Comparative study on leaf anatomical structures and photosynthetic characteristics of three Geodorum species

To explore leaf anatomical structures and photosynthetic characteristics of Geodorum plant, the anatomical structure of leaves, daily variation of photosynthesis, light response curve, CO2 response curve, chlorophyll content and other indexes of the narrowly endangered Geodorum eulophioides and widely spread G. densiflorum and G. attenuatum were measured. The results were as follows: (1) Three species of Geodorum did not have spongy and fenestrated tissue differentiation in their chloroplasts, and stomata were distributed only in the lower epidermis. Compared with G.densiflorum and G.eulophioides, G. attenuatum had a greater leaf thickness and smaller stomatal density, exhibiting structural characteristics that were more adaptable to low light environments. (2) The daily changes of net photosynthetic rate (Pn) of three species of Geodorum showed a “bimodal” curve, and the photosynthetic “lunch break” was mainly caused by non-stomatal limitation. The daily mean values of Pn and water use efficiency (WUE) showe