Study On The Difference Of Chlorophyll Synthesis And Photoinhibition Ability Of Carya Cathayensis Pseudo-peel Under Cross-pollination

Hickory(Carya cathayensis Sarg.)and pecan(C.illinoensis K.Koch)are economic trees in Carya widely planted in the world.The pseudo-peel becomes green,the dry matter of fruit and kernel significantly increased after pollinated by pecan pollen.The size of fruit depends not only on the amount of photosynthetic products transported to the fruit,but also on its photosynthetic capacity and anti-photoinhibition ability.When the light energy exceeds the amount available to the plant,PSII will transfer the remaining light energy to O2,resulting in the accumulation of reactive oxygen species.However,the plant has a series of antioxidant enzyme systems and the light protection mechanism of non-enzyme substances.Previous studies have shown that 65 days after pollination,the genes related to porphyrin and chlorophyll metabolism in hickory pseudo-peel pollinated by pecan are significantly up-regulated,and the expression of light harvesting protein II(LHCII)and its light repair related protein is significantly up-regulated,which may be the reason why the pseudo-peel of hickory fruit pollinated by pecan is obviously green and its anti-photoinhibition ability is enhanced.In this study,the changes of photosynthetic rate,chlorophyll content and key genes of synthesis of Pecan fruit pollinated by two kinds of pollens(hickory pollen,hp;pecan pollen,pp)during the critical period of fruit development were measured,combined with the determination of subcellular location,and the molecular mechanism of hickory fruit' pseudo-peel turning green after pollen pollination was preliminarily revealed.The changes of chlorophyll fluorescence parameters,RuBPC,antioxidant enzyme activities and non-enzyme substances of the two kinds of pollen pollinated hickory pseudo-peel were analyzed by simulating the high light environment in summer.and the physiological basis of the different light inhibition ability of the two kinds of pollen pollinated hickory pseudo-peel was further revealed,which could provide theoretical basis for xenia,fully tap the potential of increase production of xenia,and further improve the yield of hickory.The main results are as follows:1.The pseudo-peel of pp was thicker than that treated with hp,and the number of chloroplasts in the pseudo-peel of pp was more than that of hp,and its chloroplast area was larger.The expression of CcHEMA1 gene in hickory treated with pecan pollination was significantly higher than that in hickory treated with hickory pollination,and the relative expression of CcHEMA1 gene was significantly correlated with chlorophyll content.Therefore,more chloroplasts and more chloroplasts may be the main reasons for the higher photosynthesis of pp.CcHEMA1 is the key gene involved in the synthesis of chlorophyll in the pseudo-peel of hickory.3.After high light(HL)treatment,he light energy absorbed by hp and pp hickory pseudo-peel was excess,and the electron transport rate decreased.At the late stage of fruit development(81 DAP),no matter HL treatment or not,the activity of RuBPC in pp pollinated hickory pseudo-peel was significantly higher than that of hp.Compared with hp pollinated hickory,the MDA,O2·-and H2O2 contents of pp pollinated hickory were lower,and the activities of antioxidant enzymes(POD,SOD,CAT),AsA-GSH system,GR and DHAR enzyme in pp treated hickory were significantly higher than that of hp pollinated hickory.Therefore,at the late stage of fruit development,pp pollinated hickory fruit's pseudo-peel is stronger than hp pollinated in scavenging active oxygen,anti-membrane lipid peroxidation and other aspects,showing stronger anti-photoinhibition ability,which is one of the reason for the larger fruit.