Author:
Botwright Tina,Rebetzke Greg,Condon Tony,Richards Richard
Abstract
Coleoptile length in wheat (Triticum aestivum L.) can be
affected by several factors, including genotype, height-reducing genes and
environmental factors, including temperature. There is little information on
how these factors influence rate and duration of coleoptile growth to
determine final coleoptile length in wheat. Coleoptile growth was determined
for eight genotypes representing four different height-reducing genes:
gibberellic acid (GA)-sensitive, standard height (rht),
GA-sensitive semidwarfs (Rht8); and GA-insensitive,
semidwarfs (Rht2). These were grown in the dark at three
temperatures (12, 16 and 20˚C) and coleoptile lengths measured every
12˚Cd. Logistic growth curves were fitted to coleoptile growth data for
each genotype with thermal time as the explanatory variable. Differences in
final 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 achieved through the fastest rate of
coleoptile elongation. Coleoptiles of Rht8 wheats were
equivalent in final length to rht wheats at 107 mm, but
achieved this through a slower growth rate (2.10 mm
˚Cd–1) combined with an increased duration of
growth (57˚Cd). In contrast, the shorter coleoptiles of
Rht2 wheats resulted from 25% slower rates of
elongation than either Rht8 or
rht. There were no interactions between the components
of coleoptile growth and temperature, although a longer duration and a fast
rate of growth combined to increase coleoptile length at 12˚C compared
with either 16 or 20˚C. In a second experiment, dry matter partitioning
and length of coleoptile, subcrown internode (SCI), shoot and roots were
determined after 200˚Cd. In Rht2, the SCI and shoot
were short while roots were longer than either Rht8 or
rht. Reduced dry matter (DM) partitioning to the
coleoptile and SCI and DM retention in the seed reduced the endosperm-use
efficiency (EUE) of Rht compared with
rht. EUE was poor also in Rht8,
apparently through increased respiratory losses. Reduced partitioning 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 rate or duration
of coleoptile growth could be targeted in a breeding program that aims to
increase coleoptile length in wheat.
Subject
Plant Science,Agronomy and Crop Science
Cited by
17 articles.
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