Improvement of vegetative growth through physiological and agronomic approaches to increase the yield of mungbean

Rate of basic vegetative growth phrase before flowering in mungbean was extremely low. In variety U-thong l, dry matter accumulation, crop growth rate (CGR), net assimilation rate (NAR) and leaf area index (LAI) were small especially during 2-4 weeks of growth. Improvement of basic vegetative growth could be done by selecting varieties which had higher vegetative growth rate. Improvement of agronomic practices such as increasing plant populations or irrigation would also increase the basic vegetative growth and also increase the yield of mungbean. Indeterminate growth habit of plant in which the vegetative growth still occurred after mungbean had flowered and paralally continued as pod and seed developed. The indeterminate growth inhibited the yield of mungbean by directing portion of organic food reserve to the vegetative organs and reduced the amount of food reserve for supporting pods and seeds. Even the assimilates from the photosynthetic process during pod and seed development period had to be divided to both vegetative organs and reproductive organs. It was clearly demonstrated from the experiments that, the indeterminate growth habit of mungbean caused the reduction in translocation efficiency of assimilate from vegetative to reproductive organs, and resulted into decreasing the amount and size of yield components, harvest index, and subsequently decreased the yield. The possibility of using growth retardant chemicals to inhibit or reduce the indeterminate growth of mungbean. Although, we were not able to demonstrate clearly that indeterminate growth habit was reduced after spraying with some growth retardant chemicals. However, Mapiquat chloride at the rate of 200 ppm sprayed before flowering, increased the dry matter accumulation, pod production and yield of five mungbean accessions tested. Spraying Ethaphon at the rate of 200 ppm before flowering, although did not improve the growth and dry matter as it happened with Mapiquat chloride, however, Ethaphon improved the uniformity of pods and seeds maturity, increased the translocation efficiency of assimilate from vegetative to reproductive components and subsequently increased the yield of mungbean.