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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. [ABSTRACT FROM AUTHOR]

Grapes are one of the main economic crops in the arid area of Northwest China. Understanding its photosynthetic production process is very important for planting and cultivation. In order to analyze the physiological characteristics of grape photosynthesis and the main influencing factors affecting grape photosynthesis under natural conditions in the field, the daily variation of net photosynthetic rate of grape(variety: Seedless White) leaf and its daily variation of physiological and ecological factors in typical season of grape were measured from June to September in 2019. The path analysis method is used to analyze the direct and indirect effects of various factors on the net photosynthetic rate of grape leaf, and to determine its main influencing factors. In addition, the response of the net photosynthetic rate of grape leaf to various physiological and ecological factors was further analyzed in the whole day time-phased mode. The results were as follows: (1) The daily variation of net photosynthetic rate of grape leaf showed a single peak pattern, which first increased and then decreased; (2) The net photosynthetic rate of grape leaf was positively correlated with photosynthetic active radiation, vapor pressure deficit, air temperature, stomatal conductance and transpiration rate, and negatively correlated with relative humidity and intercellular CO2 concentration. Among them, the correlation coefficient with stomatal conductance and transpiration rate was the largest; (3) The main determinant that affected the variation of net photosynthetic rate of grape leaf was the transpiration rate in June, August and September, and the stomatal conductance in July; (4) The net photosynthetic rate of grape leaf in each month showed a “hysteretic loop” relationship with air temperature, photosynthetic active radiation, vapor pressure deficit, and a good linear relationship with transpiration rate and stomatal conductance(R²>0.85), and an exponential function relationship with intercellular CO2 concentration(R²=0.53). Studies have shown that grapes have a strong ability to adapt to the environment in the arid area of Northwest China. In cultivation, we can optimize management and increase yield by controlling transpiration rate and stomatal conductance, but the direct and indirect effects of other factors need to be considered. [ABSTRACT FROM AUTHOR]