Influence of Seed Formation of Corn on Accumulation of Vegetative Dry Matter and Stalk Strength 1

C. M. Campbell MANY experimental corn (Zed mays L.) hybrids with high yield potential must be rejected because of their excessive susceptibility to lodging. On the other hand, plants which produce no ears rarely lodge. The association between high yield and high incidence of lodging in certain years generally has been attributed to the greater mechanical stresses placed on stalks of high-yielding hybrids by the weight of ears. Another possible cause might be the differential development of stalk structural tissues in highand low-yielding hybrids. The hypothesis forming the basis for this study proposes that high-yielding hybrids divert a disproportionately large amount of the net photosynthetic product to developing ears and an inadequate amount to the development of stalk-strengthening tissues. The studies of Sayre (6) and Kiesselbach (2) were concerned in part with total stalk dry matter, and those of Loomis (5) and Van Reen and Singleton (8) with the readily soluble portion of stalk dry matter. No work was found in the literature which involved both soluble and insoluble fractions of stalk dry matter. Open-pollinated single-ear varieties were studied most frequently. Sayre (6) used a double-cross hybrid, Ohio K35, and found that once grain formation began, further increases in dry weight of other plant parts stopped, and slight losses were subsequently recorded. A variety studied by Kiesselbach (2) continued to increase in dry matter of stem for four weeks after grain formation began. Thereafter stem dry weight declined to a point approximately equaling that recorded when grain formation began. Kiesselbach attributed the decline to translocation of plant substance from stalk and leaves to the ear. Corn hybrids apparently may differ in ability to continue accumulating stalk dry matter after grain formation begins. Also, type of growing season and the amount of grain produced undoubtedly influence the degree of accumulation. Stalk dry matter might fall into three broad categories: structural tissues and vascular system which are insoluble; a readily soluble fraction dissolved in the moisture of the stalk; and possibly a water-insoluble portion composed of storage polysaccharides. Barr (1) found no starch in the vegetative tissues of maize. Loomis (4) concluded that starch-like polysaccharides do not constitute an important fraction of the vegetative maize plant. In a later paper Loomis (5) reported that nearly all the carbohydrate in