Residue reviews. Residues of pesticides and other foreign chemicals in foods and feeds: Vol. 30. Edited by F. A. Gunther. Springer-Verlag, Berlin, 1969. pp. ix + 169. DM 58

Abstract

Aminolevulinic acid, one of the key precursors involved in chlorophyll biosynthesis, was applied exogenously to assess its role in improving seedling drought stress tolerance in two wheat cultivars (Shafaq-2000 and Auqab-06). Varying levels (0, 50, 100 and 150 mg L− 1) of 5-ALA were foliarly applied to one month old seedlings. Data showed that plant growth (shoot and root fresh and dry weights), chlorophyll a and b contents, chlorophyll a/b ratios, and leaf and root P of seedlings of both wheat cultivars decreased considerably at both drought stress regimes i.e. 80% and 60% of field capacities. In contrast, water-use efficiency (WUE) calculated as A/E and proline contents accumulated considerably under drought conditions in both wheat cultivars. However, none of the two water regimes altered sub-stomatal CO2 concentration (Ci), photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E) and Ci/Ca ratio (Ca; ambient CO2 concentration), glycine betaine (GB) contents, leaf and root N, Ca2 +, and K+ concentrations, activities of enzymatic antioxidants such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and total soluble proteins in the seedlings of both wheat cultivars. 5-ALA enhanced shoot and root fresh and dry weights, chlorophyll pigments, GB contents, root K+, and N (leaf & root) in both wheat cultivars at the different water stress regimes. Of all ALA levels, 50 and 100 mg L− 1 were most effective in improving seedling growth. However, shoot and root fresh weights, shoot dry weights, chlorophyll a and b contents, A, E, gs, Ci and Ci/Ca, and proline contents were not affected by ALA treatments. Of the wheat cultivars, cv. Shafaq-2000 showed significantly higher shoot fresh and dry weights, chlorophyll b contents, gs and Ci, while cv. Uqab-06 was relatively better at proline accumulation, leaf and root P and root N concentrations. Overall, foliar-applied 5-ALA improved growth, chlorophyll a and b contents, GB, root K+, leaf and root N contents in both wheat cultivars at different water stress regimes, while all other attributes were not affected significantly.