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.

Soil temperature and drying cycle effects on water relations of Pinus radiata

1977 ◽  
Vol 55 (18) ◽  
pp. 2413-2418 ◽  
Author(s):  
Merrill R. Kaufmann
Keyword(s):  
Water Absorption ◽  
Flux Density ◽  
Pinus Radiata ◽  
Stomatal Closure ◽  
Atmospheric Conditions ◽  
Root Temperature ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
The Relationship

The influence of edaphic and atmospheric conditions on the development of plant water stress, water absorption by roots, and transpiration was studied with 2-year-old seedlings of Monterey pine (Pinus radiata D. Don). The slope of the relationship of xylem pressure potential to transpirational flux density was influenced by root temperature. Increased root resistances (separated from viscosity changes of water) occurred at root temperatures of 12 to 13 °C and became more limiting for water absorption at lower temperatures. Transpirational flux density was not affected by root temperature because xylem pressure potentials were not sufficiently low to close stomata. However, at the end of 9- and 12-day drying cycles, transpiration was lower than in well watered controls as a result of stomatal closure. The relationship between xylem pressure potential and transpiration exhibited hysteresis after 9 days of drying, but hysteresis was minimal upon rewatering or in unstressed control plants.

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.

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.

A Cold Temperature Error in the Pressure Chamber Technique

1974 ◽  
Vol 4 (3) ◽  
pp. 413-416
Author(s):  
A. Kent Evans ◽  
C. P. P. Reid
Keyword(s):  
Pressure Chamber ◽  
Cold Temperature ◽  
Temperature Error ◽  
Pressure Potential ◽  
Xylem Pressure ◽  
Engelmann Spruce ◽  
Severe Water Stress ◽  
Xylem Pressure Potential ◽  
Temperature Heat ◽  
Soil Temperatures

Pressure chamber data for Engelmann spruce indicate that a cold temperature error causes artificially low (more negative) xylem pressure potential (Ψxp) values below −0.5 °C xylem temperature. Heat of compression in the chamber causes partial thawing of the frozen sample allowing some water to be forced from the twig at a reasonable, although artificially low, Ψxp value. It is important that the investigator know sample temperature in order not to misinterpret these low Ψxp values as indicative of severe water stress due to decreased absorption of water by root systems at low soil temperatures.

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.

A simulation of water relations of white oak based on soil moisture and atmospheric evaporative demand

1977 ◽  
Vol 7 (2) ◽  
pp. 400-409 ◽  
Author(s):  
D. R. Thompson ◽  
T. M. Hinckley
Keyword(s):  
Soil Moisture ◽  
Surface Resistance ◽  
Vapor Pressure Deficit ◽  
Leaf Surface ◽  
White Oak ◽  
Pressure Potential ◽  
Evaporative Demand ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Predicted Values

A model was described which simulated xylem pressure potential and leaf surface resistance for a white oak (Quercusalba L.) tree and several saplings in central Missouri. The simulation was accomplished using a deterministic approach and was applicable from after leaf maturation in the spring to leaf senescence in the fall. Soil moisture content, vapor pressure deficit, and solar radiation were the required driving variables. The Ohm's law analogy describing water potentials and fluxes in the soil–plant–atmospheric continuum served as the basis for the model. The model was tested with data not used in the original parameter estimation, and very close agreement between observed and predicted values was found. The patterns of xylem pressure potential and leaf surface resistance obtained from simulation runs imply that white oak has a significant amount of stress tolerance and an ability to avoid severe dehydration.

Xylem Embolism in the Palm Rhapis Excelsa

IAWA Journal ◽  
1985 ◽  
Vol 6 (4) ◽  
pp. 283-292 ◽  
Author(s):  
John S. Sperry
Keyword(s):  
Flow Resistance ◽  
Stomatal Closure ◽  
Gas Embolism ◽  
Hydraulic Architecture ◽  
Pressure Potential ◽  
Xylem Embolism ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Prolonged Drought ◽  
Xylem Flow

Xylem failure via gas embolism (cavitation) was investigated in Rhapis excelsa (Palmae). Embolism was detected using measurements of xylem flow resistance in excised stems and petioles: a decrease in resistance after the removal of flow-impeding embolisms by a pressure treatment indicated their previous presence in the axis. Results suggested that Rhapis avoids serious damage from embolism in at least four ways. 1) Xylem pressure potentials reached embolism-inducing levels (c. -2.90 MPa) only during prolonged drought. 2) When embolism did occur, it was confined to leaf xylem; stem xylem, most critical to shoot survival, remained fully functional. This is due in part to hydraulic architecture: 70 to 85% of shoot xylem resistance is in the leaf, and thus xylem pressures are much lower in leaves than stems. 3) Even during prolonged drought, the amount of embolism is probably limited by complete stomatal closure, which occurred at xylem pressure potentials of -3.20 ± 0.18 MPa. 4) Embolism is potentially reversible during prolonged rains, since embolism dissolved within 5 h at zero pressure (atmospheric), and xylem pressure potential can reach zero during extended rain.

Water relations of white spruce (Piceaglauca (Moench) Voss) at tree line in north central Alaska

1985 ◽  
Vol 15 (6) ◽  
pp. 1080-1087 ◽  
Author(s):  
Guillermo H. Goldstein ◽  
Linda B. Brubaker ◽  
Thomas M. Hinckley
Keyword(s):  
Water Flow ◽  
Near Field ◽  
White Spruce ◽  
Boundary Line ◽  
Tree Line ◽  
Pressure Potential ◽  
Evaporative Demand ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Northern Alaska

Factors affecting xylem pressure potential and stomatal behavior during the growing season were studied on white spruce (Piceaglauca (Moench) Voss) at tree line in the central Brooks Range of northern Alaska. Leaf conductance and xylem pressure potentials were low during days of moderate and high evaporative demand, even though soil moisture was near field capacity. Boundary line diagrams, regression analysis, and laboratory experiments indicate that stomata are sensitive to changes in vapor pressure deficit and xylem pressure potential. A correlation between resistance to water flow through the tree and soil temperature suggests that soil temperatures less than 9 °C are associated with increased resistance to water flow and may partially explain the position of white spruce tree line in northern Alaska.

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.

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