THESIS This is to certify that the thesis entitled Germination and Dormaror huracteristics of Woody Crucifers presented by Peter Anfirow Frank has been accepted towards fulfillment of the requirements for ii..— degree in Jazm— 499% Major professor Date I V 0-169 of Sixteen Species PLACE IN RETURN Box to remove this checkout from your record. To AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. "m ‘_._ 2/05 pVCIRCIDatoDuehdd-pj GERMINATION AND DORMANCY CHARACTERISTICS OF SIXTEEN SPECIES OF WEEDY CRUCIFERS By Peter Andrew'Frank i" AN ABSTRACT Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF-SCIENCE Department of Botany and Plant Pathology Year 1952 Approved ’{7' THESIS 1 Peter Andrew Frank The purpose of this paper is to determine the dormancy and germin- ation characteristics of the seeds of sixteen species of weedy Crucifers and to set up the most satisfactory laboratory procedure for germinating these seeds. The species of seeds selected for this work included: 1. 2. 3. u. 5. b. 7. 8. 9. 10. 11. 12. 13: 15e 16. Arabia glabra (L.) Bernh. Garbarea Berteroa Brassica Brassica Brassica EElE§£l§.R- Br. incana (L.) DC. arvensis (L.) Ktze. campestris L. nigra (L.) Koch. Camelina Qapsella microcarpaglndrz. bursa—pastoris (L.) Medic. Erysimum Lepidium Lgpidium Radicula Raphanus cheiranthoides L. apetalum Willd. campestre (L.) R. Br. palustris (L.) Moench. raphanistrum.L. Sisymbrium altissimum L. Sisxmbrium officinal3.(L.) Scop. Thlaspi arvense L. Where the seeds were available, germination tests were made on ma. ture, immature, and old seeds of each of the species tested. flhe germ. ination tests were made in petri dishes on a blotter paper substrate 'using two replicates of 100 seeds per replicate. Germination was consid- ered to have occurred when the cotyledons and radicle emerged from.the seed coat. The germinating temperatures used in making the tests were: constant temperatures of 20°C., 25°C.; 30°C. and alternating temperatures of 20°C. and 30°C. Germination tests using the above temperatures were made both in light and in darkness. In addition to germinating each of the samples under the above con— ditions, some samples were given special treatments in.en effort to break their dormancy. These treatments were: a prechill treatment for five 2 Peter Andrew Frank days at a temperature of 5°C., the use of 0.2 percent solution of potassium nitrate for moistening the substrate, and treatment of the seed coats of two samples were removed to determine what effect this treatment would have on the percent germination. The mature, immature, and old seed samples were germinated to deter- mine what differences in the germination characteristics, if any, existed in seeds differing in age and stage of maturity. Ehe data obtained show that practically every sample of freshly harvested seed was in a dormant state and that this dormancy was, in most cases, lost to some extent as the seeds aged. In.a few cases, the dormancy was lost entirely. The temperature condition found most favorable for germination in most samples, was the alternating temperatures of 20°C. and 30°C. Many of the samples showed considerable light sensitivity, some samples genu- inating better in light, while others germinated better in darkness. The old seed samples showed considerably less sensitivity to tempera- ture than did the freshly harvested seeds. The light sensitivity appeared to be as prominent in the old seeds as in the freshly harvested seeds. In.most cases, there were not many differences in.the germination char- acteristics of freshly harvested mature and immature seeds of the same age. The potassium nitrate treatment was found, in most cases to promote genmination and in some samples, the dormancy was completely broken. The sulphuric acid treatment was found difficult to use but did break the dormancy in two samples of seed. The prechill treatment did not prove effective in breaking dormancy but did increase the percent germination 3 Peter Andrew Frank in a number of samples, notably those relatively unaffected by the potassium.nitrate treatment. The two samples having the seed coats removed, germinated 100 percent. Some samples did not germinate under any of the conditions used in this work and some other treatment will have to be found to promote germ- ination in these. Tables showing all of the results obtained in these germination tests and the treatments giving the best results are presented. GEBMINATION AND DORMANCY CHARACTERISTICS OF SIXTEEN SPECIES OF WEED? CRUCIFFES By Peter Andrew Frank A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Botany and Plant Patholog School of Science and Arts 1952 ACKN OWLEDG-MEN TS The writer wishes to express his sincere thanks and appreciation to Dr. G. P. Steinbauer for collecting the materials used and for his advice and supervision throughout the course of this work. The writer also expresses his appreciation to Dr. C. L. Gilly for his help and advice in preparing the manuscript. He is also indebted to his friends and others for their interest and helpful suggestions. INTRODUCTION REVIEW OF LITERATURE MATERIALS AND PROCEDURES EXPERIMENTAL RESULTS DISCUSSION SUMMARY AND CONCLUSIONS LITERATURE CITED TABLE OF CONTENTS Page 12 #3 1+6 INTRODUCTION The first requirement in attempting to germinate seeds is a know- ledge of the environmental conditions under which the seeds will success- fully germinate. That these conditions vary greatly can easily be seen by attempting to germinate a number of different seed