The effect of rht genotype and temperature on coleoptile growth and dry matter partitioning in young wheat seedlings

T. Botwright et al., The effect of rht genotype and temperature on coleoptile growth and dry matter partitioning in young wheat seedlings, AUST J PLAN, 28(5), 2001, pp. 417-423
Citations number
Categorie Soggetti
Plant Sciences","Animal & Plant Sciences
Journal title
ISSN journal
0310-7841 → ACNP
Year of publication
417 - 423
SICI code
Coleoptile length in wheat (Triticum aestivum L.) can be affected by severa l factors, including genotype, height-reducing genes and environmental fact ors, including temperature. There is little information on how these factor s influence rate and duration of coleoptile growth to determine final coleo ptile length in wheat. Coleoptile growth was determined for eight genotypes representing four different height-reducing genes: gibberellic acid (GA)-s ensitive, standard height (rht), GA-sensitive semidwarfs (Rht8); and GA-ins ensitive, semidwarfs (Rht2). These were grown in the dark at three temperat ures (12, 16 and 20 degreesC) and coleoptile lengths measured every 12 degr ees Cd. Logistic growth curves were fitted to coleoptile growth data for ea ch genotype with thermal time as the explanatory variable. Differences in f inal coleoptile length were largely attributable to differences in rate of coleoptile elongation although there were small differences in duration of growth between genotypes. The longer coleoptile of the rht wheats was achie ved through the fastest rate of coleoptile elongation. Coleoptiles of Rht8 wheats were equivalent in final length to rht wheats at 107 mm, but achieve d this through a slower growth rate (2.10 mm degrees Cd-1) combined with an increased duration of growth (57 degrees Cd). In contrast, the shorter col eoptiles of Rht2 wheats resulted from 25% slower rates of elongation than e ither Rht8 or rht. There were no interactions between the components of col eoptile growth and temperature, although a longer duration and a fastest ra te of growth combined to increase coleoptile length at 12 degreesC compared with either 16 or 20 degreesC. In a second experiment, dry matter partitio ning and length of coleoptile, subcrown internode (SCI), shoot and roots we re determined after 200 degrees Cd. In Rht2, the SCI and shoot were short w hile roots were longer than either Rht8 or rht. Reduced dry matter (DM) par titioning to the coleoptile and SCI and DM retention in the seed reduced th e endosperm-use efficiency (EUE) of Rht compared with rht. EUE was poor als o in Rht8, apparently through increased respiratory losses. Reduced partiti oning of dry matter to coleoptiles and the SCI in Rht2 increased the root : shoot ratio compared with rht or Rht8. We conclude that either increased r ate or duration of coleoptile growth could be targeted in a breeding progra m that aims to increase coleoptile length in wheat.