Nitrogen-15 Uptake by Eggplant Under Sodium Chloride Stress
Plant growth and nutrient uptake are adversely affected under salt stress conditions. This study was conducted to examine the effects of NaCl stress on growth of eggplant (Solanum melongena L., cv. Syria), and 15N uptake and distribution in plant shoots and roots. Absorption pattern of 15N by eggplant from normal (−0.03 MPa osmotic potential) and NaCl salinized (−0.3 and −0.6 MPa osmotic potentials) nutrient solutions was investigated in a growth chamber. The 21-d-old seedlings were grown for 7 d in complete Hoagland solution before and 7 d after the completion of salt treatments. This was followed by 3-d growth in minus N solution with respective salinity levels, and a 90-d 15N uptake period after 15NH415NO3 addition to nutrient solutions. Nutrient solutions were sampled at 5-d intervals for 15N disappearance from the pots (plant absorbed). Plant tissues were analyzed for distribution of 15N in shoots and roots. Lowering the osmotic potential of culture solution decreased total N and 15N uptake by plants at all salinity levels. Increasing salinity decreased dry matter production and water uptake to a greater extent than 15N absorption. Nitrogen-15 concentration was substantially higher in shoots and roots of salinized plants as compared with the controls at the 90-d harvest. Only at the 30-d harvest was 15N concentration in shoots significantly higher than in roots at each salinity level. Any level of NaCl in the root medium appears to be detrimental to eggplant growth in terms of dry matter production as well as nitrogen (N and 15N) and water uptake.
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