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Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene At PAP15(OXp) or the soybean expansin gene Gm EXPB2(OXe) can improve phosphorous(P) ef ficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean-soybean mixed cultures were employed to illuminate P acquisition among plants in mixed stands of transgenic and wild-type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild-type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean-maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean inmixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.
Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene At PAP15 (OXp) or the soybean expansin gene Gm EXPB2 (OXe) can improve phosphorous (P) ef ficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean -soybean mixed cultures were employed to illuminate P acquisition among plants in mixed stands of transgenic and wild-type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild-type soybean in mixed culture in both low P calcareous and acid soils. OXe plants had an advantage in calcareous soils when mixed with OXp, but the latter performed much better in acid soils. In soybean-maize mixed culture, transgenic soybean had no impact on maize growth compared to to controls in both acid and calcareous soils with different P conditions. As for soybean in mixed culture, OX plants have no significant advantages regardless of P av ailability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.