Journal Article

How are leaves plumbed inside a branch? Differences in leaf-to-leaf hydraulic sectoriality among six temperate tree species

Smith, Sigrid D.P., Sack, Lawren, Orians, Colin M.

2005

Overview

The transport of water, sugar, and nutrients in trees is restricted to specific vascular pathways, and thus organs may be relatively isolated from one another (i.e. sectored). Strongly sectored leaf-to-leaf pathways have been shown for the transport of sugar and signal molecules within a shoot, but not previously for water transport. The hydraulic sectoriality of leaf-to-leaf pathways was determined for current year shoots of six temperate deciduous tree species (three ring-porous: Castanea dentata, Fraxinus americana, and Quercus rubra, and three diffuse-porous: Acer saccharum, Betula papyrifera, and Liriodendron tulipifera). Hydraulic sectoriality was determined using dye staining and a hydraulic method. In the dye method, leaf blades were removed and dye was forced into the most proximal petiole. For each petiole the vascular traces that were shared with the proximal petiole were counted. For other shoots, measurements were made of the leaf-area-specific hydraulic conductivity for the leaf-to-leaf pathways (kLL). In five out of the six species, patterns of sectoriality reflected phyllotaxy; both the sharing of vascular bundles between leaves and kLL were higher for orthostichous than non-orthostichous leaf pairs. For each species, leaf-to-leaf sectoriality was determined as the proportional differences between non-orthostichous versus orthostichous leaf pairs in their staining of shared vascular bundles and in their kLL; for the six species these two indices of sectoriality were strongly correlated (R2=0.94; P <0.002). Species varied 8-fold in their kLL-based sectoriality, and ring-porous species were more sectored than diffuse-porous species. Differential leaf-to-leaf sectoriality has implications for species-specific co-ordination of leaf gas exchange and water relations within a branch, especially during fluctuations in irradiance and water and nutrient availability.

• Publisher: Oxford University Press,Oxford Publishing Limited (England)
• Subject: Agronomy. Soil science and plant productions / anatomy & histology / Biological and medical sciences / Biological Transport / Birch trees / Branches / Connectivity / Deciduous trees / Diffuse-porous / Dyes / Economic plant physiology / forest trees / Fundamental and applied biological sciences. Psychology / Gas exchange / hydraulic conductance / Hydraulics / leaf area / leaf conductance / Leaves / Magnoliopsida / metabolism / Nutrient availability / Ordination / orthostichy / Petioles / phyllotaxy / physiology / Plant Leaves / Plant Leaves - anatomy & histology / Plant Leaves - metabolism / Plant Leaves - physiology / Plant species / plant vascular system / plant-water relations / Plants / Research Papers / ring-porous / sap flow / sectoriality / Shoots / Sugar / sugars / temperate deciduous trees / translocation (plant physiology) / Trees / Trees - anatomy & histology / Trees - metabolism / Trees - physiology / vascular architecture / Vascular bundles / Water / Water - metabolism / Water relations / Water relations, transpiration, stomata / Water transport / Xylem