种源地对两种红树叶片结构和功能的影响:对温度的适应性遗传

Effects of provenance on leaf structure and function of two mangrove species:the genetic adaptation to temperature

植物叶片具有根据不同环境状况调整表型特征的能力,叶片性状对环境的适应能力直接影响植物在气候变化背景下的生存、分布和迁移。受全球气候变暖的影响,红树林正向高纬度地区扩张,然而关于红树植物叶片性状对不同生长地点温度变异的适应性遗传仍缺乏了解。该研究采用同质园法以来自6个不同纬度种群的木榄(Bruguiera gymnorhiza)和5个不同纬度种群的秋茄树(Kandelia obovata)幼苗为研究对象,测定了其叶片解剖结构和生理功能参数,分析红树幼苗叶片的解剖结构特征与生理功能之间的关系及对种源地温度的适应性遗传。结果发现:木榄幼苗的叶片厚度、栅栏组织和表皮厚度与种源地年平均气温均呈显著负相关关系,角质层厚度随年平均气温的升高呈下降的趋势;与木榄幼苗相比,秋茄树幼苗叶片具有较厚的表皮和角质层,较小的气孔密度和叶脉密度,叶片解剖结构未与种源地年平均气温表现出相关性。两种红树不同种源地幼苗的数据合在一起,叶片栅栏组织和海绵组织厚度均与光合速率呈正相关关系,与海绵组织厚度的相关性更强,说明叶肉组织厚度变化对红树光合作用有影响;叶脉密度与气孔密度、最大气孔导度也均呈显著正相关关系,说明两种红树在遗传适应上能够维持叶片水平的水分供需平衡。综上所述,两种红树叶片解剖结构存在差异,对种源地温度的适应性遗传有显著区别,木榄对长期生长环境形成适应性遗传;秋茄树通过建成性的叶片结构特征遗传适应种源地温度;叶片结构的差异引起了红树光合作用、最大气孔导度等生理功能发生相应的变化,从而有利于红树在气候变化的背景下得以生存和繁衍。

Aims Plant leaves have the ability to adjust phenotypic characteristics according to different environmental conditions.The adaptability of leaf traits to the environment directly affects the survival,distribution and migration of plants under climate change.With global warming,mangrove forests have been expanding to higher latitudes.However,there is still a lack of understanding about the genetic adaptation of leaf traits of different mangrove species to temperature variation of native habitats.Methods The leaf anatomical structure and physiological function parameters of the seedlings from 6 provenances of Bruguiera gymnorhiza and 5 provenances of Kandelia obovata were measured,which were grown in a common garden.The relationships between the leaf anatomical traits and physiological function of mangrove seedlings were analyzed,and the genetic adaptation of two mangrove species to the temperature of provenance was analyzed.Important findings The leaf thickness,thickness of palisade tissue,cuticle and epidermis of B.gymnorhiza seedlings were significantly negatively correlated with the mean annual temperature of their native habitats.Compared with the seedlings of B.gymnorhiza,the K.obovata seedlings had thicker leaf epidermis and cuticle,and the anatomical traits of K.obovata were not correlated with the annual average temperature of the provenances.Pooling the data of the seedlings of different provenances of the two species together,the palisade tissue and to a lesser extend spongy tissue were positively correlated with photosynthetic rate,suggesting an important role of palisade tissue for photosynthesis in mangroves.There was also a significant positive correlation between vein density and stomatal density,maximum stomatal conductance,revealing genetic adaptation for the balance between leaf transpirational demand and water supply.In conclusion,B.gymnorhiza showed the significant genetic adaptation to the temperature of the provenance,while K.obovata did not.The leaf anatomical structure of K.obovata adapts to the temperature of provenance through the persistent inheritance of stress resistance of leaf structure.The differences of leaf structure lead to the corresponding changes of physiological functions such as photosynthesis and maximum stomatal conductance of mangroves,which is conducive to the survival and reproduction of mangroves under the climate change.