Transpiration characteristics of three poplar tree clones
The characteristics of transpiration of 3 poplar clones which are NL 895,I-69 and WL1 were measured by LI-6400 portable photosynthesis system in May,July,August and October.The result indicated that the daily variation and annual variation of daily average transpiration rates of the 3 tested poplar tree clones were approximately the same,displaying single peak in May and October,and double-peak in July and August.The maximum and minimum values of their transpiration rates appeared in July and May.The monthly order of the daily average transpiration rates in each month were as follows: I-69(1.87,7.61,2.52 and 3.34 mmol·m-2·s-1 NL895(1.71,5.57,1.79 and 2.71 mmol·m-2·s-1 WL1(1.13,3.55,1.4 and 1.96 mmol·m-2·s-1.Correlation coefficient and direct path coefficient showed that all clones' transpiration rates had different degree correlation with environmental factors.The factors which affect transpiration rates are of the following order: Ta(air temperature)RH(relative humidity)Gs(stomatal conductance)PAR(photosynthetic active radiation),in exception to NL895 and I-69 varieties in October,which is in the order of GsTaRHPAR.The daily total transpiration quantities for single plant of three clone standard woods were listed as: NL 895,42 020.84g;I-69,61 866.03 g;WL1,23 346.43 g.