STUDIES ON THE PHYSIOLOGICAL PROPERTIES OF NITROGEN PHOSPHORUS AND POTASSIUM IN WETERMELON PLANTS
Chen Minzhi and Tao Qinnan ( Zhejiang Agriculture University ) Chen Yunxiang ( Jin Hua Agriculture Science Research Institute )
There are obvious interrelations between the metabolization of nitrogen and carbon in leaves, between the growth of upper ground and underground part in watermelon plants. The physiological role of nitrogen, phosphorus and potassium in watermelon plant has its own properties that the processes of metabolism are sensitive to nitrogen but moderate to phosphorus and potassium. Applying potassium and appropriate amount of nitrogen could promote greately nitrogen metabolization in leaves, with increasing the proportion of protein-N to non-protein-N and the content of chlorophyll a and total chlorophyll. It will also strengthen the coordinate growth of plant and the expansion of fruit. But the activities of matabolism all decreased by applying excessive amount of nitrogen. Nitrogen does not obviously affect the activity of sucrose-phosphate synthase ( SPS ) , but increase that of acid sucrose Invertase in leaves, therefore, it is unfavourable for the accumulation of sucros in watermelon. Potassium not only increase the activity of SPS, but also decrease that of acid sucrose Invertase. It is most favourable for the accumulation of sucrose and promotion of the fruit quality There are positive interactions between nitrogen, phosphorus and potassium.The reasonable and joint application of these fertilizers could achieve a ideal output and quality of fruit.Statistics and analysis show that Under the conditions of the field test the optimum applicate amount of three fertilizers are. N 10kg/mu, P2O5 5.9kg/mu, K2O llkg /mu.