 to 200 lm/ftz) of each light color and found pink light was superior to white, which was better than blue. MacDonald (51) reported 400 ft—c or higher is needed to supplement the natural daylight if photosynthe— sis is to be increased sufficiently to influence carbo- hydrate levels in many plant species. The objective of this study was to determine if high intensity supplemental lighting during some critical per- iod between sticking cuttings and short-day (SD) treat- ment was as beneficial as lighting during the entire per- iod. Groups of plants were harvested at the beginning of the SD treatment, 5 weeks later (half-way to flowering) and at flowering. Since treatment differences occurred 41 42 during the early stages of growth, it was important to see the duration and extent of the differences as the plants matured. Materials and Methods Adjoining 4.6 m by 7.7 m greenhouse sections oriented E-W were divided by aluminum foil covered paper to create four 4.6 m by 3.85 m sections. Beginning in Oct. 1971, a Lucalox (400 W) sodium vapor and a Multivapor (400 W) mer- cury vapor lamp were placed below the greenhouse ridge in one section 2 m apart, while in the other section 2 Luca- lox and a Multivapor lamp were spaced 1 m apart. After Dec. only 2 lamps were used in each lighted section. Lamp luminaires were 1.4 m above the propagation bench, each lamp emitting 58 W/m2 of light. A coarse sharp sand medium was maintained 210C with buried Famco propagation mats while the air temperature was 16°C nights and 21°C days. Ninety-six cuttings of Chrysanthemum morifglium Ramat. cv. Bright Golden Anne were propagated in each section monthly from Oct. to Mar. All cuttings received inter- mittent mist (6 sec. per 6 min., 24 hours daily) and 2 applications of a complete fertilizer solution (100 ppm) weekly. In a preliminary study, all cuttings receiving supplementary light without misting became dehydrated and 43 many died. Twenty-four chrysanthemum cuttings in each lighted and unlighted replicate were removed 14 days after placement in the propagation bench. After Dec. 1971 cut- tings were harvested when root lengths became 2 cm. Re- cords for individual cuttings included number of days to root, root number, length and fresh weight, and top length and fresh weight. The remainder (72) of the rooted cuttings from each plot were potted 4 to a 6 inch clay pot in a medium of equal parts of soil, peat moss, and Turface. A randomized block experimental design was established to permit 36 plants from each section to continue receiving high in— tensity supplemental lighting (116 W/mz) 24 hours daily during the 3 week vegetative period from potting until the SD treatment began (referred to as stage 2). A second group received only incandescent lighting 4 hours nightly during stage 2 to prevent flower bud initiation. The 4 treatments included: (a) continuous lighting (116 W/mz) during propagation and stage 2, (b) only photoperiodic lighting during propagation and stage 2, (c) lighted (116 W/m2) during propagation but only photoperiodic lighting during stage 2, (d) only photoperiodic lighting during propagation but lighted (116 W/mz) during stage 2. Recommended cultural practices for chrysanthemum were followed (46) and no supplemental lighting was used after the SD treatment began. Lu. Twelve plants from each replication were harvested at: (a) the end of stage 2 (3 weeks after potting), (b) half-way to flowering (5 weeks after SD treatment began) and (c) at flowering. Records at the end of stage 2 in- cluded the length and fresh and dry weight for both roots and shoots. After 5 weeks of short days, major and minor nodes (nodes showing evidence of producing a flowering shoot and nodes not likely to produce a flowering shoot) were counted and recorded in addition to other data. Flowering data included plant height and fresh top weight. and flower number, diameter and fresh weight were deter- mined when the second circle of petals expanded. From Jan. to Mar. 1973 the propagation studies were repeated using two cultivars, 'Bright Golden Anne' and 'Puritan.’ The experimental design was identical to the previous year. Only one Multivapor lamp emitting 58 W/m2 was used since earlier studies had indicated that a Luca- lox (400 W) sodium vapor lamp alone was as effective in promoting rooting as the Lucalox and Multivapor lamps in combination. The daily lighting duration was reduced from 24 to 20 hours to overcome a slight foliar chlorosis, but this did not significantly decrease rootability of the cuttings. When root lengths became 2 cm rooting measure- ments were made that included days from planting to har- vest: root number, length and fresh weight; and top length and fresh weight. Data were analyzed statistically 45 according to Duncan's Multiple Range Test. Greenhouse air temperatures were measured on the propagation benches receiving 0, 116, and 174 W/m2 of supplementary light using thermocouples and a 24-point recording potentiometer. Leaf temperatures under mist were measured in Dec. using a temperature radiometer. East Lansing's incident solar radiation during the course of the study was obtained from the U.S. Weather Service. Greenhouse light intensities during nights, cloudy days and sunny days were measured by a Weston 756 Illumination Meter. Total radiation input from natural daylight and lamps during the trial period was calculated in KW-hrs/m2 according to guidelines by Noesen and Spacil (54). When chrysanthemum cuttings under 174 W/m2 of supple- mental light developed foliar chlorosis, leaf tissue sam- ples were prepared for foliar analysis and leaf sections were prepared and examined under a light microscope. Leaf tissue was killed and fixed in FAA and prepared by the paraffin technique according to Knobloch (41). A double Safranin-Fast Green stain enhanced the visibility of the sections. 46 Results Propagation Rooting. Cuttings receiving 116 W/m2 of supplemen- tary light from combined Lucalox and Multivapor lamps during prOpagation had larger numbers of roots, longer roots from earlier initiation, and higher root fresh weights than those non-lighted or lighted at 174 W/m2 (Table 3). In Oct. the roots of cuttings lighted at 116 W/m2 were 37% heavier than cuttings unlighted during the 14 days in the propagation bench. Lighting at 174 W/m2 during the same trial reduced cutting weight 34% below unlighted cuttings. Differences in fresh root weight between cuttings lighted 174 W/m2 and unlighted were smaller during Nov. and Dec. than in Oct. (Figure 2). When cuttings were harvested after a standard root length had been reached, those receiving 116 W/m2 of supplemen- tary light had significantly larger fresh root weight than the unlighted controls. During the second year's trials only Lucalox lamps (58 W/mz) were used. The number of days needed to initi- ate and develop roots of 2 cm from Jan. to Mar. was re- duced 3 to 4 days by supplementary lighting compared with cuttings propagated under normal greenhouse light con- ditions (Table 4). Cvs. Bright Golden Anne and Puritan responded well to high intensity supplemental lighting. 47 .sm .Pmme owsmm oamfipasz m.