Research on the Limitation of Stomatal and Non-stomatal to Ban Photosynthesis under the Na_2CO_3

[Objective] The effect of the salt stress on the seedling growth and the photosynthetic parameters of broad bean and other indicators and its mechanism was studied.[Method] The photosynthetic index the broad bean seedling was measured under the treatment of 0,5,10,15 and 25 mmol/L of Na2CO3,respectively,after 6 days when it was in the final concentration.[Results] Under the treatment of 5 mmol/L Na2CO3,the net photosynthetic rate reached the maximum,which was 176.83% of the control,with significant difference;however in 15 mmol/L Na2CO3 the net photosynthetic rate was inhibited,at this time,the content of Gs and Ci was decreased and Ls,increased;in 25 mmol/L Na2CO3,the net photosynthetic rate was inhibited,which was 26.68% of the control,with the significant difference.[Conclusion] The net photosynthetic rate of broad bean was consistent with its growth status.The plant photosynthesis and others of broad bean affected the salinity stresses were mainly attributed to stomatal and non-stomatal factors.