ABA Accumulation in Dehydrating Leaves Is Associated with Decline in Cell Volume, Not Turgor Pressure

Sack, Lawren; John, Grace P.; Buckley, Thomas N.

doi:10.1104/pp.17.01097

Cited by 70 publications

(78 citation statements)

References 33 publications

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“…Chloroplast density is reduced by 41% in mesophyll cells of manganese‐deficient pecan leaves, while the existing chloroplasts preserved their full photochemical competence (Henriques, ). Recent publications have shown that a reduction in RWC at the cellular level is the primary trigger of leaf ABA biosynthesis (McAdam and Brodribb, ; Sack et al ., ), being mesophyll cells the main site of biosynthesis (McAdam and Brodribb, ). As plants treated with Cl − have a better water status, with significantly higher values of RWC (Figure S2b), a lower ABA baseline content could be expected to occur in leaves of CL plants.…”

Section: Discussionmentioning

confidence: 99%

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO₂

et al. 2019

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Summary Chloride (Cl−) has been recently described as a beneficial macronutrient, playing specific roles in promoting plant growth and water‐use efficiency (WUE). However, it is still unclear how Cl− could be beneficial, especially in comparison with nitrate (NO3−), an essential source of nitrogen that shares with Cl− similar physical and osmotic properties, as well as common transport mechanisms. In tobacco plants, macronutrient levels of Cl− specifically reduce stomatal conductance (gs) without a concomitant reduction in the net photosynthesis rate (AN). As stomata‐mediated water loss through transpiration is inherent in the need of C3 plants to capture CO2, simultaneous increase in photosynthesis and WUE is of great relevance to achieve a sustainable increase in C3 crop productivity. Our results showed that Cl−‐mediated stimulation of larger leaf cells leads to a reduction in stomatal density, which in turn reduces gs and water consumption. Conversely, Cl− improves mesophyll diffusion conductance to CO2 (gm) and photosynthetic performance due to a higher surface area of chloroplasts exposed to the intercellular airspace of mesophyll cells, possibly as a consequence of the stimulation of chloroplast biogenesis. A key finding of this study is the simultaneous improvement of AN and WUE due to macronutrient Cl− nutrition. This work identifies relevant and specific functions in which Cl− participates as a beneficial macronutrient for higher plants, uncovering a sustainable approach to improve crop yield.

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Section: Discussionmentioning

confidence: 99%

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO₂

et al. 2019

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“…Importantly, there is a need to distinguish the water in the apoplast versus symplast. The symplastic RWC threshold for given levels of PLRC can be calculated on the basis of estimates of apoplastic fraction, though these are subject to uncertainty (Sack et al, ). Further, for strongly dehydrated leaves, in which embolism forms in the xylem, the apoplastic fraction will change, especially when large proportions of midrib water are lost, as this can account for up to >40% of leaf water in some species with exceptional midrib xylem volume per leaf area (unpublished data), which confers a level of uncertainty to the meaning of PLRC in highly dehydrated leaves, that is, PLRC 25 and PLRC 50 .…”

Section: Discussionmentioning

confidence: 99%

“…The Ψ leaf corresponding to the RWC for given PLRC was determined from the pressure–volume parameters of each species (Sack, John, & Buckley, ).…”

Section: Methodsmentioning

confidence: 99%

Leaf rehydration capacity: Associations with other indices of drought tolerance and environment

John

Henry

Sack

2018

Plant Cell & Environment

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Clarifying the mechanisms of leaf and whole plant drought responses is critical to predict the impacts of ongoing climate change. The loss of rehydration capacity has been used for decades as a metric of leaf dehydration tolerance but has not been compared with other aspects of drought tolerance. We refined methods for quantifying the percent loss of rehydration capacity (PLRC), and for 18 Southern California woody species, we determined the relative water content and leaf water potential at PLRC of 10%, 25%, and 50%, and, additionally, the PLRC at important stages of dehydration including stomatal closure and turgor loss. On average, PLRC of 10% occurred below turgor loss point and at similar water status to 80% decline of stomatal conductance. As hypothesized, the sensitivity to loss of leaf rehydration capacity varied across species, leaf habits, and ecosystems and correlated with other drought tolerance traits, including the turgor loss point and structural traits including leaf mass per area. A new database of PLRC for 89 species from the global literature indicated greater leaf rehydration capacity in ecosystems with lower growing season moisture availability, indicating an adaptive role of leaf cell dehydration tolerance within the complex of drought tolerance traits.

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“…). Similar results were reported for leaves forcibly dehydrated in a pressure chamber (McAdam & Brodribb, ; Sussmilch et al ., ), which suggests leaf ABA synthesis is driven by anything that reduces leaf water content (Sack et al ., ). Together these data suggest that de novo synthesis of ABA in leaves is the mechanism of hydroactive feedback responses to humidity in these species.…”

Section: New Ideas and New Evidence About Stomatal Responses To Watermentioning

confidence: 97%

“…Fourth, vapor transport through the leaf airspaces can be driven by small temperature gradients, independent of water potential, which means that water movement and, hence, water potential of tissues outside the xylem are sensitive to variables that influence temperature gradients, such as light absorption, leaf thickness and airspace fraction (Buckley et al ., ). Fifth, because stomata may not sense water potential per se , but instead a closely related variable such as turgor or cell volume (Sack et al ., ), I use the more general term ‘water status’ in this review.…”

Section: Background: Stomatal Water Relationsmentioning

confidence: 99%

How do stomata respond to water status?

2019

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Summary Stomatal responses to humidity, soil moisture and other factors that influence plant water status are critical drivers of photosynthesis, productivity, water yield, ecohydrology and climate forcing, yet we still lack a thorough mechanistic understanding of these responses. Here I review historical and recent advances in stomatal water relations. Clear evidence now implicates a metabolically mediated response to leaf water status (‘hydroactive feedback’) in stomatal responses to evaporative demand and soil drought, possibly involving abscisic acid production in leaves. Other hypothetical mechanisms involving vapor and heat transport within leaves may contribute to humidity, light and temperature responses, but require further theoretical clarification and experimental validation. Variation and dynamics in hydraulic conductance, particularly within leaves, may contribute to water status responses. Continuing research to fully resolve mechanisms of stomatal responses to water status should focus on several areas: validating and quantifying the mechanism of leaf‐based hydroactive feedback, identifying where in leaves water status is actively sensed, clarifying the role of leaf vapor and energy transport in humidity and temperature responses, and verifying foundational but minimally replicated results of stomatal hydromechanics across species. Clarity on these matters promises to deliver modelers with a tractable and reliable mechanistic model of stomatal responses to water status.

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ABA Accumulation in Dehydrating Leaves Is Associated with Decline in Cell Volume, Not Turgor Pressure

Cited by 70 publications

References 33 publications

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO₂

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO₂

Leaf rehydration capacity: Associations with other indices of drought tolerance and environment

How do stomata respond to water status?

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ABA Accumulation in Dehydrating Leaves Is Associated with Decline in Cell Volume, Not Turgor Pressure

Cited by 70 publications

References 33 publications

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO2

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO2

Leaf rehydration capacity: Associations with other indices of drought tolerance and environment

How do stomata respond to water status?

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Product

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Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO₂

Chloride as a macronutrient increases water‐use efficiency by anatomically driven reduced stomatal conductance and increased mesophyll diffusion to CO₂