Response of leaf anatomical structure of Larix gmelinii to climate warming and provenance variation.

Exploring the response of leaf anatomical structure to climate warming is helpful for understanding the adaptive mechanisms of trees to climate change. We conducted a warming experiment by transplanting seedlings of Larix gmelinii from 11 provenances to two common gardens, and examined the response of leaf anatomical structure to climate warming. The results showed that warming significantly increased leaf thickness (T_L), upper epidermal mesophyll thickness (T_UEM), lower epidermal mesophyll thickness (T_LEM), endodermal thickness (T_E), vascular bundle diameter (D_VB), transfer tissue thickness (T_TT), and the percentage of mesophyll thickness to T_L(P_MT), and significantly decreased the upper epidermal thickness (T_UE) and the percentage of epidermal thickness to T_L (P_E). The mesophyll thickness was positively associated with chlorophyll concentration and maximum net photosynthetic rate. The responses of T_L, T_UEM, T_LEM, T_E, D_VB, T_TT, T_UE, P_MT and P_E to warming differed among all the provenances.As the aridity index of the original site increased, the magnitude of the warming treatment's effect decreased for T_L, T_UEM, T_LEM, T_TT and P_MT, and increased for T_UE and P_E. Warming increased the thickness and proportion of profit tissue (e.g., mesophyll) and decreased the thickness and proportion of defensive tissue (e.g., epidermis), and those changes varied among provenances. L. gmelinii could adapt to climate warming by adjusting leaf anatomical structure, and this ability was weak for trees from provenance with high aridity index.