Performance of chlorophyll a fluorescence parameters in Dracocephalum kotschyi and Nepeta crassifolia plants growing at low and high altitudes

The main focus of the present study was to better understand the effects of altitudinal gradient factors on the photochemical processes as reflected in changes in fast chlorophyll a fluorescence kinetics and related biophysical parameters in low and high-elevation ecotypes of Dracocephalum kotschyi and Nepeta crassifolia (located in Mazandaran, adjacent Central Alborz mountain range, central-northern part of Iran). In both Dracocephalum kotschyi and Nepeta crassifolia, high-altitude plants exhibited higher fluorescence parameters as compared to low-altitude plants, which was coupled with higher levels of carotenoids, suggesting proper functioning of PSII. Increased photochemical activity in high-altitude plants was achieved by increased levels of the activity of the oxygen-evolving complex (Fv/Fo), the performance index (PIabs) and the quantum yield for electron transport (φEo). In addition, a clear increase in the relative amplitude of the IP (Fm) phase from the OJIP curve was observed in high-altitude plants as compared to low-altitude plants. These results indicated a significant variation in the performance of chlorophyll a fluorescence parameter, between low- and high-altitude plants, which is apparently due to eco-physiological differences in relation to their altitudinal distributions. Summarizing, high-altitude plants have developed a series of mechanisms with respect to photosynthetic apparatus efficiency to protect themselves from adverse environmental threats.

Performance of chlorophyll a fluorescence parameters in Dracocephalum kotschyi and Nepeta crassifolia plants growing at low and high altitudes Keywords:

Altitudinal gradient , Carotenoids , High-altitude plants , Photochemical processes , Altitudinal gradient , Carotenoids , High-altitude plants , Photochemical processes