Response of Fluorescence Parameters in Detached Leaves of Several Tree Species in HuaBei District to Drought Stress

By analyzing the water-holding capacity of detached leaves,change of fluorescence parameters with the extent of water stress and the relationship between fluorescence parameters and water parameters,the response of fluorescence parameters in detached leaves of several tree species in Huabei district to drought stress was discussed.Four main conclusions were drawn as follows :(1)coniferous trees generally had stronger water-holding capacity than broadleaf trees,their water-holding mechanism,however,were quite different;(2)the length of water-losing time essentially affected the change of fluorescence parameters,and during the course of water stress,fluorescence parameters Fv/Fm and Fm/Fo of five coniferous trees had obvious linear relationship with water-losing rate,the difference lied in that the variation curve of parameter Fv/Fm presented a protruding design and parameter Fm/Fo presented a eurve of inverted "S";(3)under different stress extent,the relationship between fluorescence parameters and water parameters showed significant difference,the higher the water stress was,the more significant the correlationship was;(4)fluorescence parameters could give a qualitative description for drought-resistant quality of tree,but as a quantitative index,they showed some extent of limitations.