Studies On Mechanism Of Calcium Uptake By Pear Fruit And Its Transferring, Affecting Factors

The aim of the study was to make clear changes of calcium in different parts during different development stages of pear(Pyrus pyrifolia NaKai) fruit, meanwhile, calcium preparation and growth regulators were used to spray pear trees, and the changes were associated with changing dynamics of physiological substances such as pectin, pectin decomposing enzyme and introhormones to testify mechanism of calcium uptake, transferring and its affecting factors. The main results were as follows:1 Huanghua and Xiangnan pears that were significantly different in storage and texture trait were used to investigate contents of Ca²⁺, total calcium in flesh, seeds and pectin, the results showed that: 1) contents of Ca²⁺ and total calcium were highest in young fruit stage, then they decreased with fruits development. Content of calcium in flesh of Huanghua was significantly higher than that of Xiangnan when harvest. 2) Total calcium content in seeds was much higher than that in flesh, and it increased with fruits development gradually. Content of total calcium in seeds of Huanghua kept rising after rapid expanding stage of middle July, while that of Xiangnan stopped rising after late July. A Ca²⁺ rapid rising peak in seeds of two cultivars appeared in late fruit development. 3) Fertilization could promote calcium uptake by ovary (fruitlet), and content of calcium in ovary (fruitlet) increased rapidly after fertilization, while that in overay (fruitlet) without fertilization was much lower.2 In order to make clear the relationship between calcium and endogenous hormones content in flesh and seeds of pear, Huanghua pear was used as materials. The results showed that: 1) The highly correlation indexes were shown between calcium and 1AA content in flesh, calcium and IAA content in seeds, calcium and ZR content in flesh, calcium and ABA content in flesh, and the values of them were 0.77, -0.73, 0.72 and 0.77 respectively. The relationship between calcium and endogenous hormones was discussed. Content of GA₃ in flesh and seeds reached peaks during rapid expanding stage. The relationship between calcium and endogenous hormones was discussed in the paper. 2) The dynamics of calcium in ovary (fruitlt) was similar to that of IAA and GA₃. NAA and GA3 treatments both could promote calcium uptake by fruit. 3) Content of proto pectin increased first, and then it began to decrease. The period when proto pectin in Huanghua stopped increasing was earlier than that of Xiangnan, and proto pectin of Huanghua was significantly lower than that of Xiangnan in late fruit development. Water-soluble pectin contents of two cultivars increased gradually, and they were adjacent. 4) The concentration of calcium in 'Huanghua' pear was studied in order to make clear the calcium dynamic in pear fruits and its regulation role by the plant growthregulators. The result showed that IAA and GA₃ treatments both were capable to improve calcium concentration in fruits during harvest time, but the time when concentration peak appeared was deferred. The calcium concentration peaks of IAA+CaCl₂ and GA₃+ CaCl₂ treatment were higher than the peaks of the treatment of only IAA or GA3 respectively, and the time when peaks came was earlier than treatments of only IAA or GA₃. The NAA treatment put off the total calcium peak, but NAA treatment did not increase the total calcium content in flesh, and the calcium content of NAA+ CaCl₂ treatment was similar to the control in both time and quantity. The rapid expanding stage was the crucial time when Ca²⁺ increased and total calcium decreased no matter which treatment was; Furthermore, method about how to improve calcium uptake by fruits and physiological significance of total calcium and Ca²⁺ changes were discussed.3 Changes of specific radioactivity and distribution ration of calcium in different parts of fruit were determined after radioactive ⁴⁵Ca was introduced to fruit through flesh, core and peduncle during different fruit development stages using Huanghua as materials. The results showed th...