EFFECT OF DIFFERENT REDUCING LIGHT INTENSITIES ON THE MORPHO-PHYSIOLOGY AND YIELD OF CUCUMBER

Abstract

An investigation was made to study the morpho-physiological changes and yield performance of cucumber (variety Baromashi) under different light intensities (100, 7S, SO and 2S% PAR). Main stem length, internode length and individual leaf area were increased, but main stem diameter, leaf number per plant and specific leaf weight were decreased significantly under reduced light intensities. Leaf chlorophyll and leaf nitrogen content increased but leaf ~carotene content decreased markedly with the reduction of light. Chlorophyll alb ratio started to decrease when light was lowered to SO% PAR (photosynthetically active radiation) because of the less increase of chlorophyll "a" compare to chlorophyll "b". The highest fruit number per plant (21.83) and the heaviest individual fruit (267.3 g) were recorded at 7S% PAR level. Compare to full sunlight, reduction of PAR at 2S% resulted in significantly lower fruit number per plant (6.67) and the individual fruit weight (199.3 g). The highest fruit yield was obtained at 7S% PAR level (16.09 t/ha), followed by SO% PAR level (11.73 tlha), 100% PAR level (11.28 t/ha) and 2S% level (4.S7 t/ha). Under reduced light intensities shade tolerant parameters, namely leaf number per plant, individual leaf area and leaf chlorophyll content exerted positive effect on the yield of cucumber. Consequently fruit yield did not decrease significantly up to SO'Y<,reduction of PAR level. Beyond 73.08% PAR level, fruit yield decreased at the rate of 0.0048 t/ha.