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Echinochloa oryzoides is a serious weed of rice worldwide and one of the most important weeds of water-seeded rice in California, USA, where resistance to most available herbicides has been detected. Developing new integrated weed management strategies that include rice suppression of E. oryzoides growth requires understanding their relative responses to resource limitation. The effects of shade on the growth, morphology and CO 2 exchange rates (CER) of E. oryzoides and rice (cv. M-202) were assessed in glasshouse and growth chamber experiments. Plants were grown at 100, 50 or 18% of full sunlight (glasshouse) or at 500 and 250 µmol PPFD m-2s-1 (growth chamber) within a completely randomized design with two factors and four replicates. Shade was imposed at 21 days after seeding (d.a.s.) (glasshouse) and at 14 d.a.s. (growth chamber). Height, leaf area, tillers, and leaf, stem, root and seed dry weights were determined for both species. CER were determined for plants in the growth chamber. Both species increased dry-matter allocation to leaves and maintained CER when subjected to low light. However, in contrast to rice, E. oryzoides maintained or increased leaf area, specific leaf area and leaf area ratio (LAR) in response to shade. E. oryzoides tiller number and seed output were reduced only at 18% sunlight. Rice lacked such adaptive ability and tiller number and seed were reduced at 50% sunlight. Shade alone may not prevent the seed production of E. oryzoides. However, E. oryzoides increased LAR at the expense of allocation to roots. Thus, for substantial E. oryzoides control, early nutrient deprivation by rice roots may be as relevant as improving rice ability to intercept light. 相似文献
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水资源的短缺是全球性问题,水资源优化分配是重要的农业节水措施,是目前农业节水研究的重大课题之一。当水资源优化分配中未知量较多时,传统的手工计算方法已不能满足需要,必须用计算机模型来计算。GAMS是国外应用较广的计算机语言,能通过很简单的计算程序迅速求解线性规划、非线性规划、整数规划问题。通过GAMS语言,建立了简单的灌区水资源分配模型,求解了不同水库泄水条件下的各用户最优水量分配方式。 相似文献
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企业选择进入工业园区的根本原因在于能获得园区外企业所不具备的资源配置优势。工业园区生产性服务业发展促进了园区企业的外部资源获取,能够监测园区企业所获取的资源质量,并保证园区企业从外部获取资源的长效性。我国工业园区应着力完善生产性服务业和制造业互动模式,政府应创造良好的园区硬环境和软环境。 相似文献