水稻分蘖期干物质积累对大气CO_(2)浓度升高和氮素营养的综合响应差异及其生理机制

Difference in the Comprehensive Response of Dry Matter Accumulation of Rice at Tillering Stage to Rising Atmospheric CO_(2) Concentration and Nitrogen Nutrition and Its Physiological Mechanism

【目的】探究不同类型水稻品种物质生产响应大气CO_(2)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CO_(2)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CO_(2)浓度(A-CO_(2),400μmol·mol^(-1))和CO_(2)浓度升高(E-CO_(2),600μmol·mol^(-1))两个CO_(2)处理,高氮(HN,1.25 mmol·L^(-1) NH_(4)NO_(3))和低氮(LN,0.25 mmol·L^(-1) NH_(4)NO_(3))两个氮水平。分析CO_(2)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。【结果】(1)E-CO_(2)显著增加了LY总冠根数、总根长(LN水平除外)、总根表面积和平均直径,提高其根系呼吸速率和维持较高的根系氧化力,而对NJ无显著影响或表现相反;(2)无论氮水平如何,E-CO_(2)显著提高了LY叶片和根系CTKs含量,但显著降低了HN水平下NJ根系中玉米素核苷(ZR)含量;(3)在LN水平下,E-CO_(2)显著提高了LY叶片GOGAT、GDH活性,显著降低了NJ叶片NR活性。在HN水平下,LY氮同化酶活性在E-CO_(2)条件下都表现为提高,NJ仅NR活性提高;(4)在LN水平下,E-CO_(2)使得LY和NJ净光合速率(P_(n))分别提高了28.0%和29.4%。在HN水平下,两品种分别提高了41.0%和28.1%。LY光合响应大幅度提高归因于叶片最大羧化效率(V_(c,max))、最大光合电子传递效率(J_(max))、核酮糖-1,5-二磷酸羧化酶(Rubisco)含量、叶绿素含量、叶片氮含量等显著提高;(5)E-CO_(2)显著增加了不同氮水平下LY单株叶面积,对NJ无显著影响;(6)E-CO_(2)显著增加了LY各器官及总生物量,且HN水平增幅明显大于LN水平。E-CO_(2)并未显著影响不同氮水平下NJ的总生物量,显著降低了HN水平下NJ地下部生物量(-16.7%)。【结论】无论在HN还是LN水平下,LY物质生产和生理特征对E-CO_(2)的响应幅度与NJ相比更高。生育前期LY较优的根系形态性状和根系活力、较高的CTKs含量、较强的氮素同化能力、较大的绿叶面积以及光合响应能力是其干物质生产对E-CO_(2)响应幅度较高的重要原因。

【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 CO_(2)concentration and nitrogen nutrition.【Method】In this study,a rice cultivar Liangyoupeijiu(LY)with high response to CO_(2)(high-response rice cultivar)and a rice cultivar Nanjing 9108(NJ)with low response to CO_(2)(low-response rice cultivar)were selected as materials.Hydroponic experiments were carried out in the climate chamber.Two CO_(2)treatments and two nitrogen treatments were set up with ambient CO_(2)concentration(A-CO_(2),400μmol·mol^(-1))and elevated CO_(2)concentration(E-CO_(2),600μmol·mol^(-1)),and high nitrogen(HN,1.25 mmol·L^(-1) NH_(4)NO_(3))and low nitrogen(LN,0.25 mmol·L^(-1) NH_(4)NO_(3)),respectively.The effects of elevated CO_(2)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-CO_(2)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-CO_(2)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-CO_(2)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-CO_(2)condition,but only NR activity increased in NJ.(4)At LN level,E-CO_(2)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-CO_(2)significantly increased the leaf area per plant of LY under different nitrogen levels,but had no significant effect on NJ.(6)E-CO_(2)significantly increased the organs and total biomass of LY,and the increased level under HN was significantly higher than that under LN level.E-CO_(2)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-CO_(2)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-CO_(2)conditions.