Comparative study on chloroplast pigment concentration and morphology between two ecotypes of Leymus chinensis in Inner Mongolia

Leymus chinensis is a high-quality forage widely distributed in grasslands of Inner Mongolia. It can be classified as either the gray-green type or the yellow-green type according to its leaf color. Previous studies have shown that the gray-green grass has a higher photosynthetic capability and stronger environmental adaptability than the yellow-green type under stressful conditions. However, the mechanism underlying this difference is still unclear. Gray-green and yellow-green grass of the Huhetala grassland in Inner Mongolia were sampled in this study. The concentrations of chlorophyll and carotenoids in the leaves of the two L. chinensis ecotypes were quantitatively determined by a spectrophotometer. The number, size, and morphology of chloroplasts were characterized by transmission electron microscopy. The photosynthetic protein complexes of the gray-green and yellow-green grass were separated via blue native gel electrophoresis (BN-PAGE). The results indicated that the gray-green type had higher concentrations of chlorophyll and carotenoids in its leaves compared with the yellow-green type. Even though there were more chloroplasts per cell in the yellow-green leaves, chloroplasts were larger with a higher number of grana thylakoid in the gray-green leaves. In addition, two kinds of chloroplasts with different morphologies were allocated into different cells in the yellow-green leaves. A higher level of photosystem Ⅱ (PSⅡ) dimers and photosystem Ⅰ (PSⅠ) complexes were detected in the gray-green type through BN-PAGE. It can, therefore, be inferred that the higher concentrations of chlorophyll, carotenoids, and PSⅠ and PSⅡ protein complexes are an important basis for more efficient photosynthesis and stronger environmental adaptability of the gray-green grass ecotype.