An inbred line of popcorn and a line that contained teosinte germ plasm were compared with respect to the inflorescences of the numerous tillers produced by plants of these lines. In both lines, all terminal and axillary apices of the tillers initiated inflorescences. No axillary tassels were found on the tillers of either line. On a popcorn tiller, a terminal inflorescence was either a tassel, a tassel that bore a few scattered kernels, an ear, or an ear that had basal tassel branches. Every tiller of the  teosinte-contaminated  corn had a terminal tassel

Sass, John E.

English

University of Northern Iowa

Proceedings of the Iowa Academy of ScienceVolume 69 | Annual Issue Article 221962Development of Axillary Buds of the Tillers of ZeaJohn E. SassIowa State UniversityCopyright © Copyright 1962 by the Iowa Academy of Science, Inc.Follow this and additional works at: https://scholarworks.uni.edu/piasThis Research is brought to you for free and open access by UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academyof Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu.Recommended CitationSass, John E. (1962) "Development of Axillary Buds of the Tillers of Zea," Proceedings of the Iowa Academy of Science: Vol. 69: No. 1 ,Article 22.Available at: https://scholarworks.uni.edu/pias/vol69/iss1/22142 IOWA ACADEMY OF SCIENCE [Vol. 69 ing their growth. Botan. Rev. 20: 201-225. Sacher, J. A. 1956. Observations on pine embryos grown in vitro. Botan. Gaz. 117: 206-214. Sterling, C. 194!). Preliminary attempts in larch embryo culture. Botan. Gaz. 111: 90-94. Stone, E. C. 1948. Auxin and respiration changes during stratification of sugar pine, P. lambertiana Dougl., seed and their relation to subse-quent embryo growth. Ph.D. Thesis. Unviers1ty of California, Berkeley, California. White, P. R. 1954. The Cultivation of A..nimal aml Plant Cells. 239 pp. The Ronald Press Co., New York. Development of Axillary Buds of the Tillers of Zea 1 Abstract. An inbred line of popcorn and a line that con-tained teosinte germ plasm were compared with respect to the inflorescences of the numerous tillers produced by plants of these lines. In both lines, all terminal and axillary apices of the tillers initiated inflorescences. No axillary tas-sels were found on the tillers of either line. On a popcorn tiller, a terminal inflorescence was either a tassel, a tassel that bore a few scattered kernels, an ear, or an ear that had basal tassel branches. Every tiller of the "teosinte-contami-nated" corn had a terminal tassel. The recent revival of interest in the development of axillary buds of Zea has been due in part to agronomic considerations, in particular the production of commercially valuable hybrids that produce more than one harvestable ear on a plant. The breeding program has thus called for a search for multiple-eared types of maize as possible sources of the desired germ plasm. Some lines of popcorn are typically multiple-eared and also exhibit con-siderable tillering, a character that is undesirable in field com. The introduction of germ plasm of teosinte, Euchlaena mexicana into Zea has yielded plants that have many ears and many tillers. These characteristics suggested examination of the shoot apices, especially the apices of the axillary buds, as well as all meriste-matic apices of tillers. The structure of the pistillate inflorescence of maize had been described in detail in past years, and the extensive literature on the subject has been reviewed by Bonnett ( 1948), and Kiessel-bach ( 1949). Studies that were related to specific agronomic 1 Journal Paper No. J-4333 of the Iowa Agricultural and Home Economics Experi-ment Station, Ames, Iowa, Project No. 1335. 2 Professor of Botany, Department of Botany and Plant Pathology, Iowa State Uni-versity, Ames, Iowa. 1Sass: Development of Axillary Buds of the Tillers of ZeaPublished by UNI ScholarWorks, 19621962] DEVELOPMENT OF ZEA TILLERS 143 problems, such as barrenness, have been reported by Sass and Loeffel ( 1959) and Sass ( 1960). The lines that were used for the present study were a very early popcorn, designated Canadian ::1±3, and a yellow dent corn that contains teosinte germ plasm. Diagnoses were made of the stage of inflorescence development in the more or less elon-gated axillary shoots of the main stem and of the tillers. The data presented here will be limited to the relative length, and the status of floral development of the inflorescence axes which become the kernel-bearing cob, at successive nodes of the main stem and tillers, at specified dates after planting.3 OBSERVATIONS AND DISCUSSION The possible occurrence of precocious axillary buds in the embryos of the foregoing types of corn was investigated, and it was found that axillary buds do not occur in the mature, dor-mant embryos. Furthermore, well defined bud primordia do not become evident until several days after germination. The acro-petal formation of axillary buds on the main axis and basipetal transition of these buds to the flowering phase follow the pattern that has been known to occur in many highly diverse types of com. Figure 1 shows the growth habit of a typical plant of "Cana-dian 3" popcorn, 59 days after planting. Plants of this line con-sistently have three "empty" leaf axils between the tassel and the major ear. The meristematic activity that initiates bud for-mation is detectable in these upper axils of seedlings, but no bud is evident at anthesis. The lowermost tiller, # 1 in the figure, developed from the lowest surviving axillary bud. The major ear, on which silks had emerged, developed from bud 6, counted acropetally. Thus, this ear is in the axil of the fourth Ieaf below the tassel. An axillary shoot may be a small, unexpanded bud, a long leafy tiller, or a large ha.rvestable ear on a leafy shank. The terms sucker and stool are also used for elongated leafy axillary branches. The lengths of these axillary structures were measured from the node to the tip of the longest leaf of the tiller. Table 1 gives these lengths on the plant shown in Figure 1. Tillers were analyzed by dissecting out the bud in the axil of each leaf of the tiller, as well as at the apex. The total length of an axillary bud was found to be of less significance than the length of the inflorescence axis and the extent of floral initiation on the axis. The term "cob" is used herein for a definitely pistil-• The plants used in this study were obtained from the breeding plots of the Agronomy Department, by courtesy of Dr. W. A. Russell, Agronomy Department. 2Proceedings of the Iowa Academy of Science, Vol. 69 [1962], No. 1, Art. 22https://scholarworks.uni.edu/pias/vol69/iss1/22144 IOWA ACADEMY OF SCIENCE [Vol. 69 r. '· t'. t Figure 1. Growth habit of typical plant at anthesis, 59 d ays after planting. Table 1. Length of each tiller (axillary branch) of the plant shown in Figure 1. The terminal tassel of the main axis had been shedding pollen, 59 days after planting. Node 9, 8, 7; empty Node 6; 12 cm cob with emerged silks " 5; 42 cm tiller 4· 32cm " 3; 31 cm " 2· 78cm " 1; 87 cm " (from lowest surviving bud ) 3Sass: Development of Axillary Buds of the Tillers of ZeaPublished by UNI ScholarWorks, 19621962) DEVELOPMENT OF ZEA TILLERS 145 late inflorescence CL'Cis, regardless of its length. The pertinent diagnostic characters are illustrated in Figures 2-4. In several lines and hybrids that have been studied previously, and in Canadian 3 popcorn, the axillary buds undergo floral transition when the axis is 1 to 2 mm long, and a l.5 mm axis may have spikelet primordia on its lower half. The 3.5 mm axis shown in Figure 2 has paired spikelet primordia on the lower 3.4 mm, and only the terminal 1 mm is still meristematic. Figures 1-5. Inflorescences of "Candian 3" p~pcorn . Figure 2. A 3.5 mm inflorescence with paired spilcelet primordia along most of its length. Figure 3. An 11 mm inflorescence with paired ovaries and a short undifferentiated apex. Figure 4. A 20 mm "ear," with elongating silks and a very s1nall undifferentiated apical m eristem. Figure 5. A terminal ear with basal tassel branches, on an 87 cm leafy tiller. Before an inflorescence attains a length of 10 mm, the lower florets become clearly pistillate, style primordia may be evident, and the undifferentiated apical region may be little more tl:tan 1/10 of the total lengtl1 (Fig. 3). A 20 mm cob invaraibly has long styles (silks ) on the lower ovaries, and the residual meriste-matic apex, which is still elongating, may be a small fraction of the total length. Table 2 gives the diagnostic data on tiller l of Figure 1. All ~urviving axillary b~ds had become inflorescences. At the basi-petally successive nodes, the inflorescences were shorter and had spikelet primordia along less of the total length. All tillers of this 4Proceedings of the Iowa Academy of Science, Vol. 69 [1962], No. 1, Art. 22https://scholarworks.uni.edu/pias/vol69/iss1/22146 IOWA ACADEMY OF SCIENCE [Vol. 69 plant had the same pattern of axillary bud development as tiller 1. By way of comparison with the longest tiller (Table 2), the diagnosis of the shortest tiller, located below the major ear, is shown in Table 3. Table 2. Length and stage of floral transition of the inllorescence in each axil of an 87 c:m tiller of popcorn, 59 days aftt>r planting. Terminal has basal tassel branches. Node 6; 19 mm cob; silks on basal ovaries "' 5; 22 mm cob; " "' n " 4; 16 mm cob; " " '' " 3; 12 mm coh; most of axis in transition. 2; 4 mm cob; % of axis in transition. l; aborted bud. Table 3. Length and stage of floral transition of the inflorescence in the axil of each leaf of a 42 cm tiller of popcorn, 59 days after planting. Terminal 82 mm cob, silks on all ovaries. Node 6; 16 mm cob; str,le primordia on basal ovaries ,, 5· 8 mm cob· ' " " " " " 4~ 16mmcob~ " "' " " " " 3; 18 mm cob; " " 2; 25 mm cob; " " " l; basal bud, aborted. All tillers of this plant had terminal inflorescences as follows: tiller #6, a 120 mm cob with emerged silks (the major ear in Figure 1); #5, an 82 mm cob; #4, a 45 mm cob; #3, a 28 mm cob; #2, a tassel, bearing a few ovaries with silks; # 1, a 55 mm cob with basal tassel branches (Figure .5). Additional measurements and diagnoses were obtained from tillers of Canadian 3 popcorn, collected 40 to 59 days after planting. The course of floral initiation and development in the axillary apices was so similar to the data in the foregoinf!. tables that detailed tabulation would be repetitious. Only the terminal inflorescences, which may presumably produce harvestab1e ears, merit special attention here. Of the 28 apices examined, 5 had a tassel, 18 had an ear, 3 had an ear and some tassel branches, and 2 had a tassel bearing a few ovaries. No vegetative apices were found in the 40-day ancl later collections. Although the apex of a tiller can produce an entirely staminate inflorescence, or one that has both staminate and pistillate florets, the predomi-nant type of terminal inflorescence on the tillers of this popcorn was a purely pistillate ear. The limited supply of seed of "toesinte-contaminated" maize that was available yielded plants that had 3 to 6 tillers. Pre-liminary sampling of 3-tillcred plants collected 56-60 days after planting showed that the apices of the tillers were either vegetative or in early floral transition. Subsequently, plants that had 4 to 6 tillers were sampled between 60 and 76 days. Only staminate terminal inflorescences were found on the 33 tillers that were available, differing strikingly from popcorn, which 5Sass: Development of Axillary Buds of the Tillers of ZeaPublished by UNI ScholarWorks, 19621962 DEVELOPMEl\T OF ZEA TILLERS 147 bore predominantly pistillate inflorescences in comparable posi-tions. Further comparison with other types that produce many long, leafy tillers will be needed to determine whether the ex-tent of elongation of an axillary shoot is correlated with the shift of inflorescence primordia to either staminate or pistillate flower-ing. It is possible that environmental condiitons, especially condi-tions of stress, may influence the type of terminal inflorescence that is produced on tillers. Literature Citecl Bonnett, 0. T. 1948. Ear ancl tassel development in maize. Ann. Mo. Bot. Gard. 35:269-287. Kiesselbach, T. A. 1949. The structure and reproduction of corn. Nebraska Agr. Exp. Sta. Bui. 161. Sass, J. E. and Frank A. Loeffel. 1959. Development of axillary buds of maize in relation to barrenness. Agronomy Jonrnal 51 :484-48fi. Sass, John E. 1960. The development of ear primordia of Zea in relation to position on the plant. Proc. Iowa Acad. Sci. Vol. 67, pp. 83-85. The Latex System of Some Native Spurges ROBERT c. LOMMASSON1 Abstract. Eight species of Euplwrbia in the subg!'.nus Chamaesyce were invcstigakd anatomically from collections made in Kansas. The latex system is composed of branched nonarticulated laticiferous cells. These laticifers arc dis-tributed regularly or apparently at random through the cor-tex of root and stem dependinµ; 1.ipon the species. \Vhen the outer cortex is destroyed by peridenn as in the root or ~he inner cortex by crushing as in the stem, them are still hti-ciferous cells apparent in these two organs. The most ex-tensive branching network of bticifers is developed in the leaf. ;\'o anastomoses were found. The con1monest latex system in the leaf was found to be the subcpidermal system. The latex system of plants was one of the features subjected to investigations of various sorts during the 19th century. By the middle of that ccnturv sufficient research on the structure of the latex system had b~cn completed to get a fairly accurate idea of the elements composing those systems in a few of the more common families. During the latter part of that century investigations as to the function of the latex system had prodnced some theories which were in disagreement (De Barry, 1884; Groom, 1889). Not much progress in the understanding of the function of latex has been made even until today. Textbooks in plant physiology gen-erally omit any discussion of latex. 1 Department of :Potany, University of Nebraska, Lincoln 8, Nebraska 6Proceedings of the Iowa Academy of Science, Vol. 69 [1962], No. 1, Art. 22https://scholarworks.uni.edu/pias/vol69/iss1/22

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