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An ecophysiological and developmental perspective on variation in vessel diameter

Publication at Faculty of Science |
2017

Abstract

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 (D-v) across biomes, intra-specific variation of D-v under natural and controlled conditions, and intra-plant variation. We found that the D-v measured in young branches tends to stay below 30 mu m 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. D-v varies 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.