Stomatal Conductance and ABA Concentration in the Xylem Sap of Barley Lines of Contrasting Genetic Origins

1997 ◽  
Vol 24 (5) ◽  
pp. 607 ◽  
Author(s):  
Ch. Borel ◽  
Th. Simonneau ◽  
D. This ◽  
F. Tardieu
Keyword(s):  
Stomatal Conductance ◽  
Water Status ◽  
Xylem Sap ◽  
Cycle Duration ◽  
Response Curves ◽  
Hordeum Vulgare L ◽  
Drought Tolerant ◽  
Series Of Experiments ◽  
Stomatal Sensitivity ◽  
Unique Relationship

We investigated the controls of ABA concentration in the xylem sap and of stomatal conductance in five barley (Hordeum vulgare L.) lines of contrasting origins (Syrian or French), genetic backgrounds and previously field-evaluated drought resistances. Controlled water deficits were applied to young plants in a series of experiments in the greenhouse with contrasting evaporative demands. There was a unique relationship between soil water status and the concentration of ABA in the xylem sap measured at the end of the night. This relationship applied to all experiments for a given line, and was common between lines. Concentrations measured in the sap collected by pressurising leaves were similar to those in the sap of pressurised roots. Stomatal conductance was related to the concentration of ABA in the sap, with relationships which were common for all experiments within each line. Response curves of gs to concentration of ABA in the sap differed among two groups of lines which slightly differed in life cycle duration. Apparent stomatal sensitivity to ABAwas lower in earliest anthesing lines. Both groups comprised lines of either Syrian or French origins, and either ‘drought tolerant’ or ‘drought susceptible’ lines. We conclude that stomatal control had a low genetic variability in the studied range of lines, in spite of the large genetic differences between lines.

Effects of growth temperature on the response of lupin stomata to drought and abscisic acid

1999 ◽  
Vol 26 (6) ◽  
pp. 549 ◽  
Author(s):  
M. Leonor Osório ◽  
M. Lucília Rodrigues ◽  
M. Manuela Chaves ◽  
Maria João Correia
Keyword(s):  
Abscisic Acid ◽  
Growth Temperature ◽  
Water Status ◽  
Lupinus Albus ◽  
Xylem Sap ◽  
Effect Of Temperature ◽  
Exogenous Aba ◽  
Higher Temperature ◽  
Stomatal Sensitivity ◽  
The Relationship

To assess how growth temperature affects stomatal responses to xylem-transported abscisic acid (ABA), leaf conductance (g), the concentrations of ABA and calcium ions, and the pH of the xylem sap were measured in well-watered and water-stressed Lupinus albus L. plants grown under two thermal regimes: 10/15°C and 20/25°C, night/day temperature. Moderate water deficit was imposed, at the same thermal time, and induced a significant reduction in g regardless of temperature. In the morning, g was higher in plants grown at 20/25°C than in cooler conditions, and these differences could not be explained by dissimilarities in shoot water status or xylem ABA concentration. At midday, the apparent stomatal sensitivity to xylem-carried ABA was increased and the effect of temperature on the relationship between g and xylem ABA was no longer observed. A positive effect of higher temperature on stomatal aperture was also evident when artificial sap containing ABA was fed to leaves of well-watered plants. In response to exogenous ABA, stomata closed to the same extent as observed in the morning in water-stressed plants. However, exogenous ABA feeding could not mimic the relationship between g and xylem ABA determined at midday in intact plants. The pH and the concentration of calcium in xylem were not affected by temperature. At midday, however, the calcium concentrations were higher in water-stressed than in well-watered plants. These changes in the concentrations of calcium or other xylem components, such as ABA conjugates, together with possible changes in the ability of the leaves to degrade and/or to compartmentalise ABA, may partly explain the midday increase in the apparent stomatal sensitivity to xylem ABA.

scholarly journals Xylem Sap Abscisic Acid Concentrations and Stomatal Conductance in Mycorrhizal Cowpea

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 838A-838
Author(s):  
Robert C. Ebel ◽  
Xiangrong Duan ◽  
Robert M. Augé
Keyword(s):  
Abscisic Acid ◽  
Stomatal Conductance ◽  
Water Status ◽  
Xylem Sap ◽  
Mycorrhizal Colonization ◽  
Mycorrhizal Symbiosis ◽  
Leaf Water Status ◽  
Host Nutrition ◽  
Mycorrhizal Plants ◽  
Induced Changes