£dossm hp gpsoe m Canvas massaoo CH mosam> mo sowpmsmmom ssoss was.m nmo.oH oss.a nm.m no.0m ass mmm.m nmo.m mmm.m mm.m mfi.sm was mmo.m ans.m nmo.a om.a om.sH o .ooa mmm.m omfi.ofi pmm.H os.m om.mfi ass Nam.m Qmm.m mmm.m mm.m mm.#N QHH mmm.m ems.m omm.H nm.m pm.ma o .>oz mms.m omo.ofi omm.a ofi.m om.oa ass mem.m osm.m mem.m mo.n mm.om was mmo.m «mo.m pmm.a oo.m pm.fim o .poo Amv Asov Amv AEOV .os NE\3 space 92 .LL apmcoa a; .Le apmcoa pemaa coapam ems poom ooooa -aaohm N.Anoson soapmmmgosa esp Ca coomam ohms mmsflwpso Loews mama :Hv mmeH somm>wpasz csm xoamosq UosHQEoo Eons pnwfia mo s\3 35H new .ofifi .o mswsmasoo .mss< cocaoo pamfism .>o .sssonpssmSLSO Mo Coapmm -mmOnQ o>aphpomo> one so Spamsmpsfi pswfia Suspsmsmammsm mo mososamsfi onenn.m manna .sm .pmoe mmsmm magwpass m.smossn an pesos m Canvas massaoo CH mosam> mo sowpmpmmmm swoSN mos.m mmm.m mem.o mo.m «3.0m m mm was.m ems.s nsm.o mo.m pm.ma «H o .hmz mmm.m mem.m mae.o ao.m «a.mm OH mm asa.m pso.s nom.o mo.m os.sfi ea 0 .nom .cmpaham. mam.m Ems.m mso.H mo.m mm.fim Ha mm mom.m nae.s pmm.o mo.m no.0m ea 0 .cme mmo.s mmm.ofi mmm.o mo.m om.om m mm mam.m nmo.m pom.o mo.m nm.mfi NH o .Lms mmm.m was.m mmm.o mo.m om.om HH mm .occ< was.m ass.m nem.o mo.m no.mfi as o .oom. cooaoo mmo.m mam.a mmfi.fi mo.m am.:m Ha mm pgmasm. mam.m omo.m nem.o mo.m pH.mN ma 0 .cme masses mums mmo.m msm.m mom.~ as.m mm.mm as was mmm.m mem.m nec.fi no.m pm.mm as o .LRE mam.m mam.m mom.a mo.m mm.fim ea was .occ< muo.m pmm.s omw.o pa.m pm.om SH 0 .nom cooaou mmm.m meo.a aso.a ma.m mm.em as was pemahm. mmm.m has.s pmm.o ps.a nm.ma SH 0 .cme waste Hmma Amv AEoV Amv Asov .os pmo>smn op Ams\sv spsoe am>wpaso 93 .sw nemsoa #3 .HM spmsoa mass .02 infia seesaw woe poom coco< Immopm a.msssonpssmzsso mo soapmmmmopm o>flpmpmmo> one so masmH xoamosq Souk sawed Suspsoangmsm mo mososassfl oganu.: magma 49 ,\ 2 - ___ 6 w $9 2.5 El_l /m e. 3 2.0 '- 3 control 5 1.5 .. :1: Ff E I 1 l Oct. Nov. Dec. PROPAGATION MONTH Figure 2.--Fresh root wt of chrysanthemum cuttings propa- gated under 0, 116, 174 W/m2 of supplementary light from combined Lucalox and Multivapor lamps. 10.0 _. E o E o 9-0 ' E. r—l V 0.. O B 800 h l l 1 Jan. Feb. Mar. PROPAGATION MONTH Figure 3.--Top length of chrysanthemum cuttings propa- gated under 0 and 58 W/m2 of supplementary light from Lucalox lamps. 5O Lighted 'Puritan' cuttings had 35% more roots and 63% heavier roots than unlighted cuttings during the Feb. trial. Lighted and unlighted cuttings averaged 23.9 and 17.7 roots per cutting with a fresh weight of 0.49 g and 0.30 g respectively. Similar increases in root number and root fresh weight were observed for cv. Bright Golden Anne. The consistent benefit from lighting over the trial period was seen graphically when the monthly averages of fresh root weight were plotted (Figure 3). Tgp growth. Growth of cuttings in length during propagations from Oct. to Dec. was 10% and 15% larger for lighted 116 W/m2 and 174 W/m2 respectively than unlighted cuttings. Top fresh weights were not significantly dif- ferent (Table 3). These data were supported by Jan. to Mar. trials comparing cuttings lighted 116 W/m2 from com- bined Lucalox and Multivapor lamps and unlighted cuttings (Table 4). Cuttings lighted 58 W/m2 from Jan. to Mar. with a Lucalox lamp had significantly greater top length but non-significant top fresh weight compared with un- lighted controls (Table 4). Cuttings lighted 24 hours daily at 174 w/m2 from com- bined Lucalox and Multivapor lamps developed foliar chlor- osis during propagation. In certain leaves this culmin- ated in the development of necrotic areas before the 14th day in the propagation bench. 51 Temperature and light measurements. Air temperatures among cuttings were 1.2OC and 1.700 warmer in sections re- ceiving 116 W/m2 and 174 W/m2 respectively than in non- lighted sections. Cuttings under 116 W/m2 and 174 W/m2 of light had leaf temperatures 1.3OC and 2.500 higher at night and 2.700 and 5.1OC higher on sunny days in Dec. than those in non-lighted sections (Figure 4). Greenhouse light intensities during nights, cloudy days and sunny days in late Dec. were increased 1000 and 1500 ft-c from 116 W/m2 and 174 W/m2 of irradiation (Table 5). Mean radiation values from sunlight averaged 237, 104 and 178 calories of sunlight per cm2 per min. for Oct., Dec. and Feb. respectively (Appendix B). Total radiation input from natural daylight and lamps during the trial period is listed in Tables 6 to 8. Anatomical observations. Chrysanthemum cuttings propagated under 174 W/m2 of supplementary light from com- bined Lucalox and Multivapor lamps developed foliar chlor— osis with dispersed necrotic areas after 2 weeks in the propagation bench. Examination of leaf cross sections through necrotic areas under the light microscope at 10x showed disorganization and death of pallisade cells and dissolution of the spongy mesophyll. 52 .HoQEoomQ mesa CH NE\3 :mH vss mHH spas asp hss5m m msflsdc psmfla SuspsoEoHQQSm on msH>HoooH omens MCHHMQEOO msflpmfls psoppflshmpsfi Hmcsz COHPMWmQOHQ mcflhsu moHSPMHoQEoP mama Essenpsmmhsgoun.d madman Han so mess sooz m N H NH HH 0H s m H H H H _ H H H - 0\ -1w H b. -‘\O —‘-Q -d' eoesmHHss we} oHH 82qu 13 NE\3 ssH oopewHH 00 HHHIVHHdWEL JVHT 53 Table 5.--Mean light intensities in late December in non-lighted and lighted greenhouses at night and cloudy and sunny days. Night Treatment Intensities Light intensities ft-c (ft-c) Cloudy Sunny Greenhouse 0 725 2450 Greenhouse + 116 Wu.2 1050 1675 3610 Greenhouse + 174 W/m2 1490 2100 4175 Growth after transplanting Root length and weight. Chrysanthemum plants con- tinuously lighted 116 W/m2 with combined Lucalox and Multivapor lamps during propagation and from transplanting to SD treatment had fresh root weights 26%, 36%, 34%, and 34% greater than unlighted plants during Nov., Dec., Jan. ' and Feb. respectively. Plants harvested at the beginning of SD treatment that only had been lighted during prOpa- gation or after transplanting had fresh and dry root weights of intermediate values between those lighted con- tinuously and unlighted (Table 6). Plants harvested 5 weeks after initiating the SD treatment had fresh and dry root weight differences simi- lar to those of the same treatment at the beginning of short days (Table 7). Lighting continuously during a Jan. propagation and from transplanting to short days increased dry root weight 32% over unlighted plants harvested half- way from starting short days to flowering. Results were consistent during the 4 trial periods (Figure 5). Sig- nificantly greater root length was found for continuously lighted plants than unlighted at the beginning of short days for plants propagated in Nov. and Dec. Root lengths could not be accurately measured 5 weeks after short days began. Top length and weight. Plants lighted 116 W/m2 con- tinuously during Dec. propagation and from transplanting 55 .Rn .pmme owsmm onHpHss m.:hossn an spsos s Canvas msssaoo CH mosam> mo sofipmummom amass oes.o os.HH sm.sH oso.o om.m sm.m mmm Honpsoo omm.o ps.mH sm.mH oms.o ons.m so.m cos HssHaossee Hopes nsmm.o ns.mH ss.mH pes.o as.oH sm.m mam coHpsmsaoLd sma.o so.mH sm.mm smm.o sm.mH sm.m eoHH Hopes ens .sosd .nom oms.o ne.HH ss.sH omo.o os.m no.s mom Hohpsoo omm.o pso.mH so.mH nso.o no.m nsH.m mHs essHaonsse Hopes omm.o oss.mH sm.mH nms.o p~.oH nsm.m mum soHesmssonm som.o ss.mH ss.mm has.o sm.HH sm.m sooH hopes one .dosa .sse oss.o nm.mH sH.mH oes.o os.m as.m NmH Hospsoo nmm.o nes.sH ss.sH osHm.o nm.oH psm.m oos esstossap Hopes omm.o nsH.sH so.om nsmm.o QS.HH nsH.s omm soHHsmseoHd sHo.H sm.eH so.Hm smm.o so.mH sm.m smoH poems ens .aonn .ooa omm.o os.sH ss.om noo.H no.0H s:.m mom Hosesoo onsm.o oom.mH ss.mm psmH.H nss.HH ss.m ass essHsossnp hopes peso.o nsH.oH so.mm nsHm.H pso.mH sm.m mom soHpsmssond ssH.H sm.sH ss.sm smm.H «a.mH sm.OH mHHH HoeHs one .aoHa .