Water relations and gas exchange of the root hemiparasite Santalum acuminatum (quandong)

2001 ◽  
Vol 49 (4) ◽  
pp. 479 ◽  
Author(s):  
Beth R. Loveys ◽  
Brian R. Loveys ◽  
Stephen D. Tyerman
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Water Relations ◽  
Leaf Gas Exchange ◽  
Xylem Sap ◽  
Significant Proportion ◽  
Tissue Water ◽  
Root Hemiparasite ◽  
Transpirational Water Loss ◽  
Neighbouring Plant

The water relations and leaf gas-exchange characteristics of the root hemiparasite quandong (Santalum acuminatum (R.Br.) A.DC) and its neighbouring plants were examined at three field sites in central Southern Australia. This paper examines the role of water potential and osmotic gradients in facilitating the movement of water from host plants to quandong. Quandong exhibited a significantly more negative water potential than the neighbouring plant species at both field sites during summer and winter. A significant proportion of the osmotic potential was accounted for by mannitol, Na + , K + and Cl - . A water potential difference of 1.7 MPa was maintained between quandong and its putative host over a measurement period of 24 h. Xylem sap and leaves of quandong contained considerable concentration (0.1–0.4 mol (kg tissue water) –1 ) of mannitol. Stomatal conductance and assimilation of quandong were lower than those of the neighbouring plants at both Middleback and Aldinga during both summer and winter measurements. Measurements of transpiration for quandong differed between the two sites. The lower transpirational water loss resulted in quandong at Middleback having an instantaneous water-use efficiency higher (0.13–2.2 µmol (CO 2 ) mmol –1 (H 2 O)) than the neighbouring plants. Daily sap flow and calculated hydraulic conductivity were not significantly different between quandong and putative host plant.

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.

Responses to drought of five Brachiaria species. II. Water relations and leaf gas exchange

2004 ◽  
Vol 258 (1) ◽  
pp. 249-260 ◽  
Author(s):  
Orlando Guenni ◽  
Zdravko Baruch ◽  
Douglas Marín
Keyword(s):  
Gas Exchange ◽  
Water Relations ◽  
Leaf Gas Exchange

scholarly journals Physiological Performance of Pyrus pyraster L. (Burgsd.) and Sorbus torminalis (L.) Crantz Seedlings under Drought Treatment

Plants ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1496
Author(s):  
Viera Paganová ◽  
Marek Hus ◽  
Zuzana Jureková
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Water Scarcity ◽  
Prolonged Exposure ◽  
Leaf Gas Exchange ◽  
Total Biomass ◽  
Drought Treatment ◽  
Water Regimes ◽  
Sorbus Torminalis ◽  
Pyrus Pyraster

In this study, seedlings of Pyrus pyraster and Sorbus torminalis were grown for 60 days in the regulated environment of a growth chamber under different water regimes. The measured indicators were the growth and distribution of mass to organs, total biomass, root to shoot mass ratio (R:S), and gas exchange parameters (gs, E, An, and water use efficiency (WUE)). The amount of total biomass was negatively affected by drought. Differences between species were confirmed only for the dry matter of the leaves. P. pyraster maintained the ratio of the mass distribution between belowground and aboveground organs in both variants of the water regime. S. torminalis created more root length for a given dry-mass under drought treatment, but its R:S was lower compared to P. pyraster. The water potential of the leaves (Ψwl) was affected by substrate saturation and interspecific differences. P. pyraster had a demonstrably higher water potential and maintained this difference even after prolonged exposure to drought. After 30 days of different water regimes, Pyrus maintained higher values of gs, An, and E in control and drought treatments, but over a longer period of drought (after 50 days), the differences between species were equalized. The changes of the leaf gas exchange for Pyrus were accompanied by a significant increase in WUE, which was most pronounced on the 40th day of the experiment. A significant and strong relationship between WUE and gs was demonstrated. The results confirmed the different physiological performances of seedlings of tree species and the different mechanisms of their response to water scarcity during drought treatment. P. pyraster presented more acclimation traits, which allowed this taxon to exhibit better performance over a longer period of water scarcity.

