カキ果実の成熟に及ぼすジャスモン酸とサリチル酸処理の影響(発育制御)  [in Japanese] Effect of Jasmonate and Salicylic Acid Treatments on Fruit Maturation in Japanese Persimmon(Growth Regulation)  [in Japanese]

植物界に広く分布し,新規植物ホルモンとして注目されているジャスモン酸と,エチレンや活性酸素種の代謝に関与するとされるサリチル酸が,カキ'富有'果実の成熟に及ぼす影響を知る目的で実験を行った.ジャスモン酸メチル(MeJA),サリチル酸(SA),エスレルおよび過酸化水素(H_2O_2)溶液を果実に処理し,着色,落果および収穫時の果肉硬度を調査した結果,H_2O_2は強く着色を促進し,MeJAとSAも促進効果を示したが,エスレルの効果は認められなかった.また,MeJAとSA処理果では,収穫時の果皮中のリコピン含量が高く,クロロフィル含量が低かった.H_2O_2とエスレル処理は,激しい落果を誘発して収穫時の果肉硬度も有意に低下させたが,MeJA 500ppm区での落果はほとんど観察されず,果肉硬度の低下も認められなかった.MeJA処理は果実からのエチレン放出量を増大し,SA処理はエチレン放出時期を早めた.このように,MeJAとSAは内生エチレンと活性酸素種の生産を通じてカキ果実の成熟に関与していると推察され,MeJAはカキ果実の着色促進剤として利用できる可能性がある.

Jasmonic acid (JA) is widely distributed in higher plants and its derivatives are considered novel plant hormones, while salicylic acid (SA) regulates various physiological responses including fruit ripening through the production of reactive oxygen species and ethylene in some plant species. To elucidate the involvement of JA and SA in the maturation of persimmon fruit (Diospyros kaki Thunb. cv. Fuyu), the effects of methyl jasmonate (MeJA), SA, ethrel and hydrogen peroxide (H_2O_2) on fruit maturation were evaluated in this study. H_2O_2 most strongly enhanced coloration as determined by "color chart", followed in order by MeJA and SA, whereas ethrel did not show any effect on color promotion. H_2O_2, MeJA and SA also increased lycopene and decreased chlorophyll concentration in the skin at harvest. Severe fruit drop was caused by both H_2O_2 and ethrel treatments, but there was almost no effect of MeJA treatment at 500 ppm. MeJA at 500 ppm did not soften the fruit flesh at all, although H_2O_2 and ethrel softened the fruit significantly. Persimmon fruit treated with MeJA emitted about 10 times more ethylene than the control, and SA treatment hastened the ethylene emission peak about 6 days compared to the control. Thus, JA and SA appear to be involved in maturation of persimmon fruit, possibly through the production of endogenous ethylene and reactive oxygen species. MeJA is a promising chemical for enhancing coloration of persimmon fruit.