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Males J, Griffiths H. Specialized stomatal humidity responses underpin ecological diversity in C3 bromeliads. PLANT, CELL & ENVIRONMENT 2017; 40:2931-2945. [PMID: 28722113 DOI: 10.1111/pce.13024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Revised: 06/26/2017] [Accepted: 07/02/2017] [Indexed: 06/07/2023]
Abstract
The Neotropical Bromeliaceae display an extraordinary level of ecological variety, with species differing widely in habit, photosynthetic pathway and growth form. Divergences in stomatal structure and function, hitherto understudied in treatments of bromeliad evolutionary physiology, could have been critical to the generation of variety in ecophysiological strategies among the bromeliads. Because humidity is a key factor in bromeliad niches, we focussed on stomatal responses to vapour pressure deficit (VPD). We measured the sensitivity of stomatal conductance and assimilation rate to VPD in eight C3 bromeliad species of contrasting growth forms and ecophysiological strategies and parameterised the kinetics of stomatal responses to a step change in VPD. Notably, three tank-epiphyte species displayed low conductance, high sensitivity and fast kinetics relative to the lithophytes, while three xeromorphic terrestrial species showed high conductance and sensitivity but slow stomatal kinetics. An apparent feedforward response of transpiration to VPD occurred in the tank epiphytes, while water-use efficiency was differentially impacted by stomatal closure depending on photosynthetic responses. Differences in stomatal responses to VPD between species of different ecophysiological strategies are closely linked to modifications of stomatal morphology, which we argue has been a pivotal component of the evolution of high diversity in this important plant family.
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Affiliation(s)
- Jamie Males
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
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Sussmilch FC, McAdam SAM. Surviving a Dry Future: Abscisic Acid (ABA)-Mediated Plant Mechanisms for Conserving Water under Low Humidity. PLANTS (BASEL, SWITZERLAND) 2017; 6:E54. [PMID: 29113039 PMCID: PMC5750630 DOI: 10.3390/plants6040054] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 10/29/2017] [Accepted: 11/01/2017] [Indexed: 12/15/2022]
Abstract
Angiosperms are able to respond rapidly to the first sign of dry conditions, a decrease in air humidity, more accurately described as an increase in the vapor pressure deficit between the leaf and the atmosphere (VPD), by abscisic acid (ABA)-mediated stomatal closure. The genes underlying this response offer valuable candidates for targeted selection of crop varieties with improved drought tolerance, a critical goal for current plant breeding programs, to maximize crop production in drier and increasingly marginalized environments, and meet the demands of a growing population in the face of a changing climate. Here, we review current understanding of the genetic mechanisms underpinning ABA-mediated stomatal closure, a key means for conserving water under dry conditions, examine how these mechanisms evolved, and discuss what remains to be investigated.
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Affiliation(s)
- Frances C Sussmilch
- School of Biological Sciences, University of Tasmania, Hobart TAS 7001, Australia.
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082 Würzburg, Germany.
| | - Scott A M McAdam
- Purdue Center for Plant Biology, Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907, USA.
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Sweet KJ, Peak D, Mott KA. Stomatal heterogeneity in responses to humidity and temperature: Testing a mechanistic model. PLANT, CELL & ENVIRONMENT 2017; 40:2771-2779. [PMID: 28777880 DOI: 10.1111/pce.13051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Revised: 07/11/2017] [Accepted: 07/30/2017] [Indexed: 06/07/2023]
Abstract
The role of stomatal heterogeneity in the response of stomatal conductance (gs ) to the mole fraction difference in water vapour between the inside of the leaf and the ambient air (Δw) was determined using thermography and gas exchange for 3 species. The value of Δw for the leaf was varied in 2 different ways: first by varying air humidity while holding leaf temperature constant and second by varying leaf temperature while holding air humidity constant. Stomatal heterogeneity was explored by examining the response of gs in small areas of the leaf (as determined by thermography) and comparing them to each other and to the average value of gs (as determined by gas exchange). These analyses show that despite substantial heterogeneity in gs values, the response of gs to Δw was qualitatively similar in all areas of the leaf, and all responses of gs to Δw were well predicted by a recently proposed, vapour-phase mechanism for stomatal responses to temperature and humidity. Remarkably, the 2 model parameters, Θ and Z, that depend on leaf anatomy were constant for a given species, and only the maximum conductance varied in different regions of the leaf.
