| Litchi (Litchi chinesis Sonn) is an important special local fruit tree in Hainan. Feizixiao and Zinangxi are two major litchi species planted in Hainan that grow ripe in mid-May and early June. Therein, the growth of pericarp coloration and pulp relish of Feizixiao are not synchronous, thus it’s necessary to probe into the cause to realize its inherent economic value and work out a reasonable cultivation technique to regulate pericarp coloration. In this paper, Feizixiao fruit and Ziniangxi fruit were adopted as test materials to carry out a comparative study on their dynamic change in pericarp coloration, pigment content of pericarp, pulp relish quality, endogenous hormone content of the pulp, pericarp coloration related enzyme and dynamic change in the content of K, Ca, Mg in pericarp so as to probe into the inner mechanism that results in unsatisfactory pericarp coloration.The test results are as follows:1. The growth of pericarp coloration and pulp relish of Feizixiao are not synchronous. The time for pericarp coloration lags behind the time when pulp relish reaches optimal; the growth of pericarp coloration and pulp relish of Zixiniang are synchronous.2. The main reason for the unsatisfactory pericarp coloration of Feizixiao litchi is insufficient anthocyanin accumulation; the primary cause for the sugar content decline in pulp lies in decline in contents of soluble sugar.3. During the development process of fruit, anthocyanin content and a value in the pericarp of Feizixiao and Ziniangxi fruit were on the rise while chlorophyll content, h value and b value were declining. Thus the pericarp coloration of two kinds of fruits owes to the rise of anthocyanin or decline of chlorophyll while irrelevant with changes in carotenoid content.4. The K content of Feizixiao litchi pericarp was on a declining curve in "N" shaped curve, while the total Ca content was on a rise and reached the peak on May22; there was no significant change in Mg content; water-soluble K content didn’t change in earlier stages whole presented a change curve in reverse "N" shape in middle and later stages; water-soluble Ca content reached a valley one week before fruit picking and remained stable in the rest of time; water-soluble Mg content was on a rise. As for Zixiniang litchi fruit, its total Ca, water-soluble Mg and Ca content were on the rise while there was no significant change in total Mg content and the total K and water-soluble K contents were declining. The total K, Ca, Mg and water-soluble K, Mg and Ca contents of the two kinds of pericarps were on a declining trend in the contemporary comparison. It is thus clear that different kinds of pericarps’ K, Ca and Mg contents have different dynamic changes but their simultaneous trends were consistent.5. According to the analysis on relevant multiple linear dependence of pericarp’s K, Ca and Mg contents and water solubility content, there was a significant positive correlation between the coefficient of partial correlation between Feizixiao litchi pericarp’s water-soluble Ca and water-soluble K, total Ca and water-soluble K, total Mg and total Ca; the multiple correlation coefficient of water-soluble K, water-soluble Ca, total Ca and total Mg was significant or remarkable; as for Zixininiang litchi pericarp, there was a significant coefficient of partial correlation between water-soluble Ca and water-soluble Mg, total Ca and total Mg, total Ca and total K, in which former two contents presented positive correlation while the latter presented negative correlation; the multiple correlation coefficient of the three elements’total contents and water-soluble contents were significant. Thus it can be seen that interaction of metabolism of K, Ca and Mg in pericarps in different kinds of fruits is different.6. There was remarkable correlation between pericarp’s K, Ca and Mg contents and pericarp’s pigment and coloration index in both kinds of litchi fruits. In Feizixiao litchi fruit, the pericarp’s total Ca content presented a positive correlation with a value while negative correlation with b value and h value. In Ziniangxi litchi, the pericarp’s Ca content presented a positive correlation with anthocyanin content and a value while negative correlation with chlorophyll content, b value and h value. It explains that during the pericarp coloration development of the two kinds of litchi fruit, the pericarp’s total Ca content is a key factor the accelerates the pericarp coloration of red.7. In Feizixiao litchi fruit, the pericarp’s anthocyanin content presented a positive correlation exponential functional regression relationship with Mg content and Ca content respectively and chlorophyll content presented a negative correlation exponential functional regression relationship with water-soluble Mg and Ca content respectively, while changes in K content may have nothing to do with the pericarp’s coloration of red. In Zixiniang litchi fruit, the pericarp’s anthocyanin content presented a positive and negative correlation unary exponential functional regression relationship with total Ca content and total K content respectively and chlorophyll content presented a negative, negative and positive correlation unary exponential functional regression relationship with water-soluble Mg and total Ca content and total K content respectively. Thus it can be seen that pericarp’s total Ca and water-soluble Mg contents significantly affect the pericarp coloration of both kinds of litchi fruits, while the influence of K content on pericarp coloration varies according to different species of litchi fruits.8. As the pericarp turned red, two litchi kinds’chlase and PaO activity significantly rose while presented negative correlation with chlorophyll content. The significant rise in UFGT activity presented positive correlation with changes in anthocyanin.9. The variation in both kinds of litchi fruits’IAA, ABA, GA and Eth was the same and in a significant rising trend. The iPAs content in Feizixiao litchi’s pericarp significantly rose while there was no such change in that of Ziniangxi’s pericarp.10. In both kinds of litchi’s pericarp, there was a significant correlation between K content, Ca content, Mg content and pericarp’s endogenous hormone content. The test results of Feizixiao litchi’s pericarp indicated that its total Ca content presented significant correlation with ABA,GA and Eth contents; as for Zixiniang litchi’s pericarp, its total Ca presented significant correlation with ABA,GA and Eth contents, while its ABA,GA and Eth were key hormones that affected pericarp coloration. Thus it can be seen that total Ca content in pericarp is the key that significantly affects endogenous ABA,GA and Eth contents in both kinds of litchi fruits’pericarp.11. There was a significant correlation between pericarp coloration index and pericarp endogenous hormone in both kinds of litchi fruits. And there was a significant negative correlation between ABA and Eth contents and chlorophyll content in pericarp of both kinds of litchi, while there was a significant positive correlation between ABA and Eth contents and anthocyanin. Significant correlation was found between Feizixiao litchi pericarp’s iPAs and anthocyanin content.12. There was a significant correlation between pericarp coloration related enzyme activity and pericarp’s endogenous hormone content in both kinds of litchi fruits. The pericarp’s ABA content presented a positive correlation with Chlase, UFGT and Pao activity in both kinds of litchi fruits; GA content presented a positive correlation with UFGT activity. The Eth content was in a positive correlation with PaO and Chlase activity.In brief, difference in the dynamic changes of pericarp’s K, Ca and Mg contents determine dynamic differences in pericarp’s pigment content, pericarp’s endogenous hormone and pericarp coloration related enzyme activity. Therefore, the Feizixiao litchi’s pericarp coloration can be adjusted by regulating the pericarp’s K, Ca and Mg contents. |
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