关于[CO₂]升高和降水变化等多因子共同作用对植物的影响报道较少, 制约着人们对植物对全球气候变化响应的认识和预测。玉米(Zea mays)作为重要的C₄植物, 受[CO₂]和降水影响显著, 但鲜有[CO₂]升高和降水增加协同作用对其产量及生长发育影响的报道。该研究利用开顶式生长箱模拟[CO₂]升高(390 (环境)、450和550 μmol·mol^-1), 降水增加量设置为增加自然降水量的15% (以试验地锦州1981-2010年6至8月月平均降水量为基准), 从而形成6个处理: C₅₅₀W_+15%、C₅₅₀W₀、C₄₅₀W_+15%、C₄₅₀W₀、C₃₉₀W_+15%和C₃₉₀W₀。试验材料选用玉米品种‘丹玉39’。结果表明: [CO₂]升高和降水增加的协同作用在玉米的籽粒产量和生物产量上均达到了显著水平(p< 0.05), 二因子均起正作用, 使籽粒产量和生物产量均升高。籽粒产量在[CO₂] 390、450和550 μmol·mol^-1水平下的降水增加处理较自然降水处理分别增加15.94%、9.95%和9.45%, 而生物产量分别增加13.06%、8.13%和6.49%。因为籽粒产量的增幅略大于生物产量的增幅, 所以促进了经济系数的升高。穗部性状变化显著, 其中, 穗粒数、穗粒重、穗长和穗粗等性状值均随[CO₂]升高而升高, 且各[CO₂]水平下均表现为降水增加处理>自然降水处理, 而瘪粒数相反。但是, [CO₂]升高和降水增加的协同作用也促进了轴粗的升高, 对玉米产量的增加起着限制作用。二因子协同作用在净光合速率(P_n)和叶面积上达到了极显著水平(p< 0.01), 而在株高和干物质积累量上达到了显著水平(p< 0.05)。二因子协同作用使玉米叶片的P_n升高, 植株高度升高, 穗位高升高, 茎粗增加, 叶面积变大, 从而促进了干物质积累量的升高, 为玉米增产打下了良好的基础。这表明: 在未来[CO₂]升高条件下, 一定程度的降水增加对玉米的产量具有正向促进作用。

Aims The yield and growth of maize (Zea mays) have changed due to the influence of climate change. Increasing CO₂ concentration ([CO₂]) and changes in precipitation are two important aspects of climate change affecting maize. Our objective was to explore the interactive effects of elevated [CO₂] and an increase in precipitation on yield and growth in maize, in order to evaluate the effects of future changes in climate change on plant in Northeast China.
Methods This experiment was conducted in Jinzhou, with the maize cultivar ‘Danyu 39’ as plant materials. Open top chambers (OTCs) were used to simulate the elevated [CO₂] (control at 390 μmol·mol^-1, and elevated at 450 and 550 μmol·mol^-1, respectively) and increased precipitation (0 and +15% increase based on the average monthly precipitation from June through August during 1981-2010). Totally six treatments, i.e. C₅₅₀W_+15%, C₅₅₀W₀, C₄₅₀W_+15%, C₄₅₀W₀, C₃₉₀W_+15% and C₃₉₀W₀ were included in this study.
Important findings Significant interactive effects between elevated [CO₂] and increased precipitation on corn grain yield and biological yield (p< 0.05) were found. The grain yield and biological yield were increased by the positive effects of the two factors. An increase in precipitation increased the grain yield by 15.94%, 9.95% and 9.45%, and the biological yield by 13.06%, 8.13% and 6.49%, respectively, at [CO₂] of 390, 450 and 550 μmol·mol^-1. The increase in grain yield was slightly greater than that of the biological yield, resulting in an increase in the economical coefficient. The ear characteristics of maize were significantly affected by the two factors. For example, kernels number, kernels weight, ear length and ear diameter were all increased by elevated [CO₂], as well as by an increase in precipitation. However, the shriveled kernels showed a reversed trend of changes. It is noteworthy that the axle diameter was increased by the interactive effects between elevated [CO₂] and an increase in precipitation, which constrained the increase in the grain yield. Moreover, there were highly significant interactive effects between elevated [CO₂] and an increase in precipitation on net photosynthetic rate (P_n) and leaf area (p< 0.01), and significant interactive effects on plant height and dry matter accumulation (p< 0.05). An increased precipitation increasedP_n of the leaves at each [CO₂] level. The results also showed that plant height, ear position height, stem diameter, leaf area were all increased by the interactive effects between the two factors, leading to enhanced dry matter accumulation and the yield. It can be concluded that future elevated [CO₂] may favor the growth of maize if coupled with increasing precipitation.