Effect of Defoliation and Depodding on Long Distance Translocation and Yield in Y‐Shaped Soybean Plants 1

Abstract

During early vegetative growth, field-grown soybean plants were forced to develop a Y-shaped stem consisting of two symmetrical branches. After flowering, the plants were treated by selectively removing leaflets and pods from the two branches. One-third of the leaflets and one-third of the pods were removed from each of the branches of plants subjected to the even treatment whereas two-thirds of the leaflets from one branch and two-thirds of the pods from the other branch were removed in the uneven treatment. The photosynthetic rates per unit leaf area and the rate of growth of the pods were similar for all branches. Since the leaf area of one branch was three times the leaf area of the other branch in the uneven treatment, long distance translocation from one branch to the other was necessary to support the growth of the seeds. The rate of abortion of the seeds appeared to be much less on the branches having fewer pods in the uneven treatment. The final yield (g/m2) for each of the individual branches of both treatments was the same, indicating that the uptake of carbohydrate by the seeds was not limited by resistance to long distance translocation.