Mepiquat chloride (MC) is essential to reduce shoot growth and improve cotton (Gossypium hirsutum L. var. latifolium Hutch) harvest index, but the effect of high rates on cotton root growth is not known yet. The objective of this study was to evaluate the effect of different rates of MC application on root and shoot growth of different cotton cultivars. Two studies were conducted in a greenhouse to (a) characterize the stage of greatest susceptibility to high rates of MC and (b) evaluate the response to MC on root growth of cultivars of different maturity cycles (FM 906GLT, early; TMG 44B2RF, mid-early; TMG 81WS, late; and FM 985GLTP, late). Regardless of the cultivar, spraying of MC in the early reproductive stage (B3) reduced root length. These reductions began approximately 2 wk after spraying. But spraying MC in the late reproductive stage (F1) can increase root length. Application of up to 30 g ha⁻¹ of MC hindered shoot growth for 2 wk, but applications of 60 g ha⁻¹ hindered shoot growth for 3 wk. We recommend a maximum application of 30 g ha⁻¹ of MC in the first application to reduce root growth damage and balance biomass production.

中文翻译：

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棉花根系生长对生殖早期施用强效氯化物的反应依赖于品种

Mepiquat 氯化物 (MC) 对减少芽生长和改善棉花（Gossypium hirsutum）至关重要L. 变种 latifolium Hutch) 收获指数，但高比率对棉花根系生长的影响尚不清楚。本研究的目的是评估不同施用量的 MC 对不同棉花品种根和芽生长的影响。在温室中进行了两项研究，以 (a) 描述对高 MC 率最敏感的阶段和 (b) 评估对 MC 对不同成熟周期品种（FM 906GLT，早期；TMG 44B2RF，中期）根生长的反应-早；TMG 81WS，晚；和 FM 985GLTP，晚）。无论品种如何，在生殖早期 (B3) 喷洒 MC 都会减少根长。这些减少在喷洒后大约 2 周开始。但是在生殖后期（F1）喷洒MC可以增加根长。施用高达 30 g ha ^-1MC 阻碍了芽生长 2 周，但 60 g ha ^{-1 的}施用阻碍了芽生长 3 周。我们建议在第一次施用时最多施用 30 g ha ^-1的 MC，以减少根系生长损伤并平衡生物量生产。