ON THE EFFECTS OF CERTMN VOLAHLE CHEWCALS ON THE PRODUCTION OF FORCED RHUBARB WWB ME THE DEGREE 8? E. S. Pritam Singh Didi 1933 . . f ’agt/I ,, 3;: at? ca . fl; Iii-rill '3'!!! fiiniikfi.\d¢t\’nfl 3i. EEH.P!F Studiee on the Effects of Certain Vblatile Chemicals on the Produc- tion of Forced Rhubarb Thesis Submitted to the Faculty of the Mich. State College of Agriculture and.Applied Sci- ence in partial fulfillment of the requirements for the degree of master of Science By P. S’-2121 fif/W‘Q 2472/ #33. KW...- THESL; ‘>"/&r4f’ (I Table of Contents Introduction Literature Review Materials and.Methods Presentation of Data Discussion and Conclusion Summary Acknowledgments Literature Cited Page 15 18 19 20 1. Introduction The wdnter forcing of rhubarb is one of the important forcing industries in Michigan. Since that portion of the crOp that is placed on the market relatively early in the season is more pro- fitable than that which matures later, the growers often attempt to start forcing by the latter part of November. Experience has shown that plants forced this early produce a much smaller crap than is secured when forcing is started twenty to forty days later. Occasionally the roots started as early as November do not yield until the following march. It is obvious that the breaking of the rest period is an important factor in the for- cing of this crop. It was thought that a study of the factors affecting the production of early rhubarb might give results that would have not only practical application, but might throw some light upon the problem of "rest period" in this herbaceous pe- rennial. 2. Literature Review The use of volatile chemicals as an aid in the forcing of shrubs, tuberous and bulbous plants, and herbaceous perennials, has been stu- died by a number of investigators. Among the first workers was Johanp nsen (1), who studied the effects of other on lilacs and other hardy wooded plants. His results showed that plants subjected to ether va- pors in the early part of the "rest period" bloomed from.two to three weeks earlier than untreated plants. Stuart (9) found that anesthe- tics imparted a decided growth impulse when applied to plants in a state of complete rest. Howard (4) studied the rest period of bulbs and herbaceous perennials and found that freezing was the most ef- fective treatment for causing early growth, especially in the case of herbaceous perennials. Doville (12) found that the freezing of dormant hardwooded.plants is a prerequisite to their resumption of normal growth in spring. Bramble (17) found that ethylene chlorhy- drin has proven to be very successful in breaking the rest period of both sugar maple and chestnut seedlings. Denny (16) found that ethy- lene chlorhydrin was remarkably effective for breaking the rest period of potatoes. Lazenly (5), Sayre (10), and Horse (11) reported that freezing of rhubarb roots is essential before they can be forced profitably. Sayre (10) also found that light freezing (20%.) gave the best growth, and severe freezing (—lOOF.) proved detrimental and reduced the yield. Card (13) found that frozen rhubarb roots gave greater yields than un- frozen ones. Unfrozen roots were far behind in activity, which showed clearly the necessity of freezing the roots before attempting to force them. Stuart (2) (3), studying the effect of ether on forcing, found that ether treatment gave a decided impulse to dormant rhu- barb roots by hastening the "vital processes" in the plant, and re- sulted in more vigorous growth and increase in weight of product, but stated that it did not seem to replace freezing, and that free- zing rhubarb roots early in the season was necessary. Hepler (6) found that other accelerated growth very pronouncedly in the first two pickings, but on the third picking its effect disappeared. He stated that ether hastened maturity seven times more than the treat- ment of the check.plots at the first picking. He also found that the higher yield of