Reproductive Growth and Dry Matter Production of Glycine max (L.) Merr. in Response to Oxygen Concentration

摘要

Reproductive as well as vegetative parameters of mature soybean (Glycine max [L.] Merr. cv. Wye) plants grown in chambers in which the aerial portion was exposed to altered pO2 during all or part of the growth cycle were measured. Oxygen concentration was found to be a key factor controlling all phases of reproductive development. Exposure to 5% O2 from early seedling stage to senescence increased leaf, stem, and root dry weights and reduced seed yields when compared to 21% O2; exposure to low O2 during the vegetative growth stage from early seedling to mid-flowering arrested pod but not seed development; exposure from mid-flowering to mid-pod filling almost completely arrested seed but not pod development; exposure from mid-pod filling to senescence arrested seed development at the mid-filling stage.Exposures to 5% O2 initiated at mid-flowering for 1, 2, 3, 5, 10, and 15 days had no effect on seed development when the exposure was up to 3 days and produced almost total arrest when the exposure was 10 or more days, suggesting reversibility. The requirement for O2 in seed development is independent of CO2 concentration with similar results produced by subambient O2 combined with ambient CO2, elevated CO2 up to 2000 μl/l or depressed levels of CO2 with the CO2/O2 ratio as in air. An elevated O2 atmosphere containing 40% O2 and ambient or elevated CO2 inhibited total growth but did not affect the balance of vegetative to reproductive growth.We conclude that an unknown reaction or process requiring at least atmospheric concentrations of O₂ but independent of CO₂ in contrast to photorespiration is necessary for optimization of all phases of reproductive growth and the effect is reversible for exposures of up to 3 days but not for exposures of 10 days or more. We propose that this O₂ phenomenon may be the result of a unique physical process or chemical reaction associated with translocation and accumulation of assimilates in reproductive structures.