27 6 月
Discontinuity of xylem function during maturation associated with quality development and calcium allocation in wax apple (Syzygium samarangense Merr. & Perry) fruit
|關鍵字： Taiwan； wax apple； Syzygium samarangense； apoplastic dye； calcium deficiency； corky calyx end disorder veraison
|摘要： Introduction - Wax apple (Syzygium samarangense Merr. & Perry) is an economically important fruit crop in tropical Asia. The developmental changes of wax apple fruit, calcium (Ca) accumulation and allocation, and xylem functionality within the fruit were assessed in this study. Materials and methods - Fruits were sampled at eight developmental stages and subjected to analyses for quality associated properties. Functionality of xylem inside fruit was evaluated with a methyl blue dye-infusion approach and the spatial distribution of Ca in mature fruit was assessed. Results and discussion - The growth of a wax apple fruit expressed a typical single sigmoidal curve against time. The breaker stage or the beginning of skin coloration signaled the onset of maturation process as indicated by a rapid increase in total soluble solids and skin anthocyanin content, and a simultaneous decrease in titratable acidity. Xylem remained fully functioning through the whole fruit before the breaker stage. However, a sharp functional decline in xylem toward the distal end of the fruit was observed after the breaker stage. Total Ca content continued to increase but overall Ca concentration reduced after the breaker stage. At harvest, a mature fruit expressed a high to low Ca conc. gradient from the proximal to the distal end. Conclusion - The low Ca conc. in the flesh near the distal end could be attributed to the loss of xylem function after the breaker stage. Therefore, early and efficient Ca uptake is essential for maintaining high Ca conc. in the distal end where corky calyx end disorder, a speculative Ca deficiency symptom of wax apple fruit, may occur.