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Affiliation(s)
- Kathryn J Sweet
- Department of Physics, Utah State University, Logan, UT, 84322, USA
| | - David Peak
- Department of Physics, Utah State University, Logan, UT, 84322, USA
| | - Keith A Mott
- Department of Biology, Utah State University, Logan, UT, 84322, USA
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54
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Qiu C, Ethier G, Pepin S, Dubé P, Desjardins Y, Gosselin A. Persistent negative temperature response of mesophyll conductance in red raspberry (Rubus idaeus L.) leaves under both high and low vapour pressure deficits: a role for abscisic acid? PLANT, CELL & ENVIRONMENT 2017. [PMID: 28620951 DOI: 10.1111/pce.12997] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The temperature dependence of mesophyll conductance (gm ) was measured in well-watered red raspberry (Rubus idaeus L.) plants acclimated to leaf-to-air vapour pressure deficit (VPDL) daytime differentials of contrasting amplitude, keeping a fixed diurnal leaf temperature (Tleaf ) rise from 20 to 35 °C. Contrary to the great majority of gm temperature responses published to date, we found a pronounced reduction of gm with increasing Tleaf irrespective of leaf chamber O2 level and diurnal VPDL regime. Leaf hydraulic conductance was greatly enhanced during the warmer afternoon periods under both low (0.75 to 1.5 kPa) and high (0.75 to 3.5 kPa) diurnal VPDL regimes, unlike stomatal conductance (gs ), which decreased in the afternoon. Consequently, the leaf water status remained largely isohydric throughout the day, and therefore cannot be evoked to explain the diurnal decrease of gm . However, the concerted diurnal reductions of gm and gs were well correlated with increases in leaf abscisic acid (ABA) content, thus suggesting that ABA can induce a significant depression of gm under favourable leaf water status. Our results challenge the view that the temperature dependence of gm can be explained solely from dynamic leaf anatomical adjustments and/or from the known thermodynamic properties of aqueous solutions and lipid membranes..
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Affiliation(s)
- Changpeng Qiu
- Department of Plant Sciences, Laval University, Quebec, Canada
| | - Gilbert Ethier
- Department of Plant Sciences, Laval University, Quebec, Canada
| | - Steeve Pepin
- Department of Soils and Agri-Food Engineering, Laval University, Quebec, Canada
| | - Pascal Dubé
- Institute of Nutrition and Functional Foods (INAF), Laval University, Quebec, Canada
| | - Yves Desjardins
- Department of Plant Sciences, Laval University, Quebec, Canada
| | - André Gosselin
- Department of Plant Sciences, Laval University, Quebec, Canada
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Affiliation(s)
- Jingjing Yin
- School of Integrative Plant Science, Horticulture Section, Cornell Univ.; Ithaca NY USA
| | - Taryn L. Bauerle
- School of Integrative Plant Science, Horticulture Section, Cornell Univ.; Ithaca NY USA
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56
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Deans RM, Brodribb TJ, McAdam SAM. An Integrated Hydraulic-Hormonal Model of Conifer Stomata Predicts Water Stress Dynamics. PLANT PHYSIOLOGY 2017; 174:478-486. [PMID: 28341770 PMCID: PMC5462058 DOI: 10.1104/pp.17.00150] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 03/23/2017] [Indexed: 05/07/2023]
Abstract
A simple model combining leaf hydraulics and abscisic acid sensitivity can predict stomatal dynamics to short-term changes in plant water status in a conifer.
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Affiliation(s)
- Ross M Deans
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia
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57
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Buckley TN, Sack L, Farquhar GD. Optimal plant water economy. PLANT, CELL & ENVIRONMENT 2017; 40:881-896. [PMID: 27644069 DOI: 10.1111/pce.12823] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/22/2016] [Accepted: 08/24/2016] [Indexed: 05/13/2023]
Abstract
It was shown over 40 years ago that plants maximize carbon gain for a given rate of water loss if stomatal conductance, gs , varies in response to external and internal conditions such that the marginal carbon revenue of water, ∂A/∂E, remains constant over time. This theory has long held promise for understanding the physiological ecology of water use and for informing models of plant-atmosphere interactions. Full realization of this potential hinges on three questions: (i) Are analytical approximations adequate for applying the theory at diurnal time scales? (ii) At what time scale is it realistic and appropriate to apply the theory? (iii) How should gs vary to maximize growth over long time scales? We review the current state of understanding for each of these questions and describe future research frontiers. In particular, we show that analytical solutions represent the theory quite poorly, especially when boundary layer or mesophyll resistances are significant; that diurnal variations in hydraulic conductance may help or hinder maintenance of ∂A/∂E, and the matter requires further study; and that optimal diurnal responses are distinct from optimal long-term variations in gs , which emerge from optimal shifts in carbon partitioning at the whole-plant scale.
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Affiliation(s)
- Thomas N Buckley
- Plant Breeding Institute, Faculty of Agriculture and Environment, The University of Sydney, Narrabri, New South Wales, 2390, Australia
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, 90095, United States
| | - Graham D Farquhar
- Research School of Biology, Australian National University, Canberra, 0200, Australia
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59
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Sussmilch FC, Brodribb TJ, McAdam SAM. Up-regulation of NCED3 and ABA biosynthesis occur within minutes of a decrease in leaf turgor but AHK1 is not required. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:2913-2918. [PMID: 28449122 PMCID: PMC5853609 DOI: 10.1093/jxb/erx124] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Accepted: 03/27/2017] [Indexed: 05/20/2023]
Abstract
A major environmental signal influencing day-time stomatal aperture is the vapour pressure deficit between the leaf and atmosphere (VPD). In angiosperms, increased VPD triggers biosynthesis of abscisic acid (ABA), prompting rapid stomatal closure. Altered cell turgor has been proposed as the trigger for ABA biosynthesis, but the timing and nature of the genetic signals linking these processes have remained uncertain. We investigated this in Arabidopsis by examining changes induced by a decrease in leaf turgor, simulating a natural increase in VPD. We found that the rate-limiting gene within the de novo ABA biosynthesis pathway, 9-cis-epoxycarotenoid dioxygenase 3 (NCED3), was induced and ABA levels increased within just 5 min of decreased leaf turgor. This rapid induction matches the time-frame for initiation of stomatal closure in response to a doubling in VPD. We further examined Arabidopsis histidine kinase1 (AHK1) as the most likely candidate for the turgor-sensing receptor involved, but found no significant difference between wild-type and an ahk1 null mutant in the induction of ABA-biosynthetic genes, ABA production, or stomatal behaviour. We show that decreased leaf turgor triggers de novo ABA biosynthesis within the time-frame of the stomatal response to VPD, but that AHK1 does not fulfil a critical role as a turgor-sensing receptor within this pathway.
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Affiliation(s)
- Frances C Sussmilch
- School of Biological Sciences, University of Tasmania, Hobart, TAS, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, TAS, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, TAS, Australia
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60
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McAdam EL, Brodribb TJ, McAdam SAM. Does ozone increase ABA levels by non-enzymatic synthesis causing stomata to close? PLANT, CELL & ENVIRONMENT 2017; 40:741-747. [PMID: 28042679 DOI: 10.1111/pce.12893] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 12/19/2016] [Accepted: 12/21/2016] [Indexed: 06/06/2023]
Abstract
Reactive oxygen species (ROS) are widely recognized as important regulators of stomatal aperture and plant gas exchange. The pathways through which stomata perceive ROS share many common linkages with the well characterized signalling pathway for the hormone abscisic acid (ABA), a major driver of stomatal closure. Given reports that ABA receptor mutants have no stomatal response to ozone-triggered ROS production, as well as evidence that all steps in the ABA biosynthetic pathway can be non-enzymatically converted by ROS, here we investigated the possibility that ozone closes stomata by directly converting ABA precursors to ABA. In plants where stomata were responsive to ozone, we found that foliar ABA levels rapidly increased upon exposure to ozone. Recovery of gas exchange post-exposure occurred only when ABA levels declined. Our data suggest that stomatal closure in response to ozone exposure occurs as a result of direct oxidation of ABA precursors leading to ABA production, but the importance of this ROS interaction remains uncertain under normal photosynthetic conditions.
