Relations between efficiency of water transport and duration of leaf growth in some deciduous and evergreen trees

Abstract.

Shoot and leaf growth rate as well as shoot hydraulic conductance per unit leaf area (K _SL) were measured on three evergreen (Viburnum tinus L., Prunus laurocerasus L., Laurus nobilis L.) and three deciduous (Corylus avellana L., Juglans regia L., Castanea sativa L.) trees growing under the same environmental conditions. The times required to complete shoot growth (27 days for P. laurocerasus to 51 days for V. tinus) and leaf expansion (24 days for C. sativa to 42 days for C. avellana) were very different among the studied species. These species also differed in K _SL that ranged between 1.5 and 3.5 e-4 kg s^–1 m^–2 MPa^–1 in C. avellana and C. sativa, respectively, with intermediate values recorded in the other species. A strong, negative and statistically significant correlation was found to exist between K _SL and the time required for complete leaf expansion. This suggests that duration of leaf growth is shortened by the high hydraulic efficiency of the shoot. In contrast, no statistically significant relationship was found to exist between K _SL and shoot growth rate. Whether a high leaf growth rate can be interpreted as advantageous to plants or it is only an epiphenomenon of the high efficiency in the vertical water transport is discussed.