Plant Growth, Nitrate Content and Ca Signaling in Wheat (Triticum aestivum L.) Roots under Different Nitrate Supply
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摘要: 以小麦品种‘石麦15’和‘衡观35’为材料进行营养液水培试验, 研究不同浓度硝态氮供应对小麦苗期根系形态、钙离子流特征及钙调蛋白(CaM)含量的影响。结果表明, 与适宜浓度硝态氮处理(2.5 mmol/L)相比, 无外源硝态氮供应时小麦地上部鲜重、硝态氮含量均降低, 侧根数量显著减少;高浓度硝态氮处理(50 mmol/L)下两个小麦品种地上部硝态氮含量升高, 根系总长度降低, ‘石麦15’侧根数量减少。无硝态氮和高浓度硝态氮处理下, 根系中钙调蛋白含量降低, 且‘衡观35’的降低幅度大于‘石麦15’。无外源硝态氮供应时小麦根尖表现出较为明显的钙离子外流特征;与适宜浓度硝态氮处理相比, 高硝态氮处理下小麦根尖Ca2+的内流速度显著下降。说明硝态氮供应不足和高浓度硝态氮供应会影响小麦根系生长, 根系Ca2+外流或Ca2+内流速度下降, CaM含量减少, Ca2+/CaM可能介导硝态氮调控小麦根系生长发育。Abstract: Nitrate (NO3-) is the main source of inorganic nitrogen for plants in aerobic soil conditions. Nutrient solution experiments were conducted with two winter wheat (Triticum aestivum L.) cultivars, ‘Shimai 15’ and ‘Hengguan 35’, as the tested crops. The objective was to investigate the changes in Ca2+-CaM signaling and root growth of wheat under different concentrations of nitrate supply. Net Ca2+ ion fluxes in different root zones were measured non-invasively using the scanning ion-selective electrode technique. Calmodulin (CaM) content in the roots was determined by enzyme-linked immunosorbent assay. Results showed that shoot fresh weight, nitrate content in shoots, and lateral root numbers of both wheat cultivars were reduced without nitrate supply compared with those under 2.5 mmol/L nitrate treatment. High levels of nitrate (50.0 mmol/L) significantly increased nitrate content in shoots, but reduced the number of lateral roots in ‘Shimai 15’. The CaM content in roots declined under conditions of no nitrate or excess nitrate (50.0 mmol/L), and were more drastically reduced in ‘Hengguan 35’. The roots without nitrate supply showed net Ca2+ ion efflux. However, the roots with 50.0 mmol/L nitrate supply showed net Ca2+ ion influx, the speed of which was significantly slower than that with 2.5 mmol/L nitrate supply. These results suggested that when wheat seedlings were grown under the stress of nitrate deficiency or excess, the influx or efflux of Ca2+ became slower and the content of CaM declined, which might inhibit the root growth of wheat.
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Keywords:
- Wheat (Triticum aestivum L.) /
- Nitrate /
- Roots /
- Net Ca2+ flux /
- Calmodulin
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