Mycorrhizal colonization can alter stomatal behavior of host leaves before or during soil drying, but the mechanism of influence is not always clear. We examined the possibility that mycorrhizal symbiosis might result in either altered stomatal sensitivity to abscisic acid (ABA) moving from roots to shoots in xylem sap, or altered movement of ABA in xylem as a function of soil water content (θ). Mycorrhizal colonization of Vigna unguiculata did not change the relationship between stomatal conductance (gs) and xylem [ABA] during drying of whole root systems. Stomatal conductance was higher in mycorrhizal than in similarly sized and similarly nourished nonmycorrhizal plants when soil moisture was relatively high, perhaps related to lower xylem [ABA] in mycorrhizal plants at high soil θ. Neither gs nor xylem [ABA] was affected by mycorrhizae at low soil θ. Higher gs in mycorrhizal plants was evidently not related to a mycorrhizal effect on leaf water status, as neither gs/shoot Ψ nor shoot Ψ/soil θ relationships were altered by the symbiosis. Stomatal conductance was much more closely correlated with xylem [ABA] than with soil θ or shoot Ψ. Decreased xylem [ABA] may explain why mycorrhizal colonization sometimes increases gs of unstressed mycorrhizal plants in the absence of mycorrhizae-induced changes in host nutrition. This work was supported by USDA NRICGP grant 91-37100-6723 (R.M.A).

scholarly journals ABA AND STOMATAL RESPONSES IN TEPARY AND COMMON BEAN

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 682b-682
Author(s):  
Maria G. Janssen ◽  
Albert H. Markhart
Keyword(s):  
Common Bean ◽  
Xylem Sap ◽  
Drought Tolerant ◽  
Detached Leaves ◽  
Stomatal Sensitivity ◽  
Root Signal ◽  
Response To Water ◽  
Aba Content ◽  
The Relationship

Tepary beans (Phaseolus acutifolius Gray) are more drought tolerant and have stomata that are more sensitive to low leaf water potentials (ψ w) than common beans (P. vulgaris L.). This study was designed to examine the role of ABA in controlling stomatal behaviour in these species. Comparison of the bulk leaf ABA content does not explain why tepary stomata are more sensitive to low leaf ψ w compared to common bean (at -1.4 MPa ABA content increased 40-fold in common bean and 25-fold in tepary). We hypothesize that the greater sensitivity of tepary stomata to low leaf ψ w is related to a higher concentration of ABA in the xylem sap, and/or to a greater sensitivity of tepary stomata to ABA. Xylem sap of well-watered and water stressed plants is analyzed to determine the concentration of ABA, and whether ABA is a putative candidate serving as a chemical root signal in response to water stress in Phaseolus. To test stomatal sensitivity to ABA, epidermal strips and detached leaves are exposed to a range of ABA concentrations. The relationship between stomatal aperture and different ABA concentrations is discussed.

Stomatal conductance and growth of five Alnusglutinosa clones in response to controlled water stress

1988 ◽  
Vol 18 (4) ◽  
pp. 421-426 ◽  
Author(s):  
T. C. Hennessey ◽  
E. M. Lorenzi ◽  
R. W. McNew
Keyword(s):  
Water Stress ◽  
Stomatal Conductance ◽  
Drought Tolerance ◽  
Leaf Area ◽  
Water Status ◽  
Height Growth ◽  
Plant Water ◽  
Black Alder ◽  
Severe Water Stress ◽  
Progressive Water Stress

An experiment to quantify the response of unnodulated, fertilized European black alder (Alnusglutinosa (L.) Gaertn.) seedlings to progressive water stress showed contrasting drought tolerance among five clones, using stomatal conductance, leaf area, and height as indices of drought sensitivity. In particular, one rapidly growing clone (AG 8022-14) showed the ability to moderate changes in water stress more efficiently than the more slowly growing clones. After 30 days of moderate levels of water stress, clones that had higher stomatal conductance also had greater leaf area and height growth. Leaf area and height were both sensitive to plant water status, although no threshold of stress associated with a cessation of leaf area or height expansion was found even though stomatal conductance decreased to 0.05 cm s−1 under severe water stress.

