A comparison of systematic errors between the Richards and Hammel methods of measuring tissue – water relations parameters

Abstract

TYREE, M. T., M. E. MACGRECOR, A. PETROV, itnd M. I. UPENIEKS. 1978. A comparison of systematic errors between the Richards and Hammel methods of measuring tissue -water relations parameters. Can. J . Bot. 56: 2153-2161. The pressure bomb is being used to a much greater extent to measure some tissue -water relations parameters such as osmotic pressure, turgol-pressure. and cell wall elasticity. Recently, Richards has developed a faster pressure-bomb method of obtaining these and other parameters than the method used by Hammel and modified by 11s. In this paper. we compare the two methods and conclude that Richards' method should not be used when accu~xcy is deemed important. The Richards method usually overestimatesosmotic pressure by 0.2 MPa(= 2 bars)and sometimes by 0.8 MPa (= 8 bars). TYREE. M. T., M. E. MACGRECOR, A. PETROV et M. I. UPENIEKS. 1978. A comparison of systematic errors between the Richards and Hammel methods of measuring tissue -water relations parameters. Can. J. Bot. 56: 2153-2161. La bombe $ pression est utilisee de plus en plus pour rnesurer certains parametres ayant trait aux relations plante-eau, telles que la pression osmotique, la pression de turgescence et I'elasticite de la pzuoi cellulaire. Pour mesurer ces dernieres ainsi que d'autres pammetres. Richards a ricemment dkveloppe une methode de bombe i~ pression plus lapide que In methode utilisee par Hammel et modifiee par les auteurs. Dnns cet article. les auteurs comparent lesdeux methodes et concluent que celle de Richards ne doit pas itre utilisee lorsque la precision des mesures est importante. La methode de Richards surestime ktbituellement la pression osmotique de 0.2 MPa (= 2 bars) et parfois de0.8 MPa (= 8 bars).[~r a d u i t par le journal]

Some observations of the adaptations of sandy shrubs to the arid environment in the Mu Us Sandland: leaf water relations and anatomic features

“…In summer, leaf samples were obtained only near the OSES, so the standard Hammel method (Cheung et al, 1975) was used. Although the Richards method may overestimate the balance pressure as compared with the Hammel method (Tyree et al, 1978), it is especially useful for rapid measurement in field studies (Ritchie & Hinckley, 1975). The analysis of the PV curves followed a two-step curve-fitting procedure.…”

The kinetics of rehydration of detached sunflower leaves from different initial water deficits

“…Dehydration was effected in the same way that pressure-volume curves are obtained by the Hammel method (Tyree et al, 1978); at the end of each ofthe six to fifteen dehydration steps the weight of water expressed, V^, and the equilibrium balance pressure were obtained; from this a plot of PB versus V^ could be constructed.…”

Evidence of osmoregulation in Larix decidua at Alpine treeline and comparative responses to water availability of two co-occurring evergreen species

“…Samples were always taken from the S exposed canopy at a height of 1.5-2.5 m from the ground in the evening hours of the day previous to the day of the measurement, sealed in a polythene bag to reduce evaporative loss of water and taken to the laboratory. Here cut ends of the shoots were immersed in water and the shoots were left rehydrating for 12-15 hours in the darkness for the whole night [26,34].…”

“…A wet piece of blotting paper was enclosed in the pressure chamber in order to prevent evaporative loss during the measurements [31,34]. Pressure was increased slowly (0.01 MPa s -1 ) during the measurements, until a droplet of xylem sap appeared on the section of the shoot.…”