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Affiliation(s)
- Erin L McAdam
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia
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61
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Sussmilch FC, Brodribb TJ, McAdam SAM. What are the evolutionary origins of stomatal responses to abscisic acid in land plants? JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:240-260. [PMID: 28093875 DOI: 10.1111/jipb.12523] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Accepted: 01/15/2017] [Indexed: 05/20/2023]
Abstract
The evolution of active stomatal closure in response to leaf water deficit, mediated by the hormone abscisic acid (ABA), has been the subject of recent debate. Two different models for the timing of the evolution of this response recur in the literature. A single-step model for stomatal control suggests that stomata evolved active, ABA-mediated control of stomatal aperture, when these structures first appeared, prior to the divergence of bryophyte and vascular plant lineages. In contrast, a gradualistic model for stomatal control proposes that the most basal vascular plant stomata responded passively to changes in leaf water status. This model suggests that active ABA-driven mechanisms for stomatal responses to water status instead evolved after the divergence of seed plants, culminating in the complex, ABA-mediated responses observed in modern angiosperms. Here we review the findings that form the basis for these two models, including recent work that provides critical molecular insights into resolving this intriguing debate, and find strong evidence to support a gradualistic model for stomatal evolution.
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Affiliation(s)
- Frances C Sussmilch
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
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62
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Mitchell PJ, McAdam SAM, Pinkard EA, Brodribb TJ. Significant contribution from foliage-derived ABA in regulating gas exchange in Pinus radiata. TREE PHYSIOLOGY 2017; 37:236-245. [PMID: 28399262 DOI: 10.1093/treephys/tpw092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 08/20/2016] [Indexed: 06/07/2023]
Abstract
The complex regulatory system controlling stomata involves physical and chemical signals that affect guard cell turgor to bring about changes in stomatal conductance (gs). Abscisic acid (ABA) closes stomata, yet the mechanisms controlling foliar ABA status in tree species remain unclear. The importance of foliage-derived ABA in regulating gas exchange was evaluated under treatments that affected phloem export through girdling and reduced water availability in the tree species, Pinus radiata (D. Don). Branch- and whole-plant girdling increased foliar ABA levels leading to declines in gs, despite no change in plant water status. Changes in gs were largely independent of the more transient increases in foliar non-structural carbohydrates (NSC), suggesting that gradual accumulation of foliar ABA was the primary mechanism for reductions in gs and assimilation. Whole-plant girdling eventually reduced root NSC, hindering root water uptake and decreasing foliar water potential, causing a dramatic increase in ABA level in leaves and concentrations in the xylem sap of shoots (4032 ng ml-1), while root xylem sap concentrations remained low (43 ng ml-1). Contrastingly, the drought treatment caused similar increases in xylem sap ABA in both roots and shoots, suggesting that declines in water potential result in relatively consistent changes in ABA along the hydraulic pathway. ABA levels in plant canopies can be regulated independently of changes in root water status triggered by changes by both phloem export and foliar water status.
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Affiliation(s)
| | - Scott A M McAdam
- School of Biological Sciences, University of Tasmania, College Rd, Hobart, Tasmania 7005, Australia
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63
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Fanourakis D, Bouranis D, Giday H, Carvalho DRA, Rezaei Nejad A, Ottosen CO. Improving stomatal functioning at elevated growth air humidity: A review. JOURNAL OF PLANT PHYSIOLOGY 2016; 207:51-60. [PMID: 27792901 DOI: 10.1016/j.jplph.2016.10.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 10/07/2016] [Indexed: 05/05/2023]
Abstract
Plants grown at high relative air humidity (RH≥85%) are prone to lethal wilting upon transfer to conditions of high evaporative demand. The reduced survival of these plants is related to (i) increased cuticular permeability, (ii) changed anatomical features (i.e., longer pore length and higher stomatal density), (iii) reduced rehydration ability, (iv) impaired water potential sensitivity to leaf dehydration and, most importantly, (v) compromised stomatal closing ability. This review presents a critical analysis of the strategies which stimulate stomatal functioning during plant development at high RH. These include (a) breeding for tolerant cultivars, (b) interventions with respect to the belowground environment (i.e., water deficit, increased salinity, nutrient culture and grafting) as well as (c) manipulation of the aerial environment [i.e., increased proportion of blue light, increased air movement, temporal temperature rise, and spraying with abscisic acid (ABA)]. Root hypoxia, mechanical disturbance, as well as spraying with compounds mimicking ABA, lessening its inactivation or stimulating its within-leaf redistribution are also expected to improve stomatal functioning of leaves expanded in humid air. Available evidence leaves little doubt that genotypic and phenotypic differences in stomatal functioning following cultivation at high RH are realized through the intermediacy of ABA.
