Abstract:
An intensive investigation was conducted to study the morpho-physiological changes and yield
performance of yard long bean under different light levels (100, 75, 50 and 25%). Main stem length,
internode length and individual leaf area were increased but main stem diameter, leaves plant" and SLW
decreased significantly under reduced light intensity. Leaf chlorophyll and leaf nitrogen content were
increased but leaf p-carotene content decreased markedly under reduced light levels. Chlorophyll a : b
ratio significantly decreased when light intensity was lower to 50% because of the less increase of
chlorophyll a compared to chlorophyll b. The highest number of fruits plant" (255.2) and the maximum
individual fruit weight (15.78 g) were recorded at 75% light level. Significantly the lower fruits plant"
(138.7) and individual fruit weight (11.98 g) were achieved from 25% light level. The highest fruit yield
was obtained at 75% light level (12.91 t ha") was followed by 100% light level (12.16 t ha'), 50% light
level (10.21 t ha") and then by 25% light level (5.73 t ha'). Under reduced light level shade tolerant
parameters viz. leaves plant", individual leaf area and leaf chlorophyll content exerted positive effect on
the yield of yard long bean. Consequently fruit yield did not decrease significantly up to 50% reduction of
light intensities.
