الفهرس 
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Abstract
Three experiments are carried out to investigate the effect of light duration, light intensity and night temperature on growth and tuber formation of polato plant. Four other experiments are performed to investigate the effects of planting date and nitrogen level in both spring and fall plantings on growth, tuber for mation, sugars and starch contents of potato plants. Variety aplpha is used in these studies. The results obtained show that under ten hours light duration, plant growth is accelerated, particularly at early stages of growth. The plant is shorter under short day conditions than long day. Number of tubers seems to be higher on short day at the early stages of growth. Under full day light intensity, vegetative growth, dry weight and number tubers is higher. 150c night temperature is the suitable degree for the dry weight.