望天树苗期叶片对低温胁迫的生理响应及抗寒性评价
Physiological Response and Cold Resistance Evaluation of the Leaves of Parashorea chinensis Seedlings to Low Temperature Stress

为明确望天树的抗寒机理，以2年生望天树幼苗为试验材料，研究了0℃低温胁迫（0、1、2 d，以25℃常温培养为对照）下望天树的生理指标和外部形态的变化。结果表明，随着低温（0℃）胁迫时间的延长，望天树幼苗叶片中保护酶系统（SOD、POD）、渗透调节物质（可溶性糖和可溶性蛋白）、叶绿素以及丙二醛（MDA）和相对电导率呈现出持续增长的变化趋势，在0℃处理2 d时达到最大值，且均>对照；待温度回升到25℃后，望天树幼苗叶片中的抗氧化酶（SOD、POD）活性、渗透调节物质（可溶性糖和可溶性蛋白）含量、叶绿素以及相对电导率和丙二醛（MDA）含量则均有所下降。表明望天树苗期叶片在0℃低温胁迫中受到一定程度的伤害，0℃处理2 d可作为早期筛选耐寒材料的时间节点；待温度回升到25℃后，渗透调节物质含量及抗氧化酶活性开始下降，表明望天树幼苗在遭受低温胁迫后具有一定的自我修复机制。
In order to clarify the cold-resistant mechanism of Parashorea chinensis,2-year-old seedlings were used as materials,which were treated under 0℃ or 25℃ (control) for 0,1,2,and 5 d.The physiological indicators of the seedlings were studied.The results showed that with the increase of stress time,the protective enzyme system (SOD,POD),osmotic adjustment substances (soluble sugar and soluble protein),chlorophyll and malondialdehyde (MDA) and the relative conductivity trended to increase continuously,reaching maximum values at 2 d,and higher than the control.After the temperature rose back to 25℃,the antioxidant enzyme (SOD,POD) activity in the leaves of the seedlings,osmotic adjustment substances (soluble sugar and soluble protein) content,chlorophyll and relative conductivity and malondialdehyde (MDA) content decreased.The results showed that the leaves of P.chinensis seedlings suffered some damage under stress at 0℃,and treatment at 0℃ for 2 days could be used as the time node for early screening of cold-resistant materials; after the temperature rose back to 25℃,the content of osmotic adjustment substances and antioxidant enzymes activity began to decline,indicating that the seedlings of the P.chinensis had a certain self-repairing mechanism after suffering from low temperature stress