Response On The Accumulation Of Flavonoids And Synthetase Activities Among Different Peanut Cultivars To Drought Stress

Flavonoids is fine active oxygen scavenger and non-enzymatic antioxidant in plants,which play an important role in drought adaptive.This paper taked twenty-nine varieties ofpeanut (Arachis hypogaea L) as research objects and studied accumulation trend of flavonoidsin peanut leaves under different drought degrees,controlled by PEG stress in sand cultures andpotted planting. Article explored the mechanism in response on the accumulation offlavonoids and synthetase activities among different peanut cultivars to drought stress andcarried out initial evaluation the changes of flavonoids of different peanut varieties inresponse to drought stress, which could provide evidence for identifying and evaluatingdrought-tolerant mechanism among different peanut varieties.The study reached conclusionsas follows:（1）Experiments under PEG gradient treatments defined accumulation trend offlavonoids in peanut leaves under different drought degrees:flavonoid contents decreasedfirstly and increased subsequently with prolongation of time at the same degree of PEGstress，flavonoids accumulation accelerated and peak ahead of time with the increasing degreeof PEG stress. Flavonoid contents peaked and difference was obvious among peanut varietiesat nine hours after treated by20%PEG. The pot experiment showed that the accumulation offlavonoid in peanut leaves increased significantly under moderate drought stress, the longdrought or severe drought led to decrease of flavonoid contents. Results indicated that droughtcould induce to accelerate the synthesis of flavonoids, and the flavonoid contents tend to dropoff with consumption of antioxidant motions.（2）The constitutive flavonoid contents in29peanut varieties had a significantdifference from6.65to21.05mg/g and the difference up to10times more, range of variation offlavonoids in different varieties is up to1.8at9th hours after20%PEG treatment. So peanutvarieties may be separated into four categorise according to flavonoid: one is low level ofconstitutive contents and high extents of variation which contains low level of constitutive contents and extents of variation which contains huayu31, xuzhou68-4, luhua8, shanhu7,huayu22, fenghua2, dabiayu,,baizhenzhu,huayu20,hua17,ICG6848,baisha1016; other is highlevel of constitutive contents and low extents of variation which contains laibindadou,A596,nongda818,haihua1, penglaiyiwohou; the third is low level of constitutive contents andhigh extents of variation which contains fenghua5, fenghua1, rugaoxiyangsheng,luhua14,kangqing19,huayu24,huayu30,shanhu8,79266; the last is high level of constitutivecontents and extents of variation which contains shanhua11, shanhu9, lipudahuasheng.（3）The activities of PAL and CHS with CHI,relative biosynthetic enzymes of flavonoidin peanut, were significantly correlated with gene exptessions of themselves,which showedthat enzymes activities were regulated by gene expressions at the transcriptional level. Rangesof flavonoid contents and enzyme activities with gene expressions reached an extremelysignificant level.Both enzyme activities and gene expression participated metabolic regulationof flavonoid under PEG stress, and caused changes of flavonoid contents. The ranges of threeenzyme activities and gene expressions of different cultivars were significantly different.Thelevels of activities and genes expressions of enzymes in shanhua11and fenghua5are highand the increasing rate under stress is big which could speed up flavonoid synthesis;PALactivities and genes expressionsf nongda818would improved a little after stress so as tolimite the accumulation of flavonoid;the lower levels of bothactivities with genes expressionsof enzymes and the increasing rate after treatment in hua17led to low contents offlavonoid.（4）The flavonoids in peanut leaves have excellent activity to scavenge freeradicals,order from big to small of the activity are DPPH·，O2-·，·OH. Correlation analysisshowed that there was a significantly positive correlation between flavonoid contents withchanges and antioxidant activity under drought stress. The proper concentration of Rutincould significantly reduce MDA、H2O2、O2-contents and increase chlorophyll and flavonoidscontents and SOD activities in peanut leaves under PEG stress, so that it could enhanceantioxidative capacity of peanut. These results all proved that flavonoids had the antioxidantfunctions.There were differences in the effect of Rutin to different cultivars.The chlorophylland flavonoids contents and SOD activities of fenghua5significantly improved under PEGstress after preprocessing of Rutin, the MDA and O2-contents of shanhua11and H2O2contents of nongda818were decreased mostly after preprocessing of Rutin, while hua17wasless response effective to Rutin.