以 来源于不同产地的10 个香椿[Toona sinensis (A. Juss.) Roem.]种 源 为 研 究 对 象、以温度 25 ℃为对照,对 5  ℃ 、0  ℃ 、-5  ℃和-10  ℃低温胁迫条件下叶片的水分含量指标(包括总含水量、自由水含量、束缚水含量和自由水含量与束缚水含量比值)和渗透调节物质含量(包括可溶性糖含量和脯氨酸含量)的变化进行了比较,并对这些指标与低温半致死温度(LT₅₀ )的相关性进行了分析。 结果表明:在 5  ℃至-5  ℃ 条件下,各种源幼苗叶片的总含水量、自由水含量以及自由水含量与束缚水含量比值均低于对照,并且大多种源的上述指标随温度降低不断下降;各种源幼苗叶片的束缚水含量则均高于对照,并在 0  ℃条件下达到最高值;多数种源幼苗叶片的可溶性糖含量及脯氨酸含量则随温度降低而持续上升。 在-10  ℃条件下,所有种源幼苗叶片的总含水量和自由水含量以及绝大多数种源的自由水含量与束缚水含量比值均高于-5  ℃ 条件下,但束缚水含量、可溶性糖含量和脯氨酸含量则均低于-5  ℃条件下。 相关性分析结果表明:在5  ℃条件下,束缚水含量与 LT50呈显著负相关、自由水含量与束缚水含量比值与 LT50呈显著正相关,而在 0  ℃ 、-5  ℃和-10  ℃条件下这 2 个指标与 LT₅₀则分别呈不显著的负相关和正相关;在5  ℃和-5  ℃条件下叶片的自由水含量与 LT₅₀呈显著正相关,而在 0  ℃ 和-10  ℃ 条件下则呈不显著正相关;在 5  ℃条件下叶片的可溶性糖含量和脯氨酸含量与 LT50呈不显著负相关,而在 0  ℃ 、-5  ℃ 和-10  ℃ 条件下则与 LT50呈显著负相关。 研究结果表明:供试的 10 个香椿种源均不能耐受-10  ℃的低温胁迫,应在-5  ℃至-10  ℃范围内进一步研究确定其低温耐受阈值。

 

Taking ten provenances of Toona sinensis ( A. Juss.) Roem. from different locations as researching subjects and temperature 25  ℃ as the control, changes in water content indexes ( including contents of total water, free water and bound water, and ratio of free water content to bound water content) and osmoregulation substance content ( including soluble sugar and proline contents) in leaf under low temperature stress conditions of 5  ℃ , 0  ℃ , - 5  ℃ and - 10  ℃ were compared, and correlations between these indexes and the low semilethal temperature (LT50) were analyzed. The results show that under conditions from 5  ℃ to -5  ℃ , total water content, free water content and ratio of free water content to bound water content in leaf of T. sinensis seedlings from different provenances all are lower than those of the control, and above indexes of most provenances decrease gradually with decreasing of temperature; bound water content in leaf of seedlings from different provenances is higher than that of the control and reaches the highest value under condition of 0  ℃ ; contents of soluble sugar and proline in leaf of seedlings from most provenances increase continuously with decreasing of temperature. Under condition of -10  ℃ , total water content and free water content in leaf of all provenances and ratio of free water content to bound water content in leaf of most provenances all are higher than those under condition of -5  ℃ , but contents of bound water, soluble sugar and proline all are lower than those under condition of -5  ℃ . The results of correlation analysis show that under condition of 5  ℃ , there is significantly negative correlation between bound water content and LT50, and there is significantly positive correlation between ratio of free water content to bound water content and LT 50, while under conditions of 0  ℃ , -5  ℃ and -10  ℃ , there is no significantly negative and significantly positive correlations between the two indexes and LT 50, respectively. There is significantly positive correlation between free water content in leaf and LT 50 under conditions of 5  ℃ and -5  ℃ , while there is no significantly positive correlation between them under conditions of 0  ℃ and -10  ℃ . There is no significantly negative correlation between contents of soluble sugar and proline and LT50 under condition of 5  ℃ , while there is significantly negative correlation between them under conditions of 0  ℃ , -5  ℃ and -10  ℃ . It is suggested that ten provenances tested of T. sinensis all are not tolerant to - 10  ℃ low temperature stress, the tolerance threshold of T. sinensis to lower temperature should be confirmed from -5  ℃ to -10  ℃ .