>oz Amv Amv “Sow va Amy Asov E\H£13x PsoEpsoHP 59:02 es see p: .sH newcoH as see es .HH semsoH es sH eanH msHesmHH . ,mos poom Hspos a.mUOHHom :Pon msflssu so .psoEHMoHp mm on msflpssagmsssp Bosh Ho .COHpmmmaopm msflhsc msflpnmfla Scum :psosw m>Hpmpowm> ESEmQPCMmzHHO so mpooseo Ams\3 wHHV msapnmwa Shapsosoamnsmun.m manna Table 7.--Supplementary lighting (116 W/mz) effects at bud development from lighting during propagation, or lighting from transplanting to SD treatment, or during both periods on chrysanthemums.Z Total Root Lighting light input length fr. wt dry wt Month treatment KW-hr/m (cm) (g) (g) Dec. prop. and after 1118 16.8a 18.3a 2.33s propagation 509 16.2a 17.1ab 2.17ab after transplant 774 15.9a 16.3ab 2.13ab control 265 15.3a 14.2b 1.83b Jan. prop. and after 1054 16.3a 17.9a 2.29a propagation 536 15.6a 15.7ab 1.92ab after transplant 700 15.2a 15.2ab 1.89ab control 182 14.7a 13.3b 1.74b Feb. prop. and after 1064 15.7a 17.4a 2.17a propagation 552 15.1a 15.6ab 1.83ab after transplant 718 14.9a 14.3ab 1.74b control 208 14.3a 13.6b 1.62b Mar. pr0p. and after 1104 15.9a 16.5a 1.96a propagation 595 15.3a 14.9ab 1.82ab after transplant 760 15.1a 14.7ab 1.73ab control 252 14.7a 13.2b 1.57b ZMean separation of values in columns within a month by Duncan's Multiple Range Test, 5%. Table 7 (cont'd.) 57 T03 no. of no. of Lighting length major minor fr. wt dry wt Month treatment (cm) nodes nodes (g) (g) Dec. prop. and after 36.5a 3.7a 3.4a 33.7a 5.1a propagation 36.2a 3.3ab 3.1a 30.4ab 4.2ab after transplant 36.5a 2.9b 2.9a 32.6ab 4.5ab control 37.4a 2.5b 2.1b 25.4b 3.8b Jan. prop. and after 36.9a 3.2a 3.0a 31.6a 4.9a propagation 36.5a 2.6ab 2.3ab 25.3ab 3.5ab after transplant 36.7a 3.1a 2.9ab 27.9ab 4.2ab control 37.4a 2.2b 1.8b 22.4b 3.2b Feb. prop. and after 35.4a 3.5a 2.9a 30.7a 4.6a propagation 37.2a 2.7ab 2.0ab 24.3b 3.3ab after transplant 35.2a 3.2a 2.5a 28.2ab 4.0ab control 36.4a 2.1b 1.7b 21.7b 2.9b Mar. pr0p. and after 36.2a 3.1a 3.2a 30.2a 4.7a propagation 36.0a 2.2b 2.2ab 24.7b 3.5b after transplant 35.9a 3.0a 2.7a 28.5ab 4.2a control 35.4a 1.9b 1.9b 20.3b 3.0b 58 .pmoe omsem oaaflpasz m.:dossa an :psoe m sages: msSSHoo ca .sm mosHm> Mo sowpesemom noose em.mH em.m om.m os.mo ee.mo mmm Honenoo es.mH em.s nem.m ns.ss em.so oos eneHnonenp noose es.mH en.s onm.m om.ms em.mo mam noHeeeesonn em.sH eo.oH em.m em.so eH.mo soHH noeHe one .nonn mes em.oH eo.m om.m om.oo em.so mom Honenoo eo.mH es.o nem.m ne.ms es.oo mHs pneHdenenp noene em.HH ea.e oom.m om.ao em.mo mom noHeemesonn em.mH em.m eo.m eH.om em.so sooH noose one .sonn .nne em.HH em.s om.m no.mo eo.mo mmH Honenoo es.mH ee.s nem.m nee.so em.oo oos eneHdenenp noose eH.mH em.s onm.m nem.mo ee.mo omm noHHeeedond eo.eH es.oH eH.m em.os em.os smoH noose one .nonn .nes eo.HH es.s om.m om.mo em.mo mom Honpnoo ee.mH es.o nem.m nem.mo eo.oo ass oneHdenenp noeHe eo.mH em.s ons.m nes.so es.mo mom noHHewenonn eo.mH em.o em.m eH.:s em.oo mHHH sense one .dons .non Amv AEov Hones: Amy 93 AEoV E\H£|3x psoEPMoHp asses es .nm noeeeeHo sop .nn oneHen nH oneHH enHeanH enosoHn eneHs Hepoe wsflpanH Ho messag wsHHemsoo wsflpozoam Pm mpooMMo ANE\3 wHHV a.msssonpsemzsno so moOHHoQ neon wsHHso .pCoEHeoHp om op msflpseamwsesp scum Ho .QOHpmmemoHQ msflsso mace oopnmfla mswpnmwa humpsosoammsmun.w manna 59 1.3 '- 102 _ 1'1 - Lighting Treatment During propagation & after transplanting During propagation 0,7 F' After transplanting Control DRY ROOT WT (g) 0 .0 t" 2.. o o l I l 0.6 1 1 Dec. Jan. Feb. Mar. MONTH Figure 5.-—Supplementary lighting (116 W/m2) effects on dry root wt at SD treatment from lighting during propaga- tion, or lighting from transplanting to SD treatment, or during both periods. 5.2 p Lighting Treatment 4 8 _ During propagation & 15 ' after transplanting ;: 4.4 h 3 During propagation g 4.0 — e E 3'6 ' After transplanting 3.2 - Control 2.8 l l l I Dec. Jan. Feb. Mar. MONTH Figure 6.--Supplementary lighting (116 W/mz) effects on dry top wt at bud development from lighting during propa- gation, or lighting from transplanting to SD treatment, or during both periods. 60 3 6 Lighting Treatment . During propagation & after transplanting During propagation After transplanting NO. OF FLOWERS/PLANT N u (I) O I I 2.6 .. Control 2014' _ 2.2 - l 1 l 1 Feb. Mar. Apr. May MONTH Figure 7.--No. of flowers per plant comparing those re- ceiving supplementary light (116 W/m2) 24 hrs. daily dur- ing propagation, or from potting to SD treatment, or dur— ing both periods. Lighting Treatment During propagation & after transplanting \, During propagation e. 3 a. 8 After transplanting m 70 h- ~““"///,//////r U) [211 m a. \/ Control 60 I— l 1 1 1 Feb. Mar. Apr. May MONTH Figure 8.--Fresh top wt at flowering com aring plants re- ceiving supplementary light (116 w/hZ) 2E hrs. daily dur- ing propagation, or from potting to SD treatment, or dur- ing both periods. 61 to SD treatment had 44%, 34%, and 30% greater fresh top weight at the beginning of short days, 5 weeks after short days began and at flowering respectively than unlighted controls. Differences in fresh top weight were signifi- cant and consistent for all trial periods from Nov. to May. Plants lighted only during propagation or only after transplanting had intermediate top fresh weights between continuously lighted and unlighted plants (Tables 6, 7, and 8). Top height at flowering for cv. Bright Golden Anne was not significantly different for any of the lighting treatments. Flower number and size. A significant difference in node numbers was found between plants lighted continuously during propagation and from transplanting to short days, and those not lighted. Lighted plants had 48%, 69%, 70% and 52% more nodes with the potential of developing flowering branches than unlighted plants during Dec., Jan., Feb. and Mar. respectively (Table 7). At flowering the number of flowering branches was significantly greater for plants continuously lighted to short days than unlighted plants (Table 8). Plants lighted continuously during propagation in Dec. and up to short days, only during propagation, and only after trans- planting had 3.1, 2.5 and 2.8 flowering branches per plant respectively compared with 2.3 branches for unlighted plants. This was a 36%, 14% and 27% increase over 62 unlighted controls. Differences were consistent through- out the 4 trial periods (Figure 7). Individual flower diameters for plants lighted dur- ing propagation and after transplanting averaged 