Effect of elevated CO2 level on the anatomical structure of Medicago sativa, under different fall dormancy types

Effect of elevated atmospheric CO2 concentration on plants has aroused wide concern among scholars. In this study, open-top chambers (OTC) were used to model the future CO2 concentration to study the effect of CO2 enrichment on the leaf anatomical structure of three types fall dormancy at different growth stages by using the paraffin section technique. Results showed that: the anatomical structure of leaves was significantly affected by the increase of CO2 concentration, the growth period, and the interaction effect of three factors. The leaf anatomical structure increased significantly with the increase of CO2 concentration (P<0.01), which was beneficial to increase chloroplast content,gas exchange rate, and subsequently the photosynthesis rate. Leaf thickness, cuticle thickness, palisade tissue thickness, and sponge tissue thickness increased significantly with the growth period (P<0.01). The anatomical structure of leaves showed no significant differences among three fall dormancy types (P>0.05), mainly because fall dormancy is influenced by the duration of light and temperature and is less affected by CO2. The results of this study provide a basis for predicting the effect of elevated CO2 on the anatomical structure of plant leaves for adaptation to CO2 concentration.