兴安落叶松针叶解剖结构变化及其光合能力对气候变化的适应性

Abstract

Leaf anatomy,being susceptible to environmental factors,is closely related to physiological functions of the leaf, and also reflects responses and adaptation of the tree to environmental changes. Changes in leaf anatomical structure are bound to change the physiological functions of trees. The same species growing in heterogeneous environment for a long time through natural selection and adaptation will result in variations in morphological and physiological characteristics,forming distinctive geographic populations. In addition,Matrix subjected to environmental stress will affect its offspring growth, developmental and physiological characteristics. Therefore,to understand how the morphological structure of leaves respond and adapt to environmental changes is essential for exploring the response and adaptation mechanism of plants to environmental changes. Dahurian larch( Larix gmelinii Rupr.) is a dominant tree species in boreal forest in China,mainly distributed in northeast China,but going further climate changes may change its existing distribution. There are few studies to distinguish short-term responses of leaf anatomy and physiology from their potential long-term adaptation to climate changes in field. In this study,we conducted a common garden experiment that included six provenances of Dahurian larch with different climate and site conditions with three replicate trees each provenance. The trees were 32 years old,seeded in 1980,and transplanted in 1983 at identical site and climate conditions. We measured leaf anatomical parameters using paraffin section method( i. e.,total leaf thickness,leaf adaxial epidermis cells thickness,leaf abaxial epidermis cells thickness,leaf adaxial mesophyll cells thickness,leaf abaxial mesophyll cells thickness,leaf vascular bundle tissue thickness,leaf endoderm cells thickness,leaf transporting tissue thickness,leaf epidermis cells thickness,leaf mesophyll cells thickness,and photosynthetic physiology( i. e.,photosynthetic capacity [P max-a ],stomatal conductance [g s ],water use efficiency [WUE]) in order to address the question of whether leaf anatomical structure adapts to climate changes and consequently results in physiological adaptation. The results showed that the thickness of epidermis cells,mesophyll cells, transmission tissue cells,vascular cells and endothelial cells,and the total thickness of the needles differed significantly among the provenances( P 0. 05). There was a significant difference in the proportion of thickness of each anatomical part. The thickness of mesophyll cell accounted for the largest proportion,with an average proportion ranging from 38. 4% to 43. 3%. The thickness of mesophyll cells was positively correlated( P0. 05) with P max-a,g s,and WUE. The thickness of mesophyll cells and epidermal cells,the total thickness of the needles,and the proportions of thickness of mesophyll cells or epidermal cells in the total thickness of the needle were all positively correlated with the aridity index( the ratio of mean annual evaporation to mean annual precipitation) at the origins of the provenances. These results suggest that needles of the Dahurian larch trees from different provenances alter their anatomical structures significantly due to adaptation to local climate conditions,and accordingly change their physiological functions such as photosynthesis and water use efficiency.