Comparison of leaf anatomical structure and photosynthetic characteristics between weedy rice and cultivated rice at the seedling stage.

To explore the internal factors related to the strong growth and competitive ability of weedy rice during the seedling period, we collected two biotypes of Japonica weedy rice from Northeast China, four biotypes of Indica weedy rice from Eastern China and Southern China, and two biotypes of cultivated rice, Zhendao-8 (ZD-8) and Shanyou-63 (SY-63), which were used as controls in a pot experiment. Under homogeneous garden planting conditions, we measured the vascular bundle size (VBS), vascular bundle number (VBN), leaf thickness (LT), air cavity size (ACS), stomatal size (SS), stomatal density (SD), net photosynthetic rate (Pn) and stomatal conductance (Gs) of the weedy and cultivated rice biotypes. A comprehensive analysis was performed to explore the correlation between the seedling leaf structure and the photosynthetic indices of the biotypes. The results showed the following: (1) At the seedling growth stage, the leaf structure parameters of weedy rice were significantly greater than those of ZD-8 and SY-63. (2) The Pn and Gs of weedy rice were significantly positively correlated with VBS, VBN, LT, ACS, and SD. Thus, the leaf structural features of weedy rice provide the anatomical basis for the stronger Pn and establish a strong competitive physiology at the seedling stage. Therefore, the prevention and elimination of weedy rice should start at the seedling stage.