Morphological and physiological studies on occurrence of aborted seed in soy-bean. : III. Type of aborted seeds and their frequency, position in pod and the time of occurrence

Abstract

The causes for occurrence of aborted seeds in the soy-bean pod are classified as follows : 1. Existence of ovule, failed in functioning the fertilization. 2. Collapse of embryo. 1) There are two types identified in the former case ; one is of extremely tiny structure and the other is deformed into "pod in pod". In this case, we could find out neither abnormality nor abortion of pollen and ovule throughout the morphological and physiological observations. The causes for fertilization failure which recognized more frequently at basal ovule are accounted for the protandry that behaved slightly in general and also for position of basal ovule, which is located farther from the stylar end and disadvantageous inreceiving pollen. However, on the other hand the basal ovules are situated at the position rather favorable for absorbing water and nutrients, and therefore the infertilized basal ovule, where the embryo-sac has been degenerated, developed rarely into ovary shape or small pod, shape. 2) As the second case, the collapse of embryo means the ovule that fertilized but failed to develop into mature seed. There are clearly found two critical peaks, one is at pro-embryo and the other is at cotyledonous stage. Namely, the arrested development is observed at the stage of urgent growth of embryo and then at the time of remarkable reduction of water content from the ovule. Presumably the causes for collapse of embryo are as follows ; the one is due to the insufficient water supply and the lack of proper nutrients at the time of vigorous growth of embryo, and the other cause is that at the urgent growth stage the formation of embryo is unbalanced with the vigorous division and growth of embryo-cell.