Leaf hydraulic architecture and water relations of three ferns from contrasting light habitats

2010 ◽  
Vol 37 (6) ◽  
pp. 566 ◽  
Author(s):  
Maria A. Lo Gullo ◽  
Fabio Raimondo ◽  
Alessandro Crisafulli ◽  
Sebastiano Salleo ◽  
Andrea Nardini
Keyword(s):  
Water Potential ◽  
Hydraulic Resistance ◽  
Water Relations ◽  
The Other ◽  
Vascular Bundles ◽  
Hydraulic Architecture ◽  
Turgor Loss Point ◽  
Leaf Osmotic Potential ◽  
Fern Species ◽  
Xylem Conduits

Leaf hydraulic architecture and water relations of three fern species were measured. The species selected were adapted either to deeply shaded (Woodwardia radicans), moderately shaded (Dryopteris affinis) or moderately sunny (Polystichum setiferum) habitats, as confirmed by microclimatic measurements performed in the field. Leaf water potential (Ψleaf) was lower and leaf conductance to water vapour (gL) was higher in P. setiferum than in the shade-adapted ferns. Leaf osmotic potential and water potential at the turgor loss point were lower in the sun-adapted species than in the other ferns. Leaf hydraulic resistance (Rleaf) was lowest in P. setiferum and Rleaf was correlated with gL across species. Low Rleaf was coordinated with low rachis hydraulic resistance (Rrachis). Low values of Rrachis in P. setiferum were not due to the presence of wide xylem conduits as checked on the basis of anatomical measurements, but to increased radial permeability of vascular bundles. This was a consequence of the absence of endodermis surrounding the vascular bundles in P. setiferum, which was observed in the rachis of shade-adapted species. We conclude that hydraulic adjustment of fern fronds is a key component of adaptation of pteridophytes to contrasting light habitats.

scholarly journals COMPARATIVE DROUGHT RESISTANCE AMONG SIX BIRCH (BETULA) SPECIES

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1143f-1143
Author(s):  
Thomas G. Ranney ◽  
R.E. Bir ◽  
W.A. Skroch
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Water Relations ◽  
Leaf Water Potential ◽  
Leaf Gas Exchange ◽  
Leaf Water ◽  
Mild Stress ◽  
Turgor Loss Point ◽  
Leaf Osmotic Potential ◽  
Response To Water

In order to evaluate and compare adaptability to dry sites, plant water relations and leaf gas exchange were compared in response to water stress among six birch species: monarch birch (Betula maximowicziana), river birch (B. nigra), paper birch (B. papyrifera), European birch (B. pendula), `Whitespire' Japanese birch (B. platyphylla var. japonica `Whitespire'), and gray birch (B. pendula). After 28 days without irrigation, Japanese birch maintained significantly higher stomatal conductance (gs) and net photosynthesis (Pn) than did any of the other species, despite having one of the lowest mid-day water potentials. Evaluation of tissue water relations, using pressure-volume methodology, showed no evidence of osmotic adjustment for any of these species in response to water stress. However, there was substantial variation among species in the water potential at the turgor loss point; varying from a high of -1.34 MPa for river birch to a low of -1.78 MPa for Japanese birch. Rates of Pn and gs under mild stress (mean predawn leaf water potential of -0.61 MPa) were negatively correlated with leaf osmotic potential at full turgor and the leaf water potential at the turgor loss point.

scholarly journals Leaf Physiological Responses to Drought Stress and Community Assembly in an Asian Savanna

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1119
Author(s):  
Thuy T. Nguyen ◽  
Stefan K. Arndt ◽  
Patrick J. Baker
Keyword(s):  
Drought Stress ◽  
Southeast Asia ◽  
Water Potential ◽  
Water Relations ◽  
Leaf Water Potential ◽  
Forest Type ◽  
Adaptive Strategies ◽  
Leaf Water ◽  
Turgor Loss Point ◽  
Drought Avoidance

