Analysis Of Phototoxicity Caused By Fluoroglycofen And Acetochlor On Grapevine

Weed control is one important aspect of soil managements in vineyard. In recent years,due to labour shortage and lack of knowledge on grass cover in orchards, herbicidesapplication becomes increasingly universal and general in vineyards. Just because of that,there are more and more reports about herbicide phytotoxicity. In the survey of Qufu city,Shandong province in2009, the grape leaves in vineyard became dark green, and plantgrowth power was weak. Upon this background, our study verified the damage of herbicidesto grapevines through field and pot experiments, and explored the damage physiologicalmechanisms of acetochlor and fluoroglycofen to grapevines, so the reasons of grape leavesbecoming dark green. The results were as follows:1. Verification the combined herbicide reduced photosynthesis in grape leaves of vineyardIn Qufu city, Shandong province, compared with the artificial weeding, the leaf netphotosynthesis rate (Pn) in vineyards applied with combined herbicide (paraquat, acetochlorand fluoroglycofen) in2009decreased significantly; the maximum photochemical efficiencyof PSII (Fv/Fm) and performance index (PIABS) also decreased; however, the relative variablefluorescence in the J step and K step increased, which indicated the PSII reaction center andoxygen-evolving complex (OEC) were damaged. Besides, the soluble sugar, starch, freeamino acids and soluble protein content in branches were lower.In2010, Kyoho (Vitis vinifera×V. labrusca) vineyard which used herbicides but did nothappen phytotoxicity was selected. Lower concentration of combined herbicides (paraquat,acetochlor and fluoroglycofen) reduced Pn of middle-node leaves in the earlier treatment time;while the higher level reduced Pn through the growing season, so the soluble solid andanthocyanin content of grapes, the free amino acid and soluble protein content of branchesafter defoliation.2. Effects of acetochlor and fluoroglycofen on photosynthesis in grape leaves In the soil pot experiments, the Pn in middle-node leaves of Kyoho decreased along withthe processing time, besides, acetochlor and fluoroglycofen reduced Pn in a dose-dependentmanner. In the30thday, Pn in different nodes of leaves also decreased along with acetochlorand fluoroglycofen concentration increased. Under the field maximum recommended dose,acetochlor reduced Pn in upper-and middle-node leaves, while fluoroglycofen only reduced itin middle-node leaves; higher concentration of herbicides significantly reduced Pn in all nodeleaves, which caused the greatest reduction under ten times of field maximum recommendeddose.The photosynthetic function in Kyoho leaves grown in sand shown obvious time-andspace-effect responding to acetochlor and fluoroglycofen (the concentrations were both fivetimes of field maximum recommended dose). In the earlier treatment time (13thday aftertreatment), the upper-node leaves showed significant responses to acetochlor, the Pn and Gsdecreased significantly, so the Fv/Fm and quantum yield of PSII electron transport; therelative variable fluorescence in the J step and K step of the chlorophyll fluorescencetransients increased obviously, while the PIABS, φEoand φodecreased markedly, whichindicated that the PSII reaction center and OEC were damaged, meanwhile the electrontransport ability decreased; furthermore the damage and reduction were severer than inmiddle-node leaves, but the degree of damage was alleviated along with the treatment time.However, the differences of the photosynthetic and chlorophyll fluorescence parametersbetween upper-and middle-node leaves diminished in the later stage (60thday after treatment).The bottom-node leaves appeared later responses to herbicides than that of theupper-/middle-node leaves; in the later stage, the damaged extent of PSII reaction center andOEC, and the inhibition of electron transport ability were much higher than that ofupper-/middle-node leaves. The effects of fluoroglycofen on photosynthetic apparatus wereless than acetochlor.3. Effects of fluoroglycofen and acetochlor on colour of Kyoho leavesIn the60thday after fluoroglycofen (the concentrations was five times of field maximumrecommended dose) treatment, the middle-and upper-node leaves became dark green, and thepigments increased obviously. Positive correlations between the increase of Ca, Mg content,chloroplast number and rise of pigment content were observed. However, in the60thday after acetochlor (the concentrations was also five times of fieldmaximum recommended dose) treatment, the middle-and upper-node leaves of grapevinesgrown in sand became yellow, and the pigments decreased significantly. There was a positivecorrelation between the reduction of Zn content and decrease of pigment contents.4. Effects of fluoroglycofen and acetochlor on cell ultrastructure of Kyoho leaves(1) In the13thday after fluoroglycofen (the concentration was five times of fieldmaximum recommended dose) treatment, brown