Free amino acids and glycine betaine in leaf osmoregulation of spinach responding to increasing salt stress

Abstract

Summary• The aim of the paper was to determine nitrogen compounds contributing to leaf cell osmoregulation of spinach ( Spinacia oleracea ) submitted to increasing salt stress.• Sodium, free amino acids and glycine betaine contents were determined in the last fully expanded leaf of plants stressed by daily irrigation with saline water (0.17 M NaCl).• After 20 d of treatment, when Na + content was c . 55 umol g − 1 f. wt above the control, and the reduction of stomatal conductance lowered photosynthesis to c . 60% of the control, the free amino acids of the leaves, especially glycine and serine, strongly increased. Proline and glycine betaine also increased significantly. After 27 d of treatment, when the Na + content was c . 100 umol g − 1 f. wt above the control and photosynthesis was 33% of the control, the free amino acid content, especially glycine and serine, declined. Gycine betaine, but not proline, increased further.• Glycine betaine comprised c . 15% of the overall nitrogen osmolytes at mild saltstress, but represented 55% of the total, when the stress became more severe. The increase of glycine betaine balanced the decline in free amino acids, mainly replacing glycine and serine (the precursors of glycine betaine) in the osmotic adjustment of the cells. Photorespiration, which increased during salt stress, was also suggested to have a role in supplying metabolites to produce compatible osmolytes.

Genetic, proteomic and metabolic analysis of the regulation of energy storage in rice seedlings in response to drought

“…Thus, it is not surprising that sugars (19%) were the second largest category of differentially expressed metabolites. Amino acids accounted for 16% of the differentially expressed metabolites; these metabolites were up-regulated, and these results are similar to those a previous study of NaCl treatment [51]. Among the amino acids, increased proline content has been reported as a typical physiological response to drought, salt, BLASTP (http://www.ncbi.nlm.nih.gov/BLAST/) was used to search for homologs of the unknown proteins, and the homologs with the highest similarity and known function are shown.…”

Rice Flag Leaf Physiology, Organ and Canopy Temperature in Response to Water Stress

“…These osmotic substances include soluble sugar, proline, etc., and the larger the accumulation, the stronger the drought resistance (Ashraf and Iram, 2005;Chaves and Oliveira, 2005;Martino et al, 2003). However, under severe water stress, these osmotic substances will decrease (Patakas et al, 2002;Pinheiro et al, 2001).…”

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“…Glutamate, glutamine, serine, alanine, and aspartate are the most abundant free amino acids in spinach under salt stress, while the pool of other amino acids like valine, leucine, isoleucine, lysine, tryptophan, and proline comprises approximately 1% of the overall amount with only traces of glycinebetaine 20 . Amino acids such as proline, asparagine, and aminobutyric acid can play an important role in the osmotic adjustment of the plant to saline conditions 21 .…”