水稻分蘖期干物质积累对大气CO2浓度升高和氮素营养的综合响应差异及其生理机制

【目的】探究不同类型水稻品种物质生产响应大气CO₂浓度升高和氮素营养的综合响应差异及其生理机制。【方法】以产量和物质生产对CO₂浓度升高响应有明显差异的水稻品种两优培九(LY)和南粳9108(NJ)为材料，在人工气候室进行水培试验。分别设置对照CO₂浓度(A-CO₂,400μmol·mol^-1)和CO₂浓度升高(E-CO₂,600μmol·mol^-1)两个CO₂处理，高氮(HN,1.25 mmol·L^-1 NH₄NO₃)和低氮(LN,0.25 mmol·L^-1 NH₄NO₃)两个氮水平。分析CO₂浓度升高对不同水稻品种根系形态与生理活性、叶片和根系中细胞分裂素(CTKs)含量、氮素同化酶活性、叶片生理特性、光合参数以及干物质积累的影响差异。...

Difference in the Comprehensive Response of Dry Matter Accumulation of Rice at Tillering Stage to Rising Atmospheric CO2 Concentration and Nitrogen Nutrition and Its Physiological Mechanism

【Objective】 The aim of this study was to explore the comprehensive response difference and physiological mechanism of different rice cultivars in response to elevated atmospheric CO₂ concentration and nitrogen nutrition. 【Method】 In this study, a rice cultivar Liangyoupeijiu (LY) with high response to CO₂ (high-response rice cultivar) and a rice cultivar Nanjing 9108 (NJ) with low response to CO₂ (low-response rice cultivar) were selected as materials. Hydroponic experiments were carried out in the climate chamber. Two CO₂ treatments and two nitrogen treatments were set up with ambient CO₂ concentration (A-CO₂, 400 μmol·mol^-1) and elevated CO₂ concentration (E-CO₂, 600 μmol·mol^-1), and high nitrogen (HN, 1.25 mmol·L^-1 NH₄NO₃) and low nitrogen (LN, 0.25 mmol·L^-1 NH₄NO₃), respectively. The effects of elevated CO₂ concentration on root morphology and physiological activity, cytokinin (CTKs) content in leaves and roots, nitrogen assimilation enzyme activity, physiological characteristics of leaves, photosynthetic parameters, and dry matter accumulation of different rice cultivars were analyzed. 【Result】 (1) E-CO₂ significantly increased the total crown root number, total root length (except LN level), total root surface area, and average diameter of LY, improved root respiration rate and maintained high root oxidation power, but had no significant or opposite effects on NJ. (2) Regardless of nitrogen level, E-CO₂ significantly increased CTKs content in LY leaves and roots, but significantly decreased zeatin nucleoside (ZR) content in NJ roots at HN level. (3) At LN level, E-CO₂ significantly increased GOGAT and GDH activities in LY leaves, but significantly decreased NR activities in NJ leaves. At HN level, the activity of LY nitrogen assimilation enzyme increased under E-CO₂ condition, but only NR activity increased in NJ. (4) At LN level, E-CO₂ increased the net photosynthetic rate (P_n) of LY and NJ by 28.0% and 29.4%, respectively. At HN level, P_n of the two cultivars increased by 41.0% and 28.1%, respectively. The significant increase in photosynthetic response of LY was attributed to the significant increase in leaf maximum carboxylation efficiency (V_c,max), maximum photosynthetic electron transport efficiency (J_max), ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) content, chlorophyll content, and leaf nitrogen content. (5) E-CO₂ significantly increased the leaf area per plant of LY under different nitrogen levels, but had no significant effect on NJ. (6) E-CO₂ significantly increased the organs and total biomass of LY, and the increased level under HN was significantly higher than that under LN level. E-CO₂ did not significantly affect the total biomass of NJ under different nitrogen treatments, but significantly reduced the underground biomass of NJ under HN (-16.7%). 【Conclusion】 No matter at the HN or LN treatment, the response of dry matter production and physiological characteristics of LY to E-CO₂ was higher than that of NJ. In the early growth stage, LY had better root morphological characters and root activity, higher CTKs content, stronger nitrogen assimilation ability, larger green leaf area and photosynthetic response capacity, which were important reasons accounting for the higher response of dry matter production under E-CO₂ conditions.