Physiological plasticity in water relations and leaf structure of understory versus open-grown Cerciscanadensis in northeastern Kansas

1986 ◽  
Vol 16 (6) ◽  
pp. 1170-1174 ◽  
Author(s):  
Marc D. Abram
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Stomatal Density ◽  
Structural Characteristics ◽  
Soil Water Potential ◽  
Forest Understory ◽  
Gallery Forest ◽  
Laboratory Studies ◽  
Physiological Plasticity ◽  
High Degree

Field and laboratory studies were used to evaluate physiological plasticity in water relations and leaf structural characteristics of CerciscanadensisL. (redbud) saplings growing in a gallery forest understory and an adjacent prairie in eastern Kansas. Two study periods were defined based on high (greater than −0.2 MPa in May) and low (−1.5 MPa in July) predawn soil water potential (ψsoil). Leaf conductance to water vapor diffusion (gwv) was greater for prairie than understory redbud saplings during both sampling periods (maximum gwv = 7.5–8.7 mm s−1). Moreover, gwv for prairie redbud remained high at both high and low ψsoil, but was significantly lower for understory redbud during midday at low ψsoil. Transpiration flux was also higher in the prairie than in the understory site and reached a maximum for prairie redbud (318 mg m−2 s−1) in July, in conjunction with high leaf to air vapor pressure deficits (maximum, 5.3 kPa). Leaf water potential declined significantly at both sites with decreased ψsoil and the minimum values (−3.0 MPa) were recorded in understory redbud. Leaves of prairie redbud were significantly smaller, thicker, and had higher specific leaf mass and stomatal density than leaves of understory redbud, which are consistent with differences between xeric and mesic species, respectively. These differences in water relations and leaf morphology between understory and prairie redbud suggest a high degree of physiological plasticity for this species in eastern Kansas.

Seasonal Changes in the Water Relations of Eucalyptus behriana F. Muell. And E. microcarpa (Maiden) Maiden in the Field

1984 ◽  
Vol 32 (5) ◽  
pp. 495 ◽  
Author(s):  
BA Myers ◽  
TF Neales
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Rainfall Intensity ◽  
Field Measurements ◽  
Canopy Conductance ◽  
Laboratory Studies ◽  
Short Term ◽  
The Mean ◽  
Type Response ◽  
Vapour Pressure Difference

Field observations of some parameters of the water relations of the two eucalypt species E. behriana and E. microcarpa in dry sclerophyll, mallee and woodland vegetation were made at three sites from 1980 to 1983. The mean ( n = 519) water potential measured at dawn (Ψdawn) was -3.07± 0.01 MPa and fluctuated seasonally with rainfall intensity over the range -2.0 ± 0, 1 to -4.4 ± 0.1 MPa ( n = 30). Both species behaved similarly and some osmotic adjustment took place. Mean leaf conductance (gs) varied between 0.151 ± 0.006 and 0.003 ± 0.001 mol m-2 s-1 . Maximum daily values of gs were linearly related to Ψdawn as it fluctuated seasonally. The slope of this linear regression was not significantly different from that relating these values of gs and Ψ, when both were measured concurrently. There were thus no indications of a distinction between the responses of gs to long- and short-term fluctuations of Ψ or of a threshold-type response of gs to Ψ. Field measurements indicated that gs was decreased at high values of vapour pressure difference (Δe). In laboratory studies with seedlings of the two species gs decreased from 0.5 to 0.1 mol m-2 s-I as Δe increased from 0.5 to 3.0 kPa. Leaf and canopy conductance were the predominant plant determinants of transpiration rate (Er) in this type of vegetation which has the capacity to restrict Et via the effect of water potential (Ψ) on gs and also by the response of gs to Δe. Some of the water relations parameters of E. behriana indicated that this species was better able to withstand drought than was E microcarpa.

Leaf Gas Exchange and Water Relations of Lupins and Wheat. II. Root and Shoot Water Relations of Lupin During Drought-Induced Stomatal Closure

1989 ◽  
Vol 16 (5) ◽  
pp. 415 ◽  
Author(s):  
CR Jensen ◽  
IE Henson ◽  
NC Turner
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Transport ◽  
Water Uptake ◽  
Water Relations ◽  
Leaf Gas Exchange ◽  
Stomatal Closure ◽  
Soil Water Potential ◽  
Root Water Uptake ◽  
Leaf Conductance

