Gas exchange characteristics and water relations of Larixoccidentalis

1987 ◽  
Vol 17 (11) ◽  
pp. 1364-1370 ◽  
Author(s):  
Stewart S. Higgins ◽  
R. Alan Black ◽  
Gary K. Radamaker ◽  
William R. Bidlake
Keyword(s):  
Stomatal Conductance ◽  
Moisture Stress ◽  
Sympatric Species ◽  
Growth Patterns ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Gas Exchange Characteristics ◽  
Plant Moisture ◽  
Maximum Conductance

Photosynthetic, transpirational, and stomatal responses to light, temperature, humidity, and plant moisture stress were measured for greenhouse-grown seedlings of Larixoccidentalis Nutt. Light saturation was 550 μmol photons•m−2•s−1; light and CO2 compensation points were 26 μmol photons•m−2•s−1 and 59 μL CO2•L−1, respectively. Light-saturated photosynthetic rate was over 7 μmol CO2•m−2•s−1 with a temperature optimum between 18 and 23 °C. Photosynthesis, transpiration, and stomatal conductance to water vapor declined as xylem pressure potential decreased from −1.5 to less than −2.5 MPa; above −1.5 MPa no effect was observed. Stomatal conductance declined with increasing leaf to air vapor density difference. Stomatal conductance increased with increasing irradiance. Nighttime stomatal conductance was about 50% of the daytime maximum conductance regardless of xylem pressure potential. When plants were well watered, the ratio of xylem pressure potential to transpiration (XPP/E) decreased by 1.5 × 10−3 MPa•(μg H2O•cm−2•s−1)−1 with each mg H2O•cm−2 that had been transpired. After 7 days of drought, however, XPP/E decreased at 7.9 × 10−3 MPa•(μg H2O•cm−2•s−1)−1 per mg H2O•cm−2. These characteristics are compared with other conifers and are used to suggest differences between growth patterns of L. occidentalis and sympatric species.

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.

Xylem pressure potential in black spruce in interior Alaska

1977 ◽  
Vol 7 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Jerry O. Wolff ◽  
Stephen D. West ◽  
Leslie A. Viereck
Keyword(s):  
Black Spruce ◽  
Moisture Stress ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Rooting Zone ◽  
Interior Alaska ◽  
Xylem Pressure Potential ◽  
Stress Curve ◽  
Minimum Stress ◽  
The Times

Xylem pressure potential was measured in black spruce in interior Alaska to determine the patterns of water stress under conditions of permafrost and long photoperiods. The general shape of the daily stress curve was similar to that reported for other species at lower latitudes. The primary effect of long photoperiods was to shift the times of stress maximums and decreases. Trees on sites with maximum annual thaw depths of 26 and 100 cm equilibrated daily with maximum predawn stress values of about −5 bars (1 bar = 100 kPa). Minimum stress during the day was generally −10 to −16 bars and did not exceed −18 bars for the entire growing season. An abundant water supply in the rooting zone derived from ice in the thawing soil was probably the contributing factor which prevented large seasonal changes in the daily pattern of moisture stress.

Critical Period of Weed Interference in Transplanted Tomatoes (Lycopersicon esculentum): Growth Analysis

Weed Science ◽  
1983 ◽  
Vol 31 (4) ◽  
pp. 476-481 ◽  
Author(s):  
Susan E. Weaver ◽  
Chin S. Tan
Keyword(s):  
Lycopersicon Esculentum ◽  
Critical Period ◽  
Growth Analysis ◽  
Canopy Temperature ◽  
Dry Weight ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Fruit Number ◽  
Weed Interference ◽  
Xylem Pressure Potential

The critical period of weed interference in transplanted tomatoes (Lycopersicon esculentumMill. 'Springset’) was from 28 to 35 days after transplanting. A single weeding during this period was sufficient to prevent yield reductions. A growth analysis revealed that significant differences in plant dry weight and fruit number between tomatoes from weed-free and weed-infested plots were not apparent until 56 to 70 days after transplanting. The shorter the initial weed-free period, or the longer weeds were allowed to remain in the plots before removal, the earlier reductions in tomato dry weight and fruit number appeared. Weed interference was due primarily to shading rather than water stress. Tomatoes from weed-infested plots had significantly lower stomatal conductances than those from weed-free plots, but did not differ in xylem-pressure potential or in canopy temperature. If tomatoes were kept weed-free for more than 28 days, or when weeds were present for less than 28 days after transplanting, stomatal conductances were not significantly reduced.

Comparative Studies in Selected Species of Eucalyptus Used in Rehabilitation of the Northern Jarrah Forest, Western Australia. I. Patterns of Xylem Pressure Potential and Diffusive Resistance of Leaves

1984 ◽  
Vol 32 (4) ◽  
pp. 367 ◽  
Author(s):  
IJ Colquhoun ◽  
RW Ridge ◽  
DT Bell ◽  
WA Loneragan ◽  
J Kuo
Keyword(s):  
Western Australia ◽  
Water Loss ◽  
Seasonal Patterns ◽  
Pressure Potential ◽  
Jarrah Forest ◽  
Eucalyptus Marginata ◽  
Xylem Pressure ◽  
Diffusive Resistance ◽  
Xylem Pressure Potential ◽  
The Impact

Land use which reduces tree canopy density and the impact of Phytophthora cinnamomi are believed to be altering the hydrological balance of parts of the northern jarrah forest, Western Australia. In the drier eastern zones of the forest, replacement plant communities must maintain the soil-salt-water balance to prevent significant increases in salinization of streams in water supply catchments. Daily and seasonal patterns of the diffusive resistance of leaves and xylem pressure potential were determined for the major natural dominant of the region, Eucalyptus marginata, and five other species of Eucalyptus used in rehabilitation. Three types of daily and seasonal patterns were observed. E. marginata and E. calophylla exhibited little stomatal control of water loss, and leaf resistances remained low throughout the study period (type 1). E. maculata, E. resinifera and E. saligna exhibited marked stomatal regulation during summer days when xylem pressure potentials fell below -2.O MPa (type 2). E. wandoo (type 3) also controlled water loss but developed xylem pressure potentials far lower than all other species tested (<-3.0 MPa). Although none of the species tested replicated the summer stomatal resistance and xylem pressure potential patterns of E. marginata, it is suggested that total annual water use should be examined before selecting the most appropriate species to rehabilitate disturbed sites in the eastern zones of the northern jarrah forest region.

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.

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