Effects of NORIN 10 and Tom Thumb Dwarfing Genes on Morphology, Physiology and Abscisic Acid Production in Wheat

The pleiotropic effects of three genetically related dwarfing genes were investigated in near-isogenic lines of wheat. The NORIN 10 semi-dwarfing alleles, Rht 1 and Rht 2, and the Tom Thumb allele, Rht 3, were assessed for effects on some vegetative morphological and physiological characters. The Rht alleles affected leaf size with a resultant decrease in leaf area of the whole plant. Rht 3, which had the most marked effects, reduced leaf area in young plants by as much as 30 per cent. Although flag leaf dimensions and stomatal distributions of the flag leaf were altered, the gene had no effect on its area, stomatal conductance or net CO2 exchange rate. Comparisons of Rht and tall plants revealed no differences in the abscisic acid (ABA) levels of either turgid or partially dehydrated leaves.