Abstract: Catharanthus roseus seedlings were treated with 1/2 Hoagland solutions containing different concentrations (0, 50, 100, 150, 200, and 250 mmol·L^-1)of NaCl. After 5day treatment, the seedlings biomass, relative contents of inorganic ions in cells of different tissues, leaf chlorophyll content, and photosynthetic parameters were estimated. The results showed that NaCl stress decreased the seedlings fresh mass and dry mass significantly. Under NaCl stress, the relative contents of Na⁺ and Cl^- in cells increased significantly, but the increment somewhat differed with different tissues. In root and stem, epidermal cells had the greatest increment, followed by cortex cells, and stelar cells; while in leaf, epidermal cells had the greatest increment, followed by cortex cells, spongy tissue cells, and palisade tissue cells. The relative contents of cell K⁺ and Ca²⁺ were decreased under NaCl stress, and the decrement was also differed with different tissues. In root and stem, epidermal cells had the greatest decrement, followed by cortex and stelar cells; while in leaf, palisade tissue cells had the greatest decrement. In a word, NaCl could inhibit the growth of C. roseus seedlings, and disrupt their ion balance. To avoid the damage caused by NaCl stress, the seedlings would congregate excessive Na⁺ and Cl^- in their epidermal cells. Under NaCl stress, the chlorophyll content, photosynthetic rate (P_n), intercellular CO₂ concentration (C_i), stomatal conductance (G_s) and transpiration rate (T_r) decreased while stomatal limiting value (L_s) was in adverse, indicating that stomatal limiting was the main factor reducing the photosynthetic rate of C. roseus seedlings.

Key words: Root biomass, Pinus yunnanensis forest, Stand age, Soil depth