Use of a Hydraulic Press for Estimation of Leaf Water Potential in Grain Sorghum¹

Abstract

The hydraulic press (HP) is a highly portable instrument designed for rapid measurement of leaf water potential of plants. This study compared grain sorghum [Sorghum bicolor (L.) Moench] leaf water potentials measured with a pressure chamber (PC) and using two endpoints with a HP, under glasshouse conditions. The first endpoint is when water exudes from one vein and the second endpoint when water exudes from all veins on both sides of the leaf tissue. The results showed that the HP and PC measurements agreed well in the range of −0.5 to −3.5 MPa of leaf water potentials when the second endpoint was selected for the HP. The HP can be used to measure the leaf water potential of grain sorghum, provided it is calibrated using the second endpoint against a PC or another method.

Comparison of the measurements of leaf water potential between a hydraulic press and a pressure chamber in six Sahelian woody species

“…Slowly increasing pressure was then applied until water exuded from all the cut veins of the leaf tissue. This correspond to end point 2 in Hicks et al (1986), who obtained better agreement than when only exudation from the first vein was measured (end point 1). The leaf section was observed through the plexiglass plate and pressure was read with a 0-40 bar manometer.…”

“…Water potential measured with a PC and a HP were statistically comparable for non-cropped species in uncontrolled conditions (R 2 = 36-72%, Fig. 1), although not as high as that recorded in temperate crops (Bristow et al 1981;Hicks et al 1986) or in Fig. 1 Relationships between pressure applied with the hydraulic press (Appl.…”

“…However, in Sahelian countries, where ecologists often work at inaccessible sites with limited financial means and logistics, the cost of commercial PCs and the difficulties involved in managing the supply of compressed N gas limit their use. PCs are also cumbersome, and measuring low LWP values is time consuming as pressure can only be increased slowly (Hicks et al 1986). These arguments justify the use of an alternative instrument that is both cheaper and easier to use.…”

“…To answer this question, measurements made with a HP needed to be compared with measurements made with a PC (Bennett 1990). Some previous studies showed good correlations, but mostly in temperate crops (Jones and Carabaly 1980;Bristow et al 1981;Hicks et al 1986), while others revealed poor agreement (Sojka et al 1990). The HP has not previously been tested in a large number of species and environments, and no study has reported results on a range of Sahelian shrubs, with the exception of two studies on the dominant shrub (Guiera senegalensis J. M. Gmel, Combretaceae) in Niger, in the southern Sahel (Seghieri and Laloë 2004;Seghieri et al 2005).…”

A comparison of pressure chamber, leaf-press, and canopy temperature for four species under humid conditions

“…One is the subtlety of the Ts endpoint; HICKS a ai. (10) over-estimated T, if the first exudation of sap was taken as the Tj endpoint. A one-to-one relationship existed if Tj was taken to be the pressure at which sap exuded from all leaf veins.…”