海岸不同坡向滨麦光合特性与风速异质环境的关系

在自然条件下,测定分析了夏季和秋季静风天及秋季大风天,海岸沙丘不同坡向环境因子及滨麦株高、叶片叶绿素含量、土壤含水量和光合日变化特性,以期明晰滨麦响应不同风速环境的生理调控机理。结果表明,不同坡向环境异质性明显,滨麦形态可塑性强。海岸迎风坡风大、温度低、湿度大,滨麦植株低矮、叶绿素含量较高;背风坡温度高、土壤干旱、空气流动差,滨麦植株高大,叶绿素含量低。在夏秋季静风天,迎风坡和背风坡滨麦叶片Pn出现光合"午休"现象,但迎风坡滨麦日均Gs、Tr、Pn均显著高于背风坡;而在秋季大风天,迎风坡和背风坡滨麦叶片Pn"午休"现象消失,并且背风坡滨麦日均Pn、Tr、Gs均显著高于迎风坡滨麦。同坡向相比,秋季大风天迎风坡滨麦日均Pn、Tr、Gs明显较秋季静风天低,而背风坡滨麦日均叶片Pn、Tr、Gs却较静风天分别增高126%、66.3%、134%。强海风吹袭引发迎风坡温度降低、滨麦叶片摇摆、气孔导度降低导致Pn下降,而强海风使背风坡空气流动加快、温度降低、气孔导度增大、"午休"消失使Pn增高。不同坡向滨麦对不同海风风速的适应表现出明显的光合生理可塑性,它在滨麦适应不同风力、提高其光合速率和增加物质积累上具有重要作用。而滨麦的形态和光合生理可塑性可能是其在不同海风强度下生存、生长、实现种群扩张的重要生理调控机理,这一特性在未来作物、牧草和树木抗风、抗盐育种中具有重要应用价值。

The changes in photosynthetic characteristics of Leymus mollis (Trin.) Hara leaves from coastal dunes having an environmental heterogeneity

The environmental factors, growth rate, chlorophyll content, and photosynthetic parameters in Leymus mollis (Trin.) leaves were measured during the day without wind in the fall and summer, and with high winds in the fall, in the natural environment to understand the physiological adaptation mechanisms of L. mollis to different wind speeds. The results showed that high winds, lower temperatures, and higher humidity were observed on the windward slopes, where L. mollis had higher chlorophyll contents in leaves and shorter plants. However, higher temperatures, drier soils, and poor airflow were observed on the leeward slopes, where L. mollis had lower chlorophyll contents in leaves and taller plants. There was obvious environmental heterogeneity between windward and leeward slopes, and enhanced morphological plasticity. During days of no wind in the fall and summer, L mollis on both slopes showed a midday depression of photosynthesis, but L. mollis on the windward slopes had markedly higher stomatal conductance(Gs), transpiration rate(Tr), and net photosynthetic rate(Pn)than that of the leeward slopes. However, during days of high wind in the fall, L. mollis on both slopes had no midday photosynthetic depression, and L. mollis on the leeward slopes had markedly higher Gs, Tr, and Pn than that on the windward slopes. On the same slopes, during the days of high wind, L. mollis on the windward slopes had lower Pn, Tr, and Gs than that on days with no wind, but higher Pn, Tr, Gs by 126, 66.3, and 134% on the leeward slopes than that on days with no wind. High winds resulted in lower temperatures, reduced stomatal aperture, and leaves on the windward side with reduced Pn. High winds resulted in increased air flow, and reduced temperatures on the leeward slopes, which increased L. mollis stomatal opening, but had no midday photosynthetic depression and higher Pn. L. mollis on both slopes showed significant photosynthetic plasticity to adapt to different wind speeds, enabling it to take advantage of the environmental resources and increase photosynthesis and dry matter accumulation for its sustained survival. Morphological and photosynthetic plasticity of L. mollis is an important physiological regulation mechanism to enhance survival, growth, and population expansion under high winds, which has an important application value for the breeding of crops, grasses, and trees with higher tolerance to wind in the future.