根修剪对黄土旱塬冬小麦(Triticum aestivum)根系分布、根系效率及产量形成的影响

通过田间试验研究了不同时期根修剪处理对冬小麦（Triticum aestivum）根系大小与分布、根系效率、水分利用效率及产量形成的影响。设置4个根修剪处理：越冬期小剪根（WS）、越冬期大剪根（WB），返青期小剪根（GS）、返青期大剪根（GB），未剪根小麦作为对照（CK）。结果表明，到花期时，各根修剪处理小麦的在0～120cm总根量均显著小于对照。与对照相比各根修剪处理主要是显著地减少了上层土壤中的根量。但WS和GS两小剪根处理和对照相比在中层土壤中有较大的根量；花后各处理小麦旗叶的气孔导度和蒸腾速率均显著大于对照。这说明根修剪处理减少了小麦表层的根量，从而削弱了表土干旱信号对作物与外界气体交换的抑制作用。花期时各根修剪小麦的净光合速率均显著高于对照，而单位面积上的根呼吸速率均显著小于对照，根修剪处理提高了小麦的根系效率，使更多的光合产物用于籽粒生产，从而提高了小麦的收获指数。根修剪还提高了小麦的水分利用效率，其中WS、WB、GS处理的水分利用效率显著高于对照。但是GB处理的水分利用效率却没有显著提高。因此，本研究进一步证明了由不同年代品种得到的推测，认为在旱地农业中，通过遗传育种或采用适当农艺措施优化根系分布，既可以减少生长前期作物对水分的过度消耗，又能够削弱花后表土过度干旱对作物生长抑制作用，同时降低根系对同化产物的消耗，对作物产量及水分利用效率的提高具有积极的作用。

Effect root pruning on root distribution,root efficiency and yield formation of winter wheat in Loess Plateau

A field experiment was conducted to study effects of root pruning at different growth stages on root distribution, root efficiency, yield and water use efficiency (WUE) of winter wheat. The experiment was carried out from October 2005 to June 2006 in the dry tableland on Loess Plateau. Plants were subjected to four treatments: (1) the secondary lateral roots at one side were partially cut off during over-wintering stage (WS), (2) the secondary lateral roots at both sides were partially cut off during over-wintering stage (WB), (3) the secondary lateral roots at one side were partially cut off during jointing stage (GS), (4) the secondary lateral roots at both sides were partially cut off during jointing stage (GB). The intact plants without any cutting were taken as the control (CK). Results showed that all root pruning treatments had significantly less total root biomass than CK in 0-120cm soil layer at flowering stage. Root pruning reduced significantly root biomass of winter wheat in the upper soil layer (0-20cm). Both WS and GS treatments had more root biomass than CK in the middle-layer (40-80cm). All root pruning treatments had significantly higher stomatal conductance (Gs)and transpiration rate (Tr) than CK after anthesis, which suggested that root pruning weaken the effects on gas exchange by drought signal from roots in the top soil through reducing root biomass. At flowering stage, all root pruning treatments had significantly higher photosynthesis and significantly lower root respiration rate compared to CK. Therefore, root pruning improved root efficiency, ensured more photosynthate allocation into grain and increased the harvest index of winter wheat. WUE in WS, WB and GS treatments were significantly higher compared to CK. But WUE in GB treatment was not significantly improved compared to CK. The current study approved the speculation from different wheat cultivars that by optimizing root system distribution soil water consumption in the early growing stage is reduced. Further, negative effects on growth by root drought signal from the top soil after anthesis are weakened, and reduced root respiration favours yield and WUE improvement of winter wheat in arid and semi-arid area.