Accumulation of proline and abscisic acid in relation to chilling tolerance of sorghum (Sorghum bicolor L.) seedling

高梁幼苗在低溫（5/5°C，日/夜溫）下脯胺酸迅速累積，且耐冷品系2R累積量較不耐冷品系80A高，顯然脯胺酸這種環狀胺基酸可能和高粱幼苗耐冷性有關。當幼苗經低溫處理後離層酸亦有累積現象，地上部在 低溫處理24小時後開始累積，根部在6小時有一累積兩峰而後則下降；然而，2R及80A二品系間在離層酸含量上差異不大。2R在低溫處理3小時葉 片氣孔導度即迅速下降，而80A遲至6小時才有關閉現象，且關閉幅度較2R小，所以在低溫下2R因葉片水分蒸散減少而能保持較高的水份含量，80A則因蒸散快且根部無法迅速補充水分而使植株發生脫水。由氣孔關閉速度及幅度可以部份解釋2R及80A在低溫下耐冷性的差異。 The level of proline increased rapidly in sorghum seedlings after chilling. Accumulation of proline was found to be higher in chilling tolerant line 2R than that in chilling sensitive line 80A. When seedlings were subjected to 5°C, the level of abscisic acid was increased, However, only slight difference in the level of chilling induced abscisic acid was observed between 2R and 80A. In response to 5°C treatment, 2R showed a faster and higher reduction in leaf stomatal conductance and maintained a higher water content than 80A. The difference in stomatal closure time and rate of stomatal response could partially explain the dispartiy in chilling tolerance between 2R and 80A