4' FRUIT GROWTH and EMBRYOLOGICAL DEVELOPMENT of the STUART PECAN Carya l/lin aensis BULLETIN 463/DECEMBER 1974 N 441 7- J4 Ao AGRICULTURAL EXPERIMENT STATION /AUBURN R. Dennis Rouse, Director/ Auburn, Alabama UNIVERSITY COVER ILLUSTRATIONS: Top-longitudinal section of embryo on August 9 showing the vascular system within the cotyledon; centerembryo development at beginning of cotyledon expansion (August 2) surrounded by cellular endosperm; bottom--cross-sectional view of embryo and cotyledon development on August 6. SUMMARY Growth and development studies on 'Stuart' pecan fruit indicated that growth was divisible into three stages: (1) from appearance of pistillate flowers to about the third week in June; (2) from third week in June until first week in August; (3) from first week of August to third week of October. During the first period pollination, fertilization, and development of the free nucleate endosperm occurred. This was accompanied by a slow increase in size of ovule and nut. Beginning of the second period of growth and development was when the nut began increasing rapidly in size parallel with appearance of cellular endosperm in the chalazal end of the ovule (about third week in June). The ovule increased in size until the first week in July, when ovule lobes began to develop basipetally. By the first week in August the nuts had completed size growth and lobes of the ovule had completely filled the shell cavity, ending the second growth stage. Shell hardening was initiated and completed during the 3-week period from the last week in July until the second week in August. Thus, shell lignification signaled the end of the second period and the beginning of the third. The third period of growth and development was the time of nut filling or embryo growth and maturity. The cotyledons began developing basipetally from the embryo between the ovule wall and the cellular endosperm during the first week in August. By mid-August the cotyledons had reached the distal end of the ovule, began thickening, and were growing around the middle septum encircling the cellular endosperm as they grew. By the beginning of the fourth week in August, the cellular endosperm had formed a thick succulent pad of material that encircled the remaining liquid, which previously had filled the ovule. During the last week in August the liquid substance within the ovule cavity rapidly disappeared and the cellular endosperm was dehydrated to a thin transparent layer. This was reflected by a rapid decrease in fresh weight of the ovule. The cotyledons thickened rapidly from the first week in September through the first week in October. At this time the kernel (the embryo plus the integument of the ovule) was filled. The shucks began dehiscing from the nut and fresh weight of the kernel decreased from the third week in October until harvest. CONTENTS Page SUMMARY--------------------------------------------------------------------MATERIALS AND 3 - -- - --- METHODS ----------------------- 6 6 RESULTS----------------------------------------------------- -- -- - - - ---- Shuck Thickness--- -- --Shuck Fresh and Dry Weight Shuck Length and -- -- Width-------------------------Shell Length and W idth ------------------- _ ---- - - ---- -- - --- 10 11 Shell Lignification---------------------------------Shell Color Markings ---------------------Weight - - - - Ovule Length and Width ------------------------------------ - --- - -- - - --- - - -- - - - - 12 12 Ovule Fresh and Dry Endosperm and Cotyledon Development Fresh and Dry Weight of Pecan D ISCU SSION ------ --------------------------- Nuts ---- -- -- -- 14 -- ----- -= -- -16 -- - ---- - - -- - - - - --------- 20 LITERATURE CITED-------------------------- 25 26 APPENDIX------------------------------- FIRST PRINTING 3M, DECEMBER 1974 Auburn University is an equal opportunity employer. Fruit Growth and Embryological Development of the "Stuart" Pecan, Carya Iiinoensis W. A. DOZIER, JR., and H. J. AMLING 1 SORPHOLOGICAL AND EMBRYOLOGICAL development of the pe- can fruit has been the subject of several investigations (2,3,5,6,7, 8,9,10,11). However, there were numerous discrepancies among these reports concerning rate and sequence of the developmental processes. No more recent and comprehensive an investigation on this subject has been made than McKay's in 1947 (5). He resolved many of the discrepancies on the rate and sequence of the developmental processes using the cultivar 'Greenbriar' grown at Beltsville, Maryland. McKay's work is the only detailed investigation in which both morphological and embryological development have been considered concurrently for the entire period of fruit development. Chronologically and in some cases sequentially the developmental processes for Greenbriar as shown 1 Assistant Professor and Professor, Department of Horticulture. 6 ALABAMA AGRICULTURAL EXPERIMENT STATION by McKay were not observed to be the same for the cultivar 'Stuart', the predominant one grown in Alabama. Therefore, information was needed on abnormal pecan fruit growth and development and hormonal control of pistillate flower formation, fruit set, and fruit maturity of the cultivar Stuart. The investigation reported here was done to determine the normal rate and sequence of fruit growth and development of the Stuart pecan under Alabama conditions. MATERIALS AND METHODS Stuart pecan fruit were collected from trees on the Auburn University Horticulture Farm at 4-day intervals from April 30 until October 22, 1963, and from May 22 until June 29, 1964. Collections were at 7-day intervals for the remainder of the 1964 season (until September 28). Each sample consisted of fruit collected at random from clusters located on the lower third of six, 30-year-old trees. A sample of fruit from each collection was prepared by techniques similar to those suggested by Johansen (4). Each sample was placed in Craf's Solution (Randolph's Modified Navashin Fluid) for 24 hours, dehydrated with tertiary butyl alcohol, and embedded in paraffin. Serial sections, 12-microns thick, were mounted with Haupt's adhesive and stained with safranin and fast green. Growth and development