Partial rootzone drying improves almond tree leaf-level water use efficiency and afternoon water status compared with regulated deficit irrigation

2011 ◽  
Vol 38 (5) ◽  
pp. 372 ◽  
Author(s):  
Gregorio Egea ◽  
Ian C. Dodd ◽  
María M. González-Real ◽  
Rafael Domingo ◽  
Alain Baille
Keyword(s):  
Gas Exchange ◽  
Water Potential ◽  
Leaf Gas Exchange ◽  
Water Status ◽  
Stem Water Potential ◽  
Regulated Deficit Irrigation ◽  
Leaf Level ◽  
Use Efficiency ◽  
Stem Water ◽  
Partial Rootzone Drying

To determine whether partial rootzone drying (PRD) optimised leaf gas exchange and soil–plant water relations in almond (Prunus dulcis (Mill.) D.A. Webb) compared with regulated deficit irrigation (RDI), a 2 year trial was conducted on field-grown trees in a semiarid climate. Five irrigation treatments were established: full irrigation (FI) where the trees were irrigated at 100% of the standard crop evapotranspiration (ETc); three PRD treatments (PRD70, PRD50 and PRD30) that applied 70, 50 and 30% ETc, respectively; and a commercially practiced RDI treatment that applied 50% ETc during the kernel-filling stage and 100% ETc during the remainder of the growth season. Measurements of volumetric soil moisture content in the soil profile (0–100 cm), predawn leaf water potential (Ψpd), midday stem water potential (Ψms), midday leaf gas exchange and trunk diameter fluctuations (TDF) were made during two growing seasons. The diurnal patterns of leaf gas exchange and stem water potential (Ψs) were appraised during the kernel-filling stage in all irrigation regimes. When tree water relations were assessed at solar noon, PRD did not show differences in either leaf gas exchange or tree water status compared with RDI. At similar average soil moisture status (adjudged by similar Ψpd), PRD50 trees had higher water status than RDI trees in the afternoon, as confirmed by Ψs and TDF. Although irrigation placement showed no effects on diurnal stomatal regulation, diurnal leaf net photosynthesis (Al) was substantially less limited in PRD50 than in RDI trees, indicating that PRD improved leaf-level water use efficiency.

Leaf gas exchange, water relations, nutrient content and growth in citrus and olive seedlings under salinity

2008 ◽  
Vol 52 (2) ◽  
pp. 385-390 ◽  
Author(s):  
J. C. Melgar ◽  
J. P. Syvertsen ◽  
V. Martinez ◽  
F. Garcia-Sanchez
Keyword(s):  
Gas Exchange ◽  
Water Relations ◽  
Leaf Gas Exchange ◽  
Nutrient Content

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.

scholarly journals Beyond the extreme: recovery of carbon and water relations in woody plants following heat and drought stress

2019 ◽  
Vol 39 (8) ◽  
pp. 1285-1299 ◽  
Author(s):  
Nadine K Ruehr ◽  
Rüdiger Grote ◽  
Stefan Mayr ◽  
Almut Arneth
Keyword(s):  
Heat Stress ◽  
Gas Exchange ◽  
Water Relations ◽  
Woody Plants ◽  
Leaf Gas Exchange ◽  
Experimental Studies ◽  
Drought Severity ◽  
Stress Recovery ◽  
Mild Stress ◽  
Post Stress

Abstract Plant responses to drought and heat stress have been extensively studied, whereas post-stress recovery, which is fundamental to understanding stress resilience, has received much less attention. Here, we present a conceptual stress-recovery framework with respect to hydraulic and metabolic functioning in woody plants. We further synthesize results from controlled experimental studies following heat or drought events and highlight underlying mechanisms that drive post-stress recovery. We find that the pace of recovery differs among physiological processes. Leaf water potential and abscisic acid concentration typically recover within few days upon rewetting, while leaf gas exchange-related variables lag behind. Under increased drought severity as indicated by a loss in xylem hydraulic conductance, the time for stomatal conductance recovery increases markedly. Following heat stress release, a similar delay in leaf gas exchange recovery has been observed, but the reasons are most likely a slow reversal of photosynthetic impairment and other temperature-related leaf damages, which typically manifest at temperatures above 40 °C. Based thereon, we suggest that recovery of gas exchange is fast following mild stress, while recovery is slow and reliant on the efficiency of repair and regrowth when stress results in functional impairment and damage to critical plant processes. We further propose that increasing stress severity, particular after critical stress levels have been reached, increases the carbon cost involved in reestablishing functionality. This concept can guide future experimental research and provides a base for modeling post-stress recovery of carbon and water relations in trees.

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