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在无限制因子时,作物的干物质产量可由作物冠层的光合作用有效辐射(PAR)吸收以及吸收的PAR转化成干物质的效率来确定。本文研究不同密度和发育时期对两个玉米杂交种PAR吸收和转化效率的效应。转化效率由地上部干物质积累和吐丝前2周到吐丝后6周的PAR吸收来估测。而由连续测定的入射PAR、反射PAR及PAR透射率估测PAR吸收。尽管灌浆期不同密度下的作物生产率基本相似,但PAR吸收的差异太小,不足以表明密度对转化效率具有显著影响。光合转化效率似乎受发育期的影响,不过密度对此效率的影响看来甚微。
At unlimited factors, the dry matter yield of a crop can be determined by the photosynthetic active radiation (PAR) absorption of the crop canopy and the efficiency with which absorbed PAR converts to dry matter. This article studies the effects of different densities and developmental stages on PAR uptake and conversion efficiency of two maize hybrids. Transformation efficiency was estimated from PAR uptake by shoots above ground and from 2 weeks before silking to 6 weeks after silking. The PAR absorption was estimated from the incident para-PAR, para-PAR and PAR transmissivity measured continuously. Although crop yields were similar at different densities during grain filling, the difference in PAR uptake was too small to show that density had a significant effect on conversion efficiency. Photosynthetic efficiency appears to be affected by developmental stages, but the effect of density on this efficiency appears to be negligible.