Effects of 24-epibrassinolide on nitrogen metabolism in cucumber seedlings under Ca(NO₃)₂ stress
2012
Yuan, Lingyun | Yuan, Yinghui | Du, Jing | Sun, Jin | Guo, Shirong
Ca(NO₃)₂ accumulation is a major factor that limits greenhouse production in China. The present investigation was carried out to study the effect of 24-epibrassinolide (EBL) on nitrogen metabolism (including contents of NO₃ ⁻, NH₄ ⁺ and amino acids and related enzymes activities) in cucumber seedlings (Cucumis sativus L. cv. Jinyou No. 4) under 80 mM Ca(NO₃)₂ stress. This study found that exogenous EBL significantly reduced the accumulation of NO₃ ⁻ and NH₄ ⁺ by Ca(NO₃)₂, and enhanced the inactivated enzymes activities involved in the nitrogen metabolism. In addition, EBL alleviated the inhibition of photosynthesis nitrogen-use efficiency by Ca(NO₃)₂. Increased total amino acids by EBL under stress increased the precursor of proteins biosynthesis, thus promoting the biosynthesis nitrogen containing compounds. The presence of Ca(NO₃)₂ increased polyamines level, which might result from the increased content of free putrescine that is harmful to plant growth. However, exogenous EBL induced a further increase in total polyamines. The increase is likely caused by the elevated contents of conjugated and bound forms of polyamines. In summary, exogenously EBL compensated for the damage/losses by Ca(NO₃)₂ stress to some extent through the regulation of nitrogen metabolism and metabolites.
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