Abstract: Field experiment was conducted to investigate rice yield response to the distribution of carbon-hydrates under waterlogged (paddy) conditions and upland conditions with soil surface mulched by rice-straw (upland) for the same rice variety, and to test the influence of upland cultivation on rice yield by cutting off rice root. Grain yield of upland rice (5850.9 kg/hm² ) was significantly lower than that of paddy rice (6685.7 kg/hm² ). However, straw yield of the former (5735.5 kg/hm² ) was higher than that of the latter (5489.5 kg/hm² ). Percentage of filled grains per tiller of paddy on an average was significantly higher than that of upland. Nevertheless, the percentages of leaves, sheaths and unfilled grains of upland were greater than those of paddy. Root to shoot ratio of upland rice (0.116) was remarkably bigger than that of paddy rice(0 087). Root respiration rate of the former was 2.7 times of the latter. There was a trend of grain yield increase by root-cutting under upland conditions, but to the contrary under paddy conditions. Grain yield of rice with 1/4, 2/4 and 3/4 of root cut off per hill on average decreased by 23%, 15% and 20% compared to rice without root-cutting under normal paddy conditions. However, under upland conditions, the grain yield of rice with 1/4, 2/4 and 3/4 of root cut off increased by 20%, 7% and 3% compared to that without root-cutting respectively. It could be concluded that upland conditions might block the translocation of carbon-hydrates and accumulate a lot of carbon-hydrates in leaves and sheaths, which resulted in unfilled grains. Root biomass increased under upland conditions and the redundant root growth might also consume more carbon-hydrates and decrease yield of rice under upland conditions.

Key words: rice, upland cultivation with rice straw mulched, yield response, root-cutting, root redundant growth, distribution of carbon-hydrates

摘要： 通过大田对比试验研究了常规水稻与覆草旱作水稻的产量构成、根系呼吸强度以及断根对产量的影响。 结果表明，覆草旱作水稻籽粒产量(5850.9 kg/hm[sup]2[/sup])明显低于常规水稻（6685.7 kg/hm[sup]2[/sup]），但前者的秸秆产量(5735.5 kg/hm[sup]2[/sup])高于常规水稻(5489.5 kg/hm[sup]2[/sup])。常规水稻实粒占平均单蘖总量的百分数远大于覆草旱作水稻，覆草旱作水稻叶、鞘、秕粒的比例大于常规水稻。覆草旱作的根冠比（0.116）显著大于常规水稻（0.087），前者的根系呼吸强度是常规水稻的2.7倍。旱作水稻断根后普遍有增产的趋势，而常规水稻则有减产的趋势。常规水稻断1/4、2/4和3/4根系时，平均每穴籽粒产量较不断根的分别下降23％、15％和20％。然而，旱作条件下，断1/4、2/4和3/4根系的水稻较全根的分别增产20％、7％和3％。由此可见，水稻旱作抑制了同化产物向籽粒的转运，叶和鞘中积累了较多的同化产物；旱作水稻根系冗余生长，消耗了大量碳水化合物，可能导致水稻籽粒产量下降。

关键词: 水稻, 覆草旱作, 产量效应, 断根, 根系冗余生长, 光合产物分配