Studies on the reproductive physiology of common beans, Phaseolus vulgaris L. VI

Abstract

This paper reports the results of the studies on the differentiation of flower buds and their develop-ment in the common beans, Phaseolus vulgaris L. Two tall varieties, Kentucky Wonder and Kinu-gasa, and two dwarf varieties, Masterpiece and Nagauzura, were tested. They were sown on May 15, 1949; but Kentucky Wonder was sown four times, i.e., on April 30, May 15 and 30, and June 14. 1949. (1) The differentiation of flower buds takes place in a very early stage of bean plants. Samples taken at 25 days after seed-sowing contain rather fairly many flower buds developing to some extent in dwarf varieties, and only small number of flower buds of the early stage in tall varieties. At this stage the seedlings have only four or five leaves and are still about 7cm tall. (2) While in dwarf varieties the flower buds differentiate and develop comparatively in uniform state and in short period throughout the nodes of the main stem and lateral branches, in tall varieties the flower buds are formed at the sixth or seventh node in the main vein at first and then successively at the upper nodes of main vein and lateral veins. At about 30 days after sowing tall varieties contain the flower buds as many as the number of the flowers that would open during the whole growing season. (3) Relations between the sowing dates and the formation of flower buds are studied in Kentucky Wonder. The results show that the processes mentioned in the above paragraph do not seem to differ according to the sowing dates. (4) The later the sowing date becomes, the more the number of differentiated flower buds increases and also the faster the flower buds develop. (5) The very young plant contains many rapidly developing flower buds which consist of various stages of development, and on the other hand it consumes much nutrients in plant growth. The environmental factors at such young stage of plant, therefore, seem to have some significant effects on the formation of flowers and subsequent-ly on the flowering and flower-dropping.