treated roots was due to ether, in each sepa- rate picking, up to the fifth, and that the final total yield was 49 per cent more than that of the untreated check. Hammersly (7) secured the following increase in yield of rhubarb by etheriza- tion (in per cent increase over untreated): Four year old roots, 67; three year old, 126; two year old, 21; and one year old roots, none. Roots treated with chloroform showed very little increase in growth, and etherized unfrozen roots did not make any growth until late March. Vorhees (8) found that etherization did not increase the total yield but did increase the percentage of marketable petioles, as compared to untreated plants. He also stated that ether-treated roots gave an increase in yield over the untreated check for the first picking. 4. Materials and Methods Two year old roots of the Victoria Variety were secured from a commercial forcer in Maccmb county. The roots were dug in late Novem- ber, 1952, and had been subjected to light freezing. From November 16 to 22 the temperature was low enough to freeze at least the surface buds to a limited extent. During this period the maximum air tem- ° 0 to 15 F. perature was 24° F. and the daily minima ranged from 13 However, the average amount of snow on the ground during this period was four inches, which undoubtedly protected the roots from the ef- fect of low temperature. It has been shown by Bouycuccs (18) that with 13° F. air temperature soil temperature soil temperature of un- covered ground three inches below the surface was 20.2° F. and as high as $0.60!. when the soil was covered with uncompacted snow. This shows that during the above mentioned period the minimum tem- perature two inches below the ground could not have been lower than 26° F. and was probably slightly higher. This temperature was suf- ficient, however, to freeze the tcp buds of the rhubarb roots. The roots were washed thoroughly with tap water in order that all parts could obtain the full effect of the chemicals. Tc deter- mine the influence cf size of root on yield, the weights of indi- vidual roots were taken, and the yield obtained from each root was recorded separately. Sixty four roots fairly uniform in size were selected; half of them were frozen at 2°below zero (F.), and half of them were not given any additional freezing. 0n the fourth of December the se- verely frozen roots were divided into four lots, each consisting of eight uniform clumps. The chemical reagents were ‘used at the following concentrat ions: - (l) 40 per cent commercial sulpheric ether 20 c.c. per cubic foot or 70.6 c.c. per 100 litres of air space, regardless of the space occupied by the clumps. (2) Ethylene chlorohydrine 2.8317 c.c. per cubic foot or or 10 c.c. per 100 litres of air space. (3) Ethylene dichloride 2.8317 c.c. per cubic foot, or 10 c.c. per 100 litres of air space. Two lots, severely frozen and slightly frozen roots, were exp posed twenty four hours to the vapors of the chemicals in an air tight wooden box of 3.83X2.83 1.2.41 feet. (After twenty four hours of exposure the roots were stored and covered in bushel baskets at room temperature. Two similar lots were kept untreated for the check plots. On December 8 the roots were set in beds under a green house bench used for carnations. The bench in the middle of the house was selected to minimize variations in temperature and moisture. Eight each of the frozen and slightly frozen roots which had re- ceived the same treatment were placed.in adjacent beds. Burlap and heavy black.building paper was nailed around the bench to exp elude all light. Good ventilation was provided for by an electric fan at one end of the room and an especially constructed ventila- tor at the other end. The temperature and humidity during the growing period were fairly constant, around 54° 3. and 82 per cent respectively. Just enough water was given at intervals to keep the soil surrounding the roots moist at all times. The first picking