| In the present work, the Quercus fabri were studied. The biennial seedlings of Quercus fabri were under 0%,30%,60% and 80% shading treatments and the annual seedlings of Quercus fabri were dealed with by submergence stress. Four levels of soil water content named CK, S1,S2 and S3 were set up in this study, where CK means the soil moisture was about 75% of field capacity, S1 means water surface under 15 cm of the soil surface, S2 means the soil moisture was under saturation state and S3 means the soil moisture was under super-saturation state and water surface was 15 cm higher than the soil surface. The physiological indexes and photosynthetic characteristics of leaves were studied after the shading treatment (biennial seedlings of Quercus fabri) and submergence stress (annual seedlings of Quercus fabri). The physiological response and adaptability of Quercus fabri under different light and water conditions were discussed. The results would provide a theory basis for the cultivation of Quercus fabri. The main conclusions as followed:(1)The content of chlorophyll a, chlorophyll b, total chlorophyll increased with the degree of shading treament. A negative correlation was found between the content of total chlorophyll and soluble sugar. The content of total chlorophyll was positive correlated with chlorophyll a, chlorophyll b and protens. Besides that, there was no obvious correlation between the starch, leaf relative water and total chlorophyll content.(2) The diurnal variations of net photosynthetic rate (Pn) for Quercus fabri showed single peak curves under four light intensity. The shading treatment resulted in the decrease of net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance(Gs) of Quercus fabri. The intercellular CO2 concentration (Ci) of leaves was ranging from 200 to 400μmol·mol-1. Except the light compensation points (LCP) and CO2 compensation(CCP) points, the light saturation points (LSP),CO2 saturation points (CSP), apparent quantum yield (AQY), carboxylation efficiency (CE) and the maximal net photosynthetic rates (Pn) under light and CO2 saturation conditions all decreased with the shading treatment. The maximum value of CSP and CCP was 1320μmol·mol-1 and 48.69μol·mol-1 under 0% and 80% shading treatment, respectively. The minimum value of CCP was 23.43μmol·mol-1 under 30% shading treatment.(3) The chlorophyll a fluorescence parameters of Quercus fabri were determined under different light conditions.The results showed that, the PSII primary chemical efficiency (Fv/Fm), potential activity (Fv/Fo) and photochemical quenching (qP) increased and non-photochemical quenching (qN) decreased with the shading treatment. The apparent photosynthetic electron transport rate (ETR):0%>30%>60%>80% shading treatment. The different shading treatments improved the utilization efficiency of PS II absorbing light energy in some extent. Quercus fabri has shade tolerance ability and can adjust itself to a weak light environment. The photosynthesis rate decreased greatly under 80% shading treatment which is very unfavorable to growth.(4) The content of chlorophyll a, chlorophyll b, total chlorophyll decreased with the degree of submergence stress.Under the S3 stress, the leaves of Quercus fabri changed into yellow gradually after 21 days and the situation became more serious after 35 days,50% plants have died. The results for the studies on physiological indexes showed that, there were significant negative correlation between the total chlorophyll content and soluble sugar, malondialdehyde and the leaf relative water. In addition, the negative correlation between total chlorophyll content and conductivity also obvious. On the contrary, the total chlorophyll content were remarkable positive correlated to chlorophyll a and chlorophyll b. There was no correlation between proten and the total chlorophyll content.(5) The net photosynthetic rate and stomatal conductance of Quercus fabri were decreased and water utilization efficiency was increased with the submergence stress, respectively. The diurnal trends of net photosynthetic rate under these 4 stress situations were basically consistent and all showed single peak curve. The variation of stomatal conductance before and after the submergence stress also very similar, which showed ascending-descending trend. The water utilization efficiency showed "L" trend with the peak value appeared at 8:00 AM.(6) The light compensation points and CO2 compensation points were increased and the light saturation points, CO2 saturation points, apparent quantum yield, carboxylation efficiency and the maximal net photosynthetic rate under light and CO2 saturation conditions were decreased with the submergence stress. The PSII primary chemical efficiency (Fv/Fm) and potential activity (Fv/Fo) were lowest under S3 level, which demonstrated that the photosynthetic electron transport rate was lowest. Meanwhile, the capture efficiency of reaction center to excited energy was descreased, which is an unfavorable condition to the photosynthesizes of Quercus fabri. The severe submergence stress caused the leaves chlorosis, decreased the light energy transform efficiency and made the loss of certain ornamental effect. However, the plant of Quercus fabri has a strong waterlogging tolerance for its self-adjusting function and can quickly adjust its metabolism to physiological response.
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