THE ANATOMY OF THE ABNORMAL SWELLINGS ON THE STEMS OF SOME VARIETIES OF SOYBEANS

Abstract

WHILE GROWING several species of plants in the greenhouse in short and long days and at different temperature levels to determine the environmental conditions essential to the induction of blossom buds, a type of response was observed in Glycine Max Merr., var. Illini, var. Manchu 3, and var. Minsoy in ce'rtain environmental conditions unlike that of plants of any species heretofore studied by the writer. In short days and at a cool night temperature, a swelling or thickening of the third and fourth internodes from the stem-tips and a clustering of short, swollen, and unripened pods at the nodes was characteristic of many plants of these varieties (fig. 1). A limited tendency for this condition to occur in some plants in continuously cool long days has been observed. Occasionally plants of soybean grown in the field exhibited a similar condition. The internodes near the stem-tip were short and enlarged, the plants often developed little beyond the blossom stage, and when fruits were formed, they were short and stubby. These abnormal plants remained green while the normal ones had mature fruits and had dropped their leaves (fig. 2). It was noted that at least seventy varieties, in breeding and trial plots of the Department of Agronomy of the College of Agriculture, showed this type of abnormal plant. These abnormal plants were quite infrequent except in one variety in which this habit of growth appeared in 10 to 15 per cent of the population. These types of soybean plants are referred to as duds by soybean specialists and growers. Psarev (1940) studied the variety Illini and stated that under the influence of short days the stems reached considerable thickness so that some of the internodes assumed the shape of abnormal swellings or tumors. He concludes that the diameter of short day plants was due to cambial activity, although he does not state whether he was referring to plants with swollen internodes or to normal plants. In either case this is the opposite of what nas been found in a study of the anato'mical structure of 'plants during the induction of blossoms (Struckmeyer, 1941). Psarev (1940) does not mention induction in his paper, but we have learned from our observations that this variety when grown in different environmental combinations is an indeterminate type and is induced to blossom in both