ISHS Acta Horticulturae 592: V International Peach Symposium
CRACKING AND MECHANICAL PROPERTIES OF THE STONE IN PEACH CULTIVARS AFTER SEVERE THINNING |
| Authors: | M. Nakano, M. Nakamura |
| Keywords: | pit splitting, fruit abscission, cleavage resistance, maximum strain, elastic modulus, radial tensile force |
| Abstract:
The effects of thinning of fruits, girdling of branches and pinching of shoots were examined in four midseason-maturing peach cultivars on five dates in mid May and late June, the end of stage 1 and stage 2, respectively. The treatments on May 15 and May 28 promoted fruit growth, and markedly induced stone cracking but less so fruit abscission. On the whole, flesh of peach was firm in terms of the partial compressive strength, and osmotic pressure was low during late May and mid June. On the other hand, the amount of lignin in peach stone increased linearly and the maximum strain decreased gradually from late May to maturation. The rigidity of the stone expressed by the elastic modulus increased during late May and early June, and the stone became hard until maturation as indicated by the partial compressive strength. These results showed that stone became brittle but crisp during early stage 2. Therefore, the growth of peach treated in late stage 1 and early stage 2 increased markedly, and the radial tensile force of the flesh would produce cracks in the stone. Differences in mechanical properties were observed among the cultivars, for example, a higher elastic modulus in the stone of 'Hakuho' and smaller partial compressive strength in the stone of 'Ohkubo'. Differences were also observed in the treated plots such as increased tensile strength, plasticity and Young’s modulus in the flesh of 'Beni-shimizu'. | |
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