Elevated CO2 alleviates the impact of drought on barley improving water status by lowering stomatal conductance and delaying its effects on photosynthesis

2007 ◽  
Vol 59 (3) ◽  
pp. 252-263 ◽  
Author(s):  
Anabel Robredo ◽  
Usue Pérez-López ◽  
Hector Sainz de la Maza ◽  
Begoña González-Moro ◽  
Maite Lacuesta ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Elevated Co2 ◽  
Water Status ◽  
The Impact

scholarly journals Trehalose induces tomato defenses and increases drought tolerance and bacterial wilt disease resistance

2021 ◽  
Author(s):  
April M MacIntyre ◽  
Valerian Meline ◽  
Zachary Gorman ◽  
Steven P Augustine ◽  
Carolyn J Dye ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Stomatal Conductance ◽  
Water Use ◽  
Bacterial Wilt ◽  
Xylem Sap ◽  
Wilt Disease ◽  
Tomato Plants ◽  
Bacterial Wilt Disease ◽  
Infected Tomato ◽  
Use Efficiency

Ralstonia solanacearum causes plant bacterial wilt disease, leading to severe crop losses. Xylem sap from R. solanacearum-infected tomato is enriched in host produced trehalose. Water stressed plants accumulate the disaccharide trehalose, which increases drought tolerance via abscisic acid (ABA) signaling networks. Because infected plants have reduced water flow, we hypothesized that bacterial wilt physiologically mimics drought stress, which trehalose could mitigate. Transcriptomic responses of susceptible vs. resistant tomato plants to R. solanacearum infection revealed differential expression of drought-associated genes, including those involved in ABA and trehalose metabolism. ABA was enriched in xylem sap from R. solanacearum-infected plants. Treating roots with ABA lowered stomatal conductance and reduced R. solanacearum stem colonization. Treating roots with trehalose increased ABA in xylem sap and reduced plant water use by reducing stomatal conductance and temporarily improving water use efficiency. Further, trehalose-treated plants were more resistant to bacterial wilt disease. Trehalose treatment also upregulated expression of salicylic acid (SA)-dependent defense genes, increased xylem sap levels of SA and other antimicrobial compounds, and increased wilt resistance of SA-insensitive NahG tomato plants. Additionally, trehalose treatment increased xylem concentrations of jasmonic acid and related oxylipins. Together, these data show that exogenous trehalose reduced both water stress and bacterial wilt disease and triggered systemic resistance. This suite of responses revealed unexpected linkages between plant responses to biotic and abiotic stress and suggests that that R. solanacearum-infected tomato plants produce more trehalose to improve water use efficiency and increase wilt disease resistance. In turn, R. solanacearum degrades trehalose as a counter-defense.

scholarly journals Revisiting the source of wilt symptoms: X-ray microcomputed tomography provides direct evidence that Ralstonia biomass clogs xylem vessels

2021 ◽  
Author(s):  
Brian Ingel ◽  
Denise Caldwell ◽  
Fiona Duong ◽  
Dilworth Y. Parkinson ◽  
Katherine A. McCulloh ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Light Microscopy ◽  
Bacterial Wilt ◽  
Xylem Sap ◽  
Physiological Mechanism ◽  
Bacterial Biomass ◽  
Microcomputed Tomography ◽  
Wilt Disease ◽  
X Ray ◽  
Bacterial Wilt Disease

AbstractPlant pathogenic Ralstonia cause wilt diseases by colonizing xylem vessels and disrupting water transport. Due to the abundance of Ralstonia cells in vessels, the dogma is that bacterial biomass clogs vessels and reduces the flow of xylem sap. However, the physiological mechanism of xylem disruption during bacterial wilt disease is untested. Using a tomato and Ralstonia pseudosolanacearum GMI1000 model, we visualized and quantified the spatiotemporal dynamics of xylem disruption during bacterial wilt disease. First, we measured stomatal conductance of leaflets on mock-inoculated and wilt-symptomatic plants. Wilted leaflets had reduced stomatal conductance, as did turgid leaflets located on the same petiole as wilted leaflets. Next, we used X-ray microcomputed tomography (X-ray microCT) and light microscopy to differentiate between mechanisms of xylem disruption: blockage by bacterial biomass, blockage by vascular tyloses, or sap displacement by gas embolisms. We imaged stems on plants with intact roots and leaves to quantify embolized vessels. Embolized vessels were rare, but there was a slight trend of increased vessel embolisms in infected plants with low bacterial population sizes. To test the hypothesis that vessels are clogged during bacterial wilt, we imaged excised stems after allowing the sap to evaporate during a brief dehydration. Most xylem vessels in mock-infected plants emptied their contents after excision, but non-conductive clogged vessels were abundant in infected plants by 2 days post infection. At wilt onset when bacterial populations exceeded 5×108 cfu/g stem tissue, approximately half of the xylem vessels were clogged with electron-dense bacterial biomass. We found no evidence of tyloses in the X-ray microCT reconstructions or light microscopy on the preserved stems. Bacterial blockage of vessels appears to be the principal cause of vascular disruption during Ralstonia wilt.

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