低温胁迫对不同母树年龄柠条锦鸡儿种子萌发幼苗生理和生长的影响

Effects of low temperature stress on the physiology and growth of Caragana korshinskii seedlings from different mother tree ages

为探讨母树年龄、低温胁迫及其交互作用对柠条锦鸡儿(Caragana korshinskii)幼苗叶片生理和生长的影响,该研究选取晋西北丘陵风沙区5种母树年龄(7、13、19、41和51a)人工林柠条锦鸡儿的种子进行萌发,取2个月左右幼苗为实验材料,设置低温((–8±1)℃)胁迫,进行不同时长低温处理:W1(6 h)、W2(12 h)、W3(24 h)、W4(48 h)和W5(72 h),并以常规温度(25℃)培养为对照,测定幼苗与抗冻性相关的生理和生长指标,并采用隶属函数法进行综合评价。研究结果表明:(1)低温胁迫对不同母树年龄柠条锦鸡儿种子源萌发幼苗光合作用色素和渗透调节物质的影响存在显著差异,其中母树年龄和低温胁迫对幼苗叶片叶绿素(Chl)a含量有显著影响,母树年龄、低温胁迫及其交互作用对柠条锦鸡儿幼苗的Chl b、Chl(a+b)、类胡萝卜素含量和Chl a/b均有显著影响;低温胁迫和母树年龄与低温胁迫的交互作用对可溶性糖含量有显著影响,母树年龄、低温及其交互作用对游离脯氨酸含量有显著影响。随着低温胁迫时间的增长,柠条锦鸡儿幼苗叶片内Chl a、Chl b和Chl(a+b)含量整体呈先降后升的趋势,而Chl a/b和类胡萝卜素含量呈先升后降的趋势;游离脯氨酸含量则呈上升趋势。(2)低温胁迫对不同母树年龄柠条锦鸡儿种子源幼苗生长的影响差异显著,一方面,不同母树年龄种子萌发幼苗的株高、叶片数、干质量、主根长和根冠比均存在显著差异,随母树年龄的增加呈先升后降的趋势;另一方面,低温胁迫对幼苗株高有显著抑制作用,而母树年龄和低温胁迫的交互作用则对幼苗的上述生长参数没有显著影响。(3)通过聚类分析低温胁迫下柠条锦鸡儿幼苗的抗冻性生理指标综合评价值,将5种幼苗的耐低温性划分为两大类:第一类包括7、13 a母树种源幼苗,耐低温性强;第二类包括19、41、51 a母树种源幼苗,耐低温性弱,这表明低龄(7、13 a)母树柠条锦鸡儿种子萌发幼苗比高龄(19、41、51 a)母树的具有更强的抗冻性。综上,生理指标Chl b含量、Chl(a+b)含量、类胡萝卜素含量、Chl a/b和生长指标株高、叶片数、干质量、主根长和根冠比可作为柠条锦鸡儿幼苗的抗冻性鉴定指标,同时,在人工促进柠条林天然更新时,可以选用青壮年柠条锦鸡儿的种子进行幼苗培育,进而提高人工林更新的成功率。

Aims This study investigated the effects of mother tree age,low temperature stress,and their interaction on the growth and leaf physiological characteristics of Caragana korshinskii seedlings.Methods In this study,seeds of C.korshinskii were selected from an artificial forest in the hilly and sandy area of northwest Shanxi Province,representing five mother tree ages(7,13,19,41 and 51 a).These seeds were germinated,and the resulting seedlings(about 2 months)were used as test material.The low temperature stress was applied at(–8±1)°C with varying stress levels:W1(6 h),W2(12 h),W3(24 h),W4(48 h)and W5(72 h).A control group(CK)was maintained at 25°C(normal temperature).Different growth and physiological indicators related to frost resistance were determined,and a comprehensive evaluation was conducted using the membership function method.Important findings The results showed that:(1)There were significant differences in the impact of low temperature stress on photosynthetic pigments and osmotic adjustment substances in C.korshinskii seedlings from different mother tree ages.Notably,mother tree age and low temperature stress had significant effects on chlorophyll(Chl)a content,while the contents of Chl b,Chl(a+b),carotenoid and Chl a/b in C.korshinskii seedlings were influenced by mother tree age,low temperature stress and their interaction.Low temperature stress as well as the interaction between low temperature stress and mother tree ages,had a significant effect on soluble sugar content,while mother tree ages,low temperature stress and their interaction significantly influenced free proline content.With the increasing low temperature stress duration,the contents of Chl a,Chl b,and Chl(a+b)in the leaves of C.korshinskii seedlings initially decreased and later increased,while the Chl a/b and carotenoid content exhibited an initial increase followed by a decreased,and the content of free proline increased.(2)Low temperature stress had variable effects on the growth of C.korshinskii seedlings from different mother tree ages.Plant height,leaf number,dry mass,main root length and root shoot ratio of seedlings germinated from seeds from different age plants displayed significant differences,with values initially increasing and then decreasing with the increase in mother tree age.However,low temperature stress significantly inhibited the plant height of the seedlings,with no significant interaction observed between mother tree age and low temperature stress on the aforementioned growth parameters.(3)Seedlings germinated from the seeds of young mothers(7,13 a)showed stronger frost resistance than those from older mothers(19,41,51 a).In summary,physiological parameters including Chl b content,Chl(a+b)content,Chl a/b,carotenoid content and growth parameters such as plant height,leaf number,dry mass,main root length and root shoot ratio can serve as indicators for assessing frost resistance in C.korshinskii seedlings.Besides that,when promoting the natural regeneration of C.korshinskii forest through artificial means,selecting seeds from young and middle-aged C.korshinskii plants can enhance the success of regeneration.