The Effects Of Girdling、CPPU And Water Stress On Fruit Growth And Quality Of Kiwifruit

Kiwifruit is one of New Zealand’s main export crops.In agricultural production,forchlorfenuron(CPPU)is often used to increase single fruit weight and yield.However,when CPPU was used to improve plant yield,fruit deformity,storage resistance reduction,CPPU residue and other problems had a negative impact on the fruit quality and commercial value.Therefore,it is important to develop green,healthy and pollution-free technology to improve the quality and commercial value of kiwifruit by improving cultivation and field management practices.Girdling and moderate water stress are also effective methods to improve fruit yield and quality,but there are few applications and studies on kiwifruit.In this study,the ‘Hayward’ kiwifruit grown in the North Island of New Zealand was used as the test material.The fruits and branches were treated by girdling,moderate water stress and CPPU to explore the effects of different treatments on the fruit growth,leaf photosynthesis,and fruit quality of the kiwifruit.The aim was to find ways to improve the field management technology of kiwifruit,so as to improve fruit quality,extend the storage period,and provide a reliable theoretical basis for the development of kiwifruit industry.The main research results are as follows:(1)The ‘Hayward’ kiwifruit in North Island,New Zealand,had two periods of rapid growth in the process of fruit growth.The first period was 20-40 days after full bloom,and the second period was 100-140 days after full bloom.At the time of harvest,the single fruit weight was 110.34 g,with fruit shape index at 1.16,malformation rate at 8.23%,and dry matter at 16.33%.The diurnal variation of photosynthesis in plant leaves was characterized by midday depression,which was a nonstomatal restriction type.During storage,fruit firmness,vitamin C content,titratable acid content and total chlorophyll content decreased gradually,while soluble solid content increased slowly and then stabilized.The peak of ethylene release rate appeared on the 40 th day of storage,and the peak of respiration appeared on the 20 th day of storage.The fruits were almost completely softened on the 18 th day of storage.(2)After the girdling of fruiting branches on the 20 th day after full bloom,the fruit size increased significantly,with the weight gain rate of single fruit reaching 8.47%,and the fruit shape index and malformation rate increased slightly when harvest.During the growth period,chlorophyll content and photosynthetic intensity of kiwifruit leaves decreased,and the diurnal variation of photosynthesis existed midday depression,which belonged to the nonstomatal restriction type.The ripening period of kiwifruit was advanced 5 days by girdling treatment.In the postharvest storage stage,the firmness of fruits after girdling decreased more rapidly,the content of titratable acid lower,but the content of soluble solid and vitamin C were higher than that of the control.Girdling treatment increased the peak value of ethylene release rate and respiration rate,and shortened the storage period by 3 days.(3)When the fruits were dipped with 10 ppm CPPU solution on the 40 th day after full bloom,the transverse and longitudinal diameter and volume increased significantly.The single fruit weight increased by 33.43%,with a significant decrease in fruit shape index,and the malformation rate increased to 19.36%.The water content increased significantly,and dry matter dropped to13.96%.The chlorophyll content and photosynthetic intensity of the leaves near the leave order increased under CPPU treatment,and the diurnal variation of photosynthesis existed midday depression,which belonged to a stomatal restriction type.CPPU treatment delayed the ripening of kiwifruit by 3 days.At the stage of postharvest storage,fruits treated with CPPU had lower firmness and faster softening,and the contents of soluble solid,vitamin C,titratable acid and total chlorophyll were lower than those of the control;While the ethylene release rate and respiration rate were significantly higher than those of the control,and the storage period of fruits was shortened to 9 days.(4)During the whole growth period of kiwifruit,water content in soil was 17.61% lower than that of normal irrigation.The results showed that single fruit weight decreased to 103.89 g and malformation rate increased to 13.02% under water stress.Moderate water stress increased chlorophyll content and photosynthetic rate of leaves,and water use efficiency was significantly higher than that of the control.The diurnal variation of photosynthesis was characterized by midday depression,which belonged to a stomatal restriction type.Under moderate water stress,the ripening period of kiwifruit was advanced 7 days.During storage,the contents of titratable acid and chlorophyll in flesh were slightly higher than those in control,but there was no significant effect on storage time.In conclusion,the three treatments all affected kiwifruit plants’ photosynthetic characteristics and physiological characteristics during storage.The weight gain rate of single fruit in CPPU treatment was higher than that of the other two treatments,but the malformation rate was the highest and the fruit quality was poor during storage.Water stress and girdling treatment improved fruit quality to varying degrees.