data were obtained for each sample consisting of an average of 10 fruits. Data included shuck thickness, fresh and dry weight of nuts, shucks, and ovules, and length and width of shucks, shells, and ovules. Fresh and dry weights of the ovules included the integument, embryo, and endosperm. The integument, which in later stages of development forms the seedcoat, was considered part of the ovule. Shell lignification was recorded from date of initiation until the shell was completely lignified. Observations on growth and development of endosperm and cotyledons were recorded for each sampling date. Development of shell color markings was observed and recorded. RESULTS Growth and development of the various segments of the Stuart pecan fruit was cyclic and divisible into three stages. Time of PECAN FRUIT GROWTH AND DEVELOPMENT 7 occurrence and length of embryological stages varied between years, but sequence of developmental stages was consistent. There was an overlapping of some developmental processes between stages. Data presented in figures are given by years to illustrate variations between years. Shuck Thickness A gradual increase in thickness of shuck occurred in 1963 from appearance of pistillate flowers until June 7, at which time the shuck had reached 14 percent of the final thickness, Figure 1 and Appendix Table 1. There was a rapid increase in shuck thickness from June 7 until August 29, at which time 85 percent of the final shuck thickness was attained. Shuck thickness growth during the 83-day period from June 7 until August 29 amounted to 71 percent of the final thickness. A gradual increase in thickness of the shuck continued until October 4 when the shucks started splitting at the sutures. Shuck thickness mm. 17 31 May 14 28 June 12 26 July 9 23 August 6 20 4 18 September October FIG. 1. Increase in shuck thickness during nut development in 1963. 8 ALABAMA AGRICULTURAL EXPERIMENT STATION Shuck Fresh and Dry Weight Fresh and dry shuck weights obtained for the 1963 season showed a gradual increase in both from blossoming until June 28, Figure 2 and Appendix Table 2. On June 28, the fresh and dry weights were each 11 percent of final weights. A rapid increase in fresh and dry weight occurred after June 28. Fresh weight continued to increase until October 4 when it reached 120 percent of final fresh weight, followed by a 20 percent decrease between October 4 and October 22. At that time the shucks started splitting at the sutures and drying out. Dry weight increased at a rapid rate until July 26, when it was 60 percent of the final dry weight. This was followed by a 49 percent increase in total dry weight during the 28-day period from June 28 until July 26, and then a gradual increase for the duration of the season. rI Shuck weight, grams 14 oo Fes s w ieeo h 13 12 II I09 8 7 6 5 4 3 · Fresh weight 2 o _ .. Dry weight . . . !I i i I I i .I i. l. i. m.._.r 17 31 May 14 28 June 12 26 July 18 9 23 6 20 4 August September October FIG. 2. Increase in fresh and dry weight of pecan shucks in 1963. PECAN FRUIT GROWTH AND DEVELOPMENT 9 Shuck Length and Width Length and width of the shuck were obtained for both the 1963 and 1964 seasons. Shuck development was cyclic and could be divided into three periods. In 1963 the first period comprised the time from blossoming until June 21. The second period was from June 21 until August 2, at which time 54 percent of the shell was lignified. The third period was from August 2 until maturity. Shuck length and width were 46 percent and 29 percent of the final length and width, respectively, on June 21, Figure 3 and Appendix Table 3. The 42-day period from June 21 until August 2 was the period of most rapid growth, accounting for 54 percent and 52 percent of the total increase in length and width, respectively. On August 2, the shuck length was 100 percent and the shuck width was 83 percent of final length and width, respectively. The shuck continued to gradually increase in width until October 15. In 1964, the first period was from blossoming until June 4, Figure 4 and Appendix Table 4. The second period was comprised of the 75 days from June 4 until August 17. Length Shell and shuck size, mm. 55 50 45 40 / ' / ............... Shuck length 35 30 = 25 20 / "" i .. /' ."" --*" " / 3 Shell length Shuck width Shell width 10 17 31 May 0 14 28 June 12 26 9 23 6 20 4 18 August September October July FIG. 3. Growth of pecan shell and enclosing shuck in 1963. 10 ALABAMA AGRICULTURAL EXPERIMENT STATION and width of shuck increased until September 28, when the last sample was obtained. Shell Length and Width Data on length and width of the shell, obtained during the 1963 and 1964 seasons, showed that the growth pattern could be divided into three distinct periods. In 1963 the first period was from appearance of pistillate flowers until June 21, at which time shell length and width were, respectively, 49 percent and 34 percent of final length and width, Figure 3 and Appendix Table 3. The second period was from June 21 until August 2, at which time 54 percent of the shell was lignified, see table. This was also the period of most rapid growth. Lignification of the shell was complete by August 13 and no further growth was made. The third period was from August 2 until harvest. FIG. 4. Growth of pecan shell and enclosing shuck in 1964. PECAN FRUIT GROWTH AND DEVELOPMENT PECAN FRUIT GROWVTH AND DEVELOPMENT 11 1 The three periods of the growth cycle of the shell in 1964 were: (1) from appearance of pistillate until June 4, Figure 4 and Appendix Table 4, (2) from June 4 until August 17, and (3) from August 17 until the last sample date, September 28. There was no further increase in shell length or width after August 17, at which time the shell was completely lignified. flowers Shell Lignification Lignification of the shell occurred in approximately 3 weeks, see table. In 1963, 28 percent of the shell was by July 26 and lignification was completed by August 13. Only 17 percent of the shell was liguified by July 27, 1964, and the process of lignification was completed that year by August 17. lignified LIGNIFIcATIoN OF THE SHELL EXPRESSED AS A PERCENTAGE