Abstract

Developmental changes in the levels of free amino acids of flag leaves in drought-tolerant (Triticum aestivum L. cv. Zagros) and drought-sensitive (cv. Marvdasht) wheat genotypes was investigated under controlled water deficit condition during grain filling. Cultivars were grown in pots and treated with either well-watered (control) or drought-stress (stress) from anthesis to maturity. Total soluble amino nitrogen in the leaves of two cultivars rose as relative water content (RWC) declined, the peak concentrations were attained early in the drought period (seven days after anthesis), when the Zagros and Marvdasht leaf RWC approached 80 and 70%, respectively. However, irrespective of water deficit, the total amino acids concentration declined with time. Interestingly, Zagros and Marvdasht did not accumulate the same amino acids. Zagros accumulated large amounts of proline and g-aminobutyrate, whereas Marvdasht preferentially accumulated asparagine and arginine. It is concluded that; (i) modifications in the amino acid metabolism during dehydration stress were different depending on leaf development and (ii) proline and g-aminobutyrate (Gaba) accumulation in Zagros leaves were essential for the acquisition of desiccation tolerance. On the contrary, the accumulation of large amounts of asparagine and arginine that serves as nitrogen and carbon reservoirs, in the Marvdasht during dehydration may be as a result of restriction of transport efficiency of storage material that led to low yield in drought sensitive cultivar.

Key words: Arginine, asparagine, g-aminobutyrate, proline, water stress,Triticum aestivum L.

Abbreviation

 ACC, Amino cyclopropan carboxylic acid; Ala, alanine; Arg,arginine; Asn, asparagines; Asp, aspartate; DAA, days after anthesis; Gaba,