Effects of exogenous 5-aminolevulinic acid on chlorophyll fluorescence characteristics and energy dissipation of Sarcandra glabra under drought stress / 中草药

ABSTRACT

Objective To study the effects of drought stress on chlorophyll fluorescence characteristics and energy dissipation of Sarcandra glabra and get the method of alleviating drought stress, so as to provide theoretical basis against drought in planting. Methods Several physiological indexes of S. glabra treated by 5-aminolevulinic acid (ALA) under drought stress (PEG-6000 at the concentration of 15%) were measured, such as the contents of photosynthetic pigment, chlorophyll fluorescence parameters, and energy parameters. Results Exogenous ALA obviously increased the content of chlorophyll and carotenoids, enhanced the maximum fluorescence (Fm), photochemical efficiency of photosystem II (PSII, Fv/Fm), potential photochemical efficiency (FWFo), photochemical efficiency (Fv'/Fm'), PSII actual photochemical efficiency (φPSII), photochemical quenching coefficient (qP), electronic transfer rate (ETR), and photochemistry rate (PCR), as well as significnatly decreased the level of minimum fluorescence (Fo), non-photochemical quenching (NPQ) coefficient, and heat dissipation rate (HDR). The proportion of ALA absorbed light in photochemistry (P) was increased, the fraction of antenna pigment heat dissipation (D) and excess energy (E) for NPQ was decreased. The fraction off was the main pathway for excessive energy dissipation. ALA could promote the redistribution of energy reasonablely. Conclusion Exogenous ALA (100 mg/L) could significantly reduce the dissipation of excess excitation energy, improve the photochemical electron transport efficiency, and efficiently protect leaf blade of S. glabra from PSII damage under drought stress. ALA could obviously promote the drought resistance of S. glabra plantlet.