Author : Paje, Maria M.M.

Summary : This study sought to characterize the adaptability of string bean (Vigna sesquipedales Fruw.) under pre-rice and post-rice conditions. Morphological and physiological characteristics as well as earliness, germinability, and seedling establishment were determined. Findings showed that string bean is generally not adaptable to pre-rice conditions. The pre-rice condition was characterized by drought during the early growth of the plant and three cycles of waterlogging from the peak of the vegetative growth until the plants flowered and formed pods. There was a considerable reduction in yield because of markedly reduced total leaf area, reduced total shoot dry matter, and degeneration of the tap roots as well as the inability of the plants to produce branched surface rooting. The crop also exhibited poor germinability and non-uniform growth of seedlings under low levels of soil moisture and low levels of osmotic potential. On the other hand, more conclusive evidence regarding the adaptability of string bean to post-rice conditions was obtained. The post-rice condition was characterized by water-saturated soil from germination and early seedling growth and thereafter a continuous depletion of soil moisture until the crop matured. Fresh pod yields were comparable to the control. The following mechanisms were responsible for the crop's adaptability: 1) reduction in total leaf area; 2) maintenance of high relative water content; 3) increased stomatal resistance; and 4) consequent decrease in the amount of water lost through transpiration.