DIFFERENCES IN LEAF AND STEM ANATOMY RELATED TO PLANT HEIGHT OF TALL AND DWARF WHEAT (TRITICUM-AESTIVUM L)

The anatomical basis of the effects on plant height of the GA-insensitive Rht1, Rht2 and Rht3 dwarfing genes was investigated in near-isogenic wheat lines. In a study of first leaves and peduncles the semi-dwarfing genes Rht1 and Rht2 were found to reduce length by 15 % while Rht3 caused a 50 % reduction. In the semi-dwarfs the differences were almost all accounted for by reductions in cell length, although in the Rht3 lines numbers of cells were also reduced, but not as much as cell length. Also, reduced cell size was found to be associated with reduced osmotic potential of the cell solutes. The reciprocal effect of the GAinsensitive dwarfing genes was found when exogenous GA was applied to the tall sensitive lines, where increases in leaf length were associated with increases in cell length. The effects on cell length rather than on numbers of cells of the Rht1 and Rht2 genes would explain why, under high yielding conditions, these genes have been found only to reduce plant height but not biomass, and thus may account, in part, for their success in wheat breeding. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.