Plants of Lupinus cosentinii Guss. cv. Eregulla were grown in a sandy soil in large containers in a glasshouse and exposed to drought by withholding water. Under these conditions stomatal closure had previously been shown to be initiated before a significant reduction in leaf water potential was detected. In the experiments reported here, no significant changes were found in water potential or turgor pressure of roots or leaves when a small reduction in soil water potential was induced which led to a 60% reduction in leaf conductance. The decrease in leaf conductance and root water uptake closely paralleled the fraction of roots in wet soil. By applying observed data of soil water and root characteristics, and root water uptake for whole pots in a single-root model, the average water potential at the root surface was calculated. Potential differences for water transport in the soil-plant system, and the resistances to water flow were estimated using the 'Ohm's Law' analogy for water transport. Soil resistance was negligible or minor, whereas the root resistance accounted for 61-72% and the shoot resistance accounted for about 30% of the total resistance. The validity of the measurements and calculations is discussed and the possible role of root- to-shoot communication raised.

Water relations of winter wheat: 2. Soil water relations

1978 ◽  
Vol 91 (1) ◽  
pp. 103-116 ◽  
Author(s):  
P. J. Gregory ◽  
M. McGowan ◽  
P. V. Biscoe
Keyword(s):  
Winter Wheat ◽  
Water Potential ◽  
Soil Water ◽  
Water Relations ◽  
Unit Length ◽  
Soil Water Potential ◽  
Rooting Depth ◽  
Wheat Crop ◽  
Deep Roots ◽  
Volumetric Soil Water Content

SummaryVolumetric soil water content and soil water potential were measured beneath a winter wheat crop during the 1975 growing season. Almost no rain fell between mid-May and mid-July and the soil dried continuously until the potential was less than – 20 bars to a depth of 80 cm. Evaporation was separated from drainage by denning an ‘effective rooting depth’ at which the hydraulic gradient was zero.Rates of water uptake per unit length of root (inflow) were calculated for the whole soil profile and for individual soil layers. Generally, inflow decreased throughout the period of measurement from a maximum of 2·5 × 10–3 to a minimum of 0·66 × 10–3 ml water/cm root/day. Values in individual layers were frequently higher than the mean inflow and the importance of a few deep roots in taking up water during a dry season is emphasized. A similar correlation between inflow and soil water potential was found to apply for the 0–30 cm and 30–60 cm layers during the period of continual soil drying. This relationship represents the maximum inflow measured at a given soil water potential; actual inflow at any particular time depends upon the interrelationship of atmospheric demand, soil water potential and the distribution of root length in the soil.

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.

Roles of weathered bedrock and soil in seasonal water relations of Pinus Jeffreyi and Arctostaphylos patula

2001 ◽  
Vol 31 (11) ◽  
pp. 1947-1957 ◽  
Author(s):  
K R Hubbert ◽  
J L Beyers ◽  
R C Graham
Keyword(s):  
Water Potential ◽  
Sierra Nevada ◽  
Water Relations ◽  
Soil Water Potential ◽  
Pinus Jeffreyi ◽  
Pressure Potential ◽  
Available Water ◽  
Jeffrey Pine ◽  
Plant Available Water ◽  
Arctostaphylos Patula

In the southern Sierra Nevada, California, relatively thin soils overlie granitic bedrock that is weathered to depths of several metres. The weathered granitic bedrock is porous and has a plant-available water capacity of 0.124 m3·m–3, compared with 0.196 m3·m–3 for the overlying soil. Roots confined within bedrock joint fractures access this rock-held water, especially during late summer when overlying soils are dry. We sought to determine seasonal soil and bedrock water changes in a Jeffrey pine (Pinus jeffreyi Grev & Balf.) plantation and to examine concurrent effects on the water relations of Jeffrey pine and greenleaf manzanita (Arctostaphylos patula Greene). In 1996, plant-available water in the 75 cm thick soil was depleted by late June, with soil water potential (ψsoil) <–2.2 MPa, but below 75 cm, bedrock water potential (ψbedrock) was still > –2.2 MPa. Thus, the bedrock, not the soil, supplied water to plants for the remainder of the dry season. Higher values of, and smaller fluctuations in, seasonal predawn pressure potential (ψpredawn) for Jeffrey pine indicated that it is deeply rooted, whereas active roots of greenleaf manzanita were interpreted to be mostly within the upper 100 cm. The extra rooting volume supplied by weathered bedrock is especially important to pine relative to manzanita.

scholarly journals Eucalyptus sp. seedling response to potassium fertilization and soil water.

