Morphological and Physiological Studies on Occurrence of Abortive Seeds in Leguminous Forage Crops : II. Formation of one-seeded pod in red clover

Abstract

The pod of red clover, when it matures, contains usually only one seed. But the ovary involves two ovules at its young stage. Experiments were undertaken to know of the causes concerned in formation of one-seeded pods from two-ovuled ovaries. Using plants of the variety Mammoth as materials, all their flowers were artificially cross-pollinated and examined through the paraffin method. The results obtained from three years' studies were as follows : I. At the time of flowering, (1) 30∼50 % of ovaries contained one normal and one abnormal ovules each, in the latter the embryo-sac being not normally formed ; (2) 6∼10 % contained two abnormal ovules in each ; and (3) the rest 40∼60 % contained two normal ovules. The ovaries of the case (1) should develop into one-seeded pods provided that the normal one of the ovules are fertilized. II. Even if the ovaries involve two normal ovules, as in the case (3), they might produce one-seeded pods when one of the two is not fertilized. By observation made at 48 hours after pollination, it was confirmed that (4) 20.8 % of them corresponded to above-mentioned case of one seeded pod formation. (5) The remaining 18.3 % were the ovaries consisting of two ovules both of which were non-fertilized ; while (6) 60.8 % were the ovaries containing two fertilized ovules. III. In the case (6), however, when observed on the tenth day after pollination, the two fertilized ovules never developed evenly, but one of them was arrested in its growth and degenerated without exception, so far as this experiment was concerned, and thus the ovaries grew into one-seeded pods. The degeneration was found to begin within five days after pollination.