Abstract
A study was conducted to examine the differences among cultivars and the nature of inheritance in the leaf orientation movements of kidney bean ( Phaseolus vulgaris L.). The left leaflet of the first or second trifoliate leaf of each plant grown in a pot was exposed to the artificial light. The plant was exposed to the light at an angle of 30 degrees from the horizontal onto the pulvinule and leaf blade from the base of the leaflet. Changes of vertical (up- and down-ward) and twisting (rotative on midrib) angles of each leaflet were measured during the period of light exposure. Four cultivars examined were classified into two types: one oriented the leaflet surface more perpendicularly toward the incoming light, and the other oriented more parallel toward the light. In the former type a considerable change in the vertical angle was also observed, and such a cultivar was designated as "Vertical type"; while a great change in the twisting angle was seen in the latter, which was therefore designated as "Twisting type". These two movements were seemingly, although imperfectly, independent of each other. The leaflet orientation movements of the vertical type appeared to be controlled by two kinds of dominant genetic factors with extensive modifiers, which give the plant leaflet a large vertical and small twisting movements.