samples under iden- tical conditions. Seed germination is for most purposes defined as "the resumption of growth of an embryo of a seed with the emergence of plumule and radicle from.the seed coat." For the majority of seed plants all that is required to induce germination is to expose the seed to what are generally termed "suitable" conditions of moisture, temperature, and oxygen. In plants of the temperate zone, the seeds generally have a period of dormancy following maturation. Howard (7) observed.that more than 75 percent of the species, wild and cultivated, growing around Colwmbia, Missouri have a distinct period of dormancy. This dormant period, when the seeds will not germinate even though exposed to conditions usually suitable for germination, may be due to several factors. Some of the principal factors inducing dormancy are: 1. immature embryos, 2. impermeable or hard seed coats which restrict the entrance of oxygen and water to the embryo or are too hard mechanically to allow emergence of the embryo, and 3. morphologically mature embryos requiring physiological changes to occur before being capable of germination. 2 In addition to the primary dormancy of seed there is also a condition known as secondary dormancy. This type of dormancy occurs when germin- able seeds are exposed to certain external conditions which throw them into dormancy. It has been demonstrated by many investigators that by certain treatments, the causes of primary and secondary dormancy may be comp pletely removed allowing the seed to germinate. Included in these treat- ments are: exposure to optimum.light and temperature conditions, scari- fication, and the application of various chemicals. Though the underlying causes of germination and dormancy are not fully understood, much work has been accomplished in recent years. As is usually the case, the seeds of cultivated plants have been the first and most widely investigated while the I'weedy" species have been largely neglected. There is no doubt that, in the future, as the need arises more investigation will be carried on concerning the germination of such seeds. With the increased use of herbicides in weed control, there is a definite need for determining the viability not only of treated weed seed but also of the seeds produced by herbicide treated plants. Seed producers may, in the future, object to the practice of considering all seeds in a seed sample viable without making an accurate determination of the viability. Seed analyses at the present time have very little information on which to base their germinating procedures for weedy seeds. The experi- ments herein reported have been done with the hope that additional information, with particular reference to sixteen species of weedy Cruciferae, may be added to the meager supply now available. REVIEW OF LITERATURE That many seeds require special treatment to promote gemmination was recognized as long ago as 1860 when Caspary (8) called attention to the light sensitivity of some seeds. Since that time, others have shown that there are a number of other factors capable of influencing the germination of seeds. Among these are temperature, after-ripening, scarification, chemicals applied externally, and substances contained in or produced by the seed. Everson (5) found that most weed seeds would germinate over a wide range of temperature when after-ripened but only with special treatment if not after-ripened. This after—ripening was found to be hastened by special temperature treatment. In the particular kinds of seeds tested, light was not found to be definitely inhibitive to germination.. For six species of Crucifer seeds tested, he found that an alternating temp perature of 15°C. or 20°C., maintained for 16 hours and 30°C. for eight hours, was the optimum termperature. All species were germinated in light and in the special case of seeds of Brassica kabgg_L. prechilling for five days at 2°C. to 10°C. was used to break the dormancy. Cross (2) also found that an alternating temperature gave the best results. She used an alternating temperature of 8°C. for six hours, 20°C. for ten hours, and 30°C. for eight hours. Germinations at the above temperatures in light on a soil substrate, gave the best results. Shuck (13) observed that Mustard seeds had a natural tendency to go into a dormant condition. This tendency was most pronounced in 5 in Brassica arvensis (L.) Ktze. Freshly harvested Mustard seeds were very sensitive to high temperatures. Predhilling at 6°C. for three to five days was often required before germination would take place. Seed whidh germinated.at 20°C. in light, often reverted to the dormant con- dition when put in darkness. A 0.2 percent solution of potassium nitrate was very effective in promoting germination at temperatures of 15°C. to 20°C. in light but sometimes had an inhibitory effect at temperatures of 25°C. to 30°C. Not all-of the lots of fresh seed gave good germina- tion results at the same temperature. The length of prechilling time also affected the results when the seeds were later exposed to a higher temperature. When seeds were prechilled for too long a period they did not germinate well, but this could be overcome by the use of an alternat- ing temperature. Mustard seeds generally germinated more readily follow; ing dry storage but occasionally reverted to the dormant state under such conditions. Reversion of seed to the dormant condition was consid- ered to be due to the slowing down of the metabolic processes caused by unfavorable temperature, light, or moisture conditions. In germinating seeds of herb and drug plants (6), light and potassium nitrate solution were needed to break the dormancy of lgpidium sativum L. and Barbarea g§£§§.