Summary: | <p>This study was designed to determine how endogenous AbA
levels in wheat plants changed when drought stress was imposed
at various stages of its development and to select a stage of
development at which changes in AbA levels were most sensitive
to drought stress. Sensitivity in this sense was synonymous
with the production of large amounts of AbA in response to
drought stress.</p>
<p>The variety used in this study was Pitic 62 and the
plants were grown under controlled environmental conditions.
At each of the five stages of development studied, tillering,
stem elongation, booting, inflorescence emergence and milk
development stages,stress was imposed on the plants up to five
days of stress. Control plants were sampled on days
corresponding to alternate days of stress. Parameters of plant
water status studied were total leaf water potential, leaf
osmotic potential, leaf pressure potential and relative water
content. Changes in these parameters were related to changes
in AbA levels, stomatal resistance and dry matter
accumulation.</p>
<p>It was found that there were clear differences in
drought-induced increases in AbA levels between the stages of
development. There was also a tendency to produce greater AbA
levels in response to stress at later stages of development.
The implications of these findings have been discussed.
Relative increases in AbA levels were found not to differ
greatly from stage to stage suggesting the possibility that it
may be an inherent capability of the cultivar or crop.</p>
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