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| 大气CO2倍增下水分亏缺对青椒生长、气孔特征及生理生化过程的影响
摘 要
自十九世纪工业革命以来，大量化石燃料的使用、森林的砍伐以及土地利用方式的转变，导致大气CO2浓度急剧增加。与此同时，大气CO2浓度升高通过温室效应加剧气候变暖，进一步改变全球降雨模式，从而影响全球水分的分配平衡，导致季节性降水分布不均匀和区域性干旱事件频发，造成农作物的可利用水急剧减少，尤其是我国华北平原农业粮食生产面临着更为严峻的水资源短缺问题。因此，青椒的生长发育过程将不可避免地受到水分胁迫的影响，成为限制青椒产量的重要因素之一。然而，以往大多数研究只针对CO2浓度或水分亏缺单一因素对青椒开展实验，关于CO2浓度倍增和水分亏缺对青椒生理生化特性产生协同影响的机理研究还鲜有报道。故此，本研究设置8个能够精确控制CO2浓度的大型人工气候箱，分别设置了2个不同的CO2浓度（400 μmol mol-1和800 μmol mol-1）和4个不同的水分梯度（75–85 % FC，充分灌溉；65–75% FC，轻度亏水；55–65 % FC，中度亏水；45–55 % FC，重度亏水；FC为田间持水量）对青椒进行为期90天的处理，探讨CO2倍增条件下水分亏缺对青椒生长、气孔特征及生理生化过程的影响，得到主要结论如下：
（1）当青椒处于花前期时，在大气CO2浓度倍增条件下水分亏缺使近轴面气孔密度显著增加，重度亏水胁迫使远轴面的气孔密度显著增加107.9%；当青椒处于花期时，在轻度亏水胁迫条件下，大气CO2浓度倍增使近轴面与远轴面的气孔密度分别增加65.1%和79.1%；当青椒处于成熟期时，在大气CO2浓度倍增条件下水分亏缺使叶片近轴面气孔密度分别显著降低35.2%、23.5%和21.0%，然而远轴面气孔密度并未受到水分亏缺的显著影响。
（2）当青椒处于花前期时，在大气CO2浓度倍增条件下水分亏缺使叶片远轴面气孔面积分别显著增加74.6%、39.2%和46.0%，轻度亏水胁迫使近轴面气孔长度、周长和面积显著增加；当青椒处于花期时，在大气CO2浓度倍增条件下水分亏缺对近轴面气孔宽度未产生显著影响，重度亏水胁迫使远轴面气孔长度和周长显著增加14.1%和13.0%；当青椒处于成熟期时，在大气CO2浓度倍增条件下轻度亏水胁迫使远轴面气孔宽度、周长、面积和形状指数显著增加。
（3）当青椒处于花前期时，CO2浓度倍增导致水分亏缺条件下近轴面的气孔规则程度降低，而轻度和中度亏水胁迫使远轴面气孔分布得更加规则；当青椒处于花期时，CO2浓度倍增导致轻度和重度亏水胁迫条件下近轴面气孔的规则程度降低，而轻度亏水胁迫条件下的气孔分布得更加规则；当青椒处于成熟期时，CO2浓度倍增导致中度亏水胁迫条件下近轴面气孔的规则程度降低，同时轻度亏水和重度亏水胁迫使远轴面气孔规则程度降低。
（4）在轻度、中度和重度亏水胁迫条件下，CO2浓度倍增使青椒叶片可溶性糖含量分别增加17.9%、39.5%和57.9%；与可溶性糖相比，在充分灌溉和重度亏水胁迫条件下，CO2浓度倍增显著影响了叶片淀粉和TNC含量，其中淀粉和TNC含量在充分灌溉下显著降低，但在重度亏水胁迫下显著增加。在CO2浓度倍增条件下，青椒叶片C、N含量普遍因水分胁迫而降低；同时，在CO2浓度倍增条件下，中度和重度水分胁迫较充分灌溉显著提高了叶片C/N。
（5）在充分灌溉条件下CO2浓度倍增使净光合速率（Pn）显著增加38.9%；同时，在轻度、中度和重度亏水胁迫条件下CO2浓度倍增使Pn分别显著增加14.7%、25.2%和15.6%。在充分灌溉、中度和重度亏水胁迫条件下CO2浓度倍增使叶片水分利用效率（WUE）分别提高95%、100%和56%。
（6）在充分灌溉、轻度和中度水分胁迫条件下，CO2浓度倍增使青椒总生物量分别增加35%、54%和130%。其中，在充分灌溉和轻度亏水胁迫条件下，CO2浓度倍增使地上生物量分别增加48%和42%，地下生物量增加了近一倍；在CO2浓度倍增条件下，重度亏水胁迫并未对青椒植株的总生物量、地上生物量和地下生物量产生影响。
关键词：CO2浓度倍增；水分胁迫；气孔特征；气体交换；非结构性碳水化合物；青椒
FC, severe water stress; FC is the field water holding capacity) for 90 days,and the effects of water stress on plant growth,stomatal characteristics and physiological and biochemical processes of green pepper plants were discussed. The main conclusions are as follows:
(1) When green pepper plants were in the early anthesis stage,the stomatal density on the adaxial surface was significantlyincreased by water deficit under the condition of doubling atmospheric CO2 concentration, and the stomatal density on the abaxial surface was significantly increased by 107.9% under severe water stress.When green pepper plants were in the anthesis stage, under mild water stress,atmospheric CO2 concentration doubled to increase the stomatal density of adaxial surface and abaxial surface by 65.1% and 79.1%, respectively.When green pepper plants were in the maturation stage,under the condition that the atmospheric CO2 concentration doubled, the stomatal density on the adaxial surface of leaves decreased by 35.2%, 23.5% and 21.0%, respectively.However, it had no significant effect on the stomatal density on the abaxial surface.
(2) When green pepper plants were in the early anthesis stage,the stomatal area on the abaxial of leaves increased by 74.6%, 39.2% and 46.0%, respectively, and the length,perimeter and area of the adaxial of leaves increased significantly under mild water stress. When green pepper plants were in the anthesis stage,under the condition of doubling atmospheric CO2 concentration, water deficit had no significant effect onthe width of stomata on the adaxial surface, while severe water stress significantly increased the length and circumference of stomata on the abaxial surface by 14.1% and 13.0%.When green pepper plants were in the maturation stage, the width, perimeter,area and shape index of stomata on the abaxial surface were significantly increased by mild water stress when the atmospheric CO2 concentration doubled.
(3) When green pepper plants were in the early anthesis stage,the doubling of CO2 concentration led to the decrease of stomatal regularity on the adaxial surface under water stress, while mild and moderate water stress made the distribution of stomatal on the abaxial surface were more regular. When green pepper plants were in the anthesis stage,the doubling of CO2 concentration led to the decrease of the regularity of adaxial stomata under mild and severe water stress, while the stomata were distributed more regularly under mild water stress. When green pepper plants were in the maturation stage,the doubling of CO2 concentration led to the decreaseof the regular degree of stomata in the adaxial plane under moderate water stress, while the regular degree of stomata in the abaxial plane decreased under mild and severe water stress.
(4) Under mild, moderate and severe water stress,the content of soluble sugar in green pepper leaves increased by 17.9%, 39.5% and 57.9% respectively.Compared with soluble sugar,the doubled CO2 concentration significantly affected thestarch and TNC contents in leaves under full irrigation and severe water stress, and the starch and TNC contents decreased significantly under full irrigation, but increased significantly under severe water stress. In case of doubling CO2 concentration,the content of C and N in green pepper leaves generally decreased due to water stress. At the same time, under the condition of doubling CO2 concentration,moderate and severe water stress significantly increased C/N of leaves compared with full irrigation.
(5) The net photosynthetic rate (Pn) increased by 38.9% by doubling CO2 concentration under full irrigation.Meanwhile, under mild, moderate and severe water stress,the doubling of CO2 concentration significantly increased Pn by 14.7%, 25.2% and 15.6%, respectively.Under full irrigation, moderate and severe water stress,the water use efficiency (WUE) of leaves increased by 95%, 100% and 56%, respectively.
(6) Under full irrigation, mild and moderate water stress,the doubling of CO2 concentration increased the total biomass of green pepper plants by 35%, 54% and 130%, respectively. In addition, under the conditions of full irrigation and mild water stress, the doubled CO2 concentration increased the aboveground biomass by 48% and 42% respectively, and the underground biomass nearly doubled. Under CO2 concentration doubling and severe water stress, the total biomass,aboveground biomass and underground biomass of green pepper plants had almost no change.
Keywords: doubled CO2 concentration; water stress;stomatal characteristics; gas exchange; non-structural carbohydrates; green pepper
O2 concentration significantly affected the starch and TNC contents in leaves under full irrigation and severe water stress,and the starch and TNC contents decreased significantly under full irrigation, but increased significantly under severe water stress. In case of doubling CO2 concentration,the content of C and N in green pepper leaves generally decreased due to water stress. At the same time, under the condition of doubling CO2 concentration,moderate and severe water stress significantly increased C/N of leaves compared with full irrigation.
(5) The net photosynthetic rate (Pn) increased by 38.9% by doubling CO2 concentration under full irrigation.Meanwhile, under mild, moderate and severe water stress,the doubling of CO2 concentration significantly increased Pn by 14.7%, 25.2% and 15.6%, respectively.Under full irrigation, moderate and severe water stress,the water use efficiency (WUE) of leaves increased by 95%, 100% and 56%, respectively.
(6) Under full irrigation, mild and moderate water stress,the doubling of CO2 concentration increased the total biomass of green pepper plants by 35%, 54% and 130%, respectively. In addition, under the conditions of full irrigation and mild water stress, the doubled CO2 concentration increased the aboveground biomass by 48% and 42% respectively, and the underground biomass nearly doubled. Under CO2 concentration doubling and severe water stress, the total biomass,aboveground biomass and underground biomass of green pepper plants had almost no change.
Keywords: doubled CO2 concentration; water stress;stomatal characteristics; gas exchange; non-structural carbohydrates; green pepper
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