An ecophysiological and developmental perspective on variation in vessel diameter.
Variation in xylem vessel diameter is one of the most important parameters when evaluating plant water relations. This review provides a synthesis of the ecophysiological implications of variation in lumen diameter together with a summary of our current understanding of vessel development and its endogenous regulation. We analyzed inter-specific variation of the mean hydraulic vessel diameter (Dv) across biomes, intra-specific variation of Dvunder natural and controlled conditions, and intra-plant variation. We found that the Dvmeasured in young branches tends to stay below 30 µm in regions experiencing winter frost, whereas it is highly variable in the tropical rainforest. Within a plant, the widest vessels are often found in the trunk and in large roots; smaller diameters have been reported for leaves and small lateral roots. Dvvaries in response to environmental factors and is not only a function of plant size. Despite the wealth of data on vessel diameter variation, the regulation of diameter is poorly understood. Polar auxin transport through the vascular cambium is a key regulator linking foliar and xylem development. Limited evidence suggests that auxin transport is also a determinant of vessel diameter. The role of auxin in cell expansion and in establishing longitudinal continuity during secondary growth deserve further study.
University of Alberta, Department of Renewable Resources, Edmonton, AB T6G 2E3, Canada.
Uwe G
UG
Hacke
Connecticut College, Department of Botany, New London, CT 06320, USA.
Rachel
R
Spicer
University of Alberta, Department of Renewable Resources, Edmonton, AB T6G 2E3, Canada.
Stefan G
SG
Schreiber
University of Hradec Králové, Department of Biology, Rokitanského 62, Hradec Králové, 500 03, Czech Republic.|Charles University, Department of Experimental Plant Biology, Viničná 5, Prague, 128 44, Czech Republic.
Lenka
L
Plavcová
D007210:Indoleacetic Acids / Q000378:metabolism; D019684:Magnoliopsida / Q000033:anatomy & histology / Q000502:physiology; D063245:Plant Development; D013045:Species Specificity; D052584:Xylem / Q000033:anatomy & histology* / Q000502:physiology*
D007210:Indoleacetic Acids
auxin; biomes; freezing-induced embolism; phenotypic plasticity; provenance trials; vascular cambium; vessel development; vessel tapering; xylem