EFFECT OF DIFFERENT REDUCED LIGHT LEVELS ON THE MORPHOLOGY, PHYSIOLOGY AND YIELD OF FOUR SELECTED VINE CROPS

Abstract

EFFECT OF DIFFERENT REDUCED LIGHT LEVELS ON THE MORPHOLOGY, PHYSIOLOGY AND YIELD OF FOUR SELECTED VINE CROPS BY MD. MOINUL HAQUE A study was carried out through four separate experiments at the farm of the Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur. Four vegetables (i.e. cucumber, ash gourd, sponge gourd and yard long bean) were included in separate experiments. The objective of this study was to investigate the morpho-physiological changes and yield performance of these summer vegetables under four different levels of light (100, 75, 50 and 25% PAR). In studied vegetables some of the morphological characters like main stem length, internode length, and individual leaf area increased, whereas main stem diameter and numbers of leaves per plant decreased due to the reduced light levels. At 50% PAR number of leaves per plant did not decrease significantly in cucumber and yard long bean but in ash gourd and sponge gourd leaves per plant decreased markedly. Physiological characters like leaf chlorophyll and leaf nitrogen content increased but specific leaf weight (SLW), leaf B-carotene, stem and fruit nitrogen were decreased markedly with the reduction in the amount of light. Chlorophyll a/b ratio was lower in cucumber at 50% PAR level and yard long bean but the ratio remained almost unchanged in ash gourd and sponge gourd at all light levels. Leaf weight ratio (LWR) remained more or less similar up to 50% reduction of PAR in cucumber and yard long bean, whereas it reduced in ash gourd and sponge gourd. Compared to 100% PAR the total dry matter (TDM) did not reduce in yard long bean, ash gourd and sponge gourd by reduction of light up to 75% PAR. But in cucumber the TDM did not reduce up to 50% PAR. The relative dry matter yield of cucumber, yard long bean, ash gourd and sponge gourd at 50% PAR were 0.90, 0.81, 0.75 and 0.76, respectively. Crop duration increased by different reduced PAR levels due to delayed flowering and longer fruit development period. Eventually at 100% PAR level the fruit yield was 11.28 t/ha in cucumber, 11.03 t/ha in yard long bean,21.03 t/ha in ash gourd and 24.90 t/ha in sponge gourd. Cucumber and yard long bean showed significant fruit yield reduction only at 25% PAR, level whereas significant fruit yield reduction were observed at 50% PAR in ash gourd and at 75% PAR in sponge gourd. The relative fruit yield at 75% and 50% PAR were 1.43 and 1.04 in cucumber, 1.08 and 0.84 in yard long bean, 0.83 and 0.57 in ash gourd and 0.75 and 0.18 in sponge gourd. However, considering relative TDM and relative fruit yield cucumber and yard long bean were found suitable for reduced light condition (50% PAR). But ash gourd and sponge gourd were more sensitive to any reduction of light compare to cucumber and yard long bean.