Compensatory growth of forage grass can determine its optimal biomass, which is beneficial for increasing its production. The effect of rhizosphere soil nitrification on Italian ryegrass (Lolium multiflorum Lam) regrowth was investigated on the basis of root-produced cytokinin concentration in leaves to reveal the forage grass compensatory growth mechanism. The nitrification inhibitor 3,4-dimethylpyrazole phosphate was added to inhibit soil nitrification. Without soil nitrification being inhibited, compared with no clipping one defoliation cycle increased the leaf photosynthetic rate by 43.82%–53.79%, increased the leaf cytokinin content by 33.48%–34.73%, and increased the cytokinin transport from roots to leaves by 28.88%–39.47%. Nitrification inhibitor decreased soil nitrification rates by 23.33%–84.17% in the rhizosphere and by 42.71%–68.29% in the bulk soil during regrowth. In the rhizosphere micro-environment, nitrification increased soil nitrate concentration that played an important role in the transport of cytokinin from roots to leaves during regrowth, increasing the leaf cytokinin concentration. However, bulk soil nitrification rate and nitrate content had little influence on leaf cytokinin concentration during regrowth. An increase in leaf cytokinin improved the photosynthesis and the regrowth. Without soil nitrification being inhibited, total biomass at the end of regrowth period was 1.09 times higher in plants that were defoliated once than in non-clipped plants. However, soil nitrification inhibitor and two defoliation cycles decreased Italian ryegrass regrowth. Super compensatory growth occurred in the one defoliation cycle Italian ryegrasses without adding soil nitrification inhibitor. Compensatory growth occurred in once-defoliated Italian ryegrass with adding soil nitrification inhibitor and in twice-defoliated Italian ryegrass without adding soil nitrification inhibitor. In conclusion, rhizosphere soil nitrification is the key factor that regulates the compensatory growth of Italian ryegrass.

中文翻译：

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根际土壤硝化对意大利黑麦草（Lolium multiflorum Lam）基于根系产生的细胞分裂素补偿生长的影响

牧草的补偿生长可以决定其最佳生物量，有利于提高其产量。根际土壤硝化对多花黑麦草的影响（多花黑麦草根据叶片中根产生的细胞分裂素浓度对 Lam) 的再生进行了研究，以揭示牧草的补偿生长机制。添加硝化抑制剂3,4-二甲基吡唑磷酸盐以抑制土壤硝化。在不抑制土壤硝化作用的情况下，与不剪枝相比，一个落叶周期使叶片光合速率提高43.82%～53.79%，叶片细胞分裂素含量提高33.48%～34.73%，细胞分裂素从根部向叶片的转运量提高28.88%～ 39.47%。在再生过程中，硝化抑制剂使根际土壤硝化率降低 23.33%–84.17%，大块土壤硝化率降低 42.71%–68.29%。在根际微环境中，硝化作用增加了土壤硝酸盐浓度，硝酸盐浓度在再生过程中细胞分裂素从根到叶的运输中起重要作用，从而增加了叶细胞分裂素浓度。然而，大块土壤硝化速率和硝酸盐含量对再生过程中叶片细胞分裂素浓度影响不大。叶细胞分裂素的增加改善了光合作用和再生。在不抑制土壤硝化作用的情况下，脱叶一次的植物在再生期结束时的总生物量是未修剪植物的 1.09 倍。然而，土壤硝化抑制剂和两个落叶循环减少了意大利黑麦草的再生。在没有添加土壤硝化抑制剂的情况下，意大利黑麦草在一个落叶周期中发生了超级补偿生长。添加土壤硝化抑制剂的意大利黑麦草一次脱叶和不添加土壤硝化抑制剂的两次脱叶意大利黑麦草发生补偿性生长。综上所述，根际土壤硝化作用是调控意大利黑麦草补偿性生长的关键因素。