2008 ◽  
Vol 18 (1) ◽  
pp. 47 ◽  
Author(s):  
Paulo César Teixeira ◽  
José Leonardo Moraes Gonçalves ◽  
José Carlos Arthur Junior ◽  
Cleci Dezordi
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Leaf Area ◽  
Water Deficit ◽  
Water Relations ◽  
Transpiration Rate ◽  
Dry Matter ◽  
Soil Water Potential ◽  
Eucalyptus Grandis ◽  
Eucalyptus Urophylla

A considerable portion of Brazil‘s commercial eucalypt plantations is located in areas subjected to periods of water deficit and grown in soils with low natural fertility, particularly poor in potassium. Potassium is influential in controlling water relations of plants. The objective of this study was to verify the influence of potassium fertilization and soil water potential (Ψw) on the dry matter production and on water relations of eucalypt seedlings grown under greenhouse conditions. The experimental units were arranged in 4x4x2 randomized blocks factorial design, as follow: four species of Eucalyptus (Eucalyptus grandis, Eucalyptus urophylla, Eucalyptus camaldulensis and hybrid Eucalyptus grandis x Eucalyptus urophylla), four dosages of K (0, 50, 100 and 200 mg dm-3) and two soil water potentials (-0.01MPa and -0.1 MPa). Plastic containers with 15 cm diameter and 18 cm height, with Styrofoam base, containing 3.0 dm3 of soil and two plants per container were used. Soil water potential was kept at -0.01MPa for 40 days after seeding. Afterward, the experimental units were divided into two groups: in one group the potential was kept at -0.01MPa, and in the other one, at -0.10 MPa. Soil water potential was controlled gravimetrically twice a day with water replacement until the desired potential was reestablished. A week before harvesting, the leaf water potential (Ψ), the photosynthetic rate (A), the stomatal conductance (gs) and the transpiration rate were evaluated. The last week before harvesting, the mass of the containers was recorded daily before watering to determine the consumption of water by the plants. After harvesting, total dry matter and leaf area were evaluated. The data were submitted to analysis of variance, to Tukey's tests and regression analyses. The application of K influenced A, gs and the transpiration rate. Plants deficient in K showed lower A and higher gs and transpiration rates. There were no statistical differences in A, gs and transpiration rates in plants with and without water deficit. The addition of K reduced the consumption of water per unit of leaf area and, in general, plants submitted to water deficit presented a lower consumption of water.

scholarly journals Water relations and hydraulic architecture in Cerrado trees: adjustments to seasonal changes in water availability and evaporative demand

2008 ◽  
Vol 20 (3) ◽  
pp. 233-245 ◽  
Author(s):  
Sandra J. Bucci ◽  
Fabian G. Scholz ◽  
Guillermo Goldstein ◽  
Frederick C. Meinzer ◽  
Augusto C. Franco ◽  
...  
Keyword(s):  
Water Potential ◽  
Water Relations ◽  
Seasonal Changes ◽  
Soil Water Potential ◽  
Woody Species ◽  
Dry Season ◽  
Hydraulic Architecture ◽  
Wet Season ◽  
Evaporative Demand ◽  
Water Deficits

We determined adjustments in physiology and morphology that allow Neotropical savanna trees from central Brazil (Cerrado) to avoid water deficits and to maintain a nearly constant internal water balance despite seasonal changes in precipitation and air saturation deficit (D). Precipitation in the study area is highly seasonal with about five nearly rainless months during which D is two fold higher compared to wet season values. As a consequence of the seasonal fluctuations in rainfall and D, soil water potential changes substantially in the upper 100 cm of soil, but remains nearly constant below 2 m depth. Hydraulic architecture and water relations traits of Cerrado trees adjusted during the dry season to prevent increasing water deficits and insure homeostasis in minimum leaf water potential ψL and in total daily water loss per plant (isohydry). The isohydric behavior of Cerrado trees was the result of a decrease in total leaf surface area per tree, a strong stomatal control of evaporative losses, an increase in leaf-specific hydraulic conductivity and leaf hydraulic conductance and an increase in the amount of water withdrawn from internal stem storage, during the dry season. Water transport efficiency increased in the same proportion in leaves and terminal stems during the dry season. All of these seasonal adjustments were important for maintaining ψL above critical thresholds, which reduces the rate of embolism formation in stems and help to avoid turgor loss in leaf tissues still during the dry season. These adjustments allow the stems of most Cerrado woody species to operate far from the point of catastrophic dysfunction for cavitation, while leaves operate close to it and experience embolism on a daily basis, especially during the dry season.

Sign in / Sign up

Export Citation Format

Share Document