Leaf water content

daily change of transpiration rate

leaf water potential

and the correlation of transpiration rate and environmental factors for Viburnum rhytidophyllum Hemsl

Spiraea trilobata

Ostryopsis davidiana

and Syringa oblata were studied by using precision Electronic Balance with the accuracy of 0.001 g and dew point microvokmeter. Results showed that the leaf water content in the morning and evening was higher than that at noon and its minimum lowest point was observed between 10:00 and 14:00. By the daily variation amplitude (sunny—cloudy)

the species were in the following descending order:Viburnum rhytidophyllum Hemsl (125.2%～114.2%)Syringa oblata (110.3%～59.8%)Spiraea trilobata (86.8%～46.9%)

Ostryopsis davidiana (85.4%～35.2%). The relationship between fresh weight and leaf area can be fitted by exponential curve. By the daily maximum transpiration rate (sunny—cloudy)

the species were in the following order:Viburnum rhytidophyllum Hemsl 〔4.017～3.226 mmol/(m2·s)〕Syringa oblata 〔5.628～2.918 mmol/(m2·s)〕Spiraea trilobata 〔3.742～2.908 mmol/(m2·s)〕Ostryopsis davidiana 〔3.174～2.035 mmol/(m2·s)〕. By the average transpiration rate (sunny—cloudy)

the species were in the following order:Viburnum rhytidophyllum Hemsl 〔2.687～2.252 mmol/(m2·s〕Syringa oblata 〔2.652～2.058 mmol/(m2·s)〕Spiraea trilobata 〔2.215～1.649 mmol/(m2·s)〕Ostryopsis davidiana 〔1.864～1.423 mmol/(m2·s)〕. The diurnal variation of leaf water potential presented a waveform curve. Leaf water potential and transpiration were negatively related and the relationship between them can be fitted by logarithmic curve. The dominant factors affecting transpiration rate were different in different whether conditions.