Studies on Water Regime and Nitrogen Metabolism of Citrus Seedlings Grown under Water Stress

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Abstract
N metabolism of Rough Lemon and Sweet Lime citrus seedlings, growing under water stress conditions, was investigated. Total N increased in the aerial parts of the plants due to apical translocation from the roots. A 3-phase reaction pattern of the protein level to increasing water deficit was detected an activation phase at 200-160 WD of the plants in which the protein level increased, a decrease in the protein level at medium dehydration (around 100 WD). A 3rd phase of reincreasing protein level was found at extreme dehydration stages around 60 WD. Individual amino acids corresponded differently to water stress. In leaves, 4 groups of amino acids could be distinguished, acquiring the same pattern: (a) glutamic acid, aspartic acid, serine, alanine; (b) asparagine, glutamine, arginine, threonine; (c) proline, phenylalanine, tryptophan, gamma-aminobutyric acid; (d) cysteine, glycine, leucine, histidine. Protein level and water content of the tissue per dry (lyophylized) matter were positively correlated. The protein level and the rate of water loss were inversely correlated. Water content per dry (lyophylized) matter was found to be a sensitive criterion of metabolic changes during the water stress.