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Affiliation(s)
- Dimitrios Fanourakis
- School of Agricultural Technology, Technological Educational Institute of Crete, GR 71004 Heraklio, Greece.
| | - Dimitrios Bouranis
- Plant Physiology and Morphology Laboratory, Crop Science Department, Agricultural University of Athens, Athens, Greece
| | - Habtamu Giday
- Horticulture and Product Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Dália R A Carvalho
- Horticulture and Product Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Abdolhossein Rezaei Nejad
- Department of Horticultural Sciences, Faculty of Agriculture, Lorestan University, P.O. Box 465, Khorramabad, Iran
| | - Carl-Otto Ottosen
- Aarhus University, Department of Food Science, Kirstinebjergvej 10, DK-5792 Årslev, Denmark
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64
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Chaves MM, Costa JM, Zarrouk O, Pinheiro C, Lopes CM, Pereira JS. Controlling stomatal aperture in semi-arid regions-The dilemma of saving water or being cool? PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2016; 251:54-64. [PMID: 27593463 DOI: 10.1016/j.plantsci.2016.06.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 06/14/2016] [Accepted: 06/22/2016] [Indexed: 05/24/2023]
Abstract
Stomatal regulation of leaf gas exchange with the atmosphere is a key process in plant adaptation to the environment, particularly in semi-arid regions with high atmospheric evaporative demand. Development of stomata, integrating internal signaling and environmental cues sets the limit for maximum diffusive capacity of stomata, through size and density and is under a complex genetic control, thus providing multiple levels of regulation. Operational stomatal conductance to water vapor and CO2 results from feed-back and/or feed-forward mechanisms and is the end-result of a plethora of signals originated in leaves and/or in roots at each moment. CO2 assimilation versus water vapor loss, proposed to be the subject of optimal regulation, is species dependent and defines the water use efficiency (WUE). WUE has been a topic of intense research involving areas from genetics to physiology. In crop plants, especially in semi-arid regions, the question that arises is how the compromise of reducing transpiration to save water will impact on plant performance through leaf temperature. Indeed, plant transpiration by providing evaporative cooling, is a major component of the leaf energy balance. In this paper we discuss the dilemma of 'saving water or being cool' bringing about recent findings from molecular genetics, to development and physiology of stomata. The question of 'how relevant is screening for high/low WUE in crops for semi-arid regions, where drought and heat co-occur' is discussed.
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Affiliation(s)
- M M Chaves
- Plant Molecular Physiology Laboratory, ITQBNOVA, Universidade Nova de Lisboa, Oeiras, Portugal.
| | - J M Costa
- Plant Molecular Physiology Laboratory, ITQBNOVA, Universidade Nova de Lisboa, Oeiras, Portugal; LEAF, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, Lisboa, Portugal
| | - O Zarrouk
- Plant Molecular Physiology Laboratory, ITQBNOVA, Universidade Nova de Lisboa, Oeiras, Portugal
| | - C Pinheiro
- Plant Molecular Physiology Laboratory, ITQBNOVA, Universidade Nova de Lisboa, Oeiras, Portugal; Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica 2829-516, Portugal
| | - C M Lopes
- LEAF, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, Lisboa, Portugal
| | - J S Pereira
- LEAF, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, Lisboa, Portugal
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65
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Marchin RM, Broadhead AA, Bostic LE, Dunn RR, Hoffmann WA. Stomatal acclimation to vapour pressure deficit doubles transpiration of small tree seedlings with warming. PLANT, CELL & ENVIRONMENT 2016; 39:2221-2234. [PMID: 27392307 DOI: 10.1111/pce.12790] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 06/28/2016] [Accepted: 07/01/2016] [Indexed: 06/06/2023]
Abstract
Future climate change is expected to increase temperature (T) and atmospheric vapour pressure deficit (VPD) in many regions, but the effect of persistent warming on plant stomatal behaviour is highly uncertain. We investigated the effect of experimental warming of 1.9-5.1 °C and increased VPD of 0.5-1.3 kPa on transpiration and stomatal conductance (gs ) of tree seedlings in the temperate forest understory (Duke Forest, North Carolina, USA). We observed peaked responses of transpiration to VPD in all seedlings, and the optimum VPD for transpiration (Dopt ) shifted proportionally with increasing chamber VPD. Warming increased mean water use of Carya by 140% and Quercus by 150%, but had no significant effect on water use of Acer. Increased water use of ring-porous species was attributed to (1) higher air T and (2) stomatal acclimation to VPD resulting in higher gs and more sensitive stomata, and thereby less efficient water use. Stomatal acclimation maintained homeostasis of leaf T and carbon gain despite increased VPD, revealing that short-term stomatal responses to VPD may not be representative of long-term exposure. Acclimation responses differ from expectations of decreasing gs with increasing VPD and may necessitate revision of current models based on this assumption.
