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Kupper P, Tullus A, Rohula-Okunev G. Night-time water relations and gas exchange in cut shoots of five boreal dwarf shrub species: impact of soil water availability. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2023; 29:1193-1203. [PMID: 37829697 PMCID: PMC10564692 DOI: 10.1007/s12298-023-01350-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 08/03/2023] [Accepted: 08/21/2023] [Indexed: 10/14/2023]
Abstract
Recent findings suggest that drought may affect plants' daytime and night-time stomatal regulation differently. However, knowledge of night-time stomatal behaviour in dwarf shrubs growing in boreal ecosystems is lacking. We sampled cut shoots from dwarf shrub species to elucidate their capacity to transpire at night and the effect of drought on stomatal regulation. The shoots' water relations and gas exchange were measured under controlled conditions in a growth chamber. The studied species demonstrated considerable differences in their diurnal water use. The night-time water use percentage of daytime water use (NWU) reached up to 90% in Andromeda polifolia and Vaccinium uliginosum. In Rhododendron tomentosum, Vaccinium myrtillus and Chamaedaphne calyculata, the NWU was 62, 27 and 26%, respectively. The shoots of C. calyculata showed a significant increase (P < 0.001) in the transpiration rate (E) during the night. However, in R. tomentosum, a decrease (P < 0.05) in nightly E was observed. The shoot conductance (g) at the end of the night was lower than daytime g in all studied species, but the difference was not significant for V. uliginosum. Across the species, NWU was negatively related (P < 0.001) to the soil volumetric water content (SWC) in the plant habitat. However, daytime E and g were positively related (P < 0.05) to the habitat SWC. Only in V. myrtillus was night-time E higher (P < 0.05) in dry conditions than in wet conditions. Our results demonstrate high variability in diurnal water relations in dwarf shrubs, which can keep stomata open in the dark even when drought limits daytime g and E.
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Affiliation(s)
- Priit Kupper
- Institute of Ecology and Earth Sciences, University of Tartu, Liivi 2, 50409 Tartu, Estonia
| | - Arvo Tullus
- Institute of Ecology and Earth Sciences, University of Tartu, Liivi 2, 50409 Tartu, Estonia
| | - Gristin Rohula-Okunev
- Institute of Ecology and Earth Sciences, University of Tartu, Liivi 2, 50409 Tartu, Estonia
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Nagamalla SS, Alaparthi MD, Mellacheruvu S, Gundeti R, Earrawandla JPS, Sagurthi SR. Morpho-Physiological and Proteomic Response of Bt-Cotton and Non-Bt Cotton to Drought Stress. FRONTIERS IN PLANT SCIENCE 2021; 12:663576. [PMID: 34040622 PMCID: PMC8143030 DOI: 10.3389/fpls.2021.663576] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 03/23/2021] [Indexed: 06/12/2023]
Abstract
Drought stress impacts cotton plant growth and productivity across countries. Plants can initiate morphological, cellular, and proteomic changes to adapt to unfavorable conditions. However, our knowledge of how cotton plants respond to drought stress at the proteome level is limited. Herein, we elucidated the molecular coordination underlining the drought tolerance of two inbred cotton varieties, Bacillus thuringiensis-cotton [Bt-cotton + Cry1 Ac gene and Cry 2 Ab gene; NCS BG II BT (BTCS/BTDS)] and Hybrid cotton variety [Non-Bt-cotton; (HCS/HDS)]. Our morphological observations and biochemical experiments showed a different tolerance level between two inbred lines to drought stress. Our proteomic analysis using 2D-DIGE revealed that the changes among them were not obviously in respect to their controls apart from under drought stress, illustrating the differential expression of 509 and 337 proteins in BTDS and HDS compared to their controls. Among these, we identified eight sets of differentially expressed proteins (DEPs) and characterized them using MALDI-TOF/TOF mass spectrometry. Furthermore, the quantitative real-time PCR analysis was carried out with the identified drought-related proteins and confirmed differential expressions. In silico analysis of DEPs using Cytoscape network finds ATPB, NAT9, ERD, LEA, and EMB2001 to be functionally correlative to various drought-responsive genes LEA, AP2/ERF, WRKY, and NAC. These proteins play a vital role in transcriptomic regulation under stress conditions. The higher drought response in Bt cotton (BTCS/BTDS) attributed to the overexpression of photosynthetic proteins enhanced lipid metabolism, increased cellular detoxification and activation chaperones, and reduced synthesis of unwanted proteins. Thus, the Bt variety had enhanced photosynthesis, elevated water retention potential, balanced leaf stomata ultrastructure, and substantially increased antioxidant activity than the Non-Bt cotton. Our results may aid breeders and provide further insights into developing new drought-tolerant and high-yielding cotton hybrid varieties.
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Matthews JSA, Vialet-Chabrand S, Lawson T. Role of blue and red light in stomatal dynamic behaviour. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:2253-2269. [PMID: 31872212 PMCID: PMC7134916 DOI: 10.1093/jxb/erz563] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/19/2019] [Indexed: 05/20/2023]
Abstract
Plants experience changes in light intensity and quality due to variations in solar angle and shading from clouds and overlapping leaves. Stomatal opening to increasing irradiance is often an order of magnitude slower than photosynthetic responses, which can result in CO2 diffusional limitations on leaf photosynthesis, as well as unnecessary water loss when stomata continue to open after photosynthesis has reached saturation. Stomatal opening to light is driven by two distinct pathways; the 'red' or photosynthetic response that occurs at high fluence rates and saturates with photosynthesis, and is thought to be the main mechanism that coordinates stomatal behaviour with photosynthesis; and the guard cell-specific 'blue' light response that saturates at low fluence rates, and is often considered independent of photosynthesis, and important for early morning stomatal opening. Here we review the literature on these complicated signal transduction pathways and osmoregulatory processes in guard cells that are influenced by the light environment. We discuss the possibility of tuning the sensitivity and magnitude of stomatal response to blue light which potentially represents a novel target to develop ideotypes with the 'ideal' balance between carbon gain, evaporative cooling, and maintenance of hydraulic status that is crucial for maximizing crop performance and productivity.
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Affiliation(s)
- Jack S A Matthews
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, UK
| | | | - Tracy Lawson
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester, UK
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Gao J, Tian K. Stem and leaf traits as co-determinants of canopy water flux. PLANT DIVERSITY 2019; 41:258-265. [PMID: 31528785 PMCID: PMC6743011 DOI: 10.1016/j.pld.2019.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/10/2019] [Accepted: 06/12/2019] [Indexed: 05/26/2023]
Abstract
Transpiration through stomata in tree canopies plays an important role in terrestrial water cycles. However, the empirical relationship between leaf stomata anatomy and canopy stomatal conductance (G s) is surprisingly rare, thereby the underlying biological mechanisms of terrestrial water flux are not well elucidated. To gain further insight into these mechanisms, we reanalyzed the dataset of G s previously reported by Gao et al. (2015) using a quantile regression model. The results indicated that the reference G s (G sref, G s at 1 kPa) was negatively correlated with wood density at each quantile, which confirmed previous data; however, G sref was significantly correlated with stomatal density at the 0.6 quantile, i.e., 450 stomata mm-2. This highlighted the potential of using stomatal density as a trait to predict canopy water flux. A conceptual model of co-determinants of xylem and stomatal morphology suggests that these traits and their coordination may play a critical role in determining tree growth, physiological homeostatic response to environmental variables, water use efficiency, and drought resistance.
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Affiliation(s)
- Jianguo Gao
- Department of Ecology, College of Urban and Environmental Sciences, Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, No.5 Yiheyuan Road Haidian District, Beijing, 100871, PR China
- Coastal Ecosystems Research Station of the Yangtze River Estuary, Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, Shanghai, 200438, PR China
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Chinese Academy of Sciences, South China Botanical Garden, Guangzhou, 510650, PR China
| | - Kai Tian
- School of Life Sciences, Nanjing University, Nanjing, 210023, PR China
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Henry C, John GP, Pan R, Bartlett MK, Fletcher LR, Scoffoni C, Sack L. A stomatal safety-efficiency trade-off constrains responses to leaf dehydration. Nat Commun 2019; 10:3398. [PMID: 31363097 PMCID: PMC6667445 DOI: 10.1038/s41467-019-11006-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 06/10/2019] [Indexed: 01/08/2023] Open
Abstract
Stomata, the microvalves on leaf surfaces, exert major influences across scales, from plant growth and productivity to global carbon and water cycling. Stomatal opening enables leaf photosynthesis, and plant growth and water use, whereas plant survival of drought depends on stomatal closure. Here we report that stomatal function is constrained by a safety-efficiency trade-off, such that species with greater stomatal conductance under high water availability (gmax) show greater sensitivity to closure during leaf dehydration, i.e., a higher leaf water potential at which stomatal conductance is reduced by 50% (Ψgs50). The gmax - Ψgs50 trade-off and its mechanistic basis is supported by experiments on leaves of California woody species, and in analyses of previous studies of the responses of diverse flowering plant species around the world. Linking the two fundamental key roles of stomata-the enabling of gas exchange, and the first defense against drought-this trade-off constrains the rates of water use and the drought sensitivity of leaves, with potential impacts on ecosystems.
