モモ’清水白桃’の剪定量の違いが生理的落果ならびに果実発育に及ぼす影響

Using 'Shimizuhakuto' peach trees maintained by light (LP) and heavy (HP) prunings, fruit development and shoot growth were investigated in relation ro physiological fruit drop. The rate of split-pit fruits was significantly lower in LP trees than in HP trees, and the rate of dropped fruit in the former was also lower than in the latter although there was no significant. In LP trees shoot growth ceased by the end of May, while in HP trees the shoots continued to elongate until the end of June, corresponding to the end of stage 2 of fruit development. There was no significant difference in enlargement of normal and pit-split fruits between HP and LP trees. However, the enlargement of dropped fruits was more vigorous than those of pit-split fruit in HP and was by contrast inferior in LP trees. The growth of embryo in the fruits of HP trees was smaller than in those of LP trees from the beginning of stage 2, and the size of embryos of pit-split fruit were less than 50% in size compared to normal fruits in HP trees during stage 3. On the other hand, embryo of pit-split fruits in LP trees showed a similar growth to normal fruits until the end of stage 2. There was no difference in the size of endosperm and embryo of dropped fruit between HP and LP trees. Based on these results, ther possible causes whereby light pruning might decrease physiological fruit drop in peach are discussed.

モモ‘清水白桃’について，生理的落果の軽減に有効とされている弱剪定樹の果実発育や新梢生長の様相を慣行剪定樹と比較した．弱剪定樹では核割れの発生程度が慣行剪定樹よりも有意に低く，落果率も低い傾向であった．新梢生長は，弱剪定樹では５月末までにほぼ停止したのに対し，慣行剪定樹では果実発育第２期末の６月末まで続いた．正常果と核割れ果の果実肥大には両剪定樹間に差がなかったが,落下した果実の肥大は，慣行剪定樹では核割れ果よりも旺盛であったのに対し，弱剪定樹では逆に劣った．胚乳の生長には両剪定樹間に違いがなかった．胚の生長は，慣行剪定樹では第２期初め以降弱剪定樹よりも劣り，また核割れ果の胚は正常果の半分以下の大きさであった．一方，弱剪定樹では核割れ果の胚も第２期末までは正常果と同様の生長を示した．落果した果実の胚乳と胚の大きさには両剪定樹間に差がなかった．これらの結果から，弱剪定樹で生理的落果が少ない理由について考察した．