Stomatal conductance patterns and environment in high elevation phreatophytes of Wyoming

1991 ◽  
Vol 69 (3) ◽  
pp. 647-655 ◽  
Author(s):  
Jeffrey R. Foster ◽  
William K. Smith
Keyword(s):  
Stomatal Conductance ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
High Elevation ◽  
Pressure Potential ◽  
Previous Night ◽  
Threshold Response ◽  
Populus Angustifolia ◽  
Xylem Pressure Potential ◽  
Air Vapor Pressure Deficit

High-elevation (2305 m) phreatophytes (cottonwood, Populus angustifolia James, and willows, Salix monticola Nutt. and Salix exigua Bebb) in southeastern Wyoming commonly showed a pattern of increasing stomatal conductance (g1) throughout the day, despite minimum leaf water potentials (ψ1) as low as −2.7 MPa. Diurnally, light and leaf temperature were the most important variables influencing g1, but there were also threshold values of ψ1 and leaf-to-air vapor pressure deficit for stomatal closure. Seasonally, maximum daily g1 (gmax) was similar between species, was positively related to minimum air temperature the previous night, and showed a threshold response to soil temperature. Two types of evidence existed for large soil-to-leaf conductances (gs–l) and for liquid water being available to the roots. The first was no change in ψ1 despite increasing transpiration during the afternoon. The second was rapid evening recovery of ψ1 often to values higher than mean soil water potential to 60-cm depth. The combination of low atmospheric pressures at high elevation, large gs–l, and access to a water table may explain how these phreatophytes attained gmax of 0.8–0.9 mol m−2 s−1, much higher than gmax of low-elevation phreatophytes or high-elevation nonphreatophytes. Key words: Populus, Salix, phreatophyte, stomatal conductance, xylem pressure potential.

Stomatal and photosynthetic response of sweet gum (Liquidambarstyraciflua) to flooding

1985 ◽  
Vol 15 (2) ◽  
pp. 371-375 ◽  
Author(s):  
S. R. Pezeshki ◽  
J. L. Chambers
Keyword(s):  
Stomatal Conductance ◽  
Water Status ◽  
Stomatal Closure ◽  
Net Photosynthesis ◽  
Controlled Environment ◽  
Photosynthetic Response ◽  
Short Term ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Xylem Pressure Potential

Effects of short-term flooding on stomatal conductance, net photosynthesis, and water status of sweet gum (Liquidambarstyraciflua L.) seedlings were studied under controlled environment conditions. Flooding for 9 days induced partial stomatal closure, resulting in significant declines in transpiration and net photosynthesis. The response to flooding was rapid with an average daily stomatal conductance declining from a preflood level of 0.43 cm•s−1 to 0.26 cm•s−1 by 24 h after flooding began (40% reduction). The average preflooding daily net photosynthesis was reduced from 13.7 to 10.2 mg CO2•dm−2•h−1 (25% reduction) during the same period and the average daily stomatal conductance and net photosynthesis for the 9th day of flooding were reduced by 70 and 77%, respectively, compared with preflood levels. The leaf xylem pressure potential measurements, however, indicated that water deficits did not develop as a result of flooding. Partial stomatal reopening 3 days after termination of flooding was noted with an average daily stomatal conductance approaching 63% of the preflood levels and an average daily net photosynthesis reaching 46% of its preflood levels. Maintenance of positive net photosynthesis throughout flooding, and partial stomatal and photosynthetic recovery following drainage may account for the tolerance of sweet gum seedlings to short-term flooding.

The stomatal response of red alder and black cottonwood to changing water status

1982 ◽  
Vol 12 (4) ◽  
pp. 761-771 ◽  
Author(s):  
S. R. Pezeshki ◽  
T. M. Hinckley
Keyword(s):  
Stomatal Conductance ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Soil Water Potential ◽  
Black Cottonwood ◽  
Pressure Potential ◽  
Red Alder ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Vapor Pressure Gradient

Response of stomata of newly planted red alder (Alnusrubra Bong.) and black cottonwood (Populustrichocarpa Torr. & Gray) to periods of water stress and changes in light intensity, vapor pressure gradient, and xylem pressure potential were studied in the field and in controlled environments. The results indicated that soil drought had a pronounced effect, reducing stomatal conductance in both species. Lower predawn xylem pressure potential values at the beginning of the day resulted in lower stomatal conductance irrespective of vapor pressure gradient in both species. Under field conditions of high soil water potential, stomatal conductance decreased as xylem pressure potential decreased below −1.0 MPa in black cottonwood and −1.1 MPa in red alder. As soil water potential decreased to −0.13 MPa, the threshold value of xylem pressure potential resulting in stomatal closure shifted from −1.0 to −0.5 MPa in cottonwood; it did not change in alder. Laboratory experiments indicated that cottonwood had greater rates of net photosynthesis on a per-unit leaf-area basis as compared with red alder. The mean maximum photosynthetic rates were 0.46 mg CO2•m−2•s−1 in black cottonwood and 0.25 mg CO2•m−2•s−1 in red alder. Net CO2 uptake also had a temperature optimum around 20 °C when the corresponding relative humidity was about 50%. Both species, when compared with other deciduous hardwoods, could be ranked as relatively drought sensitive.

