© 2005 Heron Publishing—Victoria, Canada
Leaf hydraulic conductance in relation to anatomical and functional traits during Populus tremula leaf ontogeny
Krõõt Aasamaa (1, 2), Ülo Niinemets (3) and Anu Sõber (4)
1. Estonian Agricultural University, Department of Silviculture, Kreutzwaldi 5, Tartu, 51014, Estonia / 2. Corresponding author (kroot@eau.ee) / 3. Department of Plant Physiology, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu, 51010, Estonia / 4. Institute of Botany and Ecology, University of Tartu, Lai 40, Tartu, 51005, Estonia / Received September 10, 2004; accepted April 9, 2005; published online August 16, 2005
Summary
Leaf hydraulic conductance (Kleaf) and several characteristics of hydraulic architecture and physiology were measured during the first 10 weeks of leaf ontogeny
in Populus tremula L. saplings growing under control, mild water deficit or elevated temperature conditions. During the initial 3 weeks of leaf
ontogeny, most measured characteristics rapidly increased. Thereafter, a gradual decrease in Kleaf was correlated with a decrease in leaf osmotic potential under all conditions, and with increases in leaf dry mass per area
and bulk modulus of elasticity under mild water deficit and control conditions. From about Week 3 onward, Kleaf was 33% lower in trees subjected to mild water deficit and 33% higher in trees held at an elevated temperature relative
to control trees. Mild water deficit and elevated temperature treatment had significant and opposite effects on most of the
other characteristics measured. The ontogenetic maximum in Kleaf was correlated positively with the width of xylem conduits in the midrib, but negatively with the overall width of the midrib
xylem, number of lateral ribs, leaf dry mass per area and bulk modulus of elasticity. The ontogenetic maximum in Kleaf was also correlated positively with the proportion of intercellular spaces and leaf osmotic potential, but negatively with
leaf thickness, volume of mesophyll cells and epidermis and number of cells per total mesophyll cell volume, the closest
relationships being between leaf osmotic potential and number of cells per total mesophyll cell volume. It was concluded that
differences in protoplast traits are more important than differences in xylem or parenchymal cell wall traits in determining
the variability in Kleaf among leaves growing under different environmental conditions.
Keywords:
intraspecies variability, leaf hydraulic architecture, leaf trait correlations, leaf water relations, poplar.
