Pod set related to photosynthetic rate and endogenous ABA in soybeans subjected to different water regimes and exogenous ABA and BA at early reproductive stages.
OBJECTIVE
The physiological reasons for reduced pod set in soybean (Glycine max) caused by drought during anthesis are not established. The objective of this study was to investigate the involvement of photosynthetic rate (A), pod endogenous abscisic acid (ABA) and exogenously applied ABA and 6-benzylaminopurine (BA) in regulating pod set in soybean during drought.


METHODS
Two pot experiments were done in a controlled-environment glasshouse. In expt I, soybeans were either well-watered (WW) or droughted by withholding water from 4 d before to 4 d after anthesis (DAA). In expt II, soybeans were drought-stressed (DS) from -4 to 4 DAA. From -2 to 4 DAA, some of the WW and DS plants were treated with 0.1 mm ABA or 1 mm BA.


RESULTS
Drought stress decreased A, but increased pod ABA concentration ([ABA]). Pod set decreased only when A had decreased by 40 %, and pod [ABA] had increased 1.5-fold. Beyond the thresholds, pod set correlated positively with A and negatively with pod [ABA]. Exogenously applied ABA decreased A and pod set in WW plants, whilst it increased A and pod set in DS plants; exogenous BA had opposite effects. In these plants, pod set correlated linearly with A.


CONCLUSIONS
Drought-induced decrease in A is significant in inducing pod abortion, probably as a consequence of carbohydrate deprivation. The effects of ABA and BA on pod set may be partially due to their effects on photosynthate supply.
Liu
Fulai
F
The Royal Veterinary and Agricultural University, Department of Agricultural Sciences, Højbakkegaard Allé 9, DK-2630 Taastrup, Denmark. fl@kvl.dk
Jensen
Christian R
CR
Andersen
Mathias N
MN
D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology*; D000225:Adenine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology*; D001593:Benzyl Compounds; D003681:Dehydration; D004190:Disasters; D007701:Kinetin; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D011687:Purines; D012044:Regression Analysis; D012098:Reproduction; D012639:Seeds / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D013025:Glycine max / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D014867:Water / Q000502:physiology*
D001593:Benzyl Compounds; D011687:Purines; D014867:Water; D000040:Abscisic Acid; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin