阴晴天条件下高CO2浓度对杂交稻光合作用影响的FACE研究

光和二氧化碳(CO₂)是绿色植物光合作用的两个基本条件.为了明确不同光照条件下,高CO₂浓度对不同杂交水稻光合特性的影响,2017年利用稻田大型FACE平台,以‘Y两优900’和‘甬优538’为供试材料,设置环境CO₂和高CO₂浓度(增200 μmol·mol^-1)两个水平,分别在拔节期和灌浆期同时测定阴、晴天气条件下顶部全展叶光合特性参数.结果表明: 高CO₂浓度使不同天气情况下两品种叶片的净同化率(P_n)均呈增加趋势,其中晴天条件下的增幅(31%)大于阴天(25%),拔节期的增幅(37%)大于灌浆期(21%),CO₂与天气、CO₂与生育期均存在显著的互作效应.叶片水分利用效率(WUE)对高CO₂浓度的响应趋势与P_n一致.高CO₂浓度环境下叶片气孔导度(g_s)、蒸腾速率(T_r)均呈下降趋势,晴天条件下的降幅略大于阴天.与晴天相比,阴天条件下叶片P_n、g_s、T_r、WUE和L_s平均分别下降41%、18%、41%、26%和27%,差异均达显著或极显著水平.相关分析表明,晴天P_n、g_s、T_r均与阴天时的参数呈极显著正相关关系.表明阴天使水稻生育中、后期叶片光合参数及其对高CO₂浓度的响应均大幅降低,且两品种表现一致.评估未来水稻产量潜力需要考虑天气条件.

Effects of elevated atmospheric CO2 concentration on photosynthsis of hybrid rice varieties in cloudy and sunny days: A FACE study

Light and carbon dioxide (CO₂) are two essential components for plant photosynthesis. To understand the effects of elevated CO₂ concentration on photosynthetic characteristics of hybrid rice under different light conditions, two hybrid rice varieties (YLY900 and YY538) were grown in the field using a free-air CO₂ enrichment facility (FACE) in 2017 with two CO₂ concentration treatments (ambient CO₂ and elevated 200 μmol·mol^-1 above ambient CO₂), the photosynthesis traits of top full expansion leaves were measured in both sunny and cloudy days at jointing and grain filling stages. Elevated CO₂ increased net photosynthetic rate (P_n) of two rice varieties. The increase in sunny days (31%) was greater than in cloudy days (21%), and the increase at jointing stage (37%) was greater than at grain filling stage (21%). There were significant interactions between CO₂ with weather, and between CO₂ with growth stage. Water use efficiency (WUE) of leaves in response to elevated CO₂ showed the similar trend as P_n. Elevated CO₂ decreased stomatal conduc-tance (g_s) and transpiration rate (T_r), and the decreases in sunny days were greater than that in cloudy days. The P_n, g_s, T_r, WUE and stomatal limit (L_s) measured in cloudy days were significantly lower than that measured in sunny days by 41%, 18%, 41%, 26% and 27%, respectively. Results from the correlation analyses showed that the P_n, g_s, and T_r in sunny days were significantly positively correlated with the corresponding parameters in cloudy days. The results indicated that cloudy weather conditions reduced photosynthesis and its response to elevated CO₂ of two hybrids rice varieties at middle and late growth stages. Therefore, weather variation should be considered when assess rice yield potential in the future environment.