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Affiliation(s)
- Christian Henry
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - Grace P John
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
- Department of Integrative Biology, University of Texas at Austin, 2415 Speedway, Austin, TX, 78712, USA
| | - Ruihua Pan
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
- School of Ecology and Environment, Inner Mongolia University, 235 University West Road, 010021, Hohhot, Inner Mongolia, China
| | - Megan K Bartlett
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
- Department of Viticulture and Enology, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
| | - Leila R Fletcher
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
| | - Christine Scoffoni
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA
- Department of Biological Sciences, California State University, Los Angeles, 5151 State University Drive, Los Angeles, CA, 90032, USA
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA.
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Zhao XW, Ouyang L, Zhao P, Zhang CF. Effects of size and microclimate on whole-tree water use and hydraulic regulation in Schima superba trees. PeerJ 2018; 6:e5164. [PMID: 30002983 PMCID: PMC6037140 DOI: 10.7717/peerj.5164] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 06/15/2018] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Plant-water relations have been of significant concern in forestry and ecology studies in recent years, yet studies investigating the annual differences in the characteristics of inter-class water consumption in trees are scarce. METHODS We classified 15 trees from a Schima superba plantation in subtropical South China into four ranks using diameter at breast height (DBH). The inter-class and whole-tree water use were compared based on three parameters: sap flux density, whole-tree transpiration and canopy transpiration over two years. Inter-class hydraulic parameters, such as leaf water potential, stomatal conductance, hydraulic conductance, and canopy conductance were also compared. RESULTS (1) Mean water consumption of the plantation was 287.6 mm over a year, 165.9 mm in the wet season, and 121.7 mm in the dry season. Annual mean daily water use was 0.79 mm d-1, with a maximum of 1.39 mm d-1. (2) Isohydrodynamic behavior were found in S. superba. (3) Transpiration was regulated via both hydraulic conductance and stoma; however, there was an annual difference in which predominantly regulated transpiration. DISCUSSION This study quantified annual and seasonal water use of a S. superba plantation and revealed the coordinated effect of stoma and hydraulic conductance on transpiration. These results provide information for large-scale afforestation and future water management.
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Affiliation(s)
- Xiao-wei Zhao
- College of Life Sciences, Yulin University, Yulin, Shan Xi, PR China
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, Guangdong, PR China
| | - Lei Ouyang
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, Guangdong, PR China
| | - Ping Zhao
- Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, Guangdong, PR China
| | - Chun-fang Zhang
- Department of Life Sciences, Yuncheng College, Yuncheng, Shan Xi, PR China
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Creese C, Oberbauer S, Rundel P, Sack L. Are fern stomatal responses to different stimuli coordinated? Testing responses to light, vapor pressure deficit, and CO2 for diverse species grown under contrasting irradiances. THE NEW PHYTOLOGIST 2014; 204:92-104. [PMID: 25077933 DOI: 10.1111/nph.12922] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Accepted: 05/17/2014] [Indexed: 05/10/2023]
Abstract
The stomatal behavior of ferns provides an excellent system for disentangling responses to different environmental signals, which balance carbon gain against water loss. Here, we measured responses of stomatal conductance (gs ) to irradiance, CO2 , and vapor pressure deficit (VPD) for 13 phylogenetically diverse species native to open and shaded habitats, grown under high- and low-irradiance treatments. We tested two main hypotheses: that plants adapted and grown in high-irradiance environments would have greater responsiveness to all stimuli given higher flux rates; and that species' responsiveness to different factors would be correlated because of the relative simplicity of fern stomatal control. We found that species with higher light-saturated gs had larger responses, and that plants grown under high irradiance were more responsive to all stimuli. Open habitat species showed greater responsiveness to irradiance and CO2 , but lower responsiveness to VPD; a case of plasticity and adaptation tending in different directions. Responses of gs to irradiance and VPD were positively correlated across species, but CO2 responses were independent and highly variable. The novel finding of correlations among stomatal responses to different stimuli suggests coordination of hydraulic and photosynthetic signaling networks modulating fern stomatal responses, which show distinct optimization at growth and evolutionary time-scales.
