Low R/FR Ratio Affects Pakchoi’s Growth and Nitrate Content under Excess Nitrate Stress
2022
Libang Chen | Jia Huang | Qinglin Liu | Zelin Li | Xu Chen | Jiaxi Han | Yirong Gan | Yuexuan He | Chenxiang Jiang | Yunxin Tang | Xiaoting Zhou
Nitrate accumulation is one of the main factors of secondary soil salinization in protected horticulture in China. Previous studies have shown that a low red(R)/far-red (FR) ratio can improve the salt tolerance of plants under NaCl stress. However, the effect of a low R/FR ratio on plant growth under nitrate stress is not clear. In order to explore the effect of a low R/FR ratio on the adaptability of pakchoi under high nitrogen stress, the growth index, soluble protein content, soluble sugar content, nitrate content, nitrate reductase activity and Nia2 gene expression of pakchoi&rsquo:s leaves were measured. The results showed that a high level of nitrogen (the addition of 80 mmol ·: L&minus:1 NO3&minus: (N80) and 160 mmol ·: L&minus:1 NO3&minus: (N160)) inhibited the growth of pakchoi and promoted the accumulation of osmoregulation substances and nitrate content, respectively. The reduction of the R/FR ratio under high nitrogen stress (L80) increased the fresh weight of the plants under it by 19.0%, reduced the nitrate content in the leaves by 22.7%, increased the NR activity by 29.9%, and made the Nia2 gene expression more significant, compared with N80. There was a similar mitigation effect of a low R/FR ratio under 160 mmol ·: L&minus:1 excessive NO3&minus: stress. Therefore, the reduction of the R/FR ratio can effectively control the nitrate content and improve the adaptability of pakchoi under high nitrogen stress. Thus, there is a practical application prospect for a low R/FR ratio for the production of pakchoi under a high level of nitrogen.
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