| Summary: | 碩士 === 國立中興大學 === 園藝學系 === 93 === Mineral concentrations of fruits and leaves were investigated during the period of growth and development of guava “Jen-Ju Bar”. Results showed that N, P, Ca, Mg, Fe, Mn, Cu and Zn concentrations decreased with the growth of fruits. Leaf N and K concentrations also decreased, but P, Ca, Mg, Fe, Mn, Zn on the other hand increased with the increasing size of the fruits. From bloom to maturity, winter crops took about 142 days while summer crops needed relatively short period of about 98 days. Growth curve displayed a double sigmiodal pattern.
“Jen-Ju Bar” tends to turn soft after harvest. This seems to be related to the Ca content in the fruits and three cultural techniques were employed to improve quality and to prevent Ca and other minerals deficiencies from happening. Regulation of leaf to fruit ratios was adopted to evaluate the Ca content and the results indicated that fruit Ca was higher in plants with 8 to 16 leaves per fruit at the time of maturation. Better fruit quality was obtained with 12 to 16 leaves per single fruit. Bagging with polyethylene in addition with white expandable polystyrene or net lining had no effect on fruit size at maturity. Neither did they affect N, P, K, Fe, Cu and Zn concentrations in fruit. By contrast, net lined bagging enhanced Ca, Mg, and Mn as well as starch content, but it contributed little to the total soluble sugar concentration. When “Jen-Ju Bar” guava scions were grafted onto 4 different stocks, mineral absorption by stock “Da-Ti” was most rapid and thus led to the accumulation of higher macro-element concentrations in leaves. Fruit soluble sugar concentration would reach the highest level whenever scion was grafted on “Jen-Ju Bar”. The starch content, however, was elevated to the highest level only when scions were grafted on “Shui-Jing” stock. No significant differences were found in leaf soluble sugar and starch in the graftage experiment.
The firmness of fruit and the total soluble solids were negatively correlated with Mg whereas the ascorbic acid was positively correlated with Mg concentration. Fruit Ca and total soluble sugar had a similar trend. In leaf P and Ca concentrations were negatively correlated with total soluble solids, while Ca and ascorbic acid were found positively correlated.
In the high quality”Jen-Ju Bar” fruits, N was found to be between 0.5 and 0.86%; P：0.061- 0.105%; K：1.04- 1.5 %; Ca：0.024-0.068%; Mg：0.023-0.039%. Leaf N concentration was 1.45-1.71%; P：0.111-0.149%; K：0.69-1.21%; Ca：1.49-2.81% and concentration of Mg ranged from 0.15 to 0.33 %. These figures could be used as a reference in the fertilization and management programs in producing good quality “Jen-Ju Bar” guava in the field.
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