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Affiliation(s)
- Chris Creese
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Box 951606, Los Angeles, CA, 90095-1606, USA
| | - Steve Oberbauer
- Department of Biological Sciences, Florida International University, Miami, FL, 33199, USA
| | - Phil Rundel
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Box 951606, Los Angeles, CA, 90095-1606, USA
| | - Lawren Sack
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Box 951606, Los Angeles, CA, 90095-1606, USA
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Merilo E, Jõesaar I, Brosché M, Kollist H. To open or to close: species-specific stomatal responses to simultaneously applied opposing environmental factors. THE NEW PHYTOLOGIST 2014; 202:499-508. [PMID: 24392838 DOI: 10.1111/nph.12667] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 11/30/2013] [Indexed: 05/07/2023]
Abstract
Plant stomatal responses to single environmental factors are well studied; however, responses to a change in two (or more) factors - a common situation in nature - have been less frequently addressed. We studied the stomatal responses to a simultaneous application of opposing environmental factors in six evolutionarily distant mono- and dicotyledonous herbs representing different life strategies (ruderals, competitors and stress-tolerators) to clarify whether the crosstalk between opening- and closure-inducing pathways leading to stomatal response is universal or species-specific. Custom-made gas exchange devices were used to study the stomatal responses to a simultaneous application of two opposing factors: decreased/increased CO2 concentration and light availability or reduced air humidity. The studied species responded similarly to changes in single environmental factors, but showed species-specific and nonadditive responses to two simultaneously applied opposing factors. The stomata of the ruderals Arabidopsis thaliana and Thellungiella salsuginea (previously Thellungiella halophila) always opened, whereas those of competitor-ruderals either closed in all two-factor combinations (Triticum aestivum), remained relatively unchanged (Nicotiana tabacum) or showed a response dominated by reduced air humidity (Hordeum vulgare). Our results, indicating that in changing environmental conditions species-specific stomatal responses are evident that cannot be predicted from studying one factor at a time, might be interesting for stomatal modellers, too.
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Affiliation(s)
- Ebe Merilo
- Institute of Technology, University of Tartu, Nooruse 1, 50411, Tartu, Estonia
| | - Indrek Jõesaar
- Institute of Technology, University of Tartu, Nooruse 1, 50411, Tartu, Estonia
| | - Mikael Brosché
- Institute of Technology, University of Tartu, Nooruse 1, 50411, Tartu, Estonia
- Division of Plant Biology, Department of Biosciences, University of Helsinki, PO Box 65 (Viikinkaari 1), FI-00014, Helsinki, Finland
| | - Hannes Kollist
- Institute of Technology, University of Tartu, Nooruse 1, 50411, Tartu, Estonia
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Sellin A, Niglas A, Õunapuu-Pikas E, Kupper P. Rapid and long-term effects of water deficit on gas exchange and hydraulic conductance of silver birch trees grown under varying atmospheric humidity. BMC PLANT BIOLOGY 2014; 14:72. [PMID: 24655599 PMCID: PMC3976162 DOI: 10.1186/1471-2229-14-72] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 03/20/2014] [Indexed: 05/04/2023]
Abstract
BACKGROUND Effects of water deficit on plant water status, gas exchange and hydraulic conductance were investigated in Betula pendula under artificially manipulated air humidity in Eastern Estonia. The study was aimed to broaden an understanding of the ability of trees to acclimate with the increasing atmospheric humidity predicted for northern Europe. Rapidly-induced water deficit was imposed by dehydrating cut branches in open-air conditions; long-term water deficit was generated by seasonal drought. RESULTS The rapid water deficit quantified by leaf (ΨL) and branch water potentials (ΨB) had a significant (P < 0.001) effect on gