Effects of Different Ammonium/Nitrate Ratios on Growth and Auxin Content of Tea Plants
[Objective]This study is aimed to clarify the optimal ammonium/nitrate ratio for growth of dif-ferent tea varieties,and provide a reference for achieving'fertilization based on variety'and nitrogen fer-tilization management in tea gardens.[Method]One-year-old cuttings of the tea plant cultivars'Xin-yang 10'and'Zhongcha 108'were cultured in a hydroponic nutrient solutions containing five ratios of NH4+/NO3-(4∶0、3∶1、2∶2、1∶3、0∶4).The growth phenotype,dry weight,total nitrogen content,root morphology parameters,and levels of free auxin IAA and IBA in the tea plant roots were analyzed.[Re-sult]Among the five ammonium/nitrate ratios,the cultivar'Xinyang 10'exhibited a superior growth per-formance at a ratio of 3∶1,as evidenced by the elevated number of leaves and buds per plant,higher dry weight of roots and bud leaves,longer average length of adventitious roots,and elevated levels of free auxin IAA and IBA in the roots compared to other treatments.Unlike'Xinyang10','Zhongcha 108'ex-hibited optimal growth characteristics when subjected to a NH4+/NO3-ratio of 4∶0,with higher plant height,stem diameter,number of buds per plant,and germination rate.It also had the highest dry weight of roots,stem,and bud leaves,the most nitrogen accumulation,and the highest number and den-sity of lateral roots,as well as the IAA and total IAA and IBA content in the roots.Correlation analysis re-sults showed that the root parameters of'Xinyang 10'were more strongly correlated with auxin content,while the root parameters of'Zhongcha 108'were more strongly correlated with nitrogen content.[Conclusion]The optimal NH4+/NO3-ratio for the growth of cultivars'Xinyang 10'and'Zhongcha 108'were 3∶1 and 4∶0,respectively.Cultivar'Xinyang 10'is more tolerate to nitrate,while the cultivar'Zhongcha 108'is more sensitive to it.
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