| Rock sugar orange is a citrus plant of the rutaceae family,which is loved by consumers for its crisp,sweet and juicy,unique flavor,excellent quality and high nutritional value.Rock sugar orange is one of the main industries in Xinping County,Yuxi City,rock sugar orange split fruit is an important problem in production,belongs to a physiological disease,mainly occurs in the expansion and ripening period of the fruit.The split fruit is mainly divided into external and internal fissure,and the external fissure is manifested as cracking from the fruit surface or top to the heart of the fruit,the cells are ruptured and deformed from the outside to the inside,and the outer epidermis is gradually broken to the white sponge layer,and the flesh is directly split as a result.Calcium is a necessary nutrient element for plant growth and development,involved in the metabolism and synthesis of cell wall,and the content of calcium in the peel determines the hardness and softness of the peel,and has a serious impact on the quality and yield of the fruit.In this study,the rock sugar orange orchard in Shuitang Town,Xinping County,Yuxi City was investigated,and the occurrence law of rock sugar orange split fruit in different orchards was clarified,and the limiting factors of split fruit were sought.On this basis,typical representative orchards were selected for field experiments with different concentrations of calcium fertilizer,and the nutrient content of the inner and outer peels of the fruits,the nutrient content of leaves,the antioxidant enzyme activity of the peels,the anatomy of the peels and the number of splits were analyzed.The following key results were obtained:(1)The soil available calcium and available potassium content of rock sugar orange orchards investigated in Shuitang Town,Xinping County,the orchards with high split-fruit incidence were significantly lower than those with low-split fruits,and the total calcium content of the inner and outer peels of the fruits was significantly lower than that in low-growth orchards.This shows that the poor effective calcium mobility in the soil of orchards is difficult to transport to leaves and fruits,resulting in low total calcium content in the inner and outer peels,and finally causing the occurrence of split fruits to be more serious.During the period of fruit expansion,the irregular distribution of rainfall aggravated the imbalance of fruit pulp and peel growth,and promoted the occurrence of fruit splitting phenomenon,which indicated that abnormal climate changes were closely related to rock sugar orange split fruit.(2)The results of field experiments showed that the application of calcium fertilizer reduced the number of split fruits of rock sugar orange and increased the yield of rock sugar orange fruit.Compared with spraying water,the yield of 8% Ca O per plant increased by 12.31%,and there were significant differences in the number of split fruits reduced by 8% Ca O at different stages,and the control effect of split fruits with different concentrations of calcium fertilizer was as follows: 8% Ca O> 10% Ca O>12% Ca O > 17%Ca O。The application of calcium fertilizer increased the brightness and color saturation of the fruit,and the effect decreased with the increase of calcium fertilizer concentration.Among them,8% Ca O is significantly higher than 17% Ca O treatment.The application of calcium fertilizer increased the fruit hardness of rock sugar orange,and the skin hardness of 8% Ca O increased by 30.68% compared with spraying water.(3)The results of field experiments showed that the application of calcium fertilizer significantly increased the contents of total calcium,total magnesium and total boron in the inner and outer peels of the fruit,and the total calcium and total magnesium contents of the inner and outer peels of the fruit decreased with the increase of calcium fertilizer concentration.Compared with spraying water,the contents of total calcium,total magnesium and total boron in the inner peel of rock sugar orange with8% Ca O increased by 32.64%,13.69% and 30.26%.The contents of total calcium,total magnesium and total boron in the peel of 8% Ca O increased by 30.68%,28.26% and 26.55%.The application of calcium fertilizer significantly increased the contents of total potassium,total calcium and total boron in rock sugar orange leaves,and there was no significant difference.The total boron content of 8%Ca O leaves was 23.95% higher than that of clean water treatment.(4)The field test results showed that the changes of the peel anatomy of rock sugar orange after calcium fertilization were compared with water spraying,and the tightness and uniformity of mesocarp cell connections in the fruits sprayed with calcium fertilizer were obvious,and the size of endocarp cells was uniform and excessive.The application of calcium fertilizer increased the activity of SOD and CAT in the peel,and reduced the content of POD,PPO and MDA.The cells of the 8% Ca O endothelial layer were closely arranged,the size was consistent,and the antioxidant enzyme activity was good. |
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