(Mill.) Asdh. The fommer germinated best at a constant temperature of 15°C., while the latter germinated better at an alternat- ing temperature of 20°C. and 30°C. A considerable number of cultivated species of Brassica were genu- inated by a number of investigators to determine the proper laboratory procedure and in practically every case an alternating temperature of 20°C. and 30°C. gave the best results (12,16). Dormant samples of cultivated Mustard were easily made germinable by treating them with a potassium nitrate solution. Dormancy in Mustard seeds and the majority of other seeds were con- sidered by Thornton (15) to be due to the impermeability of the seed coats to gases. Carbon dioxide and possibly other inhibiting substances were believed to be prevented from escaping and oxygen prevented.from entering. If the seed coats were removed, the toxic substances escaped and the oxygen supply to the embryo was increased and resulted in the germination of the excised embryos. Temperature was considered to be .very important in promoting dormancy. For each rise in temperature, the rate of respiration increased with a greater release of carbon di- oxide and a greater need for oxygen. When the temperature reached a sufficiently high value, the seeds were thrown into dormancy. Kidd. and West (10) found that dormancycould be induced in Brassica g;bg_(L.) Boise. by increasing the carbon dioxide pressure. The percent of carbon dioxide required varied with the temperature and the supply of oxygen. At 3°C., two to four percent carbon dioxide was sufficient to induce dormancy. Dormant embryos which were removed from.the seed costs were found much more sensitive to germinating conditions but still remained dormant for varying lengths of time. Kidd and West (11) also found only two methods were successful in germinating seeds of Brassica glbg.that had been forced into dormancy by carbon dioxide. One method was by redrying the seed and.the second method was by removing the seed coats. Green ripe, yellow ripe, and dry ripe seeds were all found to germinate readily when the seed coats 7 were removed. The green ripe seeds were found to be the most difficult to germinate with the seed costs intact since they had the most imperme- able seed coats. An inhibitor was found by Cox, Munger, and Smith (1) to be present in the seed coats of certain varieties of Brassica oleracea L. Freshly harvested seed was after-ripened for five days at h°C. Following this, the seed coats of one lot were removed, one lot was left with the seed coats intact, and one lot had the seed coat slit to expose the radicle and cotyledons. All lots were germinated at 30°C. in darkness. There was no difference in the germination results of the control lot and.the lot with the seed coats slit. The excised embryos germinated immediately .with a much higher percent germination than the other two lots. The average rate of growth was greatest for the lot having the seed coats removed. Treating the seed coats with cold concentrated sulphuric acid was found to be effective in promoting germination of these dormant seeds. It was believed that the acid broke up many of the cells containing the inhibiting substance which was subsequently leached.away. A water sol- uble alcohol extract was made from the ground seed coats. The extract inhibited germination, as compared to the controls, for five days. At the end of 12 days, however, germination of the extract treated seed exceeded the germination of the controls. An extract was made from.the seeds of ggphanus sativus L. by Ivan. ovics and Horvath (9). This extract, called Raphanin, was found to be highly active in preventing the germination of many seeds, including Brassica oleracea and Sinapis alba L. at a dilution of l a 1000. The germination of radish seeds was unaffected by this extract. 8 Evenari, Konis, and Ullmann (h) have shown that the essential oils extracted from the halves of Mustard fruits inhibited germination of Mustard seeds and the seeds of other plants. This inhibitor was found to be effective whether in contact with the seeds or not. Much the same was found to be true of other chemicals extracted from other plants. volatile products produced by germinating radish seeds were found to be sufficiently toxic to kill potato plants when both were enclosed in the same chamber (3). Evenari, Konis, and Ullmann (1+) suggest that the function of these inhibiting substances is to prevent the premature germination of seeds enclosed in their fruit and to prevent the germin- ation of seeds of other plants nearby. MATERIALS AND PROCEDURES The various species of seed tested in this work.were collected during the summer of 1951. All of the species were found in the vicin- ity of East Lansing, Michigan, with the exception of Raphanus raphanis- t_1;_ung_ L. and chassica campestris L. which were supplied by Dr. F. H. Steinmetz, Head of the Department of Botany and Entomology, University of Maine, Orono, Maine. Since samples of both.mature and immature seeds were needed, the harvest period was necessarily extended over a period of several weeks with samples being harvested as they reached the desired stage of maturity. The purpose in collecting samples of both mature and.immature seed was to determine, if possible, whether