Deciduous dipterocarp forest (DDF) is the most extensive forest type in continental Southeast Asia, but across much of its range is functionally more similar to tropical savannas than tropical forests. We investigated water relations and drought responses of the four dominant tree species (two Shorea and two Dipterocarpus species) of the DDF in central Vietnam to determine how they responded to prolonged periods of drought stress. We quantified leaf water relations in nursery- and field-grown seedlings of the four species and conducted a dry-down experiment on 258 seedlings to study leaf water potential and morphological responses of the seedlings following the drought stress. The two Shorea and two Dipterocarpus species differed significantly in leaf water potential at turgor loss point and osmotic potential at full turgor, but they showed similar responses to drought stress. All species shed leaves and suffered from stem loss when exposed to water potentials lower than their turgor loss point (approximately −1.7 MPa for Dipterocarpus and −2.6 MPa for Shorea species). Upon rewatering, all species resprouted vigorously regardless of the degree of leaf or stem loss, resulting in only 2% whole-plant mortality rate. Our results suggest that none of the four deciduous dipterocarp species is drought tolerant in terms of their water relations; instead, they employ drought-adaptive strategies such as leaf shedding and vigorous resprouting. Given that all species showed similar drought avoidance and drought-adaptive strategies, it is unlikely that seasonal drought directly influences the patterns of species assembly in the DDF of Southeast Asia.

Refilling of embolised conduits as a consequence of 'Münch water' circulation

2006 ◽  
Vol 33 (10) ◽  
pp. 949 ◽  
Author(s):  
Teemu Hölttä ◽  
Timo Vesala ◽  
Martti Perämäki ◽  
Eero Nikinmaa
Keyword(s):  
Water Potential ◽  
Hydraulic Resistance ◽  
Water Flux ◽  
Water Circulation ◽  
Xylem Embolism ◽  
Parenchyma Cells ◽  
Ray Parenchyma ◽  
Theoretical Paper ◽  
Ray Parenchyma Cells ◽  
Xylem Conduits

‘Münch water’ is pushed from the phloem to the xylem at locations of phloem sugar unloading. Consequently, an internal radial water potential imbalance is developed in the plant at these sugar-unloading sites. The phloem is at a higher water potential than the xylem. The magnitude of this radial water potential imbalance is determined by the magnitude of the radial water flux and the hydraulic resistance along the phloem-to-xylem pathway. If, as a result, the water potential in the ray parenchyma cells adjacent to xylem conduits is higher than that in the embolised xylem conduits, then a proportion of the water flow from the phloem would be directed towards embolised xylem conduits, in addition to conduits under tension. In this theoretical paper we demonstrate how recycled ‘Münch water’ passing from the phloem to the xylem can induce xylem embolism refilling. We also calculate the conditions and the structural composition of the phloem-to-xylem pathway that are required for embolism refilling by ‘Münch water’ circulation, and the time that is required for the complete refilling of embolised conduits in varying conditions.

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.

scholarly journals Rootstocks induce functional differences that affect carbon isotope discrimination and water relations in the apple scion

2021 ◽  
Author(s):  
Erica Casagrande Biasuz ◽  
Lee Kalcsits
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Carbon Isotope ◽  
Hydraulic Resistance ◽  
Water Relations ◽  
Water Movement ◽  
Isotope Composition ◽  
Leaf Gas Exchange ◽  
Stem Water Potential ◽  
Stem Water

Composite trees combine traits from both the rootstock and scion. Dwarfing rootstocks are used to reduce shoot vigor and improve fruit quality and productivity. Although differences in rootstock vigour have been clearly described, the underlying physiological mechanisms regulating scion vigor are not well understood. Plant water status is strongly influenced by stem hydraulic resistance to water movement. In the scion, stomata regulate transpiration rates and are essential to prevent hydraulic failure. Lower stomatal conductance contributes to enriched leaf carbon isotope composition (δ13C). Combined, the effects of increased hydraulic resistance, limited stomatal control, and subsequently, limited gas exchange can affect tree growth. These differences may also correspond to differences in scion vigor. Here, vegetative growth, gas exchange, stem water potential, and leaf δ13C were compared to determine how rootstocks affect scion water relations. B.9 had the lowest shoot vigor compared to the more vigorous rootstock, G.890. Similarly, photosynthetic rates were also lower. Rootstock vigor was closely associated with leaf gas exchange and stem water potential in the scion and were reflected in leaf δ13C signatures. Dwarfing was strongly related to hydraulic limitations induced by rootstock genotype and these changes are distinguishable when measuring leaf and stem δ13C composition.

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.

scholarly journals Water Relations and Hydraulic Architecture of a Tropical Tree (Schefflera morototoni)

1991 ◽  
Vol 96 (4) ◽  
pp. 1105-1113 ◽  
Author(s):  
Melvin T. Tyree ◽  
David A. Snyderman ◽  
Timothy R. Wilmot ◽  
Jose-Luis Machado
Keyword(s):  
Water Relations ◽  
Tropical Tree ◽  
Hydraulic Architecture
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