Leaf Physiological and Root Morphological Responses of Some Fruit Bearing Vegetables as Affected by Different Rates of Nitrogen

The aim of the present study was to determine genotypic differences in shoot growth, leaf physiological and root morphological development of some fruit bearing vegetables at different rates of nitrogen supply. A short-term hydroponic experiment was conducted between January and February in 2018 by using a non-flow nutrient film technique (NFT) in a controlled growth chamber for 28 days. Four different fruit bearing vegetable species (eggplant, tomato, watermelon and pumpkin) were evaluated under three different nitrogen levels (low: 0.3 mM, medium: 1.5 mM and high: 3.0 mM N) in a completely randomized block design with four replications. Results indicated that shoot and root growth, leaf physiological development and root morphology of four plant species were significantly (P<0.001) affected by different rates of N supply. Highly significant (P<0.001) genotypic differences were found between plant species and the growth response to supplied N, i.e. the interaction between N rate and plant species was also highly significant (P<0.001). Increasing N supply, had a substantial positive effect on the shoot growth and leaf physiological development, while the root growth and morphology was negatively affected. Based on shoot biomass yield pumpkin was characterized as ‘N-efficient' whereas eggplant as the ‘N-inefficient' species under low N supply. Similar genotypic variation existed at medium or high N rates between species and thus pumpkin was characterized as ‘N-responsive' whereas eggplant as ‘N-nonresponsive'. The results clearly indicated that ‘N-efficiency' and ‘N-responsiveness' of pumpkin are more closely related to vigorous and active root system occurred with a uniform assimilate allocation to the roots that contributed to high shoot N uptake and high photosynthesis