9.8 cm in Feb. compared with 9.4 cm for unlighted plants. These differences were small and not significant. Discussion Chrysanthemum cuttings receiving 116 W/m2 of supple- mentary light from combined Lucalox and Multivapor lamps root faster and develop into rooted cuttings of higher quality than cuttings receiving only seasonal greenhouse daylight or those receiving supplementary lighting at 174 W/mz. Benefits from supplemental lighting during propagation in northern latitudes are possible since plant growth rates and quality are substantially reduced during winter's low greenhouse light intensities. Post (62) has shown the seasonal variation in natural light intensity correlates with seasonal differences in growth and quality of greenhouse crops. The marked de- cline in fresh root weight for rooted chrysanthemum cut- tings propagated Oct. to Feb. under seasonal daylight con- ditions in this study is in accord with Post's observa- tions. During the same period cuttings receiving 116 W/m2 of supplementary light from Lucalox and Multivapor lamps 63 continued to produce stocky roots of nearly constant fresh weight. High intensity supplementary lighting can com- pensate for seasonal decline in natural light energy values and is of greatest benefit when seasonal daylight values are lowest (Dec.-Feb.). Plants grown in the greenhouse during dark winter days may be injured if transferred to growth chambers. The development of foliar chlorosis and necrosis has been attributed to high intensities in the short-wave region (81). Since chrysanthemum cuttings in this study had not been exposed to comparable energy levels prior to stick- ing in the propagation bench, the leaves may have had no wax and little or no cutin which normally shield the leaf cells from incident radiation. With poorly developed protective layers the leaves were subject to injury by exposure to the higher light intensity (174 W/mz). This speculation was supported by observations of much reduced chlorosis and no necrotic areas on cuttings originating from lighted stock (100 W/mZ) and propagated under 174 W/m2 of supplemental light. Furthermore, slightly injured rooted cuttings when potted and transferred to 116 W/m2 of supplemental light recovered within 10 days and de- veloped normally. Older leaves became greener and new growth was normal and more rapid than unlighted controls. 64 Foliar injury was also reduced when the daily light- ing period was reduced from 24 to 16 hours. This may be related to the balance between chlorophyll production and breakdown. ChlorOphyll is continually being replenished: however its breakdown by intense illumination may be sufficiently fast that renewal fails to keep pace with destruction. A daily dark period may allow a surplus of chlorophyll to be produced which in turn prevents the development of a pale green or yellowish cast in the leaves. Concurrently, a dark period with the accompany- ing reduction in leaf temperature may allow for more effi- cient utilization of photosynthate with less energy being used fc>r respiration. The larger amount of photosyn- thate available within the cutting for root development would be tied directly to improved rooting. This study indicates that if supplementary high in- tensity lighting at 174 W/m2 from Lucalox and Multivapor lamps was used for the propagation of chrysanthemums it must be accompanied by an 8 hour dark period to prevent foliar injury. However, this would be an impractical approach since at lower intensities (116 W/m2 and 58 W/mz) lighting 20 or 24 hours daily produces high quality root- ing without significant foliar injury. From an economic standpoint Lucalox (400 W) sodium vapor lamps spaced 3 m apart with luminaires 1.4 m above the propagation bench and lighted 20 hours daily to supplement natural greenhouse 65 light from Oct. to Mar. is satisfactory for the propaga- tion of chrysanthemum cuttings. This study has shown the cumulative value of high intensity supplementary lighting of pot chrysanthemum cv. Bright Golden Anne during propagation and up to short days. Large and important improvements in pot mum quality have been achieved when winter daylight intensities are continuously supplemented for a total of 5 weeks, 2 weeks during propagation and 3 weeks after transplanting, with high intensity discharge lamps. Benefits from lighting only during propagation or only after tranSplanting are similar, but intermediate between plants lighted 5 weeks and those unlighted. Plants lighted continuously during Dec. propagation and after transplanting received a total light energy in- put of 1118 KW-hrs/m2 during the 5 week period compared with 265 KW—hrs/m2 for unlighted plants, 509 KW-hrs/m2 for plants lighted only during propagation and 774 KW-hrs/m2 for plants lighted only after transplanting. The greater the total light energy input that is made during propaga- tion and up to short days (using combined Lucalox and Multivapor lamps at 116 W/mz) the higher the quality of the pot plant. The benefits of lighting cv. Bright Golden Anne only during propagation or only for 3 weeks after transplanting remain at flowering. The highest quality plant at flowering is obtained by further increasing the 66 total energy input by continuous lighting during propaga- tion and for 3 weeks after transplanting. Differences in plant quality among the various treat— ments were observed from Nov. to Mar. Plants receiving higher total energy levels during propagation and after transplanting had greater fresh and dry top weights and more flowers than those receiving less light energy. Pre- sumably this was a result of increased availability of photosynthate for plant growth. The quality of plant growth during propagation and early stages of development is often related to the sub- sequent quality of a horticultural commodity. For exam- ple, tall spindly petunia plants grown from seed under low greenhouse light conditions and planted outdoors fail to develop into well—branched floriferous plants during the summer months, while stocky well-branched plants quickly form showy mounds of color. In a similar way this study has shown that high quality chrysanthemum plants with a well-developed root system at the time SD treatment begins will proceed to develop into higher quality flowering plants with more flowers and denser foliage than plants with less developed stem and root systems. Plants lighted (116 W/mz) continuously throughout propagation and up to short days had as many as 70% more potential flowering branches than unlighted plants. The subsequent development of flower buds resulted in a larger 67 floral display for lighted plants, increasing their beauty and retail value. Lighted plants should bring at least 50 cents more on the wholesale market for a 6 inch pot chrysanthemum than for unlighted. The cost of lighting for the 5 weeks in question is less than 7 cents per 6 inch pot thus making the lighting operation economically feasible. II SHORT-TERM SUPPLEMENTARY LIGHTING OF POT CHRYSANTHEMUMS AFTER TRANSPLANTING Greenhouse high intensity supplementary lighting using mercury vapor and incandescent lamps has been found to increase plant t0p height and dry weight and reduce the number of days to flowering for peas, beans, tobacco, and snapdragon (22). Supplemental lighting with W.S. Gro-Lux fluorescent lamps at 29 lamp W/ft2 has improved the devel- 0pment of newly planted dormant and cut-back rose plants by increasing the number of flowering stems developing after a hard pinch and increasing the number of bottom breaks (20). High intensity supplemental lighting of greenhouse roses from Sept. to Apr. has increased the cut flower yield by 70% to 80% without a significant decline in quality (17, 58). The objective of this study was to determine high intensity supplemental lighting's effect during the 5 week period following transplanting of rooted cuttings on pot chrysanthemum vegetative growth and flowering. 