Abstract only

The major part of the Azerbaijan territory belongs to dryland. As a result of the global warming, water shortage in the region becomes more critical, rather complicating or even making impossible irrigation of a large area of the cropland. Under such conditions the issue of development of improved drought-tolerant varieties and their adoption in the areas with different levels of water provision has acquired particular urgency. Dynamics of CO2 gas exchange during the ontogenesis, which is associated with the structural and functional activity of the photosynthetic apparatus, has been found to be determined by genotype. This enables to alleviate drought impact not only using the crop management practices but also through introduction of the drought tolerant varieties thus establishing physiological basis of breeding for drought tolerance. Wheat varieties with different plant ideotypes were selected for investigation of ontogenetic dynamics of photosynthesis. The first group (high architectonics) included genotypes with the droopy, long and wide leaves, while the second group (low architectonics) generally consisted of genotypes with the erect, short and narrow leaves. Some differences were identified in development o the winter wheat genotypes differing by plant ideotype under the drought stress (simulated moisture stress) and without the drought stress ( check-irrigated). The rate of photosynthesis of the flag leaf in the evening and especial1y in the morning hours is higher, while the daytime depression is much lesser than in the bottom leaves, which contributes to intensive photosynthetic activity. Photosynthesis in the flag leaves was at its maximum in the 1st decade of May, i.e. at the end of booting stage, equaling in average 30.48 to 28.8 mg CO2/dm2/hour in the irrigated variant and 28.6 to 26.4 mg CO2/dm2/hour in the moisture stress variant, for the groups of high and low architectonics, respectively. The difference between the variants in the variety with high and low architectonics equaled to 6% and 8%, respectively. By the end of vegetative development and at the beginning of the wax stage, the rate of leaf photosynthesis in both variants dropped even lower, and equaled in average to 10.6 and 8.8 mg CO2/dm2 hour in the irrigated variant, and 8.8 and 5.9 CO2/dm2 hour in the moisture stress variant, for the groups of high and low architectonics, respectively. Photosynthesis dynamics in the varieties with the low architectonics differed from that of the high architectonics group to a certain extent. If in the group of high architectonics the maximum photosynthesis rate was observed at the end of booting, while in the varieties with low architectonics it reached its peak rate in heading and flowering. The photosynthesis rate of the flag leaves in the water stress and check variants were 26.2 to 22.8 CO2/dm2 hour for the high architectonics group and 25.8 to 20.2 mg CO2/dm2 hour for the low architectonics group. The difference between the variants was estimated to be 13 % and 21 % in the high and low architectonics groups, respectively. It should be noted that the groups of wheat varieties with the high architectonics are less affected by moisture stress than the groups with less favorable architectonics, which is evidenced by the data of daily dynamics of gas exchange, rate of photosynthesis, total assimilation of CO2 and its average hourly value, as well as by the critical period of water stress. These differences are reflected in grain yield. The study suggests that differences in photosynthesis rate between the studied varieties in both the water stress and check variants can be analyzed by the corresponding phases of wheat development.

English

0409|AGRIS 0401|AL-Wheat Program

Juan Carlos Mendieta

CIMMYT Publications Collection