Let $K_m-H$ be the graph obtained from $K_m$ by removing the edges set $E(H)$ of $H$ where $H$ is a subgraph of $K_m$. In this paper, we characterize the potentially $K_5-P_4$ and $K_5-Y_4$-graphic sequences where $Y_4$ is a tree on 5 vertices and 3 leaves.
Photosynthetic pathway type, based on 5*^C measurements, was determined for 48 species in 39 genera and 15 families of flowering plants from the grassiand region of Northeast China. Of this total, 10 species in 10 genera from 4 families were found to háve C4 photosynthesis; 38 species in 29 genera from 13 families had C3 photosynthesis. One C4 species in the Chenopodiaceae and three in the Gramineae had not been previously docnmented in the literatuře. The C4 species were most frequent in disturbed habitats, meadow steppe and šalině grassiand; C3 species dominated the other habitats sampled.