68 69 Materials and Methods Four hundred and eight chrysanthemum terminal stem cuttings (8 cm) cv. Bright Golden Anne were harvested Nov. 1971 and Jan. 1972 from stock plants grown under normal greenhouse light conditions and propagated in a medium of coarse sand with bottom heat (240C) and misted intermit- tently 10 sec. each 10 min. Incandescent lighting 4 hours nightly during propagation prevented flower bud initia- tion. After 14 days in the propagation bench, 48 cuttings were harvested and root number, length and fresh and dry weight and fresh top weight were determined. The remain- ing rooted cuttings were potted 4 to a 6 inch clay pot in a medium of equal parts of soil, peat moss, and Turface. Thirty pots were assigned to each of 3 lighting treatments: (1) lighted 24 hours daily with combined Lucalox (400 W) sodium vapor lamps and Multivapor (400 W) mercury vapor lamps at 116 W/mz, (2) lighted 24 hours daily with a Lucalox (400 W) lamp at 58 W/m2 and (3) only incandescent photoperiodic lighting 4 hours nightly. Each treatment had 2 replications in separate greenhouses. Lucalox and Multivapor lamps with reflectors were alternated 1.5 m above a bench in each greenhouse to pro- vide 116 W/m2 22 cm over the bench surface and Lucalox lamps were similarly placed above another bench in each house to provide 58 W/mz. Control plants were lighted 70 with incandescent lamps (60 W) 4 hours nightly to keep the plants vegetative. Cultural practices were followed as recommended for chrysanthemums (46) and a 1200-1500 ppm C02 level was maintained in the greenhouse. Twelve plants were harvested weekly from each plot for 5 weeks. Plant records included root length, fresh and dry root weight, top height and fresh top weight. Results Root length and weight. Root growth, length and fresh and dry weight, was greater for plants lighted 2 weeks at 116 We2 or 58 We2 than for plants lighted only photoperiodically during the same period after potting (Table 9). No significant differences were found in root length or weight between plants lighted 116 W/m2 with com- bined Lucalox and Multivapor lamps and plants lighted at 58 W/m2 with Lucalox lamps (Figure 9). Similar results were found after 5 weeks of lighting in Dec. and Jan. when fresh root weights averaged 9.96 g and 9.84 g for 116 W/m2 and 58 W/m2 respectively compared with 7.33 g for un- lighted plants. Top height ang_weight. Top height and weight were significantly greater for plants lighted for 3 weeks after potting than those not lighted (Table 9). There were no significant differences in top height and weight between sms.m xsm.s xsm.s xHo.: xem.s noo.s Hev n; no» es smm.m ems.oH me.oH xHe.m xom.oH xso.oH HEov nemnoH doe sos.o xmm.o me.o sme.o Ros.o xmm.o Hmv es noon sno snm.m me.m xs~.m som.m xmm.m me.m Hwy e; pooh .ns smm.m xmm.e xom.: smo.m nom.s xHo.m Hnov npmnoH noon m noes noo.m Ros.m ems.m ems.m ems.m xom.m Hmv p; non .nm emo.a xsm.a xmm.s xHH.m me.m xsm.m Anov nemnoH nos xHN.o amm.o xsm.o xmm.o on.o som.o Hev e3 noon sen xsm.H nom.H emo.m ess.H eso.m me.m Hey es noon .nn amH.m xmm.m xsm.m ems.m er.m st.m HEov newnoH noom H see; gem.m xsm.m xsm.m xmm.m ems.m xmm.m Hey e: no» .nn xes.e ems.e gee.e Ros.e xoe.e eoe.e Hsov eneneH dos eaH.o me.o st.o Rom.o nom.o Rom.o Hev es pooh sen me.H me.H me.H xsm.H st.H xsm.H Hmv es noon .nm emo.m xmo.m xmo.m xmm.m xmm.m xmm.m Hnov npenoH Hoom soapememosm Hopm< How; 8 Hausa es eeH sHe as mmH aHe seeosexme HH Hesse ooeneHHn: mn\3 mm mE\3 oHH oeeanHns mn\3 om mn\3 oHH soaeosq Home> xoaeosq Hogm> -HeHsz e -HeHsz e xOHmOsA xOHMosq .nmmn.seh .oomn.>oz e.oop£mflass one ANE\3 mmv xoanosq Sago .WNE\3 oHHv mmsea Home>HpH32 one xoaeosq new: mswpsnammsmnp Hesse hafleo mszo: 3N omen ea messam msHHemsoo .oss< smoHoo pnmwnm .>o .mpseam ESEogpsemznno mo COHpesam>o Saxooznn.m wanna 72 .&m .pmoe omsem mamflpasz m.snossm an Hmflnp e swspws mzon CH mmsHe> mo scavenemow Geese mnm.m xmm.m xmm.0H hmH.m x5:.OH x:©.oH Amv p; 909 .H& sms.mH xmm.sH me.om sHm.oH xeo.mm nos.Hm Hsov npmnoH nos Hammo xnm.o xmo.H Hammo xmm.o xmm.o Amv p; poop Spa mem.m xsm.m me.m mmm.m xHo.w xmm.m Amv p; pooh .Hm smH.s Ree.m xso.o smm.s x:m.a xom.s Hsov npmnoH eoom w some SNN.© xmm.m me.m SHH.© xm:.m xmm.m Amv 93 mo» .nm sms.HH xse.mH xso.oH sso.mH st.mH me.oH Anov npmnoH doe sso.o xHe.o eso.o sso.o xoo.o xom.o Hev H3 noon sen sss.s xmm.o xm:.o sHs.e nHm.o Rem.o Hev as soon .nm ssm.s xso.s ems.o sHm.m ems.s Rem.s Anov npmnoH noon s noes smo.m xes.o emo.o sHm.m me.o st.o Hev us How .nn sme.m Ree.mH xeo.mH sHm.oH ass.mH ems.mH Hnov nemnoH doe son.o xso.o ems.o som.o Ros.o xms.o Hmv Hz noon sen SHo.m xmm.: xmm.: mHm.m xsm.: xm:.: Amv p3 pooH .Hm sme.m eoo.m amm.m sHs.s me.o goo.o Hnov npmnoH nose m goo; oeeanHns ms\s mm ms\3 oHH ooeneHHnn mn\3 mm mn\3 oHH soamosq Hogm> xoaeosq some> -HHHss e -HeHsz e seasosg soaeosg .nmmu.seh .ooou.>oz H.o.pnoov m oHnee 73 Lucalox & M'V‘ Lucalox Control FRESH ROOT WT (g) I: I 1, l J l l l O 1 2 3 4 WEEKS AFTER TRANSPLANTING Figure 9.--Weekly evaluation of chrysanthemum fresh root wt comparing plants lighted 24 hrs. daily after trans- planting with Lucalox and Multivapor lamps (116 W/mz), only Lucalox (58 W/mZ) and unlighted. 22r- Lucalox 20 — 8‘ M'V’ Lucalox 18- Control 16- 14.. TOP LENGTH (cm) 12- l 1. l l l l O 1 2 3 4 5 WEEKS AFTER TRANSPLANTING Figure 10.--Weekly evaluation of chrysanthemum top length comparing plants lighted 24 hrs. daily after transplanting with Lucalox and Multivapor lamps (116 W/mz), only Lucalox (58 W/mZ) and unlighted. 