Appearance and Growth of Individual Leaves as Affected by Semidwarfism in Isogenic Lines of Wheat

Two experiments were carried out with three isogenic lines (standard height, semi-dwarf and double dwarf) of wheat under field conditions without water and nutritional stresses, with the objective of assessing the effects of Rhtl and Rht2 leaf alleles on leaf appearance and leaf blade area development. Possession of dwarfing genes did not affect phenological development, final number of leaves nor the rate of leaf appearance on the mainstem. The relationship between number of appeared leaves and thermal time could be described by a bi-linear model with an inflection point at the sixth-leaf stages independently of any particular ontogenic stage. Rht alleles caused significant reduction in the growth of leaves and stems, but did not affect internode diameter. Rht alleles were also associated with decreased individual leaf blade area, mainly through reductions in leaf blade length caused by reduced rates rather than durations of extension. The data presented confirm that Rht alleles affect internode growth more than leaf blade expansion; two hypotheses are discussed.