Effect Of Exogenous Nitric Oxide On The Leaf Stomatal Movement And Drought Resistance Of Populus Under Drought Stress

Drought is becoming more and more important factor that influence and restrict the efficient sustained forestry in drought region. So it is necessary to study the limitation of photosynthesis of populus under drought stress.and search a cheap drought-resistance medicament. This paper was conducted with injury of drought stress to photosynthetic mechanism in populus, and effect of exogenous nitric oxide on the leaf stomatal movement and drought resistance of populus under drought stress. Furthermore,Stomatal movement mechanism and drought resistance of populus were analyzed at molecular level. The main results were as follows:1. The reduction in photosynthetic rate under drought stress was due to the combining effects of both stomatal and non-stomatal factors. At first, the main cause of the reduction in photosynthetic rate is stomatal factors, at last, non-stomatal factors.PS II reaction center was injured, and photosynthetic electron transport rate was inhabited which inhibited activity of photophosphorylation.Drought caused photoinhibition and increased the damage of reactive oxygen. Antioxygenation of fast-growing 107 was stronger than Populus pseudo-simonii.2. As expected, both NO and ABA can induce stomatal closure of detached populus leaves. In the presence of c-PTIO, a specific NO scavenger, the guard cells were not responding to both ABA and NO treatment, but the stomatal closure percentage of the combined treatment was significantly lower than in those experimentd done with either ABA or SNP alone. All together, these experiments suggest that NO might be acting downstream of the ABA-induced signaling cascade.Treatmented with different concentration of SNP(0.2 , 0.5 , 1.0 and 2.0mmol/L SNP),a NO donor,POD activities were dramatically inhibited.However, the changes of SOD activities were not too great.In vitro experiments also indicated that the same appearance. Therefore, it is NO not ABA playing a role in regulating H2O2 levels in detached populus leaves. That means, NO is a novel component of ABA signaling in stomatal guard cells, and the effect of ABA on leaf stomatal movement was possibly connected with the inhibition of POD by NO.3.With SNP treatment, stomatal conductivity and transpiration rate decreased, while RWC and water-retaining ability of leaves increased. Fast-growing 107 was better than Populus pseudo-simonii according to the effect on the drought resistance of populus of SNP.Fv/Fm and Fv/Fo with SNP treatment dropped less than those without SNP treatment as the increase of severity of drought stress, which indicated that SNP could alleviate the stress of drought on populus. At the sametime, SNP could increase the content of soluble sugar and soluble protein, and alleviate the injury of drought stress on cell membrane.