differences existed between the dormancy and germination characteristics of the two types of seed. Sam- ples of old seed, the majority of which had been harvested the preceding year, were germinated and used as a further comparison. All germination tests were made using petri dishes with blotter paper as a substrate. Moisture was provided by wetting the substrate with distilled water. To provide the desired temperatures, thermostati- cally controlled.germinators were used. Continuous light was provided by installing incandescent lights outside the glass doors of the germin- ators and the amount of light used was six foot-candles. The seed.samh ples which were to be germinated in darkness were placed in light tight coffee containers lined with moist blotter paper. The first germination tests of sash species were made shortly after harvest. In all, four germination tests were made on the majority of 10 species. The second germination tests were made approximately two months after the first and the third germination tests were made approximately two months following the second. The last germination tests were made when most of the samples had.been harvested for a period of thiry weeks. These series of germination tests were made in an attempt to deter— mine: 1. the degree of dormancy of the freshly harvested seed, 2. the length of time required to lose this dormancy, if lost at all, and 3. the germinating conditions most effective in breaking the dor- mancy and promoting germination. The different germination conditions used were: 1. a constant temperature of 20°C. in light and darkness, 2. a constant temperature of 25°C. in light and darkness, 3. a constant temperature of 30°C. in light and darkness, and h. an alternating temperature of 20°C. for 16 hours and 30°C. for 8 hours, in light and in darkness. The first germination tests of the freshly harvested seeds were allowed to germinate for a period of 10 days. Later germinations of the freshly harvested seeds and the old seeds were made for a period of one week; A number of other treatments were used on various species to deter- mine their effectiveness in promoting germination. Among these were: 1. the use of a 0.2 percent solution of potassium nitrate in place of distilled water for moistening the substrate, 2. treating the seed coats with concentrated sulphuric acid, 3. prechilling the seeds for five days at 5°C., and N. removal and cracking of the seed coats. 11 All germination tests, except those requiring either removal or cracking of the seed costs, were made using two replicates of 100 seeds each. Germination in all cases was considered to have occurred when the radicle and cotyledons emerged from the seed coat. EXPERIMENTAL RESULTS Germination of Arabis glabra (L.) Bernh. Mature and immature seeds of Arabis glabra (L.) Bernh. were not available and only one germination test of the mature seed was possible. From the results of this germination test, it was apparent that these seeds were less dormant that were the seeds of the majority of the other species at a comparable age (Table l). The seeds germinated in light gave the best results indicating that they were light sensitive to a TABLE 1 THE RESULTS OF GERMINATING MATURE SEED OF ARABIS GLABRA Percent Germinating Germination Conditions Age of mature seedrin weeks‘ at 20°C. Light 97 _ 20°C. Dark 87 25°C. Light 98 25°C. Dark 89 30°C. Light 31 30°C. Dark 0 20.30%. Light 99 20.30%. Dark 98 * Age of seed from.date of harvest 13 certain extent. The high temperature was quite inhibitory resulting in 0 percent germination in darkness and 31 percent germination in ' light. Light sensitivity appeared to be lost when.the seeds were germ- inated using an alternating temperature. Best results were obtained by the use of alternating temperatures of 20°C. and 30°C. and light. Germination of Barbarea vulgaris R. Br. The seeds of Barbarga vulgaris R. Br., both mature and immature, were quite dormant shortly after harvest. This dormancy was lost to some extent as the seeds aged but satisfactory germination under most conditions was not obtained even at the last germination (Table 2). TABLE 2 THE RESULTS OF GERMINATING MATURE, IMMATURE, AND OLD SEED OF BARBAREA VULGARIS R. Br. Germinating Percent Germination , Conditions Age of mature Age of immature 01d seed in weeks‘ seed in weeks"I eed 1 10 17 29 . 6 in 22 3h 20°C. Light 2 #1 M5 #7 11 51 32 5° “2 20°C. Dark 0 51 68 #2 o 5 36 17 36 25°C. Light 1 32 51 7o 5 63 68 79 7o 25°C. Dark 0 19 51 51 1 11 39 21 69 30°C; Light 3 58 59 en 19 6o 75 79 72 30°C. Dark 0 22 5h 66 o 5 33 no 78 20-30°C. Light 56 77 9o 93 79 an 32 83 77 ' 20-3000. Dark 1 31 67 75 12 52 73 71 75 * Age of seed from date of harvest 134 Both the mature and immature seeds were light sensitive. The mature seed gave slightly better germination than the immature seed with the highest percent germination in both samples being obtained using the alternating temperatures of 20°C. and 30°C. in light. The old seed ap- peared to have lost all or most of the sensitivity to light and.the best results were obtained by germinating them at a temperature of 30°C. in darkness. Everson (5) also found that germinating Barbarea vulgaris in light at an alternating temperature gave the best results. Germination of Berteroa incana (L.) DC. All samples of freshly harvested seed of Berteroa incana (L.) DC. were quite dormant (Table 3). Much of this dormancy was lost as the seed TABLE 3 THE RESULTS or GERMINATING MATURE, IMMATURE AND OLD SEED 0F BERTERQA'lflCAE§_(L.) DC. Germinating Percent Germination Age of mature Age of immature Old Conditions seed in weeks. seed in weeks. Jflflfil 2 10 18 29 3 11 . 19 30 - 20°C. Light 12 35 39 5a 16 32 33 59 53 20°C. Dark 12 50 76 66 11 38 62 61 58 25°C. Light 11 39 53 80 5 - 27 3M 63 62 25°C. Dark. 17 no en. 78 16 3o 55 67 65 30°C. Light u . 36 87 88 1 13 26 6h 30°C. Dark 5 62 85 76 0 11+ 27 n1 20.3o°c. Light 18 51 66 87 11 23 ui 7n 20.3o°c. Dark 21 M2 80 82 1h 39 M8 70 * Age of seed from date of harvest £9 £9 45' 8? 15 aged. Light sensitivity did not appear to be an important factor in germinating seeds of this species. The mature seed in most cases gave higher results than the immature seed, while the old seed gave the lowa est germination. The conditions resulting in the highest germination of the mature seeds were a constant temperature of 30°C. and light, while the immature seed germdnated slightly better in darkness as the alter- nating temperatures. It is interesting to note that in Berteroa igggng, as in a number of other species, the seeds germinated better in darkness at the lower temperatures and better in light at the higher temperature. Germination of Brassica arvensis (L.) Ktze. Seeds of the species Brassica arvensis(L.) Ktze. show almost coma plete dormancy when germinated shortly after harvest (Table u). Light TABLE u THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OF BRASSICA ARYENSIS (L.) Ktze. Germinating Percent Germination Age of mature Age of immature 01d Conditions seedgin weeks‘ seed in weeks' __3229_ 0 8 15 28 u l2 19 31 20°C. Light 1 2 6 36 13 10 9 31 60 20°C. Dark 1 10 '13 31 7 20 3 20 nu 25°C. Light 1 2 11+ 26 9 13 8 28 37 25°C. Dark 1 2 u 12 2 5 5 10 2h 30°C. Light 1 2 13 23 3 5 2 l? 22 30°C. Dark 1 0 2 10 0 l 0 O 7 20-3ooc. Light 2 2 23 56 18 25 10 36 67 20-30°C. Dark 5 7 3o 52 9 6 u in 52 ‘ Age of seed from date of harvest 16 sensitivity is of considerable importance, being found in the old seeds as well as the more recently harvested seeds. Some of the dormancy was lost as the seeds aged and no great difference in the dormancy of the mature and immature seeds was found. The most favorable conditions for germination in all -the samples were the alternating temperatures of 20°C. and 30°C. and light. The above conditions were found to give the best results in germinating a number of other species of Brassica. Germination of gassica campestris L. The seeds of Brassica campestris L., in contrast to many species of Brassica, show a definite inhibition of germination in light (Figure 1). This is especially true of the mature seeds. The freshly harvested immi- ture seeds germinated better in light but as the seed aged the germina- tion results in darkness were definitely better (Table 5). The degree TABLE 5 THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OF BRASSICA CAMPESTRIS L. Germinating A Percent Germination Age of mature Age of immature Old Conditions seed in weeks‘ seed in weeks. seed 3 7 21 5 23 20°C. Light 11 7 27 92 20 2 20°C. Dark 75 65 88 3M 58 22 25°C. Light 53 21 62 #2 23 in 25°C. Dark 95 81 9t 3h 83 at 30°C. Light 60 65 90 he 22 35 30°C- Dark 97 97 97 34 47 "3 ao-3o°c. Light #5 67 83 6o 6n no 20.3000. Dark. 98 100 100 50 81 57 * Age of seed from date of harvest PERCENT GERMINATION 100 80. LIGHT __" F : EA DARK CE! I Z _ —-I — b- P—' — h—u ,— F— 7—1 -- ‘— L- _. +— _ _. F _ h- —— L— -I — —— h—i —- -—q __ _ _ r: _ _ L— _ .— — )—— |—- L— _. F'_ h— .— — — L— l— h— I—- -ll -— r-— — -- q — —1 — —- — —- —— E ._ _ _ h—i — h— -—d» ——i — — -— I h—- — h—. — — — —. L—u -— h- — — n—L 20°C. 25°C. 30°C. 20°-3o°c. TEMPERATURE Fig. 1. Germination of mature seeds of Brassica camppstris three weeks after Inrvest showing the inhibiting effect of light. 17 18 of dormancy in freshly harvested immature seeds is considerably higher than in the mature seed and is quite dormant, especially at the lower temperatures. Seeds germinated in darkness with the alternating temper- atures of 20°C. and 30°C. gave the best results for all of the samples. Germination of Brassica nigga (L.) Koch. Seeds of mature and immature Brassica gigs; (L.) Koch. are highly dormant when freshly harvested. The immature sample lost but little of its dormancy after aging thirty weeks. No temperature or light treat- ment used was particularly effective in breaking the dormancy of either the mature or inmature seeds (Table 6)., Mature seeds lost some of their dormancy on aging. At the low temperature the results were better when the mature seeds were germinated in darkness but as the temperature TABLE 6 THE RESULTS or GERMINATING MATURE, IMMATURE AND OLD SEED or BRASSICA NIGRA (L.) Koch. Germinating Percent Germination Age of mature Age of inmature Old Conditions seed in weeks. seegLiCn weeks. see; .5 8 15 28 3 10 18 3O 20°C. Light 0 5 19 18 o u 3 It 82 20°C. Dark 0 12 32 2n 0 1 2 u 73 25°C. Light 0 5 17 31 0 ll 0 it 81: 25°C. Dark 0 8 16 10 O O 1 O 71 30°C. Light 0 2 12 37 O O O 1 8M 30°C. Dark 0 5 11 O O O O 58 20-3000. Light 0 18 L17 36 1 11 it ‘7 8n 20-30°C. Dark 0 31 53 36 O 8 3 h 7% "' Age of seed from date of harvest 19 increased the seeds germinated better in light. The old seeds germinated well at all temperatures with the best results being obtained with the use of light. Germination of Camelina microcarpa Andrz. Seeds of Camelina microcarpa Andrz. were both temperature and light sensitive. The seeds of both mature and immature samples were very dor- mant when freshly harvested and remained in this condition, under all the germinating conditions used, for approximately twenty weeks (Table 7). Best germination was obtained in all three samples when germinated at a constant temperature of 20°C. in darkness and.at 20°C. and 30°C. alter- nating temperatures in darkness. The high constant temperature of 30°C. completely inhibited the germination of the mature and immature seeds and reduced considerably the germination of the old seeds. TABLE 7 THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OF CALCELINA MICROGARPA Andrz. Germinating Percent Germination Age of mature Age of immature 01d Conditions 7 seed in weeks* seeggin weeks‘I seed 2 12 18 30 u 13 2o 31 20°C. Light 0 o 5 #2 0 9 5 25 6? 20°C. Dark 0 1 12 82 2 8 32 no 96 25°C. Light 0 o 3 36 1 1 o 2 66 25°C. Dark 0 o 1 52 1 o 1 u 91 30°C. Light 0 1 o o o o o 66 30°C. Dark 0 o o 1 o o o o 614 20.3o°c. Light 0 o 1} no 1 1 8 18 83 20.3000. Dark 0 o no 83 1 1 3a 55 92 ’ Age of seed frmm date of harvest 20 Germination of gapsella bursa-pastcris (L.) Medic. Seeds of Capsella bursa-pastoris (L.) Medic., like the majority of the other species, were very dormant when freshly harvested and but little of the dormancy was lost as the seeds aged (Table 8). Differences in the germination results of the mature and immature seeds were very slight. Germination was slightly better in darkness, especially at the alternating temperatures of 20°C. and 30°C. The old seeds did not germ— inate under any of the conditions used and may possibly have lost their viability due to age. TABLES THE RESULTS OF GERMINATING MATURE, ImLATURE AND OLD SEED OF CAPSELLA BURSA-PASTORIS (L.) Medic. Germinating Percent Germination Age of mature Age of immature 01d Conditions seed in weeks' seed in week“ ~ seed 7 15 22 33 3 11 18 31 20°C. Light 0 o o o 1 5 3 u o 20°C. Dark 2 2 19 2 o u 11 8 o 25°C. Light 0 2 3 It 0 2 1 6 o 25°C. Dark 0 2 15 1 o 1 8 8 o 30°C. Light 0 2 3 6 o 1 3 5 o 30°C. Dark 0 2 12 2 o 1 6 2 0 20-3000. Light 0 2 1+ u o 1 6 22 0 20.3000. Dark 2 22 1+8 9 o 7 112 35 o * Age of seed from date of harvest Germination of grysimum cheiranthoidgg L. ersimum cheiranthoides L. is a very good example of the effect of an alternating temperature in promoting germination (Table 9, Figure 2). 21 The mature and immature seeds showed the usual dormancy of freshly har- vested seeds (Figure 2, 3). The immature seeds showed slightly less dormancy than the mature seeds at all times. Germination was promoted only by the use of the 20°C.and 30°C. alternating temperatures, with the results being slightly improved by germinating the seeds in light. The old seed germinated poorly at the low temperatures and increased germin- ation resulted with an increase in temperature. The best germination of old seed, however, was obtained when the seeds were germinated in darkness using the 20°C. and 30°C. alternating temperatures. The above results agreed well with those obtained by Steinbauer (in) in his work on germinating this species. TABLE 9 THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OF ERYSIMUM CHEIRANTHOIDES L. Germinating Percent germination Age of mature Age of immature Oldfi Conditions seed in weeks* seed in weeks"I seed , 1 9 16 29 1 1o 17 30 f 20°C. Light 2 1 1 2 u 8 10 27 13 20°C. Dark L 1 o o 1 1 13 1 8 10 25°C. Light A 2 1 2 11 17 7 11 53 25°C. Dark 0 - 1 o o 8 1+ 8 52 30°C. Light 8 3 2 ‘ u 3 16 8 1H 78 30°C. Dark 1 1 1 1 3 3 3 83 20-3000. Light u in 22 9o 65 76 90 9a 90 20.3o°c. Dafik 2 2h 20 81 58 87 80 9a 96 * Age of seed from.date of harvest 2 2 .uuebasm neama Meow emo eecuompaeaaemo snag-“mm no emcee ensues no moaanaqaaow .m .mfih __mDEr9 eOOOM!OON oOOOM 00mm E E .E E _nnHuu amen emoah S NUILVNIHEED museums ow OOH .auebaem nevus axes: mm moodonpmmaaono amanehhfi mo eueee ensues Mo moanedfiauec .m .wah nmoaamamzaa .ooom-oom .ooom .oomm .ooom U: I: r: l I l I l l 1 [Al I I I ] I 1,] 1 l l l I 1.] I I‘— f ow ,OOH NOIEVNINHIS LNEOHEH 23 Germination of Lgpidium apetalgm_Willd. Both.mature and immature samples of Lepidium apetalum Willd. were very dormant when freshly harvested and remained much the same way after aging for 33 and 30 weeks respectively (Table 10). The poor germination obtained under all of the temperature and light treatment indicates that some other means must be found to promote the germination of seeds of this species. Old seeds of Lepidium apetalum were not available for test- ing with the more recently harvested samples. TABLE 10 THE RESULTS OF GERMINATING MATURE AND IMMATURE SEED 0F LEPIDIUM APETALUM Willd. Germinating Percent Germination Age of mature Age of immature Conditions 7 seed in weeks‘ seed in.weeks* 6 11+ 22 33* u 12 3o 20°C. Light 0 o 1 5 o 1 20°C. Dark 0 2 7 18 o o 6 25%. Light 0 1 ‘ 1 1 1 1 o 25°C. Dark 0 o o 1 o o o 30°C. Light 0 o o o o o o 30°C. Dark 0 o o o o o o 20-3o°c. Light 0 o o o o 1 0 20.30%. Dark 0 o 1 u o 1 2 ' age of seed from date of harvest Germination of Lepidium campestre (L.) R. Br. From the results shown in Table 11, it can be seen that the mature seeds of Lepidium.campestre (L.) R. Br. lost the major part of their in- itial dormancy at the age of eleven weeks. At the age of 28 weeks nearly 2h 100 percent germination was obtained under all of the germdnating condi- tions with the exception of the constant 30°C. temperature. The immature seed lost very little of its dormancy with the result that very poor germination was obtained under all of the germinating con. ditions even at the age of thirty weeks. The old seeds, in contrast to the freshly harvested seeds, were to a considerable extent, light sensitive under all of the germinating con— ditions indicating that light sensitivity was acquired as the seeds be. came more aged. There also appeared to be some change in temperature requirements as the seeds became older. The freshly harvested.mature seeds germinated very poorly at the constant temperature of 30°C. while the old seeds gave the best results when germinated at the 30°C. constant temperature and the 20°C. and 30°C. alternating temperatures. TABLE 11 THE RESULTS OF GERMINATING-MATURE, IMMATURE AND OLD SEED OF LEPIDIUM QAMPESTRE (L.) R. Br. Germinating Percent Germination Age of mature Age of’immature 01d Conditions seed inweeks'I seed in weeks. seed 1 11 17 28 3 13 19 30 2000. Light 0 86 99 96 o 5 7 13 35 20°C. Dark 0 77 98 98 o 2‘ 9 12 27 25°C. Light 0 93 92 98 o 5 8 9 “2 25°C. Dark 0 89 9h 96 o 3 u. 7 22 30°C. Light 0 2 11 o It 5 8 5o 30°C. Dark 0 1 2 60 o 1 o 3 20-3o°c. Light 3 91+ 98 98 2 3 11 19 50 20.30%. Dark 0 87 98 97 o u 8 10 26 * Age of seed from date of harvest 25 Germination of Radicula palustris (L.) Moench. The high degree of dormancy and its persistence when seeds of Radicula Elustris (L.) Moench. were germinated under the conditions used in this work indicates that seeds of this species must be treated in some other manner to Secure successful germination (Table 12). The only germination procedure which resulted in more than one percent was that made on the immature seed which had aged 32 weeks and was gamin- ated using the alternating temperatures in light. TABLE 12 THE RESULTS OF GERMINATING MATURE AND IMMATURE SEED OF RADICULA PALUSTRIS (L.) Moench. Germinating Percent Germination _ Age of mature Age of imature Conditions seed in weeks* seed in weeks" 3 6 18 32 3 18 32 20°C. Light 0 o o 1 o 1 o o 20°C. Dark 0 o o o o o o o 25°C. Light 0 o o o o o o 1 25°C. Dark 0 o o o o o o o 30°C. Light 0 1 o 1 1 o . o o 30°C. Dark 0 o o o o o o 0 20.30%. Light 0 o 1 1 1 1 1 9 20.30%. Dark. 0 o o o o o o 1 "' Age of seed from date of harvest Germination of Raphanus raphanistrum L. Inmature and old seed of Raphanus raphanistrum L. were not avail- able for these germination tests. The nature seed showed the usual dor- mancy of freshly harvested seeds, some of which was lost as the seeds 26 aged (Table 13). The germinations in darkness gave the best results with the highest germination being obtained when the seeds were germ. inated using the alternating temperatures. TABLE 13 THE RESULTS OF GERMINATING MATURE SEED OF RAIHANUS RAPHANISTRUM L. Percent Germinating Germination Age of mature Conditions seed in weeks* 10 11+ 27 20°C. Light 0 1 1+ 20°C. Dark u 6 29 25°C. Light 1+ 15 25°C. Dark 2 10 26 30°C. Light 2 1 8 30°C. Dark 1 o 9 20-30°C.Light 1 5 23 20. 30°C. Dark 7 13 ha * Age of seed from.date of harvest Germination of Sisymbriumhaltissimmm L. Seeds of the species Sisymbrium altissimum L. are a good example of the differences found in the germinating characteristics of seeds of different ages and stages of maturity (Table la). The freshly harvested seeds showed the usual dormancy and the loss of this dormancy as the seeds aged (Figure 14, 5). The mature seed germ- inated better in darkness at the lowest temperature and better in light at the higher and alternating temperatures. The immature seed gave 27 better results when germinated in light at all of the temperatures used and appeared to be less dormant than the mature seeds when germinated two weeks after harvest (Figure 5). The old seed gave almost identical germination results under all the temperature conditions in darkness. The germination tests in light, however, resulted in a considerable increase in germination with an in— crease in temperature. All samples showed considerable light sensitivity. The conditions most favorable for germinating the mature seeds after they had aged for thirty weeks were an alternating temperature of 20°C. and 30°C. and light. The immature seeds germinated equally well at 25°C. in light and at the alternating temperatures in light. TABLE 1h THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OF SISYMBRIUM ALTISSIMUM L. Germinating Percent Germination Age of mature Age of immature Old Conditions seed in weeks* seed in weeks. seed 2 10 17 3o 2 10 17 3o 20°C. Light 7 19 51 56 12 33 20 59 13 2o°c. Dark 5 33 67 65 2 14 21 17 91 25°C. Light 5 35 6k 6h 20 27 43 83 7o 25°C. Dark 2 21 55 an 2 12 2o 23 92 30°C. Light '1 A 26 #1 66 o 29 16 6o _'87 30°C. Dark to 1+ 3 18 o 2 1 12 92 20.3o°c. Light 7 3t 50 72 25 51 66 8M 63— 20.3o°c. Dark 2 15 51 M1 1 1o 13 3t 9t * Age of seed from.date of harvest .3253 means ice: on 9:533: 33.3 mum mo % deem assumes.“ no manganese .m .mrm Eggs .eeen .003 .008 JJLillillL m HIJILI IIB f l l 1 l an §HA 0 ON a w e m m. m 0 8 H om OOH Josefina nevus execs m gang? guapfiaeum no ween ensuesaa Mo noaamnfianeo .: .mfm Engages .onmnoom .ooOm .oomm .ooom [ l H g , L I. L J B Ea H has 1L 3 N01 mem inseam cm 03 ‘ 'Germination of Sisymbrium officinale (L.) Scop. 29 Seeds of the species Sisymbrium officinale (L.) Scop. show the, dormancy of freshly harvested seeds common to most of the other species. ~ This dormancy is gradually lost to the extent that the percent germinap tion of mature seeds increased from N percent when germinated at 30°C. in darkness at the age of one-half week to the high of 62 percent under the same conditions when the seed had aged for 28 weeks (Table 15). Much the eame was true for the immature seeds. Both the mature and immature 0 seeds germinated better in darkness at the 20 C. and 25°C. temperatures and better in light at the 30°C. constant temperature. Best results TABLE 15 THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OE SISYMBRIUM OEEIOINAL§_(L.) Scop. Germinating Percent Germination Age of mature Age of immature J Old Conditions seed in weeks* seed in weeks' seed ‘ ‘ .5 8 16 1%? 