チューリップ球根リン片内における貯蔵デンプン分解の低温による誘導

概要

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チューリップ球根のα-アミラーゼ活性およぴ各種炭水化物成分濃度変化におよぼす低温処理の影響について調ベ,さらにα-アミラーゼのリン片内における局在性を検討した.低温区では処理期間中,α-アミラーゼ活性が徐々に高まり,それに伴いデンプンの減少とスクロースおよぴフラクトオリゴ糖の増加が見られた.定植後,茎葉部の伸長に伴いα-アミラーゼ活性は急増し,デンプンの分解は加速され,同時に可溶性糖も消費された.一方,低温に曝されなかった対照区でも夏期にリン片新鮮重あたりのα-アミラーゼ活性が上昇した.しかし,このときデンプンの減少および可溶性糖の増加は認められなかった.等電点電気泳動によりα-アミラーゼのアイソザイムパターンを調ベたところ,対照区,低温区ともに2本の主要なパンドが確認された.植え込み後,低温処理区ではすでに存在した2本のバンドの活性が著しく高まるとともに新たな活性バンドも現れた.植え込み時のリン片組織を光学顕微鏡で観察したところ,低温処理区および対照区ともに表皮部にデンプン粒の認められない細胞群の層が認められ,低温処理区では中心部も一部デンプン粒の認められない細胞が観察された.リン片におけるin situの酵素活性をデンプン薄膜法で検討したところ,リン片中心部に比ベ表皮部の方が活性が高い傾向が見られた.リン片組織を表皮部と中心部に分割後,粗酵素溶液を抽出し活性を測定したところ,対照区では表皮にのみα-アミラーゼ活性が高かったが,デンプンが大量に集積している中心部では活性が低かった.一方,低温処理区においても表皮部の活性が高かったが,リン片内部の活性も高まり,デンプン粒の分解に寄与したと考えられた.以上の結果から,低温処理はデンプンを貯蔵しているリン片中心部細胞のα-アミラーゼ活性を誘導しデンプンを分解すると考えられた.The effects of cold temperature on the activity of α-amylase and on carbohydrate composition were investigated in the bulb scales of tulip plants (Tulipa gesneriana). Some bulbs were stored at 15℃ for 3 weeks from August 30, 1991, and subsequently at 2℃ for 8 weeks. Another group of control bulbs was stored at room temperature during the same period. Both groups of bulbs were planted in a green house at about 20℃ from October 30, 1991. The α-amylase activity in cold-stored bulb scales increased gradually during the cold-storage period and the degradation of starch and the concomitant accumulation of sucrose and fructans were observed. After planting, the α-amylase activity of cold-treated bulbs increased dramatically and the degradation of starch was accelerated. On the other hand, the α-amylase activity also increased in control bulbs, although starch degradation did not occur. After separated by isoelectric focusing gel electrophoresis, α-amylase isozyme patterns were compared between cold-treated and control bulbs. The same two a-amylase isozymes occurred in bulbs receiving both treatments during the cold storage period. Starch was stained with iodine solution and the distribution of starch in the scales was observed microscopically. In control bulb scales, no starch was observed in the few cell layers immediately below the epidermis, but starch granules were filled in the inner cells. In cold-treated bulb scales, some inner cells lost their starch granules. By in situ observation of α-amylase activity by starch-film method and by the separate measurement of α-amylase activity in the outer and inner cells of scales, it was suggested that outer cells without starch contained higher activity of α-amylase both in control and cold-treated bulbs. The activity was also detected in the inner cells of cold-treated bulbs, but not in the inner cells of the control bulbs. Based on the results obtained, it was suggested that low temperature treatment induces α-amylase activity in inner cells which store a large amount of starch. Although control bulb scales also had high α-amylase activity, it was restricted to a few layers of outer cells and did not occur in the inner cells.
日本土壌肥料学会の論文
1997-02-00

チューリップ球根リン片内における貯蔵デンプン分解の低温による誘導

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概要

日本土壌肥料学会 | 論文

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