was made cn.December 30, twenty two days after the roots had been set in the beds, and subsequent picks ings were made weekly. (Until February 22, 1933.) The yields were recorded in grams according to the followdng grades:- (l) Fancy. Petioles over 3/4 inches in diameter, 15 to 18 inches long and highly colored. (2) Choice. Petioles from 3/4 to 3/8 inches in diameter, 12 to 18 inches long and fairly well colored. (3) Gulls. Petioles less than 3/8 inches in diameter, and less than 12 inches in length. Presentation of Data A. The effect of volatile chemicals on roots slightly frozen (26°- 29° F.) in the field. Only the yields of the first six.pickings are included in the following tables. The last three pickings were discarded, because the roots yielded few fancy stalks and the remainder was practi- cally all culls. Roots were set in the adjacent beds and each lot consisted of eight clumps. The first picking was made on December 30, twenty two days after the roots had been planted in the beds. Table l: The effects of treatments of slightly frozen roots upon the yield of petioles (by grades) for the first six pickings. Date of Harvest Grand Mean & §§§Q§é Dec.30 Jan.5 Jan.11 Jan.18 Jan.25 Feb.1 Total P. E. “ gms. gms. gms. gms. gms. gms. gms. kgms. 944 995 953 929 510 497 4828 613 451 640 1224 1216 627 4771 1557 1441 1593 2153 1726 1124 9599 1.20434 1222 _ 1779 2076 2000 962 294 8333 490 474 1714 1280 1285 1042 6285 712 2253 3780 3280 2247 1336 14618 2.44iz57 ancy 1217 1495 2260 1637 1216 86 7911 310 1032 655 1352 1479 1262 6090 1527 2527 2915 2989 2695 1348 14001 2.332344 1105 967 1219 1006 540 435 5272 641 797 1176 1123 1353 869 5959 1746 1764 (2395 2129 2893 . 1304 11231 1.87:.31 Table 1 and graphic representation in Fig. 1 show that ethyb lene chlorohydrine treated roots gave the highest yield of fancy product and the highest total yield. Roots treated with ethylene dichlorideerank second in production of fancy petioles and total yield per picking. This treatment also gave greater yield of fancy stalks than the ethylene chlorohydrine treated roots for the third and fifth picking. Etherized roots produced higher total yields and more fancy stalks than the check plot, but the L ‘ R (SLY e I Actuc\ Yx e\&s as Vane. Grade. m “Ac-- 1-5' ' (Stems Vex Pukun’z "' 5\\$Kt\~$fi'0 206“ Roots :- e- - U 'fi “\S to “4 a” /Ol. } ~( ’15 $1. ' 3 4“) 11¢. I rah 0.5» difference in yield was not very significant. It should be noted, however, that the production of fancy petioles and the total yield were much less than those obtained from either the ethylene chloro- hydrine or ethylene dichloride plots. Petioles from roots trea- ted with ethylene chlorohvdrine were a deep red color, whereas the petioles obtained from other treatments were pink. It is ap- parent from Table 1 that the highest yield of fancy petioles as well as the total yield for the six pickings was obtained from the plots treated with ethylene chlorohydrine, the next highest obtained from the plots treated with ethylene dichloride treat- ment. Etherized roots produced less than the above mentioned treatments. but slightly more than the check; however, the amount of culls was higher than the other treatments or that of check. Table 2. The percentage increase of fancy petioles for each picking obtained from three different treatments ever check. RE- NE. CHLOROHYDRI RTE. DICHIDRIDB Tito of TEE—Tr? s o ' s '17-) Harvest Picking Date Pigki Date Pickgg Da_te camber 30 *17.1 17.1 429.4 29.4 4 28.9 28.9 January 5 -2.9 6.8 +78.8 54.7 + 52.2 39.9 January 11 427.9 13.8 4117.8 75.5 4 137.1 71.9 January 18 4 8.2 12.5 0115.3 85.2 (4' 76.2 75.0 January 25 '+ 5.9 11.7 +ss.s 35.5 {138.4 80.7 bbruary 1 -14.2 . 9.2 -89.0 72.6 477.9 65.9 Data presented in this table and graphic representation in Fig. 2 show that at the first picking all the treatments gave a considerable percentage increase over the check plots. There was no significant difference in increase between the ethylene chlore- L4 Pew Cent. Induces owe».~ Ckeak he e‘/a ‘\/ \oyé‘lf ~00 \ e; oxy/ . t/ cfig’m‘ukg. ‘\ a. 6'” at Avg CKQCK (\ we 2.. In ex ease as Vac Cewt. 0‘5 Quack b $P\CK\\$S annex Crusoe. - filuskthb Vvobevx Roots / -’ ° / ./ °— — °'.—o\° / ' -“--m“-- I ‘i t if T Pm‘mwss hydrine and ethylene dichloride treatments; however, both gave nearly twice as much increase as that obtained from etherized roots. In the later pickings ethylene chlorohydrine treated roots gave the greatest increase of all the treatments, and the next highest was obtained from ethylene dichloride treat- ment. Etherized roots gave a slight increase over the check plots, but the differences shown in Table 2 were not of any consequence. This same treatment gave no increase for the se- cond picking. It is apparant from Table 2 that the percentage increase in yield of fancy petioles obtained from the ethylene chlorohydrine treatment for the six pickings was very signifi- cantly higher than was obtained by other treatments. The next highest percentage increase was secured from ethylene dichloride treatment. Etherized roots gave a much smaller percentage in- crease than the above treatments, and the increase obtained was not of any consequence. Table 3. Per cent increase of *marketable petioles for each picking obtained from the different treatments ever check. Ether Ethyl. Chlorohyd. Ethyl. Dichloride Date 1 This To This To This To [WWJLWm—em—Ml— cember 30412.1 12.1 1 + 9.9 -9.9 -1.9 -l.9 anuary 5 +21.9 16.9 4-55.8 32.0 -r74.7 35.0 anuary 11 +50.35 28.5 +137.9 68.7 *-82.9 51.6 January 18 -1.1 19.0 4-52.3 63.5 {38.8 47.3 January 25 4- 9.6 17.1 4 30.2 56.7 +56.1 49.3 )February 1 #16.0 17.0 418.8 52.3 +18.9 45.9 F\ not a 5. Int? ease as 9a am; 015 Check 9‘6““? Mavketc‘tfie. Sta\\\s -S\\%\t\t§v~cobem Roots. ‘ \ 47/7 8 Pet Cant increase oven leck r N I w //J J‘ g: a ‘s‘ ,0 ea} \ix°\ "‘§ \s‘ 2° #4.:’ “‘ § .. o / CV\Q¢.\\ \A 412......» 1 ‘I- 5' 10. t The term marketable was applied to all the salable stalks; under this classification, Fancy and Choice grades were combined and the percentage of increase expressed on this basis. Data presented in Table 3 and Fig. 3 show that at the first picking ether and ethylene chlorhydrine treatments gave an ins crease in percentage of marketable stalks, but the difference in increase between the above treatments was very low. Ethy- lene dichloride treated roots gave an increase in.yield ever check plots. In the subsequent pickings the increase in yield obtained from the ethylene chlorohydrine treated roots was re- markably higher than that obtained by other treatments. Ether- ized roots gave less increase as compared to ethylene dichloride treatment, and.no percentage increase for the fourth picking. On the whole, Table 3 shows very clearly that the increase in per- centage for the six pickings obtained from the ethylene chloro- ‘ hydrine treatment was very considerable. Etherized roots gave the lowest percentage increase of all the treatments. Table 4. Total yields for each grade of rhubarb expressed in grams and in percentage of the total yield for the four plots. Per cent ‘4 er cent or cent Fancy Fauna. 9 49121— GHECK 4822 ) a2,g,_l.._§_e.29___49..2____2402_.l_.19..d_..12241_ ETHYLENE CHLOROH. ~3§QQ $5,; no.5 ' 2% 15.1 1m_ mama . pICHLOR. m “a 1255 “.3 2.737 15.3 13153, . _ mm [4" H5362 34.7 6774 43.9 3286 21.3 15432 This table points out that the differences in percentage of the total yield by grades obtained from the different treatments ‘were very small. As compared to the actual yields, ethylene chloro- hydrine treatment gave 82.2 per cent increase of fancy, and 63.8 per cent of marketable stalks over check, and ethylene dichloride gave 66.1 and 62.2 per cent for the same grades. The percentage increase obtained from the etherized plot was very small in comparison to the above treatments, for it was only 11.0 per cent of fancy, and 27.2 per cent of marketable petioles. It is apparent that ethylene chlo- rohydrine treatment has proven 7.5 times, and ethylene dichloride 6 times more effective for the production of the fancy petioles than the other treatment. B. The effects of volatile chemicals on severely frozen (anF) rhu- barb roots. Table 5. ferent treatments on severely frozen and check plots. Yield of petioles by grades expressed in grams from the dif- A; A Date of Harvest \! 