74 plants lighted 116 W/m2 with Lucalox and Multivapor lamps and plants lighted 58 W/m2 with only Lucalox lamps (Figure 10). Chrysanthemum plants during 5 weeks of high inten- sity supplemental lighting in Dec. and Jan. increased in height almost 13 cm and were about 7 g heavier compared with an 8 cm increase in height and a 4 g increase in weight for unlighted plants. Discussion In these trials high intensity supplementary lighting at 116 W/m2 and 58 W/m2 significantly increased the rate and quality of plant growth from Nov. to Feb. Later studies have shown that pot chrysanthemum quality is im- proved by high intensity lighting from Sept. to Mar. (Part IV). Similar benefits were found from supplemental lighting at 116 W/m2 from combined Lucalox and Multivapor lamps and 58 W/m2 from a Lucalox lamp alone. Increasing light intensity by adding the Multivapor lamp to the Lucalox does not improve the quality of chrysanthemum cv. Bright Golden Anne. The Multivapor lamp emits a larger portion of blue wavelengths and less red than the Lucalox lamp. During cloudy winter days there are proportionately more blue wavelengths than red in natural greenhouse light since water vapor in the air filters out red wavelengths from 75 sunlight. The red part of the spectrum is more active in promoting photosynthesis than the same energy of blue light. Therefore adding more blue wavelengths to green- house light from Multivapor lamps may not greatly affect the rate of photosynthesis and thus be of little benefit to plant growth. Noesen and Spacil (54) have shown that Lucalox (400 W) lamps can provide considerably more visible light than sunlight inside the greenhouse from Nov. to Mar. Lighting 24 hours daily in Dec. with a Lucalox (400 W) lamp can result in a total energy input of 30 KW-hrs/mz/ day from lamp and daylight compared with 7 KW-hrs/mZ/day from daylight alone. Increasing the light energy 4-fold over natural light conditions results in faster growth of high quality for chrysanthemum cv. Bright Golden Anne. Differences in total light energy levels received since transplanting for lighted and unlighted plants increase over time and so do the benefits from supplemental lighting. The improved growth of lighted plants over unlighted probably results from greater net photosynthate being produced under higher energy levels. Lighting chrysanthemums after transplanting with a Lucalox lamp at 58 W/m2 should have commercial application if improvements in plant quality are maintained until flowering or if the pinch and SD treatment can be moved 76 ahead to produce earlier flowering. The addition of a Multivapor lamp to a Lucalox to double the light intensity appears to be uneconomical since initial lamp cost and operating expenses are doubled without a significant im— provement in growth rate or quality. III INTERACTION OF STOCK PLANT LIGHTING AND SUPPLEMENTARY LIGHTING OF POT CHRYSANTHEMUMS AFTER TRANSPLANTING Supplementary lighting during the winter improves the growth rate and quality of chrysanthemum stock plants (2, 77). Anderson and Carpenter (2) have shown that chrysan- themum cuttings propagated from high intensity lighted stock plants become established more rapidly after trans- planting and develop into a slightly higher quality plant at flowering than unlighted plants. The growth after transplanting for chrysanthemum is improved when natural greenhouse light intensities are supplemented with high intensity discharge lamps at 58 we2 or 116 We2 (SECTION TWO, Part II). This study was initiated to compare the separate and cumulative benefit from high intensity supplemental lighting of pot chrysan- themums after transplanting with cuttings from similarly lighted stock plants. Materials and Methods In Dec. 1971 and Feb. 1972, 164 chrysanthemum ter— minal cuttings (8 cm) of cv. Bright Golden Anne were 77 78 harvested from both lighted (100 W/m2 combined Lucalox and Multivapor lamps) and unlighted stock plants. All cut— tings were propagated under normal greenhouse light in- tensities. Root length, fresh and dry root weight, top length and fresh top weight of 36 cuttings originating from both lighted and unlighted stock were measured after propagation. The remainder of the rooted cuttings were potted 4 to a 6 inch clay pot in a medium of equal parts of soil, peat moss, and Turface. After transplanting pots were divided between supple- mentary light (100 W/mz) and natural light conditions re- sulting in 4 lighting treatments: (1) lighted as stock and after transplanting, (2) lighted as stock but not after transplanting, (3) unlighted as stock but lighted after transplanting, and (4) unlighted as stock and after transplanting. Pots were randomized within 2 identical lighted plots in separate greenhouses which provided 100 W/m2 of light 24 hours daily 22 cm above the bench sur- face. At the initiation of SD treatment (3 weeks after transplanting), 8 pots from each treatment were harvested and root length, root fresh and dry weight, top length, fresh top weight and node number were determined. The remainder of the pots were given SD treatment and normal greenhouse daylight until flowering. At flowering plant height, number of flowering branches, fresh and dry top weight and flower diameter were measured. 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'65-. Pm 15 I]: (1)-P .25: 'U (D (I) 2_ +9 90¢! a) P g2 £:h TIM ‘P .8 1100) I—IP .c: to £14 H-P I10 .,_I 1- +41; 3 "E D LIGHTING TREATMENT Figure 11.--Fresh root wt of chrysanthemum plants, 3 weeks after transplanting, lighted with HID lamps for various combinations of time as stock plants and 3 weeks after transplanting. 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Figure 13.--No. of flowering branches per pot for cv. Goldstar comparing plants lighted 58 W/m2 with Lucalox lamps for O, 7, and 14 days after transplanting. FLOWER .RANCH NO.IPOT 1. 1. 14 1. 1O TORCH DAY I LIGHYED I1 14 \ l l l L l l l A O N O J F M MONTH- Figure 14.--No. of flowering branches per pot for cv. Torch comparing plants lighted 58 W/m2 with Lucalox lamps for 0. 7. 14, and 21 days after transplanting. 97 DEEP CRIOTAL DAYS LIGHTED 1: p 21 D I. ‘3 1a 0 14 Z 1 7 0 z ‘14 4 a O I I u ‘1: O J “- 10 l 1 1 l 1 l I l A. 0. :3 an I: J F an MONTH. Figure 15.--No. of flowering branches per p0 for cv. Deep Cristal comparing plants lighted 58 W/m with Lucalox lamps for 0, 7, 14, and 21 days after trans- planting. 98 BOLDBTAR 40 DAYS LIGHTED A E 44 14 0 V 3 h an 7 u 2 S a an a > I J I 2 a. O 30 1 1 n n l 1 .1 1 1 A 0 o N a J F In MONTHS Figure 16.--Display diameter of cv. Goldstar comparing plants lighted 58 W/m2 with Lucalox lamps for 0, 7, and 14 days after transplanting. 4‘4 (“I (CO -34 DIIPLAY aIAMITIn (cm) TCHNBH DAYI LIGHTED '1 14 7 I l l l l l l I I) II II J F “I IWCflUTWII Figure 17.--Display diameter of cv. Torch comparing plants lighted 58 W/m2 with Lucalox lamps for 0, 7, 14, and 21 days after transplanting. 4. ‘4 4. GO mil-LAY Dunner-n (cm) 3‘ OIIF CHI-TAL DAYI LIGHTED O1 1‘ 7 M O I l l L l l l l A I O N O J ' M MONTH- Figure 18.--Display diameter of cv. Deep Cristal comparing plants lighted 58 w/mZ with Lucalox lamps for 0. 7. 14, and 21 days after transplanting. nun-H Wt] PLANT (a) 4. 4. 4‘ 4. 4° OOLDITAR )h I 101 DAYI HOWMD 14 INCHWTHI Figure 19.--Fr. wt of individual plants at flowering for cv. Goldstar comparing plants lighted 58 W/m2 with Luca- lox lamps for 0, 7, and 14 days after transplanting. 102 TOBOH DAYS A r”",flol1 D 14 ‘Eam ~\\‘(//// r//’ 7 ( ~——+~‘*\\*//” E .\\V//”‘~I o O :85 \/\/ / 3 1 V I4! I E \M as l l l i—l—L___ A El IO N I: J F In MONTHO Figure 20.—-Fr. wt of individual plants at flowering for cv. Torch comparing plants lighted 58 W/m2 with Lucalox lamps for 0. 7. 14, and 21 days after transplanting. 103 INIIF' CHIHIT1KL 75 DAYS LIGHTED .. WVV :2. as :‘\°\/\ : IIB ,. XV Illihrfffll FRI-H WTJPLANT (a) Figure 21.