Alleviating Effect of 5-aminolevulinic Acid on Freezing Injury of Apple Flower Organs
This study aims to study the alleviating effect of 5-aminolevulinic acid(5-ALA)on freezing injury in apple blossoms.Fuji apple flower branches were used as experimental materials to investi-gate the alleviating mechanism of different concentrations of 5-ALA treatments(25 mg·L-1,50 mg·L-1,75 mg·L-1 and 100 mg·L-1)under different temperature stresses(0 ℃,-2 ℃,-4 ℃ and-6 ℃)on freezing damage to apple styles and ovaries.Water praying was used as a control,and physiological indicators such as relative conductivity,antioxidant enzyme activity,and expression of related resistance genes were measured.The results showed that spraying 25-100 mg·L-1 of 5-ALA did not alleviate the freezing injury of apple blossoms at-6 ℃.However,spraying 25 mg·L-1 to 75 mg·L-1 of 5-ALA reduced freezing damage to apple styles and ovaries under low temperature stress ranging from-4 ℃ to 0 ℃.Compared with the control,spraying 5-ALA significantly allevia-ted frost damage and browning in flower column houses under low temperature stress.The malondial-dehyde(MDA)content in apple flower organs treated with 5-ALA was reduced by 32.16％at-2 ℃,while the activities of superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD)nearly doubled.The relative conductivity of flowers treated with 5-ALA decreased by 8.7％compared to the control,and the semi lethal temperature decreased by 0 ℃-1.65 ℃.In addition,compared to the control,the expression levels of MdADF5,MdTLP1,MdMDL2,MdDREB3,MdGSTU17,and MdEXPA1 in apple flower organs treated with 5-ALA were higher,while expression level of Md-CRPK1 was lower.The Gene Ontology(GO)enrichment analysis indicated that the most of the en-riched GO terms were related to metabolic processes,catalytic activity,and membranes;the most an-notated expressed genes(DEGs)in the Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway were distributed in plant hormone signal transduction,MAPK signaling pathway,starch and sucrose metabolism,pentose and glucuronic acid ester conversion,phenylpropanoid metabolism,and plant pathogen interaction,which improved the resistance to low temperature stress during apple flower-ing.Therefore,spraying 5-ALA before flowering in the Loess Plateau region can effectively alleviate freezing injury in apple flower organs from-4 ℃ to 0 ℃,with the optimal concentrations ranging from 25 mg·L-1 to 50 mg·L-1.
万方数据
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