Effects Of Plastic Film Mulching On Chilling Injury Of Loquat Fruit

Sichuan is a large province of loquat cultivation.However,in Chengdu Plain area,cold air tends to gather and frost often occurs in spring and winter.In addition,tree aging is common in old producing areas,and the basic conditions of orchards are poor.Winter mulch cultivation of loquat has gradually become an important way to prevent low temperature damage to young fruits of Loquat.In this study,transparent polyvinyl chloride film(PVC)and different types of polyethylene film(PE)were used for different film coating cultivation treatments,aiming to explore the effects of different film coating treatments on the growth environment,young fruit growth and development,fruit osmotic regulators and endogenous hormone contents of loquat,and to provide theoretical and practical basis for the prevention of low temperature damage in winter film coating cultivation in this loquat producing area.The main research results are as follows:(1)Effects of different mulching methods on ecological factors of loquat fruit growth.Compared with the non-mulching treatment,the average daily air temperature and relative air humidity,as well as the soil temperature and soil water content were significantly increased by the mulching treatment.However,there was no significant difference between the daily mean temperature and the minimum temperature.The warming effect of mulching treatment was significantly higher than that of mulching treatment,while the warming effect of PVC mulching treatment was significantly higher than that of PE mulching treatment,and the soil water content of silver mulching treatment was significantly higher than that of black mulching treatment.PVC ceiling film + black mulching film treatment has the best warming effect,the temperature increased by 9.5℃,PVC ceiling film + silver mulching film has obvious moisturizing effect.In addition,the laminating film will reduce the illumination to some extent,but the illumination under the film is more than 75%,and the illumination under the PVC film is significantly higher than that of the PE film,and the reflected light intensity of the silver film is higher than that of the black film.(2)Effects of different mulching methods on chilling injury of loquat fruit.Compared with non-plastic film-mulching treatment,plastic film-mulching treatment could significantly promote the growth of young fruit,and accelerate the ripening period of loquat fruit by 15-17 days,the best treatment was canopy plastic film and plastic film covering.The single fruit weight of loquat increased by 16% ～ 26%,soluble solid increased by 19% ～ 26%,soluble sugar increased by 36% ～ 76%,acid content decreased by 40%,the chilling injury rate and chilling injury index were significantly reduced.When the air temperature dropped to-2 ℃,the loquat fruit without plastic film mulching had obvious low temperature damage,but the rate of low temperature damage was very low under plastic film mulching,especially,the loquat fruits under plastic film mulching with PVCB,PEB and PVCS were not affected by low temperature.However,the effect of plastic film mulching on prevention of loquat low temperature damage was poor.(3)Effects of different mulching methods on antioxidant capacity,osmotic regulators and contents of endogenous hormones in loquat fruits showed different trends of peroxidase activity(POD),superoxide dismutase(SOD)or catalase(CAT)in Loquat fruits under different mulching treatments with decreasing temperature.POD,SOD and CAT of Loquat fruits treated with unmulched film,canopy film or mulching film increased first and then decreased,while canopy film plus mulching film increased continuously.At 0℃,POD,SOD and CAT activities of Loquat fruits treated with PVCB were significantly lower than those treated with other treatments.Compared with uncoated treatment,they decreased by 56%,49% and 47%,respectively.The contents of malonaldehyde(MDA),proline(Pro)and relative electrical conductivity of Loquat fruits treated with no mulching and single mulching were significantly higher than those treated with canopy film +mulching,while the contents of soluble protein and soluble sugar were significantly lower than those treated with canopy film + mulching.Compared with the control treatment without film coating,the contents of gibberellin(GA)and auxin(IAA)in Loquat fruits under different film coating treatments were significantly increased,and the content of abscisic acid(ABA)was decreased.Among them,the covering treatment combined with PVC canopy film and black mulch has the best preventive effect on low temperature damage.To sum up,different film mulching methods have different effects on the growth environment of loquat plants,low temperature damage of fruits,osmotic adjustment substances,antioxidant defense system and endogenous hormones in fruit tissues.Appropriate temperature,humidity,light intensity and reasonable physiological adjustment are important reasons for loquat young fruits to resist low temperature damage,and reasonable film mulching measures can effectively reduce low temperature damage of loquat,among which PVC canopy film and black plastic film are superior double film mulching measures.This provides theoretical and practical basis for further understanding of loquat cultivation in winter to prevent low temperature damage,and promotes the healthy development of loquat industry in Sichuan Basin.