OF LENGTH OF NUT AND THE INCREASE IN LENGTH AND WIDTH OF NUT AFTER LIGNIFICATION HAD BEGUN, 1963 AND 1964 Date 1963 July Shell length lignified Pct. 0 Leng mm. 32.8 mm. 17.4 19-------------- 26------------------------30---------------------August 2-----------------------6_-- 28.3 32.3 53.4 75.7 100.0 0 16.5 40.1 58.1 100.0 33.6 37.8 42.1 38.3 19.0 20.3 23.1 23.0 ------------------63.7 9----------------13---------1964 July ------ 37.5 40.1 34.1 34.8 38.7 39.3 43.0 22.0 23.2 17.4 18.3 21.3 21.6 26.0 20----------------27-------------------August 3-------------------10----------------17------------- The current studies show that lignification begins at the apex and progresses toward the base of the shell, with the regions immediately surrounding the sutures hardening in advance and the shell being divided by the sutures into two equal segments. This division of the shell is at right angles to the plane of the middle septum. It was found that the area surrounding thc sutures becomes lignified nearly the entire length of the nut before lignification begins on that portion of the shell adjacent to the plane of the middle septum. It also was noted that a thin lignified, and this lignified portion then layer of cells is thickens. The shell continued to increase in length and width until lignification was complete in both years. first 12 ALABAMA AGRICULTURAL EXPERIMENT STATION Shell Color Markings In 1963, the color markings were first detected on September 17 as light streaks near the apical end of the shell. The shuck could be slipped off the shell on September 20, and the color markings were then distinct. The streaks were more distinct by September 24 when small brown spots were located over the base of the shell. On October 1, the shuck had begun turning dark. By October 4, the color markings were very distinct, the shell was brown, and the shuck was dehiscing from the nuts. Data for 1964 show that shell color markings first appeared as streaks on the apical end of the shell on September 22. Development of the markings was the same as in 1963. Ovule Length and Width The growth of the ovule was cyclic and could be divided into three periods, Figure 5 and appendix tables 5 and 6. During the first period, the ovule showed a gradual enlargement in Ovule size, mm. 6055 50 45 40 35 30 25 2010 -' 5 17 31 May Length 1964 .. . 14 28 12 26 9 23 6 20 4 18 June July August September October FIG. 5. Length and width of pecan ovules by dates in 1963 and 1964. PECAN FRUIT GROWTH AND DEVELOPMENT 13 Ienigth and wxidlth -the same ill 1both 1963 and 1964. This period comlprisedl the time( froni blossonti ing lentili ulx 9 in 1963 an d to July 8 in 1964. Ovule lenlgth was 21 percent and 16 percent of the final length in 1963 and 1964, respectix (ix andl ox ule xwidth wxas 16 percent and 18 percent of final xx ilh, respectix cly Tihe second pe'riod xxas characterized by a rapid1 increase inl ox ule length anid xxidlth. It xxas (luring tis period that thte ovutle dev eloped basipetalix and~ filled the shell caxvix . For the 1963 season, the second~ periodl of groxwth cov eredl the time from Julyx 9 until Au gust 2. The ox ule grex 62 percent and .54 percent of final lengt and xxidlth, respectixv(Iy, during this time, reacinmm 8:3 percent and 71 percent of final length and width, respectixvely, by August 2. The secondm~ period of groxxth in 1964 xxas the 41t-(lay period b~etxxeen ijutlx 8 and Au gust 1T xxheni 75 percent and~ 61 percent of the total increase ini length and wIxxidth, respectixvely, occulrredl. By August 17 the ox ille, xas 91 percent of 1)oth the fimmal length and( xwidlth. This period of oxule groxxtlh wxas (luring the time of most rapidl groxxth of the wxhole nut. D)urin g the third period, there wxas a gradual increase in len gth an d xxidthm un til the ox lile had filled the shell cax ity and~ co)mpressedl time packim ig tissue against the shell wvall. This periodl F IG. 6. Pecan nut anid ovule development during growing season. Shown arc samples collected approximately every 2 weeks from May 21 (left) to August 9 (right). 14 ALABAMA AGRICULTURAL EXPERIMENT STATION varied among ovules in the same sample. The ovule reached 100 percent of final length by September 22 in 1963 and by September 14 in 1964 and 100 percent of final width by October 1 in 1963 and by September 22 in 1964. Growth of the ovule at 2-week intervals from May 21 until August 9 during the 1963 season is shown in Figure 6. It can be noted that on July 12 (represented by the fifth nut from the left) the ovule was growing down into the shell cavity. Examination of sections of the ovule at a magnification of 100X showed that the ovule first started growth down into the shell cavity on July 9. Ovule Fresh and Dry Weight Fresh weights of ovules were about the same until July 12 in both 1963 and 1964, when there was a sudden increase, Figure 7 and appendix tables 7 and 8. The increase in weight was due primarily to the ovule enlarging into the shell cavity and its vacuole filling with a liquid. Of the total increase in fresh weight of the ovule 79 percent g grc --I 6 5 4 1964 Fresh weight 1963 Dry weight 17 31 May 14 28 June 12 26 July 9 23 6 20 4 18 August September October FIG. 7. Fresh and dry weight of pecan ovules by dates in 1963 and 1964. PECAN FRUIT GROWTH AND DEVELOPMENT 15 occurred during the 40-day period from July 12 until August 20 in 1963 and 85 percent during the 36-day period from July 13 until August 17 in 1964. At this time the ovule was turgid and it was nearly impossible to remove the shell without rupturing the ovule wall. There was a sudden decrease in fresh weight of the ovules on August 20, 1963, and August 24, 1964, Figure 7. This decrease amounted to 23 percent from August 20 until August 29, 1963, and 24 percent from August 17 until August 31, 1964. Reason for this decrease in fresh weight was primarily the disappearance of the liquid contents from the ovule vacuole. At this time, it can be noted in orchards that branches bearing a set of fruit rise. There was an increase in fresh weight of the ovules starting in 1963 on August 29 and in 1964 on August 31. In 1963 total fresh weight