为探究不同土壤基质条件下核桃楸幼苗对干旱胁迫生理特性的响应,以两年生核桃楸幼苗为研究对象,在腐殖土、壤土和砂壤土三种基质条件下进行控水试验,水分梯度分别设置为CK(正常供水,80％田间持水量)、T1(轻度胁迫,60％田间持水量)、T2(中度胁迫,40％田间持水量)和T3(重度胁迫,20％田间持水量),测定幼苗叶片叶绿素、丙二醛、脯氨酸、抗氧化酶和光合指标.结果 表明,随着胁迫程度的加深,叶绿素含量和Chl a/b均呈逐渐降低的趋势(P＜0.05),在胁迫60d时,T3处理下的叶绿素a(Chl a)和叶绿素b(Chl b)分别比CK低65.41％和51.57％,3种基质中叶绿含量大小顺序为:腐殖土＞壤土＞砂壤土.随着胁迫程度的加深,叶片脯氨酸(Pro)、丙二醛(MDA)则呈逐渐升高的趋势(P＜0.05),胁迫60d时,砂壤土中T3处理的Pro含量最高为83.37mg·g-1,比CK高86.32％.腐殖土中幼苗叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均随胁迫程度加深而升高,壤土中叶片SOD活性则呈先升高后降低的变化规律.3种土壤基质中核桃楸叶片净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)均随着胁迫程度的加深而降低,但不同基质中幼苗叶片的气孔限制和非气孔限制发生的时间不同,T3处理的叶片胞间CO2浓度(Ci)在腐殖土中是12:00时最低,而在壤土和砂壤土中则是10:00时最低.土壤全氮、全磷、渗透速率和蒸腾速率与叶绿素含量存在显著的正相关关系(P＜0.05),土壤容重与叶绿素含量存在显著的负相关关系(P＜0.05).因此,土壤基质和干旱胁迫对核桃楸幼苗的生理生化和光合特性产生了显著的影响,重度胁迫对幼苗的叶绿素、渗透物质和酶体系产生了严重的损伤,同时降低了核桃楸幼苗的光合生产力.总体上,腐殖土中的幼苗有着较好的抗旱表现.

Rapid cold hardening can enhance the cold tolerance of some insects. To explore the effects of different cold hardening induction temperature on the cold tolerance of Arma chinensis and related physiological mechanisms, the 3rd generation A. chinensis adults reared indoor were treated with cooling at 15, 10, and 4 degrees C for 4 h, respectively, or with gradual cooling from 15 degrees C for 4 h to 10 degrees C for 4 h, and finally to 4 degrees C for 4 h. The super-cooling point, water content, and the contents of low molecular carbohydrates, glycerol, and amino acids of the adults after cooling and the adults cold tolerance at 0, -5, and -10 degrees C were measured by thermocouple, high performance liquid chromatography, and other analytical techniques. When exposed at -10 degrees C after cooling, the survival rate of the adults treated with gradual cooling or treated with cooling at 4 degrees C for 4 h was averagely 58.3%, while that of the adults reared at room temperature (25 degrees C +/- 2 degrees C) or treated with cooling at 15 degrees C or 10 degrees C for 4 h decreased significantly, with an average of 8.9%. The super-cooling point of the adults treated with gradual cooling or with cooling at 4 degrees C for 4 h was -15.6 degrees C, which was averagely 1.3 degrees C lower than that of the other treatments. The water content of the adults had no significant difference among all treatments, with an average of 61.8%, but the glucose, sorbitolum, glycerol, Ala, and Glu contents in treatments gradual cooling and cooling at 4 degrees C for 4 h increased by 2.82-fold, 2.65-fold, 3.49-fold, 51.3%, and 80.2%, while the fucose, mannose, and Pro contents decreased by 68.4%, 52.2%, and 30.2%, respectively, as compared with the other treatments. The fructose content showed no significant difference among all treatments. It was suggested that rapid cool hardening had a critical temperature to induce the physiological metabolism process of adult A. chinensis, and gradual cooling hardening could not further increase the cold tolerance of adult A. chinensis on the basis of rapid cool hardening.