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Affiliation(s)
- Renée M Marchin
- Centre for Carbon, Water and Food, University of Sydney, Camden, New South Wales, 2570, Australia.
- Department of Plant Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA.
| | - Alice A Broadhead
- Department of Plant Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
| | - Laura E Bostic
- Department of Plant Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
| | - Robert R Dunn
- Department of Applied Ecology and Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC, 27695-7617, USA
- Center for Macroecology, Evolution and Climate, Natural History Museum of Denmark, University of Copenhagen, DK-2100, Copenhagen, Denmark
| | - William A Hoffmann
- Department of Plant Biology, North Carolina State University, Raleigh, NC, 27695-7612, USA
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66
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Rodriguez-Dominguez CM, Buckley TN, Egea G, de Cires A, Hernandez-Santana V, Martorell S, Diaz-Espejo A. Most stomatal closure in woody species under moderate drought can be explained by stomatal responses to leaf turgor. PLANT, CELL & ENVIRONMENT 2016; 39:2014-26. [PMID: 27255698 DOI: 10.1111/pce.12774] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 05/17/2016] [Accepted: 05/17/2016] [Indexed: 05/21/2023]
Abstract
Reduced stomatal conductance (gs ) during soil drought in angiosperms may result from effects of leaf turgor on stomata and/or factors that do not directly depend on leaf turgor, including root-derived abscisic acid (ABA) signals. To quantify the roles of leaf turgor-mediated and leaf turgor-independent mechanisms in gs decline during drought, we measured drought responses of gs and water relations in three woody species (almond, grapevine and olive) under a range of conditions designed to generate independent variation in leaf and root turgor, including diurnal variation in evaporative demand and changes in plant hydraulic conductance and leaf osmotic pressure. We then applied these data to a process-based gs model and used a novel method to partition observed declines in gs during drought into contributions from each parameter in the model. Soil drought reduced gs by 63-84% across species, and the model reproduced these changes well (r(2) = 0.91, P < 0.0001, n = 44) despite having only a single fitted parameter. Our analysis concluded that responses mediated by leaf turgor could explain over 87% of the observed decline in gs across species, adding to a growing body of evidence that challenges the root ABA-centric model of stomatal responses to drought.
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Affiliation(s)
- Celia M Rodriguez-Dominguez
- Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes 10, 41012, Seville, Spain
- Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Seville, Spain
| | - Thomas N Buckley
- IA Watson Grains Research Centre, Plant Breeding Institute, Faculty of Agriculture and Environment, The University of Sydney, Narrabri, NSW, 2390, Australia
| | - Gregorio Egea
- Área de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agronómica, Universidad de Sevilla, Ctra Utrera, km 1, 41013, Seville, Spain
| | - Alfonso de Cires
- Departamento de Biología Vegetal y Ecología, Universidad de Sevilla, Seville, Spain
| | - Virginia Hernandez-Santana
- Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes 10, 41012, Seville, Spain
| | - Sebastia Martorell
- Research Group on Plant Biology under Mediterranean Conditions, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, 07122, Palma, Illes Balears, Spain
| | - Antonio Diaz-Espejo
- Irrigation and Crop Ecophysiology Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes 10, 41012, Seville, Spain
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McAdam SAM, Brodribb TJ. Linking Turgor with ABA Biosynthesis: Implications for Stomatal Responses to Vapor Pressure Deficit across Land Plants. PLANT PHYSIOLOGY 2016; 171:2008-16. [PMID: 27208264 PMCID: PMC4936570 DOI: 10.1104/pp.16.00380] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/07/2016] [Indexed: 05/05/2023]
Abstract
Stomatal responses to changes in vapor pressure deficit (VPD) constitute the predominant form of daytime gas-exchange regulation in plants. Stomatal closure in response to increased VPD is driven by the rapid up-regulation of foliar abscisic acid (ABA) biosynthesis and ABA levels in angiosperms; however, very little is known about the physiological trigger for this increase in ABA biosynthesis at increased VPD Using a novel method of modifying leaf cell turgor by the application of external pressures, we test whether changes in turgor pressure can trigger increases in foliar ABA levels over 20 min, a period of time most relevant to the stomatal response to VPD We found in angiosperm species that the biosynthesis of ABA was triggered by reductions in leaf turgor, and in two species tested, that a higher sensitivity of ABA synthesis to leaf turgor corresponded with a higher stomatal sensitivity to VPD In contrast, representative species from nonflowering plant lineages did not show a rapid turgor-triggered increase in foliar ABA levels, which is consistent with previous studies demonstrating passive stomatal responses to changes in VPD in these lineages. Our method provides a new tool for characterizing the response of stomata to water availability.
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Affiliation(s)
- Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia
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McAdam SAM, Manzi M, Ross JJ, Brodribb TJ, Gómez-Cadenas A. Uprooting an abscisic acid paradigm: Shoots are the primary source. PLANT SIGNALING & BEHAVIOR 2016; 11:e1169359. [PMID: 27031537 PMCID: PMC4973758 DOI: 10.1080/15592324.2016.1169359] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In the past, a conventional wisdom has been that abscisic acid (ABA) is a xylem-transported hormone that is synthesized in the roots, while acting in the shoot to close stomata in response to a decrease in plant water status. Now, however, evidence from two studies, which we have conducted independently, challenges this root-sourced ABA paradigm. We show that foliage-derived ABA has a major influence over root development and that leaves are the predominant location for ABA biosynthesis during drought stress.
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Affiliation(s)
- Scott A. M. McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Australia
- CONTACT Scott A. M. McAdam ; Aurelio Gómez-Cadenas
| | - Matías Manzi
- Ecofisiologia y Biotecnologia, Dept. Ciències Agraries i del Medi Natural, Universitat Jaume I. Castellón de la Plana, Spain
| | - John J. Ross
- School of Biological Sciences, University of Tasmania, Hobart, Australia
| | | | - Aurelio Gómez-Cadenas
- Ecofisiologia y Biotecnologia, Dept. Ciències Agraries i del Medi Natural, Universitat Jaume I. Castellón de la Plana, Spain
- CONTACT Scott A. M. McAdam ; Aurelio Gómez-Cadenas
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69
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McAdam SAM, Brodribb TJ, Ross JJ. Shoot-derived abscisic acid promotes root growth. PLANT, CELL & ENVIRONMENT 2016; 39:652-9. [PMID: 26514625 DOI: 10.1111/pce.12669] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 10/19/2015] [Accepted: 10/26/2015] [Indexed: 05/18/2023]
Abstract
The phytohormone abscisic acid (ABA) plays a major role in regulating root growth. Most work to date has investigated the influence of root-sourced ABA on root growth during water stress. Here, we tested whether foliage-derived ABA could be transported to the roots, and whether this foliage-derived ABA had an influence on root growth under well-watered conditions. Using both application studies of deuterium-labelled ABA and reciprocal grafting between wild-type and ABA-biosynthetic mutant plants, we show that both ABA levels in the roots and root growth in representative angiosperms are controlled by ABA synthesized in the leaves rather than sourced from the roots. Foliage-derived ABA was found to promote root growth relative to shoot growth but to inhibit the development of lateral roots. Increased root auxin (IAA) levels in plants with ABA-deficient scions suggest that foliage-derived ABA inhibits root growth through the root growth-inhibitor IAA. These results highlight the physiological and morphological importance, beyond the control of stomata, of foliage-derived ABA. The use of foliar ABA as a signal for root growth has important implications for regulating root to shoot growth under normal conditions and suggests that leaf rather than root hydration is the main signal for regulating plant responses to moisture.
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Affiliation(s)
- Scott A M McAdam
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Timothy J Brodribb
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - John J Ross
- School of Biological Sciences, University of Tasmania, Hobart, Tasmania, 7001, Australia
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