of the ovules increased 65 percent from August 29 until October 8 and in 1964 the increase was 37 percent between August 31 and September 28. This weight increase resulted from the cotyledons moving down into the shell cavity and thickening. In 1963, there was a decrease of 24 percent in fresh weight from October 8 until October 22, a result of the drying and maturing of the kernel. Ovule dry weight was 1 percent and 2 percent of the final dry weight on July 26, 1963, and July 27, 1964, respectively. As the ovule moved down into the shell cavity and the cotyledons began growing and moving down into the ovule, there was a corresponding increase in dry weight. In 1963 during the 26-day period from July 26 until August 20, there was an increase of 10 percent in the total dry weight. The 29-day period from July 27 until August 24, 1964, accounted for a 7 percent increase in total dry weight of the ovules. Ovules began a rapid increase in dry weight on August 20 in 1963 and August 24 in 1964. During the 56-day period from August 17 until October 15 in 1963, there was an increase of 91 percent in dry weight. In 1964 during the 35-day period from August 24 until September 28, there was an increase of 92 percent in dry weight of the ovules. This increase started about the time the cotyledons reached the end of the ovule and began to thicken, continuing as the cotyledons thickened and matured. In 1963 there was a decrease of 16 percent in dry weight during the 7-day period from October 15 until October 22. ALABAMA AGRICULTURAL EXPERIMENT STATION Endosperm and Cotyledon Development In these studies ho differentiation couldl he mule between the nuclei in the embhlryo) sac ini the early samples collected in 1963. Neither was the pollen tiube found growving dIowxn through the stigma or into the embllryo sac; therefore, the tune of pollination andl fertilization wxas not deterined. The first samples prepared for histological studv wxere collectedl on Mlax 7. On this date the integument had been initiatedi andl had groxwn up the sides of the uuucellus, b~ut it was still bifurcated as shown in Fi guure 8. The fire nucleate endo~sperm app~eared to deve(lop around the margins of the central xvacuole until june 21. Cellular endosperm startedi dexveloping in the cbalazal end at this time andl progressed1 doxxward along the sides of the ov ule wxall. By july 5 the cellular endospermn was well dev eloped andi the free nuclei had disappearedl except for a small amount in the micropy le end. On this date the v acuole wxas large wxith all material compressed to the sides of the oxvule wxall. The oxvule wxas filled wxith a liquid and wsturgid. Developmnt of the emnbryo w)xas not dletected until Aungust 2 when extending cotyledlons wee notedl, Figure 9-A. The cotyle(Ions follow ed the contour of the oxvule wxall and grew betwxeen the wvall and the cellular endosperm as they extended into the FIG. 8. Section of pecan nut showing the nucellus with the biturcated integument growing around it. PECAN FRUIT GROWTH AND DEVELOPMENT 17 mu tle cav ity. The co)tledonts NeV(e lhcd(andI pc)elfld icti Iru the plane of the middle to septum Xwith one-half of each cotxlclon (gioXwin~ into each c;IX it of the oXvole. By Auguist 6 the cotx ledonsi had extend~edl to the sidles of the ovuole and~ wXere b~eginingif~ dIown the ovuole to extend( wXall, Figrure 9-13. llo)Is On Augrust 9, the cot Xwere extenii, aloe, thetoXvule wXall lbet\ ee tihe XX all and~ the cellular (11(1sperm as5 shownX in Fi0 h(uire 9-C; the cello1lar endosperm had started thickening in the micropy le end of the oXvtle anol bx August 1:3 it had f ormed at thick gelatinous mass Xwithlin the oXvule. This thick mass of ci idospermo1 FIG. 9. This magnification shows (a) longitudinal section view of embryo on August 1 showing initial stage of cotyledon growth; (b) cross-sectional view of embryo and cotyledon development on August 6; (c) longitudinal ovule section view showing the terminal portion of the cotyledon; and (d) longitudinal section of the ovule an August 9 showing a well developed vascular system within the cotyledon (bottom arrow). emicir-cles a wxatery suilbstance, as shoXXni in Fiarore 10)- \. 13v August 1:3, the cotvle(1015 wXere extendedl 41 perc(lnt of the length of the oXvule. Thmey reached the end of the oX tile hX August anid startedl (~r(w11 )X ii rotiid towxard1 the mliddle septu tom ecircling the enidosperm n~ d thickeinig. The cotyledons at this time XXere 11 cells thick. The cells contained large Xvacumoles wXith small ntuiei. Diiin g the 40-dav period from July 12 unitil Augrust 20, there w~as an increase of 97 pereni t in fresh Nveight of the oX ule. A 511(1dli decrease in fresh XXeiht of the oX tles occurred1 durina the periodl of Auigust 20) to 29, caused by disappearance of the liquIid conten t of the Xvacumole andl the apparent dlehydration of the endosperm. By Aiiuist 27, the 1iluid had dissipatedl and the eindosperm hadl coalesced in the c(enter of the Xvacuole, Figure 10- 13. The end~ospermn XXas dlehy drated to a thin transparent lay er 18 ALABAMA AGRICULTURAL EXPERIMENT STATION - xI ., _ f . a a. FIG. 10. This magnification shows (a) cellular endosperm encompassed by the cotyledon lobes at time of its mast viscous stage on August 20; (b) cellular endosperm on August 27 showing collapsing of cells, dehydration, and folding together of the two sections of endosperm encompassed by the cotyledon lobes; (c) cellular endosperm remnant on August 29 as situated between developing cotyledon lobes; and (d) cellular endosperm remnants on October 4 as situated betweeni well developed cotyledon lobes. of cells by August 29, Figure 10-C. The thin transparent lav er of cells from the cellular endosperm is shown within the folds of the thickened cotvledons on October 4 in Figure 10-D. Growth of the cotv ledons dlown into the ov ule occulired at a later (late in 1964 than in 1963. In 1963, the cotyledons5 had reached the end of the ovule and wxere thickening b~y August 16, but on August 17, 1964, their mov ement down into the ovule could PECAN FRUIT GROWTH AND DEVELOPMENT not b)e dletected wxith the unaidled eve. They had1 extendled an average of 1.5 percent of the length of the oxvule on August 24. The nut on the right in Figure 11 wxas collectedI on August 17, 1964, andl the cotx ledonis cou1ld not he detected( mtoxving dlowxn into the ov ule. Tihe remaining nuts. collectedi August 24, shoxv the cotyledons mox ilig owux at xvarious lengths. By August :31 the cotx ledons had extendoed (Iowxn the full length of the ovu le andl had hcegpl thickening. The cellular endospermxxI id) (hhydrated to a thin lax er idil Septeu iher 8 in 1961I. FIG. 11. Varying stages of visible cotyledon development from samples collected August 24 as compared to August 17 sample (left) showing no cotyledon development. Cotx leon~ (ex elopmnt in 1964 is showyn in Fiure 12. Cot le,oois collectedl August :31 had reached the end of the oxvidle and xxere thickening ando groxxing arounid neXt to the middle, septm. At this time, the endospermi xxas a thick mucous mass xxithin the folds of the cotyledons. Ill the cotx ledons collected( September 8, the cellular cindospermn had heen redclied~ to a thin transparent laxyer of cells and the eotx ledon had thickened considlerablx since August 31. Axerage drx xweigrht of the kernels increasedl 8 percent during the 8 (laxys hetxxee n August 31 and September 8. Cotyledons collected Septembher 28 had thickened considerahly dulrilig the 20-day p)eriod preceding. xxith the axveragc dry- weight of the kernels increasing 30 percent. There xxas 16 percent (decrease in dry xxe ight of the kernel from Octoher 15 until October 22. ALABAMA AGRICULTURAL EXPERIMENT STATION FIG. 12. Cotyledon development on August 31 (left) complete development of cotyledon on September 28. is compared with more The v ascular sy stem was olserx ed to extend from the shucek through the shell and middle septum to the placenta. An elaborate v ascular sy stem was noted from the placenta to all parts of the seedcoat and the embrvo) contained a xascular system, which can be noted in Figure 9-1). Fresh and Dry Weight of Pecan Nuts The increase in average fresh and dry weights of a pecan nut corresponds closely with size development of the nut and fresh and dry wveight growxth of its oxvtle, Figure 13 and appelldlix tables 9 and 10. Fresh xxweight of the pecan samples in 1963 increased at a relatixvely sloxx rate until approximately Jule 21 xhen it reached 6 percent of the final fresh xeight. This xas folloxved by a rapid increase from june 21 until August 20. The nuts did not increase in fresh xeight betwxcl August 20()and Augrust 27, howev er, reflecting the decrease in fresh wx eight of ovIlles at the time the liquid dlisappeared from the x acuiol of the ox ule. Fresh xeight of the nut increased 20 percent from August 27 until October 1, but dropped 17 percent betxween October 1 and October 22. This October decrease in fresh wxeight of the nut is due to drying and maturing of the kernel. In 1964, nut fresh xeight ilcreased graduallx froni the appearance of pistillate flowers until June 25 and then rapidly from June 25 until August 17. A small reduction in fresh xxeight of the nuts PECAN FRUIT GROWTH AND DEVELOPMENT 21 9 i Pecan nut weight, grams 35 1964 30 25 20 15 Fresh weight 1964 10 5 17 31 May FIG. 13. 14 28 12 26 9 23 6 20 4 18 July August September October June Increase in fresh and dry weight of pecan nuts in 1963 and 1964. occurred from August 17 until August 31, reflecting the disappearance of liquid from the vacuole of the ovule. There was a rapid increase in fresh weight from August 31 until September 28, the last harvest date. Dry weight of the pecan nut increased at a low rate until July in 1963 and July 8 in 1964, at which. time it began increasing 9 at a rapid rate. Pecan nuts increased 82 percent of the total dry weight from July 9 to September 6 in 1963 and 93 percent of the total from July 8 to September 28 in 1964, the last sample date. The dry weight increased 21 percent from September 6 22 ALABAMA AGRICULTURAL EXPERIMENT STATION until October 15, and then decreased 3 percent from October 15 until October 22 in 1963. DISCUSSION This study indicated that morphological and embryological development of the pecan fruit was more logically divisible into three stages rather than two as proposed by Crane and Hardy (2) and McKay (5). Crane and Hardy collected their samples when the nuts were mature and postulated that growth and development could be divisible into two periods: (1) the time from blossoming until shell hardening occurred, and (2) from the beginning of shell hardening until separation of the nut from the shuck. They postulated the nut and all its parts grew in size during period one and filling of the nut occurred during period two, but no data were available for this assumption. McKay agreed with the division made by Crane and Hardy, and reported endosperm development occurred during the first period and embryo growth or filling during the second period. The two periods were of approximately the same length. In this study the first period consisted of the time from appearance of pistillate flowers until approximately the third week in June. Pollination, fertilization, and development of the free nucleate endosperm occurred during this period, accompanied by a slow size increase of the ovule and nut. The second period of growth and development covered the next 7 weeks, from about the third week in June until approximately the first week in August. Beginning of the second period was marked by the appearance of cellular endosperm in the chalazal end of the ovule on about June 21. Cellular endosperm completely lined the ovule walls by the end of the first week in July. Beginning the third week in June, the nut began increasing rapidly in size. A similar growth spurt, but of much shorter duration, at the time of cytokineses has been reported for peach (1). Thor and Smith's (9) data on the green weight of pecan fruits reveal a rapid increase in weight during the middle of June similar to that reported in this work. Therefore, the appearance of cellular endosperm was considered as the beginning of the second period. The ovule increased in size until the first week in July, when the ovule lobes began developing basipetally. By the first week in August, the nuts had completed size growth and the lobes of PECAN FRUIT GROWTH AND DEVELOPMENT 23 the ovule had completely filled the shell cavity. During development, the ovule was filled with a liquid that exerted pressure on the ovule walls, making the ovule turgid and easily ruptured when removed. Shell lignification was used to designate the beginning of the third period in this study. This was the same stage of development that McKay (5) used to designate the beginning of the second period. The process of lignification began during the last week in July, whereas McKay reported lignification began during the last week in August. Shell hardening was initiated and completed during the 3-week period beginning the last week in July and ending during the second week in August. The third period of growth and development was considered to be from the first week in August until the third week in October. This was the period of filling of the nut, or embryo growth and maturity. The cotyledons started developing basipetally from the embryo between the ovule wall and the cellular endosperm during the first week in August. The cotyledons had reached the end of the ovule by mid-August, and begun thickening and growing around next to the middle septum encircling the cellular endosperm as they grew. By the beginning of the fourth week in August, the cellular endosperm had formed a thick succulent pad of material that encircled the remaining liquid, which previously had filled the ovule. The liquid substance within the ovule cavity disappeared extremely rapidly during the last week in August and the cellular endosperm was dehydrated to a thin transparent layer. This was reflected by a rapid decrease in ovule fresh weight during this period. The cotyledons thickened rapidly from the first week in September through the first week in October. At this time the kernel (the embryo plus the integument of the ovule) was filled. The shucks began dehiscing from the nut and there was a decrease in fresh weight of the kernel from the third week in October until harvest. These findings indicate that initiation of lignification at the shell apex preceded by a few days the enlargement of the embryo just prior to the appearance of cotyledons. Cellular endosperm was most pronounced in the chalazal end of the ovule at the time 24 ALABAMA AGRICULTURAL EXPERIMENT STATION cotyledon growth began. Progressive development (thickening) of cellular endosperm downward along the ovule wall preceded cotyledon growth. These findings differ somewhat in sequence from those of McKay (5), who reported that maximum shell hardening coincides with maximum endosperm development and the beginning of rapid embryo growth or filling. The results are in accord with McKay's, however, in regard to endosperm actively serving its function during the initial stages of embryo growth rather than during cotyledon thickening as proposed by Finch and Van Horn (3). The endosperm was dehydrated to a thin layer of collapsed cells by the time cotyledon thickening began. McKay reported the seedcoat has a well developed vascular system composed of a network of bundles extending from the placenta to all parts of the seedcoat. Elaborated food material is translocated to the embryo by absorption from the seedcoat. In this study the vascular system was found to exist in the middle septum and seedcoat. The seedcoat was connected to the middle septum at the placenta as proposed by McKay. He reported that the meristem activity (thickening) of the cotyledon was related to the source of nutrient supply. During the early stage of cotyledon thickening the meristem activity was greater on the inner surface adjacent to the seedcoat. In this study, however, thickening of the cotyledons was found to begin in the area around the embryo. Thickening of the cotyledons proceeded from the apical to the basal end, with the folds thickening last. PECAN FRUIT GROWTH AND DEVELOPMENT 25 LITERATURE CITED (1) (2) (3) AMLING, H. J. AND C. C. CARLTON. 1961. Post-Bloom Chemical Thin- ning of Peaches, A Coming Reality. Auburn Univ. (Ala.) Agr. Exp. Sta. Highlights of Agr. Res. 8:1. CRANE, H. L. AND M. B. HARDY. 1934. Interrelations Between Cul- tural Treatments of Pecan Trees, the Size and Degree of Filling of the Nuts and the Composition of Kernels. J. Agr. Res. 49:643-661. FINCH, A. H. AND C. W. VAN HORN. 1936. The Physiology and Control of Pecan Nut Filling and Maturity. Ariz. Agr. Exp. Sta. Tech. Bull. 62. (4) JOHANSEN, D. A. 1940. Plant Microtechnique. McGraw-Hill Book Co., Inc. New York. (5) McKAY, J. W. 1947. Embryology of Pecan. J. Agr. Res. 74:263-283. (6) SHUHART, D. V. 1931. Endosperm and Embryo Development as Related to Filling of Pecans and Walnuts. Proc. Amer. Soc. Hort. Sci. 28:161-163. (7) --------1932. Morphology and Anatomy of the Fruit of Hicoria Pecan. Bot. Gaz. XCIII:1-20. Seasonal Changes in the Composition of the Pecan During Fruit Development. J. Agr. Res. 54:97-121. (8) THon, C. J. B. AND C. L. SMITH. 1935. A Physiological Study of the --.........- (9) - --......... ..... 1939. A Physiological Study of the Pre-Filling Period of Fruit Development in the Pecan. 58:905-910. (10) WOODROFF, J. G. AND N. J. Agr. Res. J. Agr. C. WooDRooF. 1927. The Development of the Pecan Nut (Hicoria pecan) from Flower to Maturity. Res. 34:1,049-1,063. (11) WOODROOF, N. C. 1928. Development of the Embryo Sac and Young Embryo of Hicoria Pecan. Amer. J. Bot. 34:417-421. 26 26 ALABAMA AGRICULTURAL EXPERIMENT STATION APPENDIX APPENDIX TABLE 1. SHUCK THICKNESS DURING NUT DEVELOPMENT BY DATES IN 1963 Date May 17----- ----- --------21 --- --------------- Thickness of shuck mm. 0.33 .39 August Date 6 9-2.25 13 -2.80 1627 ---- Thickness of shuck mm. 2.10 2.65 24 _-----------------28------------------------ .51 .52 June 31---------------------.55 4------------------------.54 11 7------------------------ 2023-3.15 29 Septem ber 3 -6-- - 3.25 3.45 ----------------- .61 .70 .75 .56 - 14-----------------------18----------------------- 3.70 3.30 3.35 21------------------------ July 25------------------28-----------2 -------- ---5 -----------9--------- --- .98 1.00 1.00 1.08 1.14 .96 1013 ----------17---------20---------24 ----- --October 27------ -----1-- - ------ 3.85 3.95 4.21 4.21 4.00 4.20 12-----------16------------------19-----------26-----------30-----------August 2 ------------ 1.10 1.10 1.70 1.90 1.85 1.95 4--------8--------15---------18--------22 --------- 4.25 4.40 4.30 4.23 4.50 4.30 APPENDIX TABLE 2. FRESH AND DRY WEIGHT OF PECAN SHUCKS BY DATES IN 1963 Shuck weight Fresh Dry Grams Grams 0.020 May 17---------- -0.522 -. 520 .027 21 .031 -. 580 -. 640 .060 .700 .097 June 7-------14--.173 .870 .165 18 -. 900 -. 980 .236 .302 28 -- - - - - - - 1.260 .334 July 2--------- -1.380 .502 5--- ------- -1.580 .649 9 --------- 2.200 12 -2.224 .764 -2.420 .802 16 - - - 1.264 4.320 19----1.657 26 .--- - - - -5.160 301.849 5.470 1.921 -5.660 August 2 1.986 9 - - - - - - - -5.615 1.884 6.057 -- ----------------Date Date 13__-__-16-20-2327-29-September 3-_--. August 10 - --13-17-2 0 --------- -- 24 October 1__-.--. .-10.195 .-10.400 .-12.050 9.814 .-10.790 .-11.163 .-13.408 13.340 .-13.572 .-13.930 .-11.820 -__ Shuck weight. Fresh Dry Grams Grams 6.520 1.918 2.057 7.772 2.234 -9.590 2.174 2.254 2.271 2.294 2.314 2.511 2.538 2.341 2.380 2.471 2.623 --- -- .-12.298 .-12.842 22 ----- .-11.651 18------- --13.965 --10.625 12.900 2.877 2.549 2.795 2.613 2.805 2752 PECAN FRUIT GROWTH AND. DEVELOPMENT 27 PECAN FRUIT GROWITH AND D.EVELO PME NT APPENDIX TABLE 2 3. GROWTH OF PECAN SHELL AND ENCLOSING SHUCK BY DATES IN 1963 Shuck at,- Shell Width mm. Length mm. -- Length mm. Width mm. May 17-- 21--24 ---28---------- - 9.8 11.8 12.9 13.0 31---------- June 4---7---------7.9 --- 16.1 17.0 17.6 19.3 21.2 23.3 11----------14--- 18-----21 -- - 2528 --------- July 2---5---------- - 22.7 5.5 26.9 31.9 9---------- 34.3 39.4--- 12---------5.0 16 19---------0.9 August 26------30 2----6----------9---- - -----13 ----------16----------20------- ---23--------- 45.4 47.------1 50.4 50.6 48.4 49.5 48.6 55.4 49.8 -2729--------- -September 3----------6--------- -10 October 13----------17----------20----------24----------27----------1---------- --4-----8 ----------15 ------ ---- 53.9 49.1 52.3 47.9 -------- 52.5 49.5 49.3 49.0 49.9 47.4 49.6 50.1 50.4 -- 18 ----------22 ----------- 51.2 50.3 3.6 3.8 4.4 4.6 5.8 7.0 7.3 7.8 8.6 8.9 9.7 9.9 10.9 12.1 13.2 14.2 15.1 18.2 19.8 23.6 25.2 27.7 27.4 27.5 28.6 28.4 30.4 30.2 30.6 31.3 31.4 31.0 31.8 31.0 31.8 32.0 32.5 32.4 32.7 32.8 33.0 33.3 33.0 33.2 6.2 6.6 7.6 8.6 10.8 11.1 12.2 12.7 16.6 10.6 19.2 16.6 19.2 19.8 23.8 25.4 26.6 27.4 32.8 83.6 37.8 42.1 38.3 37.5 40.1 40.2 40.2 40.1 39.5 39.8 41.0 40.0 39.9 39.8 39.7 39.8 44.0 42.8 39.2 41.0 39.8 40.4 38.8 39.4 2.7 2.9 3.2 3.6 4.2 5.5 6.0 6.3 7.1 7.7 8.2 8.2 10.2 10.4 12.6 14.0 13.6 14.6 16.4 19.5 21.3 23.6 23.0 22.2 23.2 23.1 23.2 23.5 23.5 23.8 23.2 23.5 23.1 23.1 22.8 23.5 24.4 24.4 23.6 23.8 24.1 24.5 23.8 23.8 28 28 ALABAMA AGRICULTURAL EXPERIMENT STATION APPENDIX TABLE 4. GROWTH OF PECAN SHELL AND ENCLOSING SHUCK BY DATES IN 1964 Date IJI Shuck Shell Width mm. Length mm. Length mm. Width mm. May June 22 29 26 2 4 11 --- ------- - ---- - - - - ----- --- - -- 1 5 - - ----- - - 18 22 25 29 July - --- -- -- ----- --- - 20- - - - - - - 27 -August 3 ----------10 - - ----- - 17 -- - - - - - - - 24 - - - --- -- -31 -- - - - - - - - 8 13 8 ---------- September 14 22 - ---_------ - - - - --- - - -- - - --- - - --- -- -- - 10.4 11.4 11.4 12.3 13.6 16.8 18.6 19.2 22.1 23.7 25.7 31.5 35.8 41.3 41.9 47.4 47.6 51.0 50.2 47.3 53.7 57.1 54.8 53.4 3.2 3.4 4.2 4.4 4.6 5.6 6.8 7.7 9.4 10.4 11.5 14.6 16.4 19.2 21.6 24.8 27.0 29.3 28.5 29.1 31.9 34.1 34.2 35.2 6.5 7.2 7.4 8.7 9.3 11.4 12.9 13.7 15.8 17.4 20.0 24.5 26.8 34.1 34.8 38.7 39.3 43.0 42.2 38.0 43.3 46.4 43.8 41.9 2.0 2.5 3.0 3.0 3.4 4.6 5.3 6.3 7.6 8.1 10.0 12.0 14.1 17.4 18.3 21.3 21.6 24.0 24.1 22.1 23.9 24.1 23.8 24.1 PECAN FRUIT GROWTH AND DEVELOPMENT APPENDIX TABLE 5. GROWTH OF PECAN OVULES BY DATES IN 1963 29 Date May 17 -----------21--24----------------------------28 31 4 .------------------------7 -----------11 14-----------------------------18 ------------------2125 ----------------28 Ovule length mm. Ovule width mm. June 1.20 1.23 1.80 1.86 2.20 2.20 2.35 2.40 3.00 3.50 3.40 3.40 4.00 4.60 2--6.05 5 6.70 9 8.85 12 11.40 16--------------------14.90 ------------------1920.90 26----------------------------------24.00 30--------------26.89 -------2--------------..--.....-August 27.50 6 -----------------------27.50 9 28.00 13 28.00 -16 .... 30.00 20 ------ ------- ---30.50 --------------------23 30.40 -------27 30.30 29 31.10 ------------September 3-----31.30 -6-----------30.30 10 8-31.30 13 32.50 17 ------------------32.00 20 --------------------31.60 24 --------------------------32.00 --------------------27 32.10 1 October 32.40 4 33.20 -----------------8-----July 15-------------------32.80 0.60 .60 .61 .60 .61 .62 .65 .69 1.15 1.50 1.64 2.25 2.20 2.10 3.00 3.10 6.00 6.20 7.40 10.80 12.90 14.10 14.90 16.10 15.40 16.90 17.40 17.80 16.80 17.90 18.80 19.10 17.90 18.80 18.90 19.30 19.10 19.60 20.00 19.50 19.80 20.70 . .. 18-. -------22 -------------------------- 83.00 -31.20 19.20 19.70 30 ALABAMA AGRICULTURAL EXPERIMENT APPENDIX TABLE 6. STATION WIDTH GROWTH OF PECAN OVULES IN LENGTH AND BY DATES IN 1964 Date May 2226---------------- - -------29-2 4 -----------------------------------11------------------------15-- - - -- - - -- - - 18 22 -....... 25 29 June 8 13 20 27 August 3 10 17 24 ...........----31 -30.40 September 8-----------------14 22-------- --------28 ------------------,, July Ovule length mm. 1.15 1.18 1.10 1.43 1 .60 1.88 2.13 2.18 3.00 3.50 4.15 5.60 7.70 12.40 15.70 23.70 27.70 31.80 32.20 33.90 36.50 35.40 34.30 , Ovule width mm. 0.80 .70 .70 .90 .85 .92 1.07 1.27 2.00 2.10 2.65 3.60 5.00 7.10 12.30 12.70 15.10 18.10 18.60 17.60 19.10 19.40 21.20 20.70 PECAN FRUIT GROWTH AND DEVELOPMENT 31 PECAN FRUIT GROWTH AND DEVELOPMENT Date May 17------------- -21 - - - - - - - - - - - - - - 24- - - - - - - - - - - - - - 28 - - - - - - - - - - - - - - 3 1 -- - - - - - - - - - - - - - 4 11 14 18 --- 31 APPENDIX TABLE 7. FRESH AND DRY WEIGHT OF PECAN OVULES BY DATES IN 1963 Ovule fresh weight Grams June - 0.00070 .00175 .00240 .00330 .00760 .01180 .03130 .03760 .08110 .16360 .25900 .91580 1.23420 2.3651 2.5053 2.5888 2.7478 3.0633 2.5232 2.1050 2.1981 2.7054 3.1046 3.2208 3.4645 3.9010 4.0543 3.7807 4.0115 4.3056 4.0936 4.6406 4.4145 4.5191 3.7551 21 -- - - - - - - - - - - 25 -- - - - - - - - - - - 28 --- - - - - - - - - - July 5--------------12-- -- ------16---------1 9 -- - - - - - - - - - - 26 ----- --- - - - - -August Ovule dry weight Grams 0.00006 .00010 .00017 .00020 .00025 .00030 .00038 .00040 .00056 .00070 .00080 .00090 .00110 .00160 .00330 .00525 .01440 .01890 .04590 .06750 .1030 .1203 .1398 .1854 .2713 .3242 .4206 .5417 .7794 1.1714 1.4264 1.6324 1.9127 2.1540 2.4870 2.3005 2.4938 3.0353 2.7163 3.2274 3.1556 3.1983 2.8232 ~ .00250 3 0 --- - - - - - - - - - 2 -------13 - - - - - - - 1 6 --- - - - - - 20 - - - - - - - - 23 - - - - - - - - - 69 - - - - - - - - --- -- --- - - ---- 29 -- - - - - - - September 3--------6 --- - - - - - 10- - - - - - - - 13 --- - - - - - 17 - - - - - - - - 20 -- - - - - - - 24 ------27 -- - - - - - - October 1--------4 -- - - - - - - 8-- -- --- -15 - - - - - - - - 22 _ -18 --- --- 27 32 ALABAMA AGRICULTURAL EXPERIMENT STATION 32 ALABAMA AGRICULTURAL EXPERIMESTIN Ovule fresh weight Grams Ovule dry weight Grams 0.00012 .00010 .00023 .00017 .00017 .00024 .00026 .00037 .00060 .00090 .00110 .00160 .00410 .01110 .03160 .06610 .14860 .19460 .28870 .60550 1.43800 2.39590 2.99370 3.49950_ Date May June 22---------------26---29---2 -----------4-----------11-----------15---18-----------22------ ------ 0.003 July 25------29__ ----8----------13---------------2 0 --- - - - - - - - - - - - 2 7-- - - - - - - --- - - --3----------- ---- - 043 -. 191 -. 0.500 .1982 August 10 -- - - - - - - - - - - - - 1 7 -- - - - - - - - - - - - 24 -- - - - - - - - - - - - - 3 1 --- - - - - - - - - - - - September 8--------------14- -- --------- 2 2 --- - - - - - - - - - - - 28 --- - - - - - - - - - - - - 2.8153 3.9625 ------ 3.8622 2.8492 5.0955 4.3584 - 4.8396 4.5945 PECAN FRUIT GROWTH AND DEVELOPMENT 33 PECAN FRUIT GROWYTH AND DEVELOPMENT 3 APPENDIX TABLE 9. FRESH AND DRY WEIGHT OF PECAN NUTS BY DATES IN 1963 May Fresh weight of nuts Grams 17-----------------------------------0.1076 21-----------------------------------.1389 -. 1813 24----------------------------------.2143 28-----------------------------------31-------------------------------.2907 4-----------------------------------_--____--_---___------------ Date June .3988 .4740 Dry weight of nuts Grams 0.0320 .0386 .0544 .0592 .0844 .1154 .1432 11-----------------------------------14 -----------------------------------18 - ------------ .6529 .7400 .8974 21-----------------------------------25 -----------------------------------28------------------------------------ 1.2330 1.5205 2.2021 .1890 .2334 .2734 .2432 .3390 .3760 July 26 -----------------------------------30---------------------August 3.5230 5 --------------------9----------------------------------4.3470 5.6660 12 -------------------------------------6.2500 16--------------------8.9530 19 ---------------------------------- 2------------------------------------ 2.3153 11.5730 13.4130 2 --------------------------6 ----------------------------------- ------- 16.7880 17 .3 9 93 .5410 .8316 .7092 1.1910 1.3010 1.8710 2.4110 2.5700 3.2720 . 8 13 -----------------------------------16--------------------------- 9--- - 17.634 18.115 20.480 20 ------------------23-----------------27---------- --------- 21.640 21.215 21.225 4.031 4 .03 1 4.852 5.174 5.584 6.338 6.784 7.015. 7.463 7.984 7.897 7.970 7.201 29-----------------September 3-----------------10-----------------13--------------- -17-----------------20-------------------------- 23.505 21.445 21.445 6 -------------------- 21.725 22.830 24.555 24.169 24-----------------27------------ 23.610 24.982 October 1-----------------4-----------------8------------------13-----------------15---------18 -------------------------- 26.380 26.315 25.450 23.500 23.180 23.720 8.223 8.913 8.075 8.184 9.116 22------------------- 21.815 8.829 34 ALABAMA AGRICULTURAL EXPERIMENT STATION APPENDIX TABLE 10. FRE~SH AND DRY WEIGHT OF PECAN NUTS BY DATES IN 1964 Date M ay June 22 -- - - - - - - 26 -- - - - - - 29 -- - - - - - - 4- - - - - - - - 11-- - - - - - - - - - - - - - - - 15 - - - - - - - - 18 - - - - - - - - 22 - - - - - - - - - 25____ 29 - - - - - - 8- - - - - - - - 13 -- - - - - - - - - - - - - - - - 2 0 --- - - - - - - - - - - - - - - 2 7 -- - - - - - - - - - - - - - - - 3-------------- - --17--- - - - - - - - - - - - - - 24 -- -- -- --- -- -- - - - 31 -- - - - - - - - - - - - - - - - Septem ber Fresh weight of nuts Grams Dry weight Grams of nuts July August 10 - - - - ---- -- - - - - - - - 22 8-------------14 ----- --- -- -- -- -- -- -- -- --- 2 8 --- - - - - - - - - - - - - - - - ,, -- -- -- - -- -- --- 0.094 .127 .163 .261 .426 .575 .643 .844 1.118 1.553 2.935 4.659 6.878 9.270 13.772 18.145 21.980 20.865 21.500 24.170 31.550 30.995 34.620 1rrr~ .0370 .0494 .0700 .1174 .1786 .1910 .2698 .63075 .4174 .6960 .9846 1.5642 2.0866 2.7808 4.1384 4.7016 5.0540 6.1868 7.8320 8.4736 9.6520 10.2370 0.0152 AUBURN UNI" ~' "" With an agricultural research unit in every major soil area, Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in Alabama. Every citizen of the State has a stake in this research program, since any advantage from new and more economical ways of producing and handling farm products directly benefits the consuming public. @ n0 -- 17 ) Main Agricultural Experiment Station, Auburn. Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Substation, Winfield. Forestry Unit, Fayette County. Thorsby Foundation Seed Stocks Farm, Thorsby. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County. Piedmont Substation, Camp Hill. Plant Breeding Unit, Tallassee. Forestry Unit, Autauga County. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction. Tuskegee Experiment Field, Tuskegee. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeville. Wiregrass Substation, Headland. Brewton Experiment Field, Brewton. Ornamental Horticulture Field Station, Spring Hill. Gulf Coast Substation, Fairhope.