1 k‘.\ [ Gr " 68.118 CECK D300 30 Jane 5 Jan.11 Jan.18 Jan.25 Babe 1 Tate-1 Pe Es “-?5' gms. gms. gms. gms. . gms. gms. gms. kgme. cy 1185 1291 1745 1856 I 1218 210 7505 ! holes 638 771 702 1158 I 1663 1280 8192 otal 1823 2082 2447 5014 ) 2881 1470 15897 2.2844582 o . I Fancy 290 905 1924 1508 , 1251 ' 779 8857 1 Choice 58 284 788 822 3 1520 787 4257 Total 548 1189 2710 2550 l 2771 1588 10914 1.8234582 LELDIQEL» ) Fancy 491 1559 1951 977 ) 1297 410 6465 Choice 364 852 1099 590 . 1102 656 4845 Total 855 2171 5050 1587 2599 1088 11108 1.8545188 $1422.. Fancy '1878 1524 1589 808 , 512 0 . 5689 Choice 1445 771 998 1525 1277 606 6420 Totals 5119 2295 2587 1955 1789 606 [L2109 2.0248299 » . LL 2.0- t 8. Ytdd - K\\o agenda P at. .‘\ F\%\KVQ 4. Actual Y\e\ds 8‘3 Va“: Grebe \vx K\\00SCQW\S Yet chkwub- Sevens1t§FV05€vx Roots '5‘ ..~_ (‘0 wait Data presented in Table 5 and Fig. 4 show that the etherized frozen roots gave a larger yield of fancy petioles, as well as total yield in the first two pickings, than was obtained from ei— ther check or the other treatments. It should be noted, however, that after the third picking the effect of ether disappeared. Ethy- lene chlorohydrine and ethylene dichloride treatments had an inhi- biting effect, as the yields obtained from both of the treatments were much less, and even less than the check plot. Table 5 also shows that ethylene chlorohydrine and ethylene dichloride treat- ments lengthen the forcing period, as the yields obtained in the last two pickings were considerably higher than the ether and check plots. It is apparent that other accelerated the growth in the first two pickings, but did not increase the total yield. The highest yield of fancy petioles as well as total yield was ob- tained from the check plot, and none of the treatments increased the total yield from these severely frozen roots. Table 6. Per cent increase of fancy petioles over the check obtained from different chemical treatments, at each picking. (0n the severely frozen roots.) 7 n of This To This 0 mwm DQQe 30 ‘9 41e‘ 4 41e‘ -30806 -308.6 "141e3 . ’141e3 (Jane 5 + 18s]. 729.2 '42s6 -107e2 * 3e? 4 35e3 Jan. 11 -27.4. +8.2 4 10.2 + 55.5 411.8 -11.6 ' Jan. 18 -205.2 -19.5 -16.4 -51.5 -89.9 -27.7 Jme 25 “137e8 -28.2 7’ 2e? -24e2 f 6e5 "ZOeB ! I Feb. 1 -~ -519,2 + 270.9 -12.8 495.2 -16.1 I Table 6 and the graphic representation in Fig. 5 indicate that ether was the only treatment that increased the percentage of fan- cy petioles over that produced by the check plot, and only in the case of the first two pickings. The total yield of the fancy grade, at the end of the picking season, was highest for the check plot. Table 7. The per cent increase or decrease in yield of mar- ketable stalks over that of the check plot for the different treat- ments. Date of . ‘ hlori Harvest 2111, To This To This To Piging page Picking Date Picking: Date 1360.30 4‘ 71.1 {71.1 423.8 423.8 -113.2 4.13.2 Jan. 8 +11.3 9'39e3 -73e4 -152e7 * 5e3 -28e4 $1811.11 .3e3 *22e9 + 10e7 49e1 + 24e6 4e2 Jan.18 '55e9 4' 3e9 + 29e3 42e1 '92e3 '22e2 Jan.25 -51e0 -6e3 '3e9 -30e8 '20e1 -21e7 Febel "14205 -13.1 4‘ 6e5 -25e5 '3709 -2503 L It is evident from the data presented in Table 7 that the pro- duction of marketable petioles was similar to that of the fancy grade e the case with the fancy grade. The only increase in product ion over the check plot was The ethylene chlorohydrine and ethylene dichloride treatments actually reduced the yield of the severely frozen roots. Keck sic Per Cent. Increase ct Decvcesc F\ ewe 5. Incense c'e Decrease a at Cent. 0% exam. 5“ Vsakmev Fame.‘ Create —- a