The present study was carried out at the Experimental Farm of Mallawi Agric. Res. Station , Minia, in 2005 and 2006 seasons, to investigate the responses of cotton cultivar Giza 83 grown in upper Egypt to some foliar treatments of ascorbic acid (vitamin C) and citric acid , both were applied twice , at the start and peak of flowering, at the concentrations of 250 , 500 and 1000 ppm, using tap water as control. The obtained results could be summarized as follows : Foliar application of ascorbic

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... cid ( AA) at the concentration of 500 ppm resulted in significant increases in leaves content of chlorophyll a, b and carotenoids , plant height, number of open bolls /plant and seed cotton yield in both seasons, numbers of main stem nodes and fruiting branches /plant and boll weight in 2006 season, and it decreased fruit shedding % in 2005 season only in comparison with the control. Similar trend was obtained by 1000 ppm AA but the differences with the control were not always significant, and it significantly decreased earliness % in both seasons. The concentration of 250 ppm AA significantly increased leaves content of chlorophyll b and plant height in 2006 season only. Citric acid (CA) at the concentrations of 500 and 1000 ppm significantly increased leaves content of chlorophyll a , number of open bolls /plant in the two seasons , plant growth parameters and boll weight in 2006 season, and seed cotton yield in 2005 season. Only 1000 ppm CA significantly increased seed cotton yield and decreased fruit shedding % in the two seasons, while 250 ppm CA exerted no significant effects on all studied traits in both seasons. It could be concluded from results of this study that most used treatments of ascorbic acid and citric acid improved growth and fruiting performance of cotton plants grown under the naturally occurring climatic conditions of upper Egypt, however, the most consistently positive effects and the best results in general were obtained by spraying ascorbic acid at the concentration of 500 ppm or citric acid at the concentration of 1000 ppm.