Effects Of Forliar Application Of Calcium Or Silicon Fertilizers On The Activities Of Related Enzymes And Nutrition Contents In Pear Fruit

Calcium(Ca)is one of essential nutrient elements in the pear growth,but it has poor mobility,which may cause some physiological diseases owing to Ca deficiency in fruit,such as brown spot disease of ’Huangguan’ pear and blossom-end rot of ’Korla fragrant’pear.Though forliar application of Ca fertilizer was often used to increase Ca content in fruits,the physiological diseases could not have been effectively prevented.Additionally,some studies showed that silicon(Si)fertilizer was beneficial to the transport of Ca.With the aim of evaluating effects of different forliar application of fertilizers on the activities of enzymes related to physiological metabolism,the nutrition contents and fruit quality,we set following treatments:separately spraying chelated calcium(SC),separately spraying silicon fertilizer(SS),cooperatively spraying both calcium and silicon(SCS),and spraying water as the control to ’Huangguan’ pear and ’Korla fragrant’ pear in their young and expansion stages both in the field and pot experiments,hoping that it could offer more theory basis for the prevention of physiological diseases in pear.The main results were as follows:With the fruit development in the pot experiments,SCS significantly inhibited the activities of wall-metabolic hydrolases such as polygalacturonase(PG)and cellulases(Cx)in fruit flesh at the stage of expansion(that is,on 100 days after full bloom),resulting in their activities at maturity(that is,on 125 days after full bloom)25.3%and 50.1%lower than control respectively.Moreover,the protopectin(PP)content at the stages of fruit expansion and maturation under this treatment were significantly increased by 41.4%and 40.7%,while the soluble pectin(SP)content at the expansion stage had a decrease of 60.7%in contrast to control,which indicated that SCS could maintain the stability of cell wall more effectively.In addition,the activities of superoxide dismutase(SOD)and peroxidase(POD),who were responsible for eliminating the active oxygen,at both stages of expansion and maturation were raised by SCS remarkably.At maturity each of them comparatively increased by 244.8%and 188.9%along with malondialdehyde(MDA)content 91.1%lower in this treatment.These results suggested that SCS was an effective way to enhance the fruits’ resistance at maturity,which could help to depress the lipid peroxidation caused by the invasion of reactive oxygen species in pear fruit.The accumulation contents of potassium(K),phosphorus(P),magnesium(Mg)in flesh of ’Huangguan’ pear were on the rise under all treatments generally,and the process of Ca accumulation all had a decreasing period.Spraying Ca or Si fertilizers on pear in the process of fruit growth could not only directly increase the Ca content in skin and flesh,but also influence the absorption of K,P and Mg indirectly.On 115 days after full bloom,SCS improved Ca content in peel and flesh by 37.1%and 36.4%respectively as well as the P and Mg accumulation contents in flesh increased by 27.4%and 5.0%compared with the control.The K accumulation content under SCS treatment was about 357.56 mg·fruit-1 at maturity,which was 11.1%higher than control.The test results of foliar application of fertilizers in fields at harvest showed that SCS made the Ca content in flesh of calyx-nearing part 41.7%higher than control,but the Mg content in peel of calyx-nearing part 17.5%lower resulting in the Mg/Ca of this part 30.9%lower.Using Ca or Si as foliar fertilizers improved the ratio of sugar and acid by an average of 40.4%.SCS significantly reduced the incidence of brown spot disease in the harvest season by 49.4%.From the results of correlation between brown spot disease incidence and nutrition concentration ratios of ’Huangguan’ pear,we could see that the disease was closely related to the ratios of nutrition concentrations in fruit nearing calyx part.Mg/Ca in the peel had a positive correlation to the incidence of disease significantly,which means higher Ca content and lower Mg content could do good to lower the incidence.The results of experiment spraying Ca and Si fertilizers on ’Korla fragrant’ pear showed that the Ca content in flesh of stalk-nearing part under SC,SS and SCS were respectively 50.6%,39.3%and 16.9%higher than control.The K content in flesh under the treatment of SCS was increased by 22.3%on average,at the same time P and Mg content in the flesh of stalk-nearing part also had increases of 31.6%and 20.2%respectively.Besides,SCS decreased Mg/Ca in the peel of calyx-nearing part by 16.2%significantly.Spraying Ca or Si fertilizers could improve the fruit hardness to varying degrees,among which SCS treatment had the most obvious improvement of 16.3%.SC increased the ratio of sugar and acid by 11.3%,while SS and SCS decreased it by 12.0%and 4.4%respectively.Above all spraying Ca fertilizer cooperated with spraying Si fertilizer two days later in young fruit(21,28,36 days after full bloom)and expansion stages(80,95 days after full bloom)could decrease the Mg/Ca in peel of calyx-nearing part and reduce the incidence of brown spot disease effectively,which showed that SCS may enhance the balance of nutritions as well as the resistance of pear fruit.