--Fr. wt of individual plants at flowering for cv. Deep Cristal comparing plants lighted 58 W/m2 with Lucalox lamps for 0, 7, 1 and 21 days after transplant- ing. 104 All 3 cultivars lighted 14 or 21 days following pot- ting from Sept. to Feb. developed into flowering plants with greater plant display diameter than those unlighted (Tables 11-13). Cv. Deep Cristal lighted 21 days between potting and SD treatment in Oct., Dec. and Feb. had floral display diameters 26%, 24% and 23% respectively greater than unlighted plants (unlighted plant means were: 34.0, 32.5 and 35.7 cm respectively). Cv. Torch lighted 21 days after potting in Oct., Dec. and Feb. developed into flowering plants with plant dis— 4 play diameters of 43.6, 41.2 and 40.2 cm (a 25%, 37% and 19% increase over unlighted plants). Cv. Goldstar lighted 14 days between potting and SD treatment in Oct., Dec. and Feb. developed into plants with average plant display diameters of 44.0, 36.0 and 38.7 cm (an 18%, 18% and 12% increase over unlighted plants). weight of flowering plant. All 3 cultivars lighted Sept. through Mar. at 58 W/m2 with Lucalox lamps for 14 to 21 days between potting and SD treatment developed into flowering plants of significantly greater fresh and dry weight than unlighted controls (Tables 11-13). Cv. Deep Cristal lighted 21 days between potting and SD treatment in Oct., Dec. and Feb. developed into flower- ing plants with 74%, 84% and 60% respectively greater fresh top weight than unlighted plants (unlighted plant means were: 37.3, 34.7 and 41.4 g respectively). 105 Cv. Torch lighted 21 days after potting in Oct., Dec. and Feb. developed into flowering plants with top weights of 60.7, 59.2 and 69.4 g (a 50%, 53% and 48% increase over unlighted plants). Cv. Goldstar lighted 14 days between potting and SD treatment in Oct., Dec. and Feb. developed into plants with average fresh weights of 50.3, 48.9, and 50.3 g (an 18%, 30% and 25% increase over unlighted plants). Cvs. Deep Cristal and Torch lighted fewer than 21 days and cv. Goldstar lighted fewer than 14 days deve- loped into flowering plants of intermediate fresh and dry weight between those lighted the full period between transplanting and short days and those not lighted (Fig- ures 19-21). Number angsize of flowers. Chrysanthemum cultivars 'Goldstar,‘ 'Torch' and 'Deep Cristal' lighted 58 W/m2 with Lucalox lamps between potting and SD treatment from Sept. through Mar. developed more flowers per 6 inch pot than those not lighted (Tables 11-13). Plants of cv. Goldstar lighted for 14 days in Nov. between potting and SD treatment produced an average of 15.3, 15.0 and 14.0 flowers per pot in Oct., Dec. and Jan. respectively (a 39%, 36% and 20% increase over unlighted plants). In— crease in number of flowers per pot resulted in a larger floral display. Cvs. Torch and Deep Cristal responded to lighting between potting and SD treatment with an increased flower 106 number per pot (Figures 14 and 15). Cv. Torch lighted 21 days after potting in Oct., Dec., and Feb. developed into plants with 15.7, 14.3 and 17.4 flowers per pot respec- tively compared with 12.0, 10.4 and 12.6 respectively on unlighted plants. Cv. Deep Cristal lighted 21 days after potting in Oct., Dec. and Feb. developed into plants with 14.7, 14.0 and 16.0 flowers per pot respectively. This was approximately a 30% increase over unlighted controls. Plants lighted 7 and 14 days between potting and short days produced an intermediate number of flowers per pot between those plants lighted 21 days and unlighted con— trols. The size of the individual flowers was unaffected by the lighting treatment. No significant difference in flower diameter was shown for any of the trials from Aug. through Mar. for cvs. Goldstar, Torch or Deep Cristal (Tables 11-13)- Discussion The quality of pot chrysanthemum flowering from'Oct. to May was increased when natural greenhouse light inten- sities from potting to short days were supplemented with Lucalox lamps at 58 W/mz. Lighting improved pot mum quality by increasing plant display diameter resulting from a 20%-40% increase in number of flowering branches ‘7 . “if“... . 107 developing from the pinch (Figure 22). The development of 4 to 5 additional flowers per plant without a reduction in individual flower size was the principal factor in the im- proved floral display for lighted plants. A stockier plant resulted from lighting due to a pro- portionately greater increase in fresh top weight than in top height. A 40%-50% increase in flowering branch diam- eter gave a sturdier plant with less need for support and better shipping quality. A slight increase in plant height resulted from high intensity supplementary lighting with significance depend- ing on cultivar and season. Lighted 'Torch' and 'Deep Cristal' had a greater increase in top height than lighted 'Goldstar.‘ 'Torch' and 'Deep Cristal' are classified as 'short' by growers because they require a longer vegeta- tive period (long days) before SD treatment is begun than the more vigorous growing 'medium' or 'tall' cultivars. 'Goldstar' is classified as 'medium.‘ It may be that cul- tivars which normally grow slowly during the winter months show greater increases in height due to lighting than cul- tivars which normally grow more rapidly under natural greenhouse light conditions. Slightly taller lighted plants with larger floral displays and dense dark green foliage are more appealing to consumers than the lower winter quality of unlighted plants. Winter 6 inch pot mum wholesale price can range ‘ 1‘. 108 Figure 22.--Cv. Deep Cristal at bud development showing a plant lighted 58 W/m2 for 3 weeks after transplanting (left) and an unlighted control (right). 109 110 from $1.75 to $2.25 depending upon plant quality and retail outlet. The higher quality plant resulting from lighting should bring the higher price and may even exceed it. Be- cause of high lamp efficacies for Lucalox lamps and close spacing of pot mums during the first 3 weeks after potting, 21 days of light can be given pot mums for about 5 cents per pot. Although lighting results in a small increase in production costs (which may average about $1.35 per 6 inch pot during the winter months), the possibility of raising the wholesale price 50 cents should make installation of a Lucalox lighting system attractive to growers. Increased quality of flowering chrysanthemums was re- lated to the total radiant energy input during the vegeta- tive growth period from potting to short days. Daily light input in the 380-700 nm band from the sun and Luca- lox lamp in the greenhouse was calculated (Figure 23). This shows the ability of the Lucalox lamp to provide more total daily radiant energy than sunlight inside the green- house during the late fall, winter. and early spring months. This is due to low seasonal light levels. filter- ing by the greenhouse glass, and differences in daily duration of lighting (8-12 hours of daylight versus 24 hours of supplemental lighting). Yield of greenhouse roses has been increased by in— creasing the total greenhouse light energy level with Lucalox lamps (54). Noesen and Spacil lighted 18 hours 111 3-5'- 3.0 - 2.5 - SUNLIGHT Clear OUTSIDE Cloudy——> KW-hrs / m2 / day LUCALOX SUNLIGHT INSIDE l l l 1 June 21 Sept. 15 Apr. 15 June 21 TIME Figure 23.