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Response of Soybean to Abscisic Acid Application Under Different Water Regimes
Dissertation Abstract:
The length of residence had a significant effect on the transmigrants' economic behavior. Therefore, it will take quite some time for newly opened transmigration sites to be ready for developmental evaluation.
Two screenhouse experiments and a field experiment was conducted at the University of the Philippines Los Banos (UPLB) from October 1990 to May 1991. The objective was to determine the influence of different abscisic acid (ABA) concentrations (0, 10-5, and 10-4 M) and times of application (vegetative and reproductive stages) on the growth, grain yield, and seed quality of two soybean cultivars (BPI-Sy4 and SJ-2) grown under screenhouse conditions (30% and I 00% available water to simulate drought and sufficient water conditions, respectively) and field conditions (irrigated and unirrigated).
Grain yield of the two cultivars grown under either drought or sufficient water conditions were not significantly affected by ABA and its time of application. However, plant maturity was significantly longer when applied with ABA than when untreated, especially those grown under drought condition. Both soybean cultivars had significantly higher yields than when under drought condition. Grain yield of SJ-2 was significantly higher than that of BPI-Sy4 under sufficient water conditions. No significant yield difference, however, was observed under drought condition.
ABA application significantly reduced the dry matter, leaf area, and root dry weight of the two cultivars grown in the screenhouse. Compared with the untreated control, these reductions were greater at 10-5M ABA than at 10-4M ABA under sufficient water conditions. Under drought conditions, however, the reverse was observed. Reduction in these parameters were also greater when ABA was applied at the vegetative stage than at the reproductive stage.
The two cultivars responded differently to ABA application in terms of stomatal conductance, dry matter, shoot dry weight, number of pods, and maturity. Generally, there were less reduction in these parameters in BPI-Sy4 than in SJ-2, although growth of SJ-2 cultivar was better than BPI-Sy4. On the other hand, ABA application had no significant effect on growth of plants grown in the field, regardless of water regimes.
Stomatal conductance, however, was significantly reduced, especially in plants grown under irrigated condition. Seed quality as measured by 100-seed weight and percentage germination were significantly reduced by ABA. Reduction was greater when ABA was applied at the vegetative stage. Percentage germination was lower in SJ-2 than in BPI-Sy4. Moreover, reduction in 100-seed weight was greater when ABA was applied at 10-4M than 10-5 M during the vegetative stage. The reverse was observed when ABA was applied at the reproductive stage.
These findings imply that ABA application under drought condition may improve the resistance of drought-susceptible plants by reducing plant growth (as shown by the reduced values of dry matter, shoot dry weight, and leaf area in the experiment), thereby decreasing plant water consumption without loss in grain yield.