The hydraulic conductance of the angiosperm leaf lamina: a comparison of three measurement methods

• Published in: Journal of experimental botany 2002-11, Vol.53 (378), p.2177-2184
• Main Authors: Sack, Lawren, Melcher, Peter J., Zwieniecki, Maciej A., Holbrook, N. Michele
• Format: Article
• Language: English
• Subjects: Acer - physiology; Agronomy. Soil science and plant productions; Biological and medical sciences; Chemistry, Physical - methods; Economic plant physiology; Equipment Design; evaporative flux method; Flow velocity; Fundamental and applied biological sciences. Psychology; Hedera - physiology; high‐pressure method; hydraulic conductance; Hydraulics; Irradiance; Key words: Angiosperms; Leaves; Light; Magnoliopsida - physiology; Petioles; Photosynthesis - physiology; Plant Leaves - physiology; Plant physiology and development; Plant Transpiration - physiology; Plants; Quercus - physiology; Regulation of Growth, Development and Whole Organism Physiology; Stomata; Transpiration; vacuum pump method; Vacuum pumps; Vitis - physiology; Water - physiology; Water and solutes. Absorption, translocation and permeability; Water pressure; Water relations, transpiration, stomata
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erf069

A comparison was made of three methods for measuring the leaf lamina hydraulic conductance (Klamina) for detached mature leaves of six woody temperate angiosperm species. The high‐pressure method, the evaporative flux method and the vacuum pump method involve, respectively, pushing, evaporating and pulling water out of the lamina while determining the flow rate into the petiole and the water potential drop across the leaf. Tests were made of whether the high‐pressure method and vacuum pump method measurements of Klamina on single leaves were affected by irradiance. In Quercus rubra, the high pressure method was sensitive to irradiance; Klamina measured under high irradiance (>1200 µmol m–2 s–1 photosynthetically active radiation) was 4.6–8.8 times larger than under ambient laboratory lighting (∼6 µmol m–2 s–1 photosynthetically active radiation). By constrast, the vacuum pump method was theoretically expected to be insensitive to irradiance, and this expectation was confirmed in experiments on Hedera helix. When used in the ways recommended here, the three methods produced measurements that agreed typically within 10%. There were significant differences in species’ Klamina; values ranged from 1.24×10–4 kg s–1 m–2 MPa–1 for Acer saccharum to 2.89×10–4 kg s–1 m–2 MPa–1 for Vitis labrusca. Accurate, rapid determination of Klamina will allow testing of the links between Klamina, water‐use, drought tolerance, and the enormous diversity of leaf form, structure and composition.