--Calculated daily natural light inputs outside the greenhouse for clear and typically cloudy days at East Lansing, Michigan, and natural and supplemental daily light inputs inside the greenhouse. Modified from Noesen and Spacil (54). 112 daily with Lucalox lamps, whose radiant energy approxi- mated that of sunlight in the greenhouse, to double the total light energy input. This was correlated with a doubling of the yield of greenhouse roses. The improved quality of pot chrysanthemums may also be correlated with an increased total energy input in the greenhouse from supplemental lighting. This study has shown that factors which reflect plant quality at flowering, including num- ber of flowers per plant, plant display diameter and fresh and dry plant weight, are increased by an increase in total energy input from natural daylight and Lucalox lamps during the period from potting to SD treatment. SUMMARY A study of high intensity supplementary lighting's effect on vegetative growth and flowering of pot chrysan— themum cultivars was made using high intensity discharge (HID) lamps. The separate and cumulative benefits of lighting plants as stock, during propagation, and after transplanting from Aug. to May were studied. Chrysanthemum stock plants lighted continuously from Sept. to May with Multivapor and Lucalox lamps at 100 W/m2 produced larger numbers of cuttings than those receiving only seasonal daylight and photoperiodic lighting. Cut- tings from plants receiving high intensity lighting root- ed in fewer days. had greater fresh and dry root weights, and greater top fresh weight than plants lighted only photoperiodically. 'After transplanting these cuttings became established more rapidly and developed into flower- ing plants of higher quality. High intensity supplementary lighting at 116 W/mz during vegetative propagation of chrysanthemums from Oct. to Mar. reduced the number of days to root and increased root number, length and fresh weight over non-lighted cuttings. Lighting benefits were lost at 174 W/m2 when 113 114 foliar chlorosis developed which delayed rooting and re- duced root growth. Benefits were similar from supplemental lighting at 116 W/m2 with combined Lucalox and Multivapor lamps and 58 W/m2 from Lucalox lamps. Increasing light intensity by adding the Multivapor lamp to the Lucalox does not significantly improve chrysanthemum growth and quality. High intensity supplementary lighting of chrysanthe- mum plants after transplanting: (a) increased the plant display diameter because more branches developed from the pinch, (b) increased branch diameter resulting in a stur- dier plant with less need for support and better shipping quality and (c) slightly increased plant height with sig- nificance depending on the cultivar. Slight additional benefits were observed when plants were also lighted during propagation and as stock plants. Increased quality of flowering pot chrysanthemums was related to the total radiant energy input during the vegetative growth period and during propagation. High intensity supplemental lighting results in a larger floral display for lighted plants, increasing their beauty and retail value. The high efficiency of Lucalox lamps and the close spacing of pot chrysanthemums through the third week after transplanting should make commercial lighting economically feasible. 115 Future work with high intensity supplemental lighting might include an attempt to reduce the number of days to flower without reducing plant quality. This study showed rapid vegetative growth following tranSplanting. It may be possible to move the pinch and SD schedule ahead to produce a good quality plant in less time. Another area not explored in this study is the possi— bility of producing pot chrysanthemums entirely under artificial light. Although exclusive use of artificial light does not utilize natural daylight, the environmental conditions of light, temperature, humidity and C02 could be more easily controlled with a substantial savings from reduced heat loss. APPENDIX A 116 E ".T‘ E ii 400'- 3 l g 300.. (I: E 200— O 04 B E; 100-— P. _.t''''"'_l1'III'AIJJV‘Il-J'J’“r :2 <1: Q: —r 350 450 €50 650 WAVELENGTH (nanometers) Figure A1.--Spectral distribution for typical 400-watt Lucalox lamps. E Q E 400 _ n v a ‘1 i? 300 - £3 3 200 - o F Q4 E‘ 100 - 3 Jv Lh-‘l :3 1 :\"/fi 1 1 350 450 550 650 WAVELENGTH (nanometers) Figure A2.--Spectral distribution for typical 400-watt Multivapor lamps. 117 Figure A3.--HID luminaire showing mounting arrangement, ballast, and faceted reflector. Figure A3 APPENDIX B 119 .. .il... . .4 VL. . ..,....- .r... run, .mmma .pmz op Hmmfi .poo EonM zmwflgofiz .wcflmcmq pmmm pow mosam> QOflpwflump pmfiom came maxomSuu.Hm musmfim mmmfi mmmfi mama mama ammfi H .pmz H .Cmm H hazh H .cmh H .900 1 _ _ _ _ 03 on loomm ms .0 loom mm TH 0G man loo /m 0 0A loos DEFINITION OF TECHNICAL TERMS Botanical Chrysanthemum morifolium Ramat. belongs to the Compositae, a plant family having a flowering head which is made up of many small separate flowers clustered to- gether. In accord with common horticulutral usage and for ease of reading, the flowering head has been referred to as a "flower" in this dissertation. Electrical A lighting installation can be described in terms of lamp watts per square meter (W/mZ). This information serves as a guide in lighting layouts planned without a light measuring device. The number of lamps required for a large area can be calculated, after the number of lamp watts per square meter is determined, using the formula: Growing area (m2) x required lamp W/m2 No. of lamps = Individual lamp watts 120 APPENDIX C 121 The term luminous flux is given to the radiant energy evaluated according to its ability to produce a visual re- sponse. The unit of luminous flux is called the lumen, which is equal to the flux in a unit solid angle from a uniform point source of one candle. One candle is the unit of luminous intensity of a radiator producing one lumen per solid angle. The rate of luminous flux is often expressed in lumen-hours. If the luminous flux of one lumen is uniformly distributed on the area of one square foot, the illumination or unit of illuminance is one foot-candle (ft-c or fc). The metric unit of work done at the rate of one joule per second is the watt. The lamp efficiency for both light sources in this dissertation is expressed in lumens per watt. With this information it is possible to relate the terminology used within this paper and that used by other authors. BIBLIOGRAPHY 10. BIBLIOGRAPHY Anderson, G.A. 1970. The effect of high intensity lighting of roses in the greenhouse. Master's Thesis, Michigan State University. Anderson, G.A. and W.J. Carpenter. 1973. High inten- sity supplementary lighting of chrysanthemum stock plants. Michigan Agricultural Experiment Station Journal Number 6456. Arthur, J.M., J.D. Guthrie, and J.M. Newell. 1930. Some effects of artificial climates on the growth and chemical com osition of plants. American Journal of Botany. 17: 16-482. Arthur, J.M. and E.K. 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