spots appeared in the young leaf ofgrapevines grown in sand. The membrane dissolved, but grana and lamellaes were clear insome chloroplasts with increased gap between lamellaes; while the inside of somechloroplasts became fuzzy. Not only the chloroplast and starch grain number was reducedobviously, but also the starch grains were smaller. In the60thday after treatment, the cellmembrane and chloroplast membrane was integrated, while the mitochondria and nuclearmembrane were impaired. In the middle-node leaves, the grana and lamellae were clear inmost chloroplasts, while the gap between lamellaes in few ones increased; not only thechloroplast and starch grain number per cell increased obviously, but also the size ofchloroplasts enhanced. The chloroplasts of upper-node leaves were same to the control ones,but lamellaes with large gap were observed; the number and length of chloroplasts enhanced;but the starch grain number was still less than that of control.Transmission electron microscope analysis on the deformed leaves of grapevines treatedwith extremely high level of fluoroglycofen (375g ai ha-1) showed that: a) in dark green parts,membrane was integrated; compared with the same size control leaves, the chloroplast, starchgrain and granum were much more, even the starch grain became obviously larger, however,the lamellae number per granum was44.4%less; but all the datas except chloroplast size werehigher than that in yellow parts; b) in yellow parts, the lamellaes in some chloroplasts wereclear, but the gap between them was obviously larger, while inside of some ones appeareddissolved phenomenon. Compared with the control, the numbers of chloroplast per cell andlamellae per granum reduced; however, the numbers of starch grain per cell and granum perchloroplast increased. Chloroplasts went larger and round, starch grains also became larger.(2) In the60thday after acetochlor (the concentrations was also five times of fieldmaximum recommended dose) treatment, the cell membrane of middle-node leaves was impaired, the gap between chloroplastic lamellaes and the starch grain number per cellincreased; while in upper-node leaves, the inside of chloroplast became fuzzy with nolamellae, and there was a opening in chloroplastic membrane. The width of chloroplast inmiddle-node leaves and the length of one in upper-node leaves were respectively21.4%,16.2%smaller than that of control.5. Effects of acetochlor and fluoroglycofen on antioxidant defense system in Kyoho leaves(1) Higher level of acetochlor and fluoroglycofen accelerated the superoxide productionrate, resulted in aggravation of the membrane lipid peroxidation, led to accumulation of MDA,which might be related with lower antioxidant enzyme (superoxide dismutase, catalase,peroxidase and ascorbic acid peroxidase) activities.(2) Higher concentration of fluoroglycofen treatment improved the glutathione reductaseand ascorbate oxidase, so the glutathione transferase and monodehydroascorbate reductase(MDHAR) in upper-and middle-node leaves. While the activities of MDHAR in bottom-nodeleaves and dehydroascorbate reductase (DHAR) in upper-node leaves increased only in14thday after treatment, the DHAR activity in middle-and bottom-node leaves increased only inthe14thand80thday. The changes might resulted in relative changes of ascorbic acid andglutathione content.6. Effects of fluoroglycofen and acetochlor on shoot growth of grapevinesFluoroglycofen (9.4g ai ha-1) and acetochlor (1123g ai ha-1) significantly improved thegrowth of new shoots in Chardonnay/SO4, while187g ai ha-1fluoroglycofen and11230g aiha-1acetochlor reduced root activity and suppressed the growth of shoots, i.e. by86.6%,70.6%respectively in the50thday. Compared with the control, IAA content in187g ai ha-1fluoroglycofen groups was significantly lower than control, while ABA content wassignificantly higher.Fluoroglycofen (187.5g ai ha-1) and acetochlor (11230g ai ha-1) reduced the total plantbiomass of Kyoho grapevines grown in sand, but there was significant difference onlybetween the former groups and control. Fluoroglycofen obviously reduced the root weightand root-shoot ratio, while acetochlor caused increase of root-shoot ratio.7. Aftereffects of herbicidesAfter the artifical weeding instead of higher concentration of combined herbicide application in2010, compared with the adjacent vineyard which used artificial weeding for along time, the reductions in Pn of upper-, middle-and bottom-node leaves were still high(34.9%,28.5%,61.2%respectively). It is indicated that herbicides have a relatively longperiod effects. And in the pot experiments, application of fluoroglycofen under the dose or theones higher than field maximum recommended in first year obviously inhibited the growth ofKyoho in the second year, especially375g ai ha-1fluoroglycofen caused the leaf deformedand could not return to normal situation. It is suggested that the orchardmen should controlthe dosage of herbicide strictly, and adopt green cover in conditional place.