In previous investigations of several maize cultivars, an improvement of the harvest index was obtained by paclobutrazol (PAC) application combined with an increase in water-use efficiency. However, so far nutrient-utilization efficiencies could not be enhanced when control and PAC-treated maize plants received the same amount of fertilizers. With adjusted fertilizer supply according to the lower requirement of the smaller, PAC-treated plants, an improvement of nutrient-utilization efficiencies may be expected. Thus, in the present study, PAC was applied at growth stage V5 to two maize cultivars (Zea mays L. cvs. Galactus and Fabregas) grown in a container experiment. Shortly after PAC application, differential NPK fertilization was introduced in order to obtain a nutrient supply according to the requirement of control plants (100% NPK), the requirement of PAC-treated plants (85% NPK) and a further slight decrease (78% NPK). Plant height and transpiration rates were significantly reduced due to PAC treatment with stronger effects on Galactus than on Fabregas. Pollen shed, silking and the anthesis-silking interval (ASI) were unaffected by PAC application and fertilizer supply. Senescence of PAC-treated plants was delayed, whereas it was accelerated with reduced fertilizer supply. The grain yield of cultivar Galactus was significantly decreased due to PAC application by 13% to 20%, and this effect was strengthened due to reduction in NPK supply. These grain yield reductions were solely caused by decreases in kernel number, which were closely linked to reductions in cob length. On the contrary, PAC treatment did not affect grain yield of Fabregas and reductions due to less NPK supply were small. Harvest index and water-use efficiency were enhanced by PAC treatment. Plant nutrient contents were similar for control and PAC-treated plants, but strongly related to fertilizer supply with significant decreases due to reductions in NPK application. The N-, P- and K-utilization efficiencies of both cultivars were either decreased or unaffected by PAC treatments. The key constraint for improvements of nutrient-utilization efficiencies is grain yield reduction due to PAC. This problem should be addressed in further studies with avoidance of grain yield decreases by delayed application time combined with fine-tuning of cultivar-specific PAC application rates.

中文翻译：

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是否可以通过减少用植物生长调节剂多效唑处理的玉米植物的肥料供应来提高养分利用效率？

在之前对几个玉米品种的调查中，通过施用多效唑 (PAC) 并提高水分利用效率来提高收获指数。然而，到目前为止，当对照和 PAC 处理的玉米植物接受相同数量的肥料时，养分利用效率无法提高。根据较小的、经 PAC 处理的植物的较低需求调整肥料供应，可以预期养分利用效率的提高。因此，在本研究中，PAC 在生长阶段 V5 应用于两个玉米品种（Zea maysL.简历。Galactus 和 Fabregas）在容器实验中生长。施用 PAC 后不久，根据对照植物的需求（100% NPK）、PAC 处理植物的需求（85% NPK）和进一步轻微减少（78% NPK）。由于 PAC 处理，植物高度和蒸腾速率显着降低，对 Galactus 的影响比对 Fabregas 的影响更大。花粉脱落、吐丝和开花-吐丝间隔 (ASI) 不受 PAC 施用和肥料供应的影响。PAC 处理的植物的衰老被延迟，而随着肥料供应的减少，它加速了衰老。由于施用PAC，品种Galactus的籽粒产量显着降低了13%至20%，并且由于NPK供应的减少，这种影响得到加强。这些谷物产量的下降完全是由籽粒数量的减少引起的，这与穗轴长度的减少密切相关。相反，PAC 处理不影响法布雷加斯的谷物产量，并且由于 NPK 供应量减少而导致的减产很小。PAC处理提高了收获指数和水分利用效率。对照植物和 PAC 处理植物的植物养分含量相似，但与肥料供应密切相关，由于 NPK 施用量减少而显着降低。PAC 处理降低或不影响两个品种的 N-、P- 和 K-利用效率。提高养分利用效率的关键制约因素是 PAC 导致的谷物产量降低。