不同种植方式下温度升高对水稻产量及同化物转运的影响

【目的】气候变暖对水稻生产系统的影响备受关注,研究不同种植方式下,水稻产量及其形成对气候变化的响应规律,为水稻种植区划、栽培措施和品种调整提供依据。【方法】 2017—2018年以南粳9108和南粳46为供试品种,模拟机插秧移栽和机械化直播2种种植方式,以常温（NT）为对照,于始穗期进行中度升温（平均增加2℃,MT）和极端高温胁迫（平均增加5℃,HT）,研究不同种植方式下温度升高对不同水稻品种的产量及其构成、同化物转运、光合生产特性的影响。【结果】在中度升温和极端高温胁迫下,南粳9108和南粳46产量降幅均为移栽<直播,长生育期品种南粳46产量降幅较小。穗干物重增长速率表现为NT>MT>HT,水稻茎叶向穗的干物质转运量、转运率均随着温度升高而递减,且南粳9108下降趋势大于南粳46。穗后21 d至成熟期,剑叶SPAD值总体随着温度的升高而增加,差异达极显著水平;剑叶净光合速率穗后14—21 d均以极端高温胁迫处理下最小,而到穗后35 d以极端高温胁迫处理下最大。剑叶气孔导度、蒸腾速率均呈NT>MT>HT趋势,生育后期差异更显著。通径分析表明,产量各构成因子对产量的影响程度为结实率>千粒重>穗数>每穗粒数,温度处理对产量各构成因子的影响都表现为负效应,且以结实率影响最大（-0.819）。相关分析表明,不同种植方式下受中度升温、极端高温胁迫后,成熟期干物质总重量、茎叶干物质转运量与产量构成因子（穗数除外）,一、二次枝梗籽粒结实率都呈极显著正相关。【结论】始穗期2—5℃升温均显著降低粳稻结实率,从而导致水稻产量降低。从光合物质特性究其原因是由于温度升高降低了干物质向穗的转运率和穗干物质积累速率,从而导致生育后期水稻剑叶SPAD值增加,延长叶片持绿时间,抑制“源”向“库”转移。从气候变暖应对措施来看,选择采用移栽种植方式和长生育期品种易于表现出对极端高温胁迫逆境较好的抗性。

Effects of Elevated Temperature on Rice Yield and Assimilate Translocation Under Different Planting Patterns

【Objective】The effect of global warming on rice production has attracted much attention, leading to changes on planting area, cultivated practices and rice varieties. Thus, it is necessary to clarify the responses of rice yield and its formation to warming under different planting patterns.【Method】During 2017 to 2018, we selected two varieties (Nanjing 9108 and Nanjing 46), two planting patterns (simulating machine transplanting and mechanized direct sowing), and three temperature treatments, including normal temperature (NT) as control, moderate temperature (average increase 2℃, MT) and extreme high temperature stress (average increase 5℃, HT), to study the effects of elevated temperature on rice yield, yield composition, assimilation transport and the characteristics of photosynthesis production.【Result】Under MT and HT treatments, the decreasing yields of Nanjing 9108 and Nanjing 46 under transplanting were less than that under direct sowing, while the yield of the long-growth variety Nanjing 46 had smaller decline. The growth rate of the spike dry material showed the trend of NT>MT>HT. The amount and rate of dry matter translocation from rice stem and leaves to spike decreased with the increase of temperature, and the decreasing effects on Nanjing 9108 was greater than that for Nanjing 46. Moreover, after 21 days of heading to maturity, the SPAD of flag leaf increased with elevated temperatures significantly. And the lowest net photosynthetic rate of flag leaf was found under HT at 14-21 days after heading period, while the highest was found at 35 days after heading period. In addition, The stomatal conductance and transpiration rate of flag leaf showed the increasing trend of NT>MT>HT, and the difference was more significant in the later growth stage. The path analysis indicated that the importance of yield components on yield was in the order of filled grain percentage>1000-grain weight>number of panicles>spikelet number per panicle, and all the elevated temperature treatments had negative impacts on yield components, with the greatest effect (-0.819) on filled grain percentage. The relevant analysis showed that the total weight of dry matter at maturity, the amount of translocation were significantly positively correlated to the yield composition factor (except the number of spikes) and the filled grain percentage of primary and secondary branches under MT and HT. 【Conclusion】Increasing 2℃ to 5℃ at the initial heading stage significantly reduced the filled grain percentage of rice, which led to the decrease of rice yield. From the perspective of photosynthetic characteristics, temperature rising reduced the rate of dry matter transported to spikes and declined dry matter accumulation in spikes, increasing SPAD of rice flag leaves in late growth period and thus prolonging the green holding time, which could inhibit the translocation from source to sink. Overall, we suggest that long-growth period varieties with proper plant patterns could have better resistance to elevated temperatures, which could be adaptive to the global warming.