Abstract: There is an acute shortage of CO₂ for winter and spring production of tomato in solar greenhouse. Here, we explored the effects of CO₂ enrichment on the photosynthetic pigment content, net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r),intercellular CO₂ concentration (C_i) and water use efficiency (WUE) of tomato cultivar ‘Xinghai 12’, to identify the suitable CO₂ concentration for tomato growth during fruiting stage and finally to provide theoretical basis for tomato production in solar greenhouse of north China. Four treatments with different CO₂ concentrations were applied in this study: (400±25) μmol·mol^-1 as control (without CO₂ enrichment, C₀), (600±25) μmol·mol^-1 (C₁), (800±25) μmol·mol^-1 (C₂), and (1000±25) μmol·mol^-1 (C₃). The results showed that CO₂ enrichment notably increased the photosynthetic pigment contents of tomato during fruiting stage. P_n, C_i and WUE were significantly improved, while G_s and T_r were significantly decreased. In addition, the C₃ treatment showed the strongest effects. It was therefore concluded that CO₂ enrichment of (1000±25) μmol·mol^-1 could effectively improve the photosynthetic system of leaves and increase the photosynthesis of greenhouse tomato plants during fruiting stage, and thus would facilitate the growth and development of tomato.

Key words: organic carbon, carbon and nitrogen coupling., forest soil, secondary succession, total nitrogen