The Effect Of Different Red To Far-red Light Ratios On Salinity Tolerance Of Tomato

In recent years,the intensification management of facility vegetables had exacerbated the degree of secondary salinization of soil in the facility.Salt stress had become one of the major abiotic stress affecting facility crops production.Phytochrome?PHY?is a important light receptors in plants,mainly absorbs red light?R?and far red light?FR?.Different red and far-red light ratio?R:FR?play an important role on increasing tolerance of salt stress through regulating the configurations of PHY,but it's lack of systematic research of the specific effects.In this study,cv.MoneyMaker?Solanum lycopersicum L.?was used as the experimental organism.The experimental plots included three treatments:T1,100 mM NaCl and R:FR=7.4;T2,100 m M NaCl and R:FR=1.2;T3,100 mM NaCl and R:FR=0.8,and CK,0 mM NaCl and R:FR=7.4.With the nutrient solution culture,the regulation effects of different red and far-red light ratio?R:FR?on photosynthesis ability,chlorophyll?Chl?biosynthesis,antioxidant ability were studied.The main results were as follows:1.T2 and T3 treatment significantly increased plant height,stem diameter,leaf area,total fresh mass and total dry mass of wild type tomato seedling under salt stress.Meanwhile,these parameters in T3 treatment were significantly higher than in T2 treatment,and had no significant differences with those in CK.Total fresh mass and total dry mass of wild type tomato in T3 treatment higher 45.06%and 50.62%than T1 treatment respectively.It showed that low R:FR value promoted the growth of tomato seedling under salt stress,when the R:FR value was 0.8 the effects for promoting tomato growth were best.2.The contents of chlorophyll biosynthesis precursors 5-aminolevulinic acid?ALA?,porphobilinogen?PBG?and uroprophyrinogen??Uro??in wild type tomato seedling increased significantly in T1 treatment,and sequentially accumulated with the extension of time.The content of protoporphyrin??Proto??,Mg-protoporphyrin??Mg-Proto??and protochlorophyll?Pchl?,chlorophyll a?Chla?,chlorophyll b?Chlb?,chlorophyll a+b?Chl?a+b??in tomato seedling decreased significantly in T1 treatment.It showed that the starting point blocked the chlorophyll synthesis was in Proto?synthesis process.T2 and T3treatment significantly decreased ALA,PBG,Uro?contents in tomato seedling under salt stress,significantly increased Proto?,Mg-Proto?,Pchl,Chla,Chlb,Chl?a+b?contents in tomato seedling under salt stress,at the same time,significantly decreased Chla/b value,T2and T3 treatment had no significant differences.Contents of Chla and Chlb of wild type tomato in T3 treatment higher 25.17%and 16.51%than T1 treatment respectively.It showed that low R:FR value alleviate the obstacles of chlorophyll biosynthesis.There was no significant difference on promoting chlorophyll biosynthesis between R:FR value at 1.2 and0.8.3.T2 and T3 treatment significantly increased maximum photochemical quantum yield of PS??Fv/Fm?,effective photochemical efficiency of PS??Fv'/Fm'?,actual photochemical efficiency??PS??,electron transfer efficiency?ETR?and photochemical quenching parameters?qP?in wild type tomato seedling under salt stress,significantly decreased non-photochemical quenching coefficient?NPQ?in tomato seedling under salt stress,the two treatments had no significant difference.The two treatments significantly increased the net photosynthetic rate?Pn?,that in T3 treatment was significantly higher than in T2 treatment.?PS?and Pn of wild type tomato in T3 treatment higher 24.00%and 58.65%than T1treatment respectively.It showed that low R:FR value effectively protect the stability of the photosynthetic mechanism,enhanced the photosynthesis of tomato,and the effects of improving the photosynthesis system??PS??activity center had no significant difference between R:FR value at 1.2 and 0.8.4.T2 and T3 treatment significantly increased soluble protein and proline?Pro?content,superoxide dismutase?SOD?,catalase?CAT?and peroxidase?POD?activity in wild type tomato leaf and root,significantly decreased the relative electrolyte leakage,malondialdehyde?MDA?and reactive oxygen species?ROS?content,improved the salt tolerance of tomato seedlings.Soluble protein in leaf and root,superoxide anion radical(O₂^·-)in leaf and root,POD activity in leaf in T3 treatment were significantly higher than those in T2 treatment.Contents of O₂^·-,H₂O₂ and MDA of wild type tomato in T3 treatment higher 27.11%,24.69%and 30.61%than T1 treatment respectively.It showed that low R:FR value enhanced the antioxidant capacity of tomato seedling under salt stress,reduced the peroxidation damage,when R:FR value was 0.8 the effects for improving antioxidant capacity were best.In general,exposure to lower R:FR value improve tomato seedling chlorophyll synthesis ability,photosynthetic ability and oxidation resistance,and improve tolerance to salt stress accordingly.When the R:FR value was 0.8 the effects were best.