Response of Chlorophyll Fluorescence Parameters of Kandelia obovata Seedlings to Light Intensity in Incubator with Different Temperature

In spring of 2017, container Kandelia ogovata seedlings were transplanted into plastic drum and in January 2019, experiments were conducted after 7 days slow rooting. Seedlings were treated in incubators with different day-night temperature such as 25/20℃ (A), 20/15℃ (B), 15/10℃ (C) and 10/5℃ (D). The results showed that the response of electron transfer rate (ETR) to the light intensity of different treated seedlings could be fitted well by the light response mechanism model and the double exponential model. The fitted values were close to the measured ones. The light saturation points of the leaves of different treated seedlings ranged from 1 000 μmol/m2/s to 1 400μmol/m2/s. Taking the result of model fitting by light response mechanism as an example, the maximum electron transfer rates of seedling leaves were significantly different at different temperatures (P<0.05), which were 124.393, 110.812, 64.153, and 33.427 μmol/m2/s, respectively. Seedligns with treatment of D had the lowest excitation energy capture efficiency of PSII (Fv'/Fm'), the actual photochemical quantum efficiency of PSII (ΦPSII), photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (qN). It indicated that the low temperature had significant effect on the photosynthesis of K. ogovata seedlings.