Drought stress can substantially alter plant metabolism by decreasing plant
growth and photosynthesis. The lack of rapid and reliable screening criteria and
measurement techniques for determining water use efficiency (WUE) of crop plants has
greatly restricted progress in this critical area of crop improvement. In grain sorghum
(Sorghum bicolor L.), WUE was associated with the transpiration ratio [CO2
assimilation (A) / transpiration rate (E), A:E] from leaf gas exchange measurements.
Research is needed to identify drought effects on plant productivity and to exploit the
use of this knowledge in breeding and agronomic efforts. Therefore, the objectives of
this study were to determine if differences in A:E and other physiological parameters
existed between two selected cotton (Gossypium hirsutum L.) genotypes and to evaluate
the response of cotton genotypes experiencing water stress at two different growth stages
on biomass production and yield.
Two experiments were conducted using two cotton genotypes differing in
drought tolerance. Each experiment was repeated three times in a randomized complete
block design with six replications. In Experiment I, the water stress treatment was
induced by withholding water when the plants reached the 4-node growth stage. The water stress treatment in Experiment II was imposed at early bloom. Gas exchange and
chlorophyll fluorescence measurements were collected during dry-down and recovery
periods to determine water stress effects on plant physiology. Biomass was partitioned
following the recovery period, to examine phenotypic responses of plants exposed to
water stress.
The results of these experiments indicate that A:E is significantly increased as
leaf water potential (ψL) decreases with no differences in A:E between the two
genotypes. Gas exchange measurements showed significant decreases with declining ψL
and significant increases upon re-watering; yet, no differences were observed between
the two genotypes. Chlorophyll fluorescence was not different between genotypes in
either light- or dark-adapted leaves. In Experiment I TAM 89E-51 had a significantly
greater seedcotton yield; however, in Experiment II TAMCOT 22 had the greater yield.
These experiments suggest that the effects of water stress on cotton are a function of the
intensity of the stress and the growth stage in which the stress is experienced.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2635 |
| Date | 15 May 2009 |
| Creators | Bynum, Joshua Brian |
| Contributors | Cothren, Joe Tom |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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