The 2011 ASHS Annual Conference

Both macro(N,P,K,Ca,Mg,S) and micronutrients(Cu,Zn,Mn,Fe, B,Mo) are fed hydroponically to plants in the production of greenhouse grown crops including cucumbers. Even though the amount of micronutrients required by plants is miniscule in comparison to that of macronutrients, yet micronutrients exert a great influence on plant growth. Most of the micronutrients serve as cofactors of antioxidant enzymes such as superoxide dismutase, catalase, peroxidase etc. and are incorporated into structural molecules. Since composts contain micronutrients (Kannangara et al, 2006) in addition to growth promotion and disease suppression properties (Kannangara et al, 2000) in this study we examined whether composts can provide adequate micronutrient for growth and production of cucumber plants in the greenhouse. Three sets of plants were grown. One set grown on sawdust potting medium was fed with hydroponic solution containing both macro and micro nutrients. A second set grown on sawdust potting medium was fed with hydroponic solution devoid of micro nutrients. A third set grown on sawdust potting medium amended with 10% vermicompost was fed with hydroponic solution devoid of micro nutrients. The activities of leaf antioxidant enzymes and isoenzyme profile of antioxidants as determined by native gel electrophoresis, leaf chlorophyll content and cucumber fruit number and fruit yields were examined. Leaf chlorophyll content, fruit yield and fruit number in plants grown without micronutrients on sawdust alone were significantly reduced compared to those grown with micronutrients and those grown without micronutrients but had 10% vermicompost compost in the potting medium. Fruit yield of plants grown without micronutrients but had compost in the potting medium were slightly higher than plants that received both macro and micro nutrients. Significant differences in the antioxidant activity and the isoenzyme profiles of the antioxidants were noted between plants grown with and without micronutrients. For example, peroxidase activities which reflect plant stress were significantly higher in plants grown without micronutrients on sawdust than those grown on potting mixes containing compost.