| Water is an important limiting factor for the survival and growth of trees. As global temperature continues to rise, the phenomenon of the water shortage is becoming more and more serious. The arid and semiarid area in China accounts for about 50% of the land area, and in the non-dryland areas, forest production sometimesl severely reduced by drought. Therefore, the study on the physiological and ecological adaptation mechanism of plants to drought has long been one of the key research issues in plant physiology and ecology. Silicon (Si) is the second most abundant element of the earth’s crust and soil, and all plants contain silicon. Although whether silicon is one of the essential elements for plant growth still not identified, recent studies have shown that, silicon plays an important role in improving resistance of plants to biotic and abiotic stresses. A large number of studies have indicates that exogenous Si can alleviate the inhibition of drought to plant growth. With Populus euramericana clone 1-214 as the experimental material and 1.6 mmol/L Na2SiO3 as silicon source, the effects of Si on growth photosynthesis, chlorophyll fluorescence parameters, antioxidant defense system, osmotic regulation system were studied and the change of physiological and biochemical characteristics was analyzed in poplar plants under stress induced by 10% polyethylene glycol (PEG-6000). That whether Si could alleviate the drought stress on poplar plants induced by polyethylene glycol and its mechanism was also discussed. The following are the main findings of this study:1. Under drought stress conditions induced by PEG, shoot and root dry weight of poplar plants grown hydro ponically decreased significantly. Under the same drought stress conditions, Si addition increased dry weight of poplar plants, and the difference was significant. The shoot dry weight, root dry weight, total dry weight increased by 8.7%,23.9% and 12.0%, respectively.2. Under drought stress conditions induced by PEG, leaf net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), Intercellular CO2 concentration (Ci) of Populus euramericana clone 1-214 decreased significantly. Under the same drought stress conditions, compared to the single drought treatment, Si addition increased photosynthetic indexes and the significant difference was significant. The increase rate was 40.9%,72.1%, 11.7%,3.3%, respectively.3. Under drought stress conditions induced by PEG, compared to the control, the content of chlorophyll a and chlorophyll b in leaves of 1-214 poplar decreased significantly. The content of chlorophyll a was significantly different from that of the control. The content of chlorophyll b and chlorophyll a in the treatments increased compared with the single drought stress treatment, but the difference was not significant. Under drought stress conditions, the initial fluorescence (Fo) increased, and maximum fluorescence (Fm), PS Ⅱ primary light energy conversion efficiency (Fv/Fm) and PS Ⅱ photochemistry underlying activity (Fv/Fo) were significantly decreased. Under the same drought stress conditions, silicon addition decreased Fo significantly, with an decrease of 12.8%. The rest of the chlorophyll fluorescence parameters were increased significantly, among which Fm increased by 19.4%, Fv/Fm increased by 12.1%, and Fv/Fo increased by 55%, respectively.4. Under drought stress conditions induced by PEG, poplar leaf relative water content, cell membrane permeability and root activity were significantly decreased. Under the same drought stress conditions, Si addition increased the above indicators, and relative water content, cell membrane permeability increased significantly, which increased by 35.1% and 55.8%, respectively.5. Under drought stress conditions induced by PEG, the content of superoxide anion free radical (O2-.), MDA and free proline of the poplar plants increased significantly. The activity of superoxide dismutase (SOD) decreased but the difference was not significant compared the control. The activity of peroxidase (POD) decreased significantly. Under the same drought conditions, Si addition significantly decreased the contents of (O2-.), MDA and free proline, which decreased by 28%,68.6% and 71.8%, respectively. The activities of SOD and POD increased by Si addition, but the difference was not significant. |
PDF Full Text Request