Regulation Of24-epibrassinolide And Chlorothalonil Treatment To Photosynthesis And Physiological Metabolism In Grape Leaves

The experimental material was potted seedlings of the Vitis vinifera L. cv. CabernetSauvignon. There were six treatments in this study:(1) Water treatment as control (CK);(2)Spraying0.10mg/L EBR (24-epibrassinolid)(EBR);(3) Spraying600-fold dilution ofchlorothalonil (CHT);(4)0.05mg/L EBR+CHT (A);(5)0.10mg/L EBR+CHT (B);(6)0.20mg/L EBR+CHT (C). During the1-9d after chlorothalonil application, relevant indicatorswere determined and the main results demonstrated as follows:(1) Compared with the control, EBR (0.10mg/L) treatment alone could improve netphotosynthesis rate (Pn)、stomatal conductance (Gs) and intercellular CO2concentration (Ci)of grape leaves significantly, while CHT treatment made them decrease significantly; The twotreatments of0.05mg/L EBR+CHT and0.10mg/L EBR+CHT made gas exchange parameterssignificantly higer than the control and CHT treatment, and0.05mg/L EBR+CHT treatmentshowed maximum increase, with Pn，Gsand Ciincreased by40%，82%and53%respectivelycompared to CHT treatment. The results indicated that lower concentrations of EBR(0.05-0.10mg/L) treatment could effectively alleviate the supression of photosynthetic gasexchange parameters caused by chlorothalonil.(2) Generally speaking, EBR（0.10mg/L）treatment alone could significantly improve thevalues of photosynthetic system II (PSII) photochemical conversion rate (Fv/Fm) andnon-photochemical quenching (NPQ), while values of actual photochemical efficiency (ΦPSⅡ)and photochemical quenching (qP) were lower than the control. Fv/Fm，ΦPSⅡand qP in CHTtreatment decreased, while NPQ increased most compared with the control. Differentconcentrations of EBR pretreatments effectively alleviated the decrease of Fv/Fm，ΦPSⅡandqP and the increase of NPQ after pesticide application, and compared with CHT,0.05mg/LEBR+CHT and0.10mg/L EBR+CHT treatments made Fv/Fm，ΦPSⅡand qP increase greatlyand made NPQ decrease significantly. Whereas the difference in chlorophyll fluorescenceparameters between0.20mg/L EBR+CHT and CHT treatment was not significant.Meanwhile, CHT treatment made chlorophyll content of gape leaves decease, while lowerconcentrations of EBR pretreatment made it increase significantly.(3) There was no significant difference between EBR (0.10mg/L) treatment alone andthe control in soluble protein content, but proline content in EBR treatment was significantly higher than the control. CHT treatment made soluble protein and proline content increase, butthe enhancement was not significant compared with the control. EBR pretreatment couldfurther promote the accumulation of soluble protein and proline in grape leaves, and0.05mg/L EBR+CHT and0.10mg/L EBR+CHT treatment had obvious promoting effect.EBR treatment alone had no significant effect on the contents of malondialdehyde（MDA）、hydrogen peroxide (H2O2) and superoxide anion (O2-), while CHT treatment (600times dilute)made their contents increase obviously.0.05mg/L EBR+CHT and0.10mg/L EBR+CHTtreatments made MDA, H2O2and O2-content decrease by5-6%,23-24%and15%respectively. While H2O2content in0.20mg/L EBR+CHT treatment was significantly lowerthan CHT, meanwhile the other two targets had no obvious difference with CHT treatment.So it indicated that EBR (0.05-0.10mg/L) pretreatment could reduce damage caused bychlorothalonil through increasing the content of osmotic adjustment substances and reducingthe accumulation of reactive oxygen species.(4) Compared with the control, EBR (0.10mg/L) treatment alone could significantlyimprove reduced glutathione (GSH) and ascorbic (AsA) content in grape leaves, as well asperoxidase (POD), superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase(APX) activity. GSH and AsA content as well as POD, CAT and APX activity in CHTtreatment were also higher than the control. Compared with CHT treatment,0.05mg/LEBR+CHT treatment made antioxidant contents and activities of antioxidant enzymesincrease significantly, while there were no significant differences in antioxidant enzymeactivities between0.20mg/L EBR+CHT and CHT treatment. Therefore, a lowerconcentration of EBR (0.05mg/L) pretreatment could enhance the antioxidant capacity ofgrape seedlings after chlorothalonil application.(5) EBR treatment alone could enhance the activities of glutathione-s-transferase (GST)and glutathione reductase (GR), and CHT treatment made them increase by around50%.Compared with CHT treatment, EBR pretreatment significantly promoted the increase of GSTand GR activity. According to chlorothalonil residues detected in grape leaves, it was foundthat0.05-0.10mg/L EBR pretreatment could accelerate chlorothalonil degradation and shortenthe half-life of chlorothalonil, while higher concentration of0.20mg/L EBR had nosignificant promoting effect.(6) It was found that there were no significant difference in GSH (glutathionesynthetase), GST (glutathione s-transferase) and GR (glutathione reductase) expression levelsbetween CHT treatment and the control overall. while GST expression in0.05mg/LEBR+CHT treatment increased significantly, together with GSH and GR expressionsignificantly higher than the control and CHT treatment in later period after pesticide application. Compared with the control, CHT and0.05mg/L EBR+CHT treatment could bothpromote expression of MRP (MRP-type transporter) and P450(P450monooxygenase)significantly, and there was no significant difference between the two treatments overall.Therefore,0.05mg/L EBR pretreatment could significantly enhance the expression of GSTand GR, and GSH, MRP and P450expression in this group were higher than those in CHTtreatment without significant difference overall.