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 h eight, semi-dwarf and double dwarf) of wheat under field conditions wi thout water and nutritional stresses, with the objective of assessing the effects of Rht1 and Rht2 leaf alleles on leaf appearance and leaf blade area development. Possession of dwarfing genes did not affect ph enological development, final number of leaves nor the rate of leaf ap pearance on the mainstem. The relationship between number of appeared leaves and thermal rime could be described by a bi-linear model with a n inflection point at the sixth-leaf stages independently of any parti cular ontogenic stage. Rht alleles caused significant reduction in the growth of leaves and stems, but did not affect internode diameter. Rh t alleles were also associated with decreased individual leaf blade ar ea, mainly through reductions in leaf blade length caused by reduced r ates rather than durations of extension. The data presented confirm th at Rht alleles affect internode growth more than leaf blade expansion; two hypotheses are discussed. (C) 1996 Annals of Botany Company.