日長がデンドロビウム (Dendrobium Ekapol cv. Panda) の Crassulacean Acid Metabolism 型光合成に及ぼす影響  [in Japanese] Effects of Day Length on Gas Exchange Characteristics in Crassulacean Acid Metabolism Plant, Dendrobium Ekapol cv. Panda  [in Japanese]

デンドロビウム (Dendrobium Ekapol cv. Panda) の Crassulacean Acid Metabolism (CAM) 型 CO_2交換に及ぼす日長の影響を調べた. 日長処理として長日, 短日及び中日の3区を設定し, 長, 短日区は各々16及び10時間日長のグロースキャビネット内で57〜60日間生育させた後, 個葉のガス交換を調査した. 中日区は自然日長下で生育させ, 日長が12時間に達した時に調査を開始した. その結果, デンドロビウムはいずれの日長条件下でもCAM型CO_2交換を示す固定的なCAM植物であった. CAM型CO_2交換の日変化における各PhaseのCO_2収支量は, 日長条件により変化した. 短日条件では Phase 1が, 長日条件では Phase 2と4のCO_2収支量が増加した. 1日の総CO_2収支量は中・短日条件下で高く, また測定葉のリンゴ酸含量の日変動幅が大きかった. 葉のホスホエノールピルビン酸カルボキシラーゼの活性は, 日長処理の影響が認められなかったが, リンゴ酸に対するホスホエノールピルビン酸カルボキシラーゼの感受性は, Phase 4からPhase 1の前半にかけて処理間差が認められ, その時期で得られたCO_2交換速度の違いと密接に関連するものと推察された.

Effects of growth day length on gas exchange characteristics were investigated in a crassulacean acid metabolism (CAM) plant, Dendrobium Ekapol cv. Panda. Long (16h) and short (10h) day lengths were treated for 57 to 60 days in a growth chamber set at day/night temperatures of 30/25℃. As a control, plants were grown under natural conditions (light period was 12h). The data showed that the diurnal CO_2 exchange of D.Ekapol was classified as typical crassulacean acid metabolism type, an obligate CAM. The CO_2 balance of each phase was affected by the day length treatments. The CO_2 balances of short-day-length grown plants were increased in phase 1, whereas those of long-day-length grown plants were increased in phases 2 and 4. The CO_2 balance of whole day and diurnal malate fluctuation was increased in natural and short-day-length grown plants. The activity of phosphoenolpyruvate carboxylase did not response to the day length treatments. However, susceptibility of phosphoenolpyruvate carboxylase to malate was detected clearly in phase 4 and at the beginning of phase 1 under different day length. It was suggested that the difference between treatments was related to the changes in the CO_2 exchange rate in those phases.