Light response and chlorophyll fluorescence parameters in Dicranopteris dichotoma with light intensity and nitrogen treatments

Abstract

This study was conducted to determine the photo-response and chlorophyll fluorescence parameters of potted Dicranopteris dichotoma for different light intensities and nitrogen application. Using one of the marker species of degraded vegetation in subtropical forests as the research material. Pot experiment were conducted to design with six treatments of different light intensities, including transmittance 35.96% (L1), 13.00% (L2) and 4.75% (L3), and nitrogen level, including nitrogen (N1) and without nitrogen (N0). All-light was used as control. The photosynthetic-light curve, photosynthetic characteristic parameters, gas-exchange, chlorophyll a fluorescence parameters and photosynthetic pigments were measured three times for each treatment. Results showed that:(1) Without nitrogen application, for L2, Pnmax and PLS were highest; PLC, Rd, and AQY were least. (2) For N0 application, the order of Pn and AQY was L2 > L1 > ck > L3, Gs was L1 > ck>L3 > L2; for N1 application the order of Pn, AQY and Gs was L1 > L2 > L3. For N1 and N0, the order of Ci was ck > L1 > L2 > L3. (3) For N0, under L2 and L3 light intensity, chlorophyll a, chlorophyll b, total chlorophyll content and carotenoids were significantly higher than those under L1 and ck(P < 0.05), and the overall performance increased with the decrease of light intensity. Chlorophyll a/b significantly decreased with a decrease in light intensity (P < 0.05). For the same light intensity, the content of photosynthetic pigments in the N application group was significantly higher than that in the non-N application group under L1 light intensity(P < 0.05), and significantly higher than that in other treatments(P < 0.05). (4) Except for L1 in N0 group, Fo and Fm under other light intensities were significantly different and increased with the decrease of light intensity(P < 0.05), the Fv/Fm of ck was significantly lower than that of other light intensities(P < 0.05). Compared with the N0 group, Fo decreased significantly, Fm of L3 decreased significantly, Fv/Fo and Piabs of L2 increased significantly(P < 0.05). In a word, under full light, the photos-inhibition of potted D. dichotoma is the most serious. N can improved the net photosynthetic rate of potted D. dichotoma to a certain extent, increased heat dissipation and alleviated the photo-inhibition, but it is not conducive to the improvement of photosynthetic pigments of L2 and L3.