2 10 “17 3O 20°C. Light 0 1 7 1 1 3 1 n O 20°C. Dark. 1 1 in 21 3 22 16 29 o 25°C. Light 1 9 19 25 u 19 9 36 O 25°C. Dark 12 13 21 n1 7 2O 11 M1 0 30°C. Light 6 32 M8 61 6 78 37 60 O 30°C. Dark u 21 23 62 1 16 1O 33 O 20.30%. Light 2 u 11+ )+8 1+ 15 1i 38 O 20.3O°c. Dark. 2 7 8 23 5 20 17 #2 o * Age of seed from date of harvest 30 were obtained by germinating both samples at the constant temperature of 30°C. in light. The old seed completely failed to germinate. Germination of Thlaspi_arvense L. Seed of the species Thlaspi arvense L. are, under most germinating conditions, almost completely dormant When freshly harvested (Table 16). All of the samples were light sensitive to some degree. When germ— inated at the low temperature of 20°C. and the alternating temperatures of 20°C. and 30°C., the results were better when the seeds were kept in darkness. Seeds germinated at the constant temperature of 25°C. gave better results when kept in light. The old seed germinated poorly under TABLE 16 THE RESULTS OF GERMINATING MATURE, IMMATURE AND OLD SEED OF THLASPI ARVENSE L. Germinating Percent Germination Age of mature . Age of immature Old Conditions seed in weeks* seed in weeks* sedd 2 13 18 29 u 15 22 33 20°C. Light 1 1 5 2 O 1 2 O 1 20°C. Dark 5 1 25 39 23 1 5 21 28* 25°C. Light 3 7 S—“hs 5O 1 12 19 29 17 25°C. Dark 1 h 17 21 1 1 u 3 {2“ 30°C. Light 0 O O O 2 23 2O 1 30°C. Dark O O O O O O O 2 0 20-3000. Light 7 8 32 M8 2 15 13 #2 12 20.3000. Dark 18 12 8h 92 23 11 59 62 27 I Age of seed from date of harvest PLATE 1 The Results of Germinating Mature Seeds of Thlaspi arvense L. Fig. Fig. Fig. Fige Fig. Fig. 1. 2. 3. h. 6. 32 Weeks after Harvest and Treated with.KNO 3’ H2S0u, and.Having Seed Coats Removed Seeds treated with 0.2 percent solution of potassium nitrate and germinated at a temperature of 25°C. in light. Result --- 98 percent germination. Seed coats treated with concentrated sulphuric acid and germinated at a temperature of 25°C. in light. Result --- 100 percent germination. Control, germinated at a temperature of 25°C. in light. Result -- 29 percent germination. Seed coats gemoved and embryos germinated at a temper- ature of 30 C. in light for two days. Result --- 80 percent germination. Sample above after germinating for four days. Result -- 100 percent germination. Control, germinated at a temperature of 30°C. in light. Result.--- 13 percent germination. PLATE 2 Germination of Mature Seeds of Thlagpi arvense L. 32 Weeks After Harvest Showing the Results of Germinating these Seeds at the Constant Temperatures of 20°C. and the Alternating Temperatures of 20°C. and 30°C. in.Light and in Darkness. Fig. Fig. Fig. Fig. 1. 2. 3e Seeds germinated at 20°C. in light, resulting in 0 per- cent germination. Seeds germinated at 20°C. in darkness, resulting in 89 percent germination. Seeds germi ted at the alternating temperatures of 20°C. and 30 C. in light and resulting in 56 percent germination. Segds germinated at the alternating temperatures of 20 C. and 30°C. in darkness, resulting in 99 percent germination. I, ‘ 3's ax. ....¢ .. .D .a‘.- . I. n a. ... a _. «6. Q . ..D ...M . . _ s . . ..J.........tn1...,o..w...w... «.1 any. u 33 all of the conditions. The treatment resulting in the highest percent germination for all samples was the alternating temperatures of 20°C. and 30°C. in light. Germination Results of Some Species After Special Treatment to Break Dormancy A number of the seed samples were given one or more of the three special treatments to determine the effectiveness of these treatments in breaking dormancy. Table 17 shows the results of these treatments. Seventeen of the seed samples were treated with the 0.2 percent solution of potassium nitrate and germinated at 25°C. The percent germ» ination on eight of these samples was quite high ranging from.8fl per- cent to 100 percent. Three samples germinated between 53 percent and 63 percent while six samples germinated 39 percent or less. Potassimn nitrate was particularly effective in breaking the dormancy of mature seeds of Thlaspi arvense L. which were highly dormant. Four of the seed samples were treated with concentrated sulphuric acid with good results being obtained on two of the samples. The mature sample of Brassica nigra (L.) Koch. germinated 9h percent and the mature sample of Thlaspi arvense L. germinated 91 percent. Samples of mature Raphanus raphanistrum and immature seeds of Sigymbrium.altissimum L. germinated 0 percent and 36 percent respectively. That these last sam- ples germinated poorly, did not mean that the sulphuric acid treatment would not be effective in promoting germination if the optimum immersion time were determined. There was some evidence that the seeds had been injured by the acid which might have accounted for the poor results. 31; Prechilling the seed samples for five days at a temperature of 5°C. was not effective in.complstely breaking the dormancy in any seed sample The percent germination was increased to some extent in a number of samples with the best results being obtained on samples relatively unp affected by the potassium nitrate treatment. 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