EFFECT OF ZINC-DEFICIENCY ON CHLOROPHYLL CONTENT, PHOTOSYNTHESIS AND WATER RELATIONS OF CAULIFLOWER PLANTS

Cauliflower (Brassica oleracea L. var. botrytis) plants subjected to Z n deficiency showed decreased leaf water potential and transpiration r ate, and increased leaf thickness, and accumulation of sugars and star ch. Zn-deficient leaves also showed decreased photosynthetic rates (P( N)) and compensation irradiance and increased apparent quantum efficie ncy. Decrease in leaf chlorophyll (Chl) content due to Zn deficiency, though significant on fresh mass unit was insignificant on leaf area u nit. Decreased P(N) was not attributable to the effects of Zn deficien cy on Chl content upto 51 d of treatment. Zn-deficient leaves showed a n insignificant decrease in photosynthetic O2 evolution at saturating irradiance and CO2 supply; significant decreases in P(N), stomatal con ductance and intercellular CO2 concentration when the leaves were supp lied with CO2 at atmospheric concentration suggest that stomatal limit ation contributes significantly towards decreased P(N) in Zn-deficient leaves.