Relationships Between the Leaf Water Status of Barley and Soil Water

Abstract

Total water potential of barley (Hordeum vulgare L.) leaves from plants grown under greenhouse and growth chamber conditions was divided into pressure and osmotic potential components, and their relationship to leaf relative water content was determined. Pressure potential approached zero at a water potential of about −32 bars, and a relative water content of about 65%. A change in the elasticity of leaves occurred at about 2 bars pressure potential and about −12 bars water potential. First visible wilting was observed between 75 and 80% relative water content. Transpiration decreased as leaf relative water content decreased but transpiration was independent of soil water content until about 16% (0.6 bar soil suction). First visible wilting of barley leaves was observed at soil water content between 9 and 13% (1–5 bars soil suction). Water potential and leaf relative water content decreased as the soil matric potential decreased. There was a shift to lower relative water content and water potential values as plants became older when the soil matric potential decreased.

Effect of Aerial Environment and Soil Water Potential on the Transpiration and Energy Status of Water in Wheat Plants1

“…A constant transpiration rate of 0.05 gjcm 2 jday was reached at about 50% relative water content. A similar pattern was observed for barley (Hordeum vulgare L.) by Millar, Duysen, and Norum (12) and agrees with reported rapid increases in the stomatal resistance of snap beans (Phaseolus vulgaris L.) as the leaf water potential drops below -11 atm (9). At any leaf water status the transpiration rate was higher as the evaporative demand increased, possibly clue to decreased stomatal and cuticular resistance to water movement (8,15).…”

“…At leaf water contents between 93 and 97%, the slope of the leaf water characteristic changed drastically. Millar et al (12) found a similar change for barley leaves and calculated that at high relative water contents the turgor pressure dropped rapidly compared with the osmotic pressure. At lower relative water contents the reverse was true.…”

Water relations of winter wheat: 3. Components of leaf water potential and the soil-plant water potential gradient

“…6) shows one way in which wheat can adapt to water stress. Large decreases in ijr n with decreasing \jr ly generally by amounts sufficient to keep \jr v positive, have been found in other species growing in drying soils (Gavande & Taylor, 1967;Millar, Duysen & Norum, 1970;Sanchez-Diaz & Kramer, 1973;Jones & Turner, 1978).…”

“…Further evidence of significant rhizosphere potential gradients comes from the slow recovery of ijf l overnight (Fig. 9), a phenomenon also observed in wheat by Campbell & Campbell (1974) and in other plants by Klepper (1968), Jordan (1970), Millar et al (1970) and Jordan & Ritchie (1971). The simplest postulate is slow equilibration of the potential at the root surface with that of the bulk soil.…”

The Water Relations of Pinus sylvestris II. Comparative Field Studies of Water Potential and Relative Water Content

“…Table 5 demonstrate significantly higher liije^j and RWC in the current season's needles than in the previous season's needles. A reasonable explanation of these differences may be a combined effect of (1) a larger amount of storage material (dry matter) in the older needles, decreasing their osmotic (Millar et aL 1970) and matric potentials, and (2) a decreased cell wall elasticity resulting from the dry matter increase (Knipling 1967), leading to a greater reduction in pressure potential.…”