Stomatal control and the development of water deficit in Engelmann spruce seedlings during drought

1979 ◽  
Vol 9 (3) ◽  
pp. 297-304 ◽  
Author(s):  
Merrill R. Kaufmann
Keyword(s):  
Flux Density ◽  
Stomatal Closure ◽  
Absolute Humidity ◽  
Pressure Potential ◽  
Evaporative Demand ◽  
Xylem Pressure ◽  
Full Sunlight ◽  
Engelmann Spruce ◽  
Xylem Pressure Potential ◽  
The Relationship

The effects of soil drying on water relations of Engelmann spruce (Piceaengelmannii Engelm.) were studied by withholding water from 4-year-old potted seedlings in full sunlight and under a shade screen transmitting 55–60% light. During a period of 2 months, xylem pressure potential, water vapor conductance, and transpirational flux density gradually declined compared with well watered controls, with drying being more rapid in full sunlight. As drying progressed, xylem pressure potential at 0 transpiration (predawn potential) decreased and the slope of the relationship between xylem pressure potential and transpirational flux density became more negative. Hysteresis in the relationship occurred when predawn xylem pressure potential was −6 bars (1 bar = 105 Pa) or lower. Needle conductance during daylight hours decreased as the absolute humidity difference from leaf to air increased but conductances were lower in September than in August for given humidity differences. Xylem pressure potentials between −15 and −19 bars had no clear effect on conductance in August but apparently caused significant stomatal closure in September. Because of humidity-induced stomatal closure, evaporative demand had little effect on transpirational flux density over a broad range of humidity gradient. Thus increased leaf-to-air vapor gradients for transpiration are not always accompanied by increased transpiration.

Water relations of loblolly pine trees in southeastern Oklahoma following precommercial thinning

1990 ◽  
Vol 20 (9) ◽  
pp. 1508-1513 ◽  
Author(s):  
Bert M. Cregg ◽  
Thomas C. Hennessey ◽  
Philip M. Dougherty
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Loblolly Pine ◽  
Soil Water Potential ◽  
Basal Area ◽  
Leaf Conductance ◽  
Pressure Potential ◽  
Precommercial Thinning ◽  
Xylem Pressure ◽  
Xylem Pressure Potential

Xylem pressure potential, leaf conductance, transpiration, and soil moisture were measured during three summers following precommercial thinning of a 10-year-old stand of loblolly pine (Pinustaeda L.) in southeastern Oklahoma. The stand was thinned to three target basal-area levels: 5.8, 11.5, and 23 m2•ha−1 (control). Soil water potential increased significantly in response to thinning during the summer of each year studied. However, plant water relations were relatively unaffected by the treatments. Significant thinning effects on diurnal xylem pressure potential were observed on only 7 of 55 measurement periods. Treatment differences in conductance and transpiration observed during the first year of the study appeared to be related to differences in light interception and crown exposure. Regression analysis indicated response of leaf conductance and transpiration to predawn xylem pressure potential and vapor pressure deficit was not affected by the thinning treatments. Overall, the results of this study are consistent with a hypothesis in which transpiration, leaf area, and water potential interact to form a homeostatic relationship.

A modelling framework to predict transpiration reductions during drought based on soil hydraulics 

2021 ◽  
Author(s):  
Andrea Carminati ◽  
Mathieu Javaux
Keyword(s):  
Hydraulic Conductivity ◽  
Stomatal Conductance ◽  
Water Potential ◽  
Soil Water ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Soil Drying ◽  
Soil Hydraulic Conductivity ◽  
Plant Hydraulics ◽  
Soil Hydraulic

<p>There is increasing need for mechanistic and predictive models of transpiration and stomatal response to drought. Global measurements of transpiration showed that the decrease in soil moisture is a primary constrain on transpiration. Additionally, a recent meta-analysis indicated that stomatal closure is explained by the loss in soil hydraulic conductivity, more than that of the xylem. Despite these evidences on the role of soil drying as a key driver of transpiration reduction, the mechanisms by which soil drying impacts transpiration, including the effect of different soil hydraulic properties, are not fully understood.</p><p>Here, we propose that stomata regulate transpiration in such a way that the relation between transpiration and the difference in water potential between soil and leaves remains linear during soil drying and increasing vapor pressure deficit (VPD). The onset of hydraulic nonlinearity sets the maximum stomatal conductance at a given soil water potential and VPD. The resulting trajectory of the stomatal conductance for varying soil water potentials and VPD depends on soil and plant hydraulics, with the soil hydraulic conductivity and root length being the most sensitive parameters.</p><p>From this hydraulic framework it follows that stomatal closure is not simply a function of soil moisture, soil water potential or leaf water potential. Instead, it depends on transpiration demand and soil-plant hydraulics in a predictable way. The proposed concept allows to predict transpiration reductions during drought with a limited number of parameters: transpiration demand, plant hydraulic conductivity, soil hydraulic conductivity and active root length. In conclusion, this framework highlights the role of the soil hydraulic conductivity as primary constrain on transpiration, and thus on stomatal conductance and photosynthesis.</p>

Changes in xylem pressure potential of red spruce seedlings treated with ozone and simulated acid rain

1989 ◽  
Vol 19 (9) ◽  
pp. 1200-1203 ◽  
Author(s):  
Bruce R. Roberts ◽  
William N. Cannon Jr.
Keyword(s):  
Acid Rain ◽  
Stomatal Closure ◽  
Turgor Pressure ◽  
Red Spruce ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Acid Rainfall ◽  
Area Expansion ◽  
Air Control

Two-year-old containerized seedlings of red spruce (Picearubens Sarg.) were exposed for 8 weeks to charcoal-filtered air (control) or to 7 and 15 parts per hundred million (pphm) ozone (O3) alone and 15 pphm O3 in combination with simulated acid rainfall at pH 4.2 and 3.0 prior to measuring shoot xylem pressure potential. Pressure potential determinations for seedlings treated with O3 alone or O3 + acid rain were always higher (less negative) than similar determinations made on comparable seedlings grown in charcoal-filtered air. These results suggest that exposure to atmospheric deposition may affect xylem pressure potential indirectly by influencing transpirational water loss via stomatal closure and (or) reductions in leaf area expansion. Calculations of osmotic potential and turgor pressure suggest the possibility of some osmotic adjustment in response to deposition stress in this species.

Early signals in field grown wheat in response to shallow soil drying

1998 ◽  
Vol 25 (8) ◽  
pp. 871 ◽  
Author(s):  
M. Ali ◽  
C.R. Jensen ◽  
V.O. Mogensen
Keyword(s):  
Stomatal Conductance ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Leaf Water ◽  
Soil Types ◽  
Extension Rate ◽  
Soil Drying ◽  
Stem Extension ◽  
Aba Content ◽  
Leaf Extension

The aim of the present work was to test under field condition earlier climate room findings that root-borne signals may control stomatal closure and leaf extension rate during mild soil drying. Stomatal conductance (g H2O) of flag leaves, leaf and stem extension rates, leaf water relations, leaf ABA content and predawn xylem [ABA] were measured daily in wheat grown in two soil types (sand and loam) in lysimeters in the field during a period of soil drying with high and low evaporative demands. At 3 days after withholding irrigation (DAI) on both soil types, when soil water potential (Ψsoil) in the upper soil profile of the droughted treatment had dropped to –70 kPa and with the lower layers still at field capacity, predawn xylem [ABA] increased. At 4 DAI the leaf extension rate decreased and midday leaf ABA content increased. Stem extension rates decreased at 5 DAI in loam and 7 DAI in sand. g H2O started to decrease 6 DAI in loam and 9 DAI in sand. These responses were observed before any detectable decrease in the midday leaf water status of the droughted plants had occurred relative to well- watered plants. The responses were closely related to Ψsoil and independent of evaporative demand. We conclude that, in wheat, root-borne signals probably control stomatal conductance and leaf extension rate during mild soil drying in the field.

Relation between root system size and water inflow capacity of Abiesamabilis growing in a subalpine forest

1985 ◽  
Vol 15 (4) ◽  
pp. 669-672 ◽  
Author(s):  
Robert O. Teskey ◽  
Charles C. Grier ◽  
Thomas M. Hinckley
Keyword(s):  
Root System ◽  
Stomatal Closure ◽  
System Size ◽  
Water Inflow ◽  
Subalpine Forest ◽  
Silver Fir ◽  
Small Contribution ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Xylem Pressure Potential

The water inflow capacity of the root systems of several 15- to 18-year-old Pacific silver fir (Abiesamabilis (Dougl.) Forbes) trees was investigated under field conditions. Severance of as much as one-third of the roots had no effect on xylem pressure potential, leaf conductance, or transpiration throughout the day following this treatment. Severance of more than half of the root system caused a decline in xylem pressure potential and partial stomatal closure. Measurements from trees which had been completely severed from their roots indicated that stored water made only a small contribution to the supply of water to the foliage of these trees. It was concluded that a balance did not exist between the capacity for water inflow and the rate of foliar water loss, at least in periods without drought. One advantage of excess absorptive capacity may be the ability to obtain adequate amounts of water from relatively small portions of the rooting zone.

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