Effects of Seed Injury and Injection with Gibberellic Acid and Paclobutrazol on Fruit Drop and Seed Development in “Beni Shimizu” Peach

The relationsships between fruit drop induced by seed injury and seed development were investigated in “Beni Shimizu” peach. Seed injury(Injury) was done by drilling from opposite side of suture line upto seed coat using an electric drill(outre diameter of 2.5mm) at 40, 50, 60, 72 and 80 days after full bloom(DAFB). Injections of gibberellic acid(GA) and paclobutrazol(PBZ) (Injection), which relate to fruit drop and seed development were carried out just after the injury for seed. In all of the Injury and Injection treatments, treated fruit dropped in 40, 50 and 60 DAFB treatments but not in 72 and 80 DAFB treatments. Weight of fruit and seed debreased rapidly at 3 days after treatment(DAT) in 60 DAFB treatment. Morphology of endosperm and embryo was compared among 60, 72 and 80 DAFB treatments. Growth of endosperm and embryo stopped from 3 DAT in 60 DAFB treatment but embryo continued to grow until 5 DAT in 72 DAFB treatment. Collapsed cell nucleus in endosperm and embryo occurred at 3 DAT in 60 DAFB treatment. On the other hend, in 72 DAFB treatment cell nuclei in endosperm collapsed in a similar manner as in 60 DAFB treatment although the cell nuclei in embryo did not collapse. When morphology of chalazal haustorium in 60 DAFB treatment was examined, chalazal haustorium began to shrink just after the treatment and percentage of seed with normal chalazal haustorium decreasedrapidly in all treatments. Based on these results, the process of seed abortion as a result of seed injury and its relationship between embryo growth and fruit drop is discussed.

モモ‘紅清水’において種子への傷害が誘起する落果と種子発育との関係を検討した．種子への傷害（傷害処理）と して果実の縫合線と逆の位置から種皮まで外径2.5㎜のドリルを満開後40，50，60，72および80日に挿入した．落果や 種子発育と関係するジベレリンとパクロブトラゾールの種子への注入（注入処理）も傷害処理後に行った．傷害処理， 注入処理ともに，満開後40～60日処理には処理した果実が全て落下したのに対し，72および80日処理では，いずれも 落下しなかった．60日処理では，果実および種子の新鮮重がともに処理３日後に減少し始めた．胚乳と胚の形態を満 開後60，72および80日処理間で比較した．胚乳および胚の成長は60日処理では処理３日後に停止したが，72日処理で は胚が処理５日後まで成長し続けた．胚乳と胚の細胞核の崩壊は，処理時の胚長が５㎜未満であった60日処理では， 処理３日後に生じた．一方，処理時の胚長が約８㎜であった72日処理では，胚乳における細胞核の崩壊は60日処理と 同様の傾向で生じたが，胚の細胞核は崩壊しなかった．60日処理において合点側吸器の形態を観察したところ，吸器 は傷害処理や注入処理によって直ちに収縮し始め，正常な合点側吸器を持つ種子の割合は急速に低下した．これらの 結果に基づいて，種子への傷害による種子の退化過程ならびに胚の成長と落果との関係を考察した