6000-L180 TEXAS AfiRlCULTURAL EXPERIMENT STATION A. B. CONNOR, DIRECTOR COLLEGE STATHDL BRAZOS COUNTY,TEXAS BULLETIN NO. 478 AUGUST, 1933 DIVISION OF {QY W - I h; QQ "Efifi AflrlouItural81Meohanfca\(‘o\ ‘f College Statnon. Texa». The Storage and Seasoning of Pecan Bud Wood AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS _ T. O. WALTON, President STATION STAFF? Administration : A. B. Conner, M. S., Director R. E. Karper, M. S., Vice-Director Clarice Mixson, B. A., Secretary M. P. Holleman, Chief Clerk J. K. Francklow, Asst. Chief Clerk Chester Higgs, Executive Assistant Howard Berry, B. S., Technical Asst. Chemistry: . S. Fraps, Ph. D., Chief; State Chemist E. Asbury, M. S., Chemist F. Fudge, Ph. D., Chemist C. Carlyle, M. S., Asst. Chemist . L. Ogier, B. S., Asst. Chemist A. J. Sterges, M. S., Asst. Chemist Ray Treichler, M. S., Asst. Chemist W. H. Walker, Asst. Chemist Velma Graham, Asst. Chemist Jeanne F. DeMottier, Asst. Chemist R. L. Schwartz, B. S., Asst. Chemist C. M. Pounders, B. S., Asst. Chemist Horticulture: S. H. Yarnell, Sc. D., Chief Range Animal Husbandry: J. M. Jones, A. M., Chief B. L. Warwick, Ph. D., Breeding Investiga. S. P. Davis, Wool Grader I"J. H. Jones, B. S., Agent in Animal Husb. Entomology: F. L. Thomas, Ph. D., Chief; State Entomologist H. J. Reinhard, B. S., Entomologist R. K. Fletcher, Ph. D., Entomologist W. L. Owen, Jr., M. S., Entomologist J. N. Roney, M. S., Entomologist J. C. Gaines, Jr., M. S., Entomologist S. E. Jones, M. S., Entomologist F. F. Bibby, B. S., Entomologist "E. W. Dunnam, Ph. D., Entomologist "R. W. Moreland, B. S., Asst. Entomologist C. E. Heard, B. S., Chief Inspector S. E. McGregor, B. S., Foulbrood Inspector i-lfiFf/JQ Veterinary Science: ‘M. Francis, D. V. M., Chief H. Schmidt, D. V. M., Veterinarian "F. P. Mathews, D.V.M., M.S., Veterinarian J. B. Mims, D. V. M., Asst. Veterinarian Plant Pathology and Physiology: J. J. Taubenhaus, Ph. D., Chief W. N. Ezekiel, Ph. D., Plant Pathologist Farm and Ranch Economic: L. P. Gabbard, M. S., Chief W. E. Paulson, Ph. D., Marketing C. A. Bonnen, M. S., Farm Management I"W. R. Nisbet, B. S., Ranch Management **A. C. Magee, M. S., Ranch Management Rural Home Research: Jessie Whitacre, Ph. D., Chief _ Mary Anna Grimes, M. S., Textiles ,_ Nutrition Soil Survey: "W. T. Carter, B. S., Chief E. H. Templin, B. S., Soil Surveyor A. H. Bean, B. S., Soil Surveyor R. M. Marshall, B. S., Soil Surveyor Botany: V. L. Cory, M. S., Acting Chief Swine Husbandry: Fred Hale, M. S., Chief Dairy Husbandry: O. C. Copeland, M. S., Dairy Husbandman Poultry Husbandry: R. M. Sherwood, M. S., Chief J. R. Couch, B.S., Asst. Poultry Husbandman Agricultural Engineering: H. P. Smith, M. S., Chief Main Station Farm: G. T. McNess, Superintendent Apiculture (San Antonio): H. B. Parks, B. S., Chief A. H. Alex, B. S., Queen Breeder Feed Control Service: F. D. Fuller, M. S., Chief James Sullivan, Asst. Chief Agronomy: S. D. Pearce, Secretary E. B. Reynolds, Ph. D., Chief J. H. Rogers, Feed Inspector R. E. Karper, M. S., Agronomist K. L. Kirkland, B. S., Feed Inspector P. C. Mangelsdorf, Sc. D., Agronomist S. D. Reynolds, Jr., Feed Inspector D. T. Killough, M. S., Agronomist P. A. Moore, Feed Inspector Publications: E. J. Wilson, B. S., Feed Inspector A. D. Jackson, Chief H. G. Wickes, D. V. M., Feed Inspector SUBSTATION S No. 1, Beeville, Bee County: No. 9, Balmorhea, Reeves County: R. A. Hall, B. S., Superintendent J. J. Bayles, B. S., Superintendent No. 2, Lindale, Smith County: P. R. Johnson, M. S., Superintendent No. 10, College Station, Brazos County: R. M. Sherwood, M. S., In Charge “B. H. Hendrickson, B. S., Sci. in Soil Erosion L. J. McCall, Farm Superintendent "R. W. Baird, M. S., Assoc. Agr. Engineer No. 3, Angleton, Brazoria County: R. H. Stansel, M. S., Superintendent H. M. Reed, M. S., Horticulturist No. 4, Beaumont, Jefferson County: R. H. Wyche, B. S., Superintendent "H. M. Beachell, B. S., Junior Agronomist No. 5, Temple, Bell County: Henry Dunlavy, M. S., Superintendent C. H. Rogers, Ph. D., Plant Pathologist H. E. Rea, B. S., Agronomist S. E. Wolff, M. S., Botanist "H. V. Geib, M. S., Sci. in Soil Erosion "H. O. Hill, B. S., Junior Civil Engineer No. 6, Denton, Denton County: P. B. Dunkle, B. S., Superintendent "I. M. Atkins, B. S., Junior Agronomist No. 7, Spur, Dickens County: R. E. Dickson, B. S., Superintendent B. C. Langley, M. S., Agronomist No. 8. Lubbock, Lubbock County: D. L. Jones, Superintendent Frank Gaines, Irrig. and Forest Nurs. Teachers in the School of Agriculture CarrIying G. W. Adriance, Ph. D., Horticulture S. W. Bilsing, Ph. D., Entomology V. P. Lee, Ph. D., Marketing and Finance D. Scoates, A. E., Agricultural Engineering A. K. Mackey, M. S., Animal Husbandry *Dean, School of Veterinary Medicine. No. 11, Nacogdoches, Nacogdoches County: H. F. Morris, M.,S., Superintendent “No. 12, Chillicothe, Hardeman County: '““J. R. Quinby, B. S., Superintendent "J. C. Stephens, M. A., Asst. Agronomist No. 14, Sonora, Sutton-Edwards Counties: W. H. Dameron, B. S., Superintendent I. B. Boughton, D. V. M., Veterinarian W. T. Hardy, D. V. M., Veterinarian O. L. Carpenter, Shepherd "O. G. Babcock, B. S., Asst. Entomologist No. 15, Weslaco, Hidalgo County: W. H. Friend, B. S., Superintendent S. W. Clark, B. S., Entomologist W. J. Bach, M. S., Plant Pathologist J. F. Wood, B. S., Horticulturist No. 16, Iowa Park, Wichita County: C. H. McDowell, B. S., Superintendent L. E. Brooks, B. S., Horticulturist No. 19, Winterhaven, Dimmit County: E. Mortensen, B. S., Superintendent "L. R. Hawthorn, M. S., Horticulturist Cooperative Projects on the Station: S. Mogford, M. S., Agronomy F. R. Brison, M. S., Horticulture W. R. Horlacher, Ph. D., Genetics J. H. Knox, M. S., Animal Husbandry A. L. Darnell, M. A., Dairy Husbandry TAs of August 1, 1933 "In cooperation with U. S. Department of Agriculture. tIn cooperation with Texas Extension Service. .._ ..._........L..._-,.;. The patch bud is the principal means employed in the propa- gation of the pecan by graftage. Buds of the current season may be used, but the work can begin much earlier if buds of the previous season are used. Such bud wood may be taken from the trees as needed, but it has been found to be more economical to cut the bud wood while dormant and keep it in cold storage. It is then “seasoned,” or brought into condition for use by providing suitable conditions of moisture’ and holding at 80° to 85° F. Seasoned wood can be returned to cold storage and will remain ready for use at a later date. It has been found that budwood cut late in the dormant period seasons in a shorter time than that cut early. Bud wood of the Delmas variety seasons more readily than that of Stuart under comparable conditions. The time required for seasoning is also influenced by the date at which the process occurs, being shorter in late than in early spring. There is evidence that bud wood held at a temperature exceeding 40° F. deteriorates with age, because of a depletion of the food supply. Results of studies on cambium activity, starch transfor- mation, and on the effect of disbudding are presented, together with a discussion of the relationship of the seasoning process to the normal rest period in the pecan. CONTENTS Page The Patch Bud and Its Use 5 Types of Bud Wood ._ 6 Current Bud Wood _ 6 Fresh Bud Wood ................................... . 6 Storage Bud Wood ' 7 Influence of Humidity on Seasoning 7 Influence of Temperature on Seasoning ..... I 8 Relation of Time of Cutting Bud Wood to Seasoning ______________________________ __ 9 Relative Response of Stuart and Delmas in Seasoning __________________________________ __1O Number of Days for Seasoning Bud Wood During Different Months_o.--12 Storage of Seasoned Bud Wood * 13 Studies Relating to Internal Changes Involved in Seasoning _________________ I15 Relationship of Rest Period to the Time Required for Seasoning.._.15 Relation of Cambial Activity to the Seasoning Process ______________________ __17 Effect of Disbudding on Cambium Activity ______________________________________ __21 Relation of Starch Transformation to Seasoning ______________________________ I22 Recommendations - 24 Acknowledgments 25 Summary .. 25 References ....... .1 . . . _ . . . . _ -. 26 BULLETIN NO. 478 AUGUST, 1933 THE STORAGE AND SEASONING OF PECAN BUD WOOD* FRED R. BRISON Propagation of named varieties of the pecan was started as early as 1885 by a few nurserymen, principally of the southeastern states. A report in 1901 of experiments conducted by the United States Department of Agriculture (1) indicates that the whip, or tongue, graft was 1n use at that time. The cleft graft and flute bud were used in the propagation of Walnuts prior to and during that time, and have since been used also on the hickories. It seems reasonable, then, to presume that these methods were also used in the propagation of pecans during the latter part of the 19th century. In 1912, Van Deman (22) stated that grafting and budding were employed in nut-tree propagation. Tongue, 0r splice, and cleft graft were used, and the patch bud was satisfactory, but the shield bud could not be used with assurance of success. Since then, the use of the patch bud and its various modifications has undoubtedly become more general. J. A. Evans (7) in 1920 demonstrated that patch buds could be successfully inserted in rough thick bark of limbs three or more inches in diameter. This possibility renders it especially valuable for top-working poor- or non-producing trees that range in diameter from one to six inches. Stuckey and Kyle (21) indicate that early attempts to use the cleft graft in pecan propagation were not entirely satisfactory: “So the ring bud was introduced, being first used by E. E. Risien. * * * The patch bud, or modified ring bud,'has become the most important method of top- working native pecan trees, and is rapidly replacing the whip grafts in the propagation of nursery trees.” Though other methods, notably the bark graft, may be used, the patch bud and its various minor modifications constitute theprincipal means by which the large majority of pecan trees of named varieties are produced at the present time. Incidentally, the use of the patch bud is no recent contribution to the art of plant propagation. Columella (4), about 23 A. D., described this method‘ of graftage, “* * * whereby the tree receives the buds themselves, with a little bark, into a part of itselfl from which the bark is taken away. * * * It is not fit for all sorts of trees, but for the most part, such as have a moist, juicy, and strong bark * * * as the fig.” His further description convinces one that he was referring to the patch bud. THE PATCH BUD AND ITS USE Essentially, patch budding consists of removing a piece of bark ap- proximately seven-eighths of an inch square from the stock and inserting into its place bark containing a bud from the tree that it is desired to *This investigation was conducted in cooperation with the School of Agriculture, A. and M. College of Texas, and the material in this Bulletin was also presented to the Michigan State College as a thesis for the degree of Master of Science. 6 BULLETIN NO. 478, TEXAS AGRICULTURAL EXPERIMENT STATION propagate. It is considered important to have the bark of the inserted bud fit snugly at the top, bottom, and at least one side. Buds are tied firmly in place and grafting wax or similar material is usually applied to exclude moisture and air. Union between the bud and stock is accomplished by regeneration where the two cambiums are in close contact and by over- walling at the margins. Satisfactory growth results from both types of union. The patch bud is found useful in the commercial propagation of seedling trees in the nursery row. It is also used in the top-working of older trees by inserting the buds in the rough bark of limbs that are one inch to two inches in diameter. This procedure in general is not recommended for trees that are larger than six or eight inches in diameter. Trees of larger sizes are cut back during a‘ dormant season and allowed to force out young shoots which may be budded during the latter part of the summer following the winter in which the trees were cut back. TYPES OF BUD WOOD Current Bud Wood In the commercial propagation of the pecan, both current and preceding season’s growth are used. Wood of the current season’s growth is suitable from midsummer until the end of the budding season. Buds from this type of bud wood are known as “current season” buds. On account of their immaturity they cannot be used earlier than perhaps June 15 with any assurance of reasonable success in even the most southern localities. Fresh Bud Wood Previous season’s wood must, of necessity, be relied upon for spring and early summer budding. There are two principal ways in which such bud wood is handled prior to its use. One practice involves the cutting of the bud wood directly from the trees as it is needed throughout the budding‘ season. This is known as “fresh” bud wood. An objection to the use of bud wood of this type is that in the spring many of the most valuable buds are forced into growth, either forming twigs or falling off, before the bud wood can be used. This is especially true of the western varieties. The eastern varieties, on the other hand, produce two to five buds at each node, occasionally more. Even though the largest and most valuable bud of the group may have advanced too far to be used, others are present which when forced properly may be depended upon for satisfactory growth. Such secondary buds, however, do not grow as quickly nor as vigorously as primary buds. In addition to the foregoing, seasonal con- ditions such as abundant rainfall or late spring frost may force practically all the suitable buds of a tree into growth and render them useless for .budding purposes. Thus fresh bud wood is a dependable source of buds for use only during a relatively short period in the early spring. It cannot be relied on for late spring and early summer work. THE STORAGE AND SEASONING OF PECAN BUD WOOD '7 Storage Bud Wood The other method of handling bud wood of previous season’s growth involves the cutting of scions about 12 to 18 inches long, from trees during the dormant season and storing them, properly insulated against desic- cation, at a temperature of 32° to 38° F. Bud wood handled in this way will be referred to hereafter as “storage wood.” Since it is cut while dormant and is favored by a low temperature, it remains in a dormant condition in storage; hence it must be subjected to conditions upon removal that will permit the slipping of the bark before it can be used. This process, known as “seasoning,” is accomplished by providing moisture and a warm atmosphere. It is considered that bud wood is seasoned when the bark may be readily peeled from the wood. Propagators frequently experience difficulty in getting bud wood to season properly. Of the factors which may be associated with delayed seasoning, temperature and humidity during season and time of cutting bud wood from trees may be suggested. Practices with regard to each of these factors vary widely in commercial work. INFLUENCE OF HUMIDITY ON SEASONING Recommendations as to optimum water conditions during seasoning vary widely and have been rather indefinite. Ordinarily the insulating material is kept “moist but not wet.” Hutchins (11) suggests “a mixture consisting of equal proportions of wet and dry sawdust or shavings” as satisfactory insulations for bud wood in storage or during seasoning. Woodward (23) advises placing the bud wood in water at a temperature of 90° to 100° F. and intimates that it will then season within two to four hours. Two series of tests were conducted to determine the influence of humidity upon the seasoning process: I Three lots of Stuart bud wood, each containing 26 bud sticks, were sea- ‘soned in sphagnum moss to which the following additions of water per 100 grams of moss were made respectively: (a) 688 cc., (b) 344 cc., and (c) 172 cc. (Water was added to moss until conditions considered optimum were reached. The amount of water added was then determined to have been 688 cc.; one-half this amount was added to a second lot, and one- fourth to the third lot.) In each instance waxed paper was used to wrap individual packages in order to restrict evaporation and maintain the respective moisture content suggested above. This test was duplicated with the Delmas variety. Somewhat later 24 bud sticks of the Stuart variety were placed for seasoning in moss that contained 1000 cc. of moisture per 100 grams of moss; and a duplicate lot of 24 bud sticks was placed in moss that contained only 150 cc. of water to each 100 grams of moss. In each test, bud wood seasoned in the same length of time regardless of the relative moisture content of the moss. These results show that the amount of moisture may vary widely without retarding the seasoning process. Bud wood seasons in as short a period in 8 BULLETIN NO. 47S, TEXAS AGRICULTURAL EXPERIMENT STATION relatively dry moss as in moss that is decidedly wet. It is known, how- ever, that some moisture is essential and it is evident that its chief beneficial effect is associated with the prevention of desiccation. The results given above are consistent with those of Shippy (19), who with respect to the callusing of apple cuttings, says, “Considerable moisture tolerance is indicated by the fact that callus formed almost equally well in media varying in water content from 97 to 437 per cent. Further, these results indicate that once the moisture content of the medium is saturated, additional quantities have little or no» stimulating effect on callus forma- tion * * *.” A limited number of tests were conducted in which bud sticks were half submerged in vertical position, some upright and others inverted, in pails of water. In no instance did the submerged portions of a bud stick season, although in every instance exposed parts of bud sticks seasoned normally. It seems likely that the inability of submerged parts of scions to begin activity was due to lack of proper aeration. Further, it has been the experience of the writer that the practice of soaking bud wood in water does not hasten the seasoning process. It is of incidental interest that bud sticks do not seem to change in Weight to any appreciable extent during this process. In two tests in which 64 bud sticks were weighed carefully before and after seasoning there was no consistent appreciable increase in weight during seasoning; in fact the weights of some bud sticks revealed slight losses. INFLUENCE OF TEMPERATURE ON SEASONING Little experimental work seems to have been done to provide a basis for regulating the temperature for seasoning bud wood. Burkett (3) recom- mends putting bud wood in wet moss, sawdust, sand, or other good material, and laying the insulated bud wood out in the sun until the bark slips. Woodward (23) advises total immersion in water at 90° to 100° F. for two to four hours. Several preliminary attempts were made to season lots of bud wood at temperatures of 95° to 100° F. No attempt was fully successful. Of these lots, a limited number of bud sticks became partly seasoned, but no entire lot seasoned normally. A series of tests was then initiated for the purpose of determining an optimum temperature for the seasoning process. Bud wood of the Stuart variety was cut in February and held in cold storage until the following May. On May 2O three lots of 8 sticks each were packed separately in sphagnum moss, to which water had been added at the rate of 688 cc. per 100 grams of moss. Each lot was then wrapped in waxed paper. One bundle was held at temperatures ranging from 93° to 98° F., a second at from 78° to 85° F., and the third from 63° to 68° F. The test was re- peated, using 18 sticks in each lot, and substantially the same results were obtained. As may be seen from Table 1, bud sticks did not season normally THE STORAGE AND SEASONING OF PECAN BUD [WOOD 9 at either the. high or 10w range of temperature. They seasoned normally at temperatures ranging from 78° t0 85° F., and throughout investigations Table 1. Relation of temperature to seasoning Total number bud sticks I Temperature Result?» 26 63°-68° F. All bud sticks dormant at end of 8 days. 26 78°-85° F. 24 bud sticks seasoned within 4 days. 26 93°-98° F. 7 bud sticks seasoned at end of 8 days. here reported this range of temperature was found effective in seasoning bud wood. RELATION OF TIME OF CUTTING BUD WOOD TO SEASONING Definite information seems to be lacking on the possible relationship between the time of cutting bud wood and the length of time required for seasoning. Hutchins (11) mentions “from January to the latter part of February” as the season for cutting bud wood from trees; Burkett (3) recommends “late Winter.” Between the 15th and 20th of each of the months of December, January, February, and March during the Winters of 1928-29, 1929-30, and 1930-31, bud wood was taken from pecan trees of the Stuart and Delmas varieties in the orchard of the Department of Horticulture of the Agricultural and Mechanical College of Texas. The trees had been planted in the orchard in 1920 and 1921, and consequently had reached bearing age prior to the beginning of this test. Individual bud sticks obtained from these trees were approximately one-half inch in diameter at the base, 12 to 18 inches long, and had been formed during the previous growing season. In general, bud sticks used in this test were of a type considered ideal for the purpose of patch budding. On the date each lot of bud wood was cut, it was packed for storage in sphagnum moss uniformly moistened with 688 cc. of water per 100 grams of moss. This wood was packed in open boxes and stored in the college ice house. The storage temperature ranged from 38° F. in the early part of the period to 32° F. during the latter part. With the approach of the season for budding each spring, samples of bud wood of each variety, cut from December through March, were taken out of storage and held for seasoning. Uniform conditions of moisture and temperature were provided by packing all the bud sticks used in a test in a single container. Sphagnum moss, with the same content as that used in storage, was used for insulation during seasoning. Waxed paper was employed to restrict evaporation of" moisture although no attempt was made to make packages air-tight. When packed, the boxes were placed in a a steam heated room, the temperatures of which could be maintained rather accurately at 80° to 85° F. 10 BULLETIN NO. 478, TEXAS AGRICULTURAL EXPERIMENT STATION The bud Wood was inspected at intervals and records were taken on all comparable lots on the date a considerable percentage of bud sticks of any lot became fully seasoned. The proportion of bud sticks seasoned on this date has been used as an index of the rate of seasoning for each lot. Results of all tests conducted for the purpose of determining thegrelation- ship between time of cutting bud Wood of the Stuart variety and the rate of seasoning are summarized in Table 2. Inspection of results presented Table 2. Relation between time of cutting bud wood and length of time required for seasoning (Stuart) Cut in Cut in Cut in Cut in nggsér Date Date test December January February March bud seasoning completed Number Number Number Number sticks began | sea- I sea- I sea- | sea- tested | soned tested soned tested soned tested g soned l 6 5-20-29 ’ 5-25-29 2 I 0 2 0 2 1 ~—— — l 6 5-20-29 5-27-29 2 1 0 ‘ 2 0 2 1 - I — l . l p16 5- 1-30 5- 3-30 | 4 ll 1 l 4 a 4 4 \ 4 I 4 I 4 16 5- 7-30 | 5- 9-30 l 4 ll 1 4 | 2 4 ll 2 4 4 16 % 5-16-30 5-17-30 4 | 1 4 1 4 a O 4 4 l 18 2-18-31 3- 3-31 6 l 1 6 0 6 3 ~— —- l I l 40 3-18-31 3-27-31 10 I 1 l 10 0 10 4 10 10 l 72 5- 4-31 5- 6-31 18 l 5 18 5 18 17 18 18 l . l Totals .................................. I 50 l 10 50 12 50 32 40 40 l in that table shows that seasoning of Stuart bud sticks cut relatively late in the dormant period takes place in a shorter time than is required for those cut early. Of 50 bud sticks cut in December only 10 were seasoned when the respective tests were concluded. Twelve of 50 cut in January, 32 of 50 cut in February, and 40 of 40 cut in March were seasoned during comparable tests. Differences in the response of Delmas bud wood cut at monthly intervals to seasoning conditions are less pronounced than those recorded for Stuart. The totals given in Table 3 show that 30 of 50 bud sticks cut in December, 45 of 50 cut in January, and all that were cut in February and March Were seasoned upon completion of the respective tests. In view of the fact that Delmas responded more readily to conditions ‘of seasoning throughout this test, it is probable that if data on seasoning had been recorded a few days earlier for each lot, differences in response of Delmas wood cut early and late would have been more pronounced. RELATIVE RESPONSE OF STUART AND DELMAS IN SEASONING Comparison of Tables 2 and 3 shows a varietal difference in the response of the two varieties to seasoning conditions. Of a total of 50 bud. sticks THE STORAGE AND SEASONING OF PECAN BUD WOOD 11 of each variety cut in December, 30 Delmas bud sticks were seasoned when the data were recorded as compared with 10 Stuart; likewise of bud wood cut in January, 45 Delmas were seasoned as compared with 12 Stuart, and of that cut in February, all 50 of the Delmas and only 32 of the 50 Stuart Table 3. Relation between time of cutting bud wood and length of time required for seasoning (Delmas) Cut in Cut in Cut in Cut in Total December January February March number Date Date test ~~ v - bud seasoning completed Number Number Number Number sticks began I sea- sea- sea- tested tested soned tested soned tested soned soned sea- I I 6 5-20-29 5-25-29 2 I 1 2 1 2 2 —- — I 6 - 5-20-29 5-27-29 2 I 0 2 2 2 2 — — I . 16 5- 1-30 5- 3-30 4 I 4 4 4 4 4 4 4 i . 16 5- 7-30 3- 9-30 4 I 4 4 4 4 4 4 4 I I e 16 5-16-30 5-17-30 4 I 3 I 4 4 4 4 4 4 I 18 2-18-31 3- 3-31 6 II 5 6 5 6 6 — —— 40 3-18-31 3-23-31 10 II 0 10 8 10 10 —— -—— 72 5- 4-31 5- 6-31 18 I 13 18 17 18 18 — —— I I Totals .................................. .. 50 I 30 50 45 50 50 12 12 I bud sticks were seasoned. The results as summarized in Table 4 emphasize these differences. It is evident that Delmas is more sensitive than Stuart in its reaction to moisture, temperature, and to whatever other factors which tend to initiate the seasoning process. This seems particularly interesting since normally the growth of Delmas trees is prolonged later in the fall than that of Stuart. In normal years the harvest period for Delmas nuts is from November 1 to 10 in the vicinity of College Station, Texas; Stuart nuts, in contrast, are ready to harvest from the 10th to the 15th of October. This constitutes an objec- tionable feature of the Delmas variety since its fruit ripens so late in the season that the crop is sometimes ruined by early frosts. Yet Delmas bud wood cut in December and January is more responsive to seasoning than bud wood of the Stuart variety cut at that time. The fact that Delmas trees initiate growth earlier in the spring than Stuart is interesting and no doubt significant also in this connection. Ordinarily by the 10th of March, Delmas trees are showing signs of growth. Bark of fresh bud wood material of this variety slips readily at that time and the wood is not considered suitable for storage purposes. It was on this account that Delmas bud wood was not stored in March in 1929 and 1931. Stuart bud. wood, on the other hand, seemed to be in a dormant condition each year until after March 12. Hence bud wood of Delmas would be expected to season more rapidly than that of Stuart. 12 BULLETIN NO. 478, TEXAS AGRICULTURAL EXPERIMENT STATION Histological cross-sections of dormant and seasoned bud wood of both Stuart and Delmas at different periods from December to May show no Table 4. Comparison of responses of Stuart and Delmas pecan bud wood to conditions considered favorable to seasoning ’ Stuart Delmas Date Date Number Numper Numher cut seasoning days Number bud Sucks Number bud Stlckds’ began seasoned bud sticks Seasoned bud sticks seasmle _ in test when test in test when test completed completed =‘ 12-14-28 5-20-29 s 2 0 2 1 1-14-29 5-20-29 5 2 0 2 1 5-21-29 5-20-29 5 2 1 2 2 12-14-28 5-20-29 7 2 0 2 0 1-14-29 5-20-29- 7 2 0 2 2 2-21-29 5-20-29 7 2 1 2 2 2-21-29 5-20-29 5 2 1 2 2 2-21-29 5-20-29 5 2 2 2 2 2-21-29 5-20-29 5 2 2 2 2 2-21-29 5-20-29 5 _ 2 1 2 2 2-21-29 5-20-29 5 2 0 2 2 2-14-30 2-14-30 10 3 0 3 3 12-20-29 5- 1-30 2 4 1 4 4 1-20-30 5- 1-30 2 4 4 4 4 2-20-30 5- 1-30 2 4 4 4 4 3-10-30 5- 1-30 2 4 4 4 4 12-20-29 5- 7-30 2 4 1 4 4 1-20-30 5- 7-30 2 4 2 4 4 _, 2-20-30 5- 7-30 2 4 2 4 4 3-10-30 5- 7-30 2 4 4 4 4 12-20-29 5-16-30 1 4 1 4 3 i 1-20-30 5-16-30 1 4 1 4 4 -; 2-20-30 5-16-30 1 4 0 4 4 i 3-10-30 5-16-30 1 4 4 4 4 ‘E 12-18-30 2-18-31 15 e 1 6 5 l 1-18-31 2-18-31 15 6 0 6 5 l 2-18-31 2-18-31 15 6 3 6 6 ' 12-18-31 3-18-31 5 10 1 10 1 , 1-18-31 3-18-31 I 5 10 O 10 8 ll 2-18-31 3-18-31 5 10 4 10 10 . 12-18-30 5- 4-31 2 18 5 18 13 ' 1-18-31 5- 4-31 2 18 5 18 17 2-18-31 5- 4-31 2 18 17 18 18 Totals 175 74 175 151 differences between the two varieties in the appearance of the cambium region. This and studies on starch translocation will be considered in later sections. NUMBER OF DAYS FOR SEASONING BUD WOOD DURING DIFFERENT MONTHS It has been shown that bud wood cut late in the Winter ‘seasons in a shorter period of time than bud wood cut early in the winter when both are seasoned at the same time. Since seasoning the bud Wood was not all done at one time there was opportunity to determine the relationship of the month of seasoning to the rate at which this process occurs. THE STORAGE AND SEASOINING OF PECAN BUD WOOD 13 Bud wood of Stuart and Delmas varieties was cut in December and held in cold storage until needed. Optimum seasoning conditions were pro- vided for representative lots in December, January, February, March, and May. The attempt at seasoning during December resulted in death of all scions of each variety by the end of 20 days. Bud wood of both varieties seasoned in January in a period of 19 days. Delmas bud wood of the same lot seasoned in 15 days during February, and in only 2 days after removal from storage in May (Table 5). Delmas bud sticks cut in February seasoned in 15 days in February, 5 days during March, and only 2 days in May. Data showing response of Stuart bud wood do not suggest so clearly a relationship between number of days required for seasoning and the date Table 5. The number of days required for seasoning bud wood on successive dates during the budding season (1931) Seasoning begun (60 Seasoning begun (90 Seasoning begun (136 days after December days after December days after December 18) Feb. 18, 1931 18) Mar. 18, 1931 18) May 4, 1931 Variety Date w: a w: a '1: cut Eases m i: imwssewia itiw-ssw i: as as; sit ‘Es a8 as: er? is as est’ 2Y3 ‘Es s3 new 5:33 s3 s3 wag =-°5 s§§ d3 avg r195 :3 Qmzvz wzgg mwz Zwzgg mmz zwzg; Stuart 12-18-30 60 15 6 1 90 5 1O 1 136 2 18 5 Stuart 1-18-31 30 15 6 0 60 5 10 O 102 2 18 5 Stuart 2-18-31 0 15 6 3 30 5 10 4 76 2 18 17 Stuart 3-18-31 -——- —- —— — 0 5 10 10 46 2 18 18 l Delmas 12-18-30 6O 15 6 5 90 5 1O 0 136 2 18 13 Delmas 1-18-31 30 15 6 5 60 5 10 8 106 2 18 17 Delmas 20-18-31 0 15 I 6 6 30 5 10 1O 76 2 18 18 at which this process occurs, as shown by Table 5. It is significant, how- ever, that of the Stuart bud sticks cut in February only 3 of 6 seasoned in 15 days in February, whereas 17 of 18 bud sticks of the same lot * seasoned in 2 days in May, after having been in cold storage '76 days. It will be recalled that the scions that composed each lot were held in cold storage from the various times they were cut until the seasoning process was begun for respective lots. The seasoning temperatures for each lot ranged from 80° to 85° F. STORAGE OF SEASONED BUD WOOD Seasoned bud wood of the Stuart variety was, as a matter of con- venience, put back in cold storage on May 4, 1929. Later examination indi- cated that the bark was still slipping and the bud wood was in good condi- tion for use. At the end of 9, 16, 23, and 37 days buds were taken from 14 BULLETIN NO. 4'78, TEXAS AGRICULTURAL EXPERIMENT STATION this lot and inserted in nursery stock. Of a total of 16 buds, 13 were found to be successful, 1 failure was recorded, and the identity of 2 others was lost. It was significant that 3 out of 4 buds inserted at the end of a storage period of 37 days grew. In 1930 and 1931 more comprehensive tests were conducted. In each year bud wood was cut about the middle of February and held in cold storage until the early part of April. At that time entire lots were removed from storage, allowed to season, and were returned to cold storage at temper- atures ranging from 32° to 38° F. They were then in ideal condition for patch budding and could be used directly out of storage without preliminary treatment. Samples of bud wood of different varieties included were taken out, as far as practicable, at weekly intervals and inserted in uniform nursery trees. Results of these tests, tabulated in Table 6, show that it is possible to hold seasoned bud wood of the varieties indicated in cold storage for a period of at least 18 to 25 consecutive days without a significant decrease Table 6. The longevity of storage bud wood held in cold storage after seasoning Number days Number buds* Number buds Per cent of in storage set growing buds growing 4 85 l 61 i 71+ 11 138 106 76-|— 18 126 98 77+ 25 124 82 66+ over 3O 44 22 50+ I *Total of buds from Burkett, Delmas, Schley, Stuart, and Sovereign (Texas Prolific). in the number of buds that will grow when used for propagation purposes. The buds made no apparent growth in storage. The type of cambial activity that results in slipping of bark, stimulated during the seasoning process, did not proceed to the extent that new cells formed in storage, though the bark continued to slip during the entire storage period. Cross sections from lots of seasoned bud wood that had been held in cold storage for 28 days showed a cambium region indistinguishable from that of normally seasoned bud Wood. No decrease in amount of starch in any of thetissues was apparent at that time. In contrast to this, buds held at 80° to 85° F. for 28 days had grown out an inch or more. The starch had disappeared from all tissues held at the higher temperature and sections from it show that new vessels had formed. The practical utility of holding seasoned buds in storage appears especially significant when it is remembered that nurserymen and propa- gators frequently experience difficulty in getting bud wood to season at the proper time. This difficulty may be due to cool weather or lack of consistency in the response of bud wood toseasoning conditions. Propa- - L- ma“. m“. . . ..-,_.;.._..m~ . m, n. THE STORAGE AND SEASONING OF PECAN BUD WOOD 15 gators who use storage buds occasionally have to suspend work, perhaps during a critical period, on account of a lack of properly seasoned bud wood; likewise it happens that the use of bud wood is often delayed by rain or other unfavorable weather conditions, or by other causes; in such cases it deteriorates. It is more convenient to have bud wood seasoned and ready for use than to have to anticipate a need for it and make preparations for its use 3 or 4 days or a week ahead of time. Further, nurserymen who follow a practice of selling bud wood might be expected to have a greater demand for wood than can be used 0n delivery than for wood that will require a period of seasoning. Some preliminary work in storing fresh wood indicates that such wood can be held practically as long as seasoned wood. Here, however, the utility involved is not so much a matter of convenience as the probability of getting better buds at the time they would be stored than might be available later in the season. STUDIES RELATING TO INTERNAL CHANGES INVOLVED IN SEASONING The varietal response of bud wood in seasoning suggests clearly that factors other than those of environment influence the process. For this reason an attempt was made to determine the more obvious internal changes that occur in connection with the seasoning process. This involved rest- period investigations and a study of starch translocation, vessel develop- ment, and the connection of bud enlargement with these processes. Relationship of Rest Period to the Time Required for Seasoning It has been shown that the length of time required for seasoning is dependent among other things upon the date of cutting the bud wood, upon the date of seasoning, and upon the variety used. These facts suggest a definite relationship between the process of seasoning and the natural breaking of’ the rest period in spring. Such a relationship has not been fully established, however, since the seasoning process involves primarily the cambium region while most rest- period studies have been concerned with bud activity, with diameter in- crease, or with the reaction of cambium near wounds. On the other hand, the small amount of definite study of cambium behavior in rest-period investigations would seem to indicate the possibility that it follows the behavior exhibited by buds. Jost (12) cites Hartig as showing that callus formation and root development in cuttings, both products of cambium activity, occur during the rest period. In addition, Jost reports experiments of his own leading to the same general conclusions. Simon (20) observed that callus formed from the cambium on cut sur- faces of cuttings as a wound reaction even during the winter rest but that it was produced more readily and ultimately in greater quantities from 16 BULLETIN NO. 478, TEXAS AGRICULTURAL EXPERIMENT STATION cuttings not in the resting condition. certain other physiological functions, so far as not inhibited by outer con- ditions, continue their course. Curtis (5) believes that true rest of woody cuttings is shownlonly by buds and that callus formation, root development, and root growth are independent of the rest period. In reporting the behavior of Ligustrum ovalifolium cuttings treated with potassium permanganate solutions he considers that the treatments did not break the rest period of the whole cutting, since bud development was alike on treated and untreated cuttings. Perhaps it is because a great deal of the rest-period investigation has been done in Europe, where the pecan is very rare, that no information is available as to its rest-period behavior, except a statement by Howard (9) that species of Hicoria are refractory in regard to ending the rest. The difference in seasoning of bud wood cut early and that cut late (Tables 2 and 3) indicates that removing wood from the tree and storing it at temperatures slightly above freezing delays the breaking of the rest period of the cambium, and that the influences governing the end of the rest period are operative in wood remaining on the tree and not fully operative in wood held at temperatures slightly above freezing. The fact that wood cut on a given date, early or late, seasons in a shorter period in late spring than in late winter, shows that the storage conditions do not completely suspend the ending of the rest period. These two rather con- tradictory manifestations suggest that the breaking of the rest period depends on more than one factor, one (or more) being affected and one (or more) being unaffected by low temperatures. During the rest period, callus forms freely at cut surfaces during sea- soning and bark slips in the region of a wound before the entire bud stick becomes seasoned. Apparently then wounding is a treatment that ends, directly or indirectly, the rest period of the cambium. It will be observed later that expanding buds have the same effect. Certain rest-breaking treatments were used early in January of 1932 on Delmas and Stuart bud wood cut fresh from trees. Buds of wood that had been previously subjected to ether gas for 24 hours began vigorous growth before buds of the checks showed any signs of activity but etherization had no direct influence upon slipping of the bark. Buds of scions treated with ether grow and burst their scales before bark of the entire bud stick will slip; following bud growth, bark in regions adjacent to growing buds begins to slip and ultimately this region extends to include the entire bud stick. In contrast to this, in late spring after the rest period has ended normally the degree of cambial activity necessary for the slipping of bark precedes the bursting of buds. This is true of both storage bud wood and twigs which remain on the tree. In brief, the studies herein reported show that cambium activity as measured by slipping of the bark before cell division begins, is limited by He concludes that the rest period is l not a time of complete inactivity but simply one during which only certain ‘ growth functions are brought to a standstill and that respiration and _- w.‘ A. .@......-- a .w..;__..ndg.__.._g.,d.._.._s._ I terial 0n a sliding microtome. This mwt_qt"ll,iv-w