海南东寨港两种红树植物旱季和雨季的光合生理特征比较

Comparison of photosynthetic physiological characteristics of two mangrove plants in dry and rainy seasons in Dongzhaigang, Hainan

关键词:  净光合速率, 季节变化, 红树植物, 通径分析, 海南东寨港

Key words:  net photosynthetic rate, seasonal change, mangrove plants, path analysis, Dongzhaigang of Hainan

摘要:

植物光合生理生态特性是退化植物群落恢复、重建植物种选择的重要依据。为研究不同红树植物光合生理生态特性,该研究于2021年旱季的4—5月、雨季的7—9月利用LI-6400光合仪,测定红树植物秋茄和海莲的光合生理参数和主要生态因子,并采用通径分析方法分析主要生态因子对净光合速率的影响。结果表明:(1)秋茄旱季净光合速率日均值(8.43 μmol^-2·s^-1)略低于雨季(8.67 μmol^-2·s^-1),差异不显著; 海莲旱季净光合速率日均值(7.03 μmol^-2·s^-1)显著低于雨季(9.41 μmol^-2·s^-1); 旱季秋茄净光合速率日均值显著高于海莲,而雨季秋茄净光合速率日均值显著低于海莲。(2)旱季、雨季秋茄蒸腾速率、气孔导度、胞间CO₂浓度等光合生理因子日均值变化幅度小于海莲,水分利用效率也低于海莲。(3)旱季、雨季两种红树植物均存在“光合午休”现象。旱季,秋茄属于非气孔限制,而海莲属于气孔限制; 雨季,秋茄和海莲均属于气孔限制。(4)旱季影响秋茄净光合速率的主要决策因子是光合有效辐射,主要限制因子是相对湿度,而生态因子对海莲净光合速率均起限制作用,其中饱和水汽压差是主要限制因子; 雨季秋茄和海莲的主要决策因子均是光合有效辐射,主要限制因子均是饱和水汽压差。综上研究表明,秋茄对于生境变化有着更强的适应性,海莲不仅具有较好耐旱性能,而且更适合高温多雨生境,该研究结果为退化红树林的恢复重建植物种选择提供了科学依据。

Abstract:

The photosynthetic physiological and ecological characteristics of plants are an important basis for the selection of plant species for restoration and reconstruction of degraded ecosystems. In order to study the photosynthetic physiological and ecological characteristics of different mangrove plants, from April to May in dry season and from July to September in rainy season of 2021, the LI-6400 photosynthetic measurement system was used to monitor the photosynthetic physiological parameters and main ecological factors of Kandelia obovata and Bruguiera sexangular in Dongzhaigang National Nature Reserve. The effects of major ecological factors on net photosynthetic rate were analyzed by using path analysis. The results were as follows:(1)The daily average net photosynthetic rate of Kandelia obovata in the dry season(8.43 μmol^-2·s^-1)was slightly lower than that in the rainy season(8.67 μmol^-2·s^-1), and the difference was not significant. In contrast, the rate of Bruguiera sexangular in the dry season(7.03 μmol^-2·s^-1)was significantly lower than that in the rainy season(9.41 μmol^-2·s^-1). The rate of Kandelia obovata was significantly higher than that of Bruguiera sexangular in dry season, while the rate of Kandelia obovata was significantly lower than that of Bruguiera sexangular in rainy season.(2)The daily average variations of transpiration rate, stomatal conductance and intercellular CO₂ concentration of Kandelia obovata were smaller than those of Bruguiera sexangular and the water use efficiency was also lower than that of B. sexangular in dry and rainy seasons.(3)There was a phenomenon of “midday depression of photosynthesis” in both dry and rainy seasons of Kandelia obovata and Bruguiera sexangular. In dry season, the main reason for the phenomenon of Kandelia obovata might be due to non-stomatal limitation, while Bruguiera sexangular due to stomatal limitation. In rainy season, the phenomena of two mangrove plants were both mainly caused by stomatal limitation.(4)In the dry season, the main decision factor affecting the net photosynthetic rate of Kandelia obovata was photosynthetically active radiation, and the main limiting factor was relative humidity, while ecological factors played a limiting role on the net photosynthetic rate of Bruguiera sexangular of which saturated water vapor pressure difference was the main limiting factor. In the rainy season, the main decision factor was photosynthetically active radiation, and the main limiting factor was saturated water vapor pressure difference for both Kandelia obovata and Bruguiera sexangular. In summary, Kandelia obovata is more adaptable to habitat changes, and Bruguiera sexangular not only has better drought tolerance performance, but also more suitable for hot and rainy habitats, which will be the scientific reference for the selection of plant for restoration and reconstruction of degraded mangroves.