| Using LI-6400P portable photosynthesis system, adopting the method of long-term observation, experiment of comparison and system analysis of forest ecosystem, through long-term observation of natural and control state in seasonal representative weather, Characteritics of photosynthesis and response to environmental factors of two dominant species were studied in Maofeng mountain evergreen broad-leaved forest, Guangzhou, south China. Diurnal changes and seasonal variations of main paramrters of gas exchange and light and CO2 responses were analyzed. Relationship between parameters of gas exchange and eco-physiological factors were studied in different seasons. Simulated the relationship between major parameters of gas exchange and principal environmental factors. Constructed light responsing models of main parameters of gas exchang, comparing different models of light response and CO2 response of photosynthesis. The main results were as follows.1,The diurnal variation curve of net photosynthetic rate of Machilus chinensis leaves was one peak curve and that of Castanopsis chinensis leaves was two peaks curve under sunny days. Average net photosynthetic rate, maximum value and average dark respiratory rate of Machilus chinensis leaves were 10.08μmol·m-2·s-1, 14.56μmol·m-2·s-1 and 1.25μmol·m-2·s-1 under sunny days of rainy season, and 6.76μmol·m-2·s-1, 11.31μmol·m-2·s-1 and 0.57μmol·m-2·s-1 under sunny days of dry season, while for Castanopsis chinensis leaves average net photosynthetic rate and maximum value were 8.52μmol·m-2·s-1 and 12.94μmol·m-2·s-1 under sunny days of rainy season, and 7.28μmol·m-2·s-1 and 12.95μmol·m-2·s-1 under sunny days of dry season. Expect that there was no significant difference between two seasons for light use efficiency, net photosynthetic rate, transpiration rate and stomatal conductance in rainy season were greater than those in dry season, but water use efficiency was less than it in dry season.2,Midday depression of net photosynthetic rate of Castanopsis chinensis leaves was induced by non-stomatal factors in rainy season, while in dry season it was induced mainly by stomatal factors. 3,The relationship between net photosynthetic rate, transpiration rate and eco-physiological factors was studied, main influence factors were ordered and optimal models were constructed by correlation analysis, step regression analysis and path analysis. Main factors influencing net photosynthetic rate of Machilus chinensis leaves were stomatal conductance, intercellular CO2 concentration and light intensity in dry season, while in rainy season those were intercellular CO2 concentration, stomatal conductance, air CO2 concentration and light intensity. Those influencing net photosynthetic rate of Castanopsis chinensis leaves were stomatal conductance, vapor pressure deficit, light intensity and intercellular CO2 concentration in dry season, while in rainy reason were intercellular CO2 concentration, light intensity, air temperature and stomatal conductance.4,The relationship between net photosynthetic rate, transpiration rate, stomatal conductance and environmental factors was simulated separately for two species in two seasons and concrete forms of models adapting to that were supplied. Net photosynthetic rate of Machilus chinensis leaves in dry and rainy season can be simulated by quadratic equation in two variables and sextic equation in one variable, transpiration rate of that can be simulated by cubic equation in one variables and quadratic equation in two variables and stomatal conductance of that can be simulated by constructed Jarvis model and Ball-Berry revising model; net photosynthetic rate in dry season and transpiration rate in rainy season of Castanopsis chinensis leaves can be simulated by equation of linear regression. Stomatal conductance of Castanopsis chinensis leaves in dry and rainy season can be simulated best by constructed Jarvis model and Ball-Berry revising model.5,Parameters of light response of photosynthesis and CO2 response of photosynthesis were different significantly. Photosynthetic capacity(Pmax), maximum carboxylation rate (Vcmax), maximum electron transferring rate (Jmax), apparent quantum yield (α), light saturation point(Qsat), light compensation point(Qcomp) and CO2 compensation point(Ccomp) of two species were both greater in rainy season than those in dry season,while carboxylation efficiency(CE) of two species was both greater in dry season than that in rainy season. Variation of dark respiratory rate (Rd) between two seasons was different between two species, dark respiratory rate of Machilus chinensis leaves was greater in rainy season than it in dry season, but for Castanopsis chinensis leaves it was reverse. During the same seasons Photosynthetic capacity(Pmax), maximum carboxylation rate (Vcmax), maximum electron transferring rate (Jmax), apparent quantum yield (α), light compensation point(Qcomp) and CO2 compensation point(Ccomp) of Castanopsis chinensis leaves were greater than those of Machilus chinensis leaves. Carboxylation efficiency (CE) and dark respiratory rate (Rd) of Castanopsis chinensis leaves were greater than that of Machilus chinensis leaves in dry season, while in rainy season that was reverse. During the same seasons light saturation point (Qsat) of both species were almost the same.6,Parameters of light response of phosynthesis were variable significantly. Apparent quantum yield (α) increased gradually in Ante Meridian, to reach maximum value at 11:00, followed by decline, to reach minimum value at 13:00, and then it increased gradually. The trend of light compensation point (Qcomp) was just opposite. Photosynthetic capacity(Pmax) reached maximum value and dark respiratory rate (Rd) had a depression at 13:00.7,Different models of light response of photosynthesis and CO2 response of photosynthesis were compared and new model were better.8,Models of light response of stomatal conductance and transpiration rate were constructed. Diurnal variation and seasonal difference of maximum stomatal conductance and maximum transpiration rate, as the main parameters of response, were studied. Maximum stomatal conductance of Machilus chinensis leaves was 0.13 mol·m-2·s-1 in dry season and 0.57 mol·m-2·s-1 in rainy season. Maximum stomatal conductance of Castanopsis chinensis leaves was 0.1 mol·m-2·s-1 in dry season and 0.45 mol·m-2·s-1 in rainy season. Maximum transpiration rate of Machilus chinensis leaves was 2.91 mmol·m-2·s-1 in dry season, while that of Castanopsis chinensis leaves was 2.24 mmol·m-2·s-1 at the same season.
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