Studies On The Physiological Changes Of 'Feicheng'Peach And Strawberry Fruits During Development, Ripening And Softening

1. The experiments were carried out for two years with two cultivars of 'Feicheng' peach (Prunus persica[L.] Batsch) , which have different softening characteristics during maturation and postharvest storage. Of the two cultivars, one was 'Hongli' with red flesh clinged to the pit which softened faster after harvest; the other was 'Baili' with white flesh clinged to the pit which softened slower than 'Hongli" after harvest and could be stored longer. The main results were as follow.1) The fruit weight growth curve of Feicheng peach exhibited the characteristic of double sigmoidal growth pattern. Sixty percent of total weight gained within one month prior to commercial harvest. Water content in flesh ranged from 80-88%. The main sugars were sucrose, glucose and frucose. Sorbitol also existed in considerable amount. The protein content decreased during fruit development, but increased in the last stage before harvest. With the ending of pit hardening around July 4, the fruit enlarged rapidly until the fruit was firm ripe. The firmness decreased gradually till harvest and the firmness of 'Hongli' peach decreased much more than 'Baili' did. During the phase of rapid expanding the firmness of fruits decreased dramatically. Fruit firmness decreased gradually during storage under 4癈, but the firmness increased a little bit after one week of storage.2) The proportion and components of cell wall in fruit changed during fruit development and storage. In the process of fruit ripening, the proportion of cell wall to fruit weight decreased. Soluble pectins increased remarkably from August 1 to Augustl6, leading to fruit firmness decrease. The ionically bound pectin remained stable in 'Baili' peach, but it decreased in 'Hongli' peach. Changes of pectins directly related to fruit firmness. Decreasing of cellulose content in cell wall also played an important role in the reduction of firmness. Of the PGRs (plant growth regulators) used, ethephon, ABA and GA3 stimulated the degradation of cell wall, and 6-BA and NAA inhibited this process.3) The respiration of peach comprises three pathways of TCA, BMP and HMP. TCA was the primary one and HMP reduced gradually to a very low level during storage. Fruit respiration climacteric occurred after two weeks of storage with fruits harvested at August 30. This peak of respiration coincided with the occurrence of chilly injury or wooliness.4) Both PME and EGases played important role in peach fruit softening. The results from the two cultivars implicated that EGases were essential in initiation of fruit softening. The PGRs have little effect on PME. ABA stimulated the activity of EGases. However theincrement of EGases was not related to fruit softening. Endo-PG had not been detected in 'Feicheng' peach. Exo-PG took part in the process of later stage of ripening.5) Activities of a -galactosidase were very high in 'Feicheng' peach and a - galactosi-dase was a kind of enzymes which ionically bound with cell wall. It was correlated with the decreasing of fruit firmness. P -galactosidase existed in the harvested fruits and was related to the softening of fruits during storage at low temperature. For glucosidases the situation were similar to P -galactosidase. No activity of mannosidase has been detected in 'Feicheng' peach. The peroxidases was related to pit hardening in 'Feicheng' peach which showed a high activity during pit hardening and then decreased.2. The results from several varieties of strawberry (FragariaX ananassa Duch) grown in field or greenhouse were as follow.1) The activities of EGases increased as the strawberry fruits developed from stage of small green to stage of overripe. After two day's storage at 4℃, the activities of EGases increased remarkably in all 7 varieties. The action patterns of NAA on EGases activities were different with fruits from various developmental stages. EGases activities were negatively correlated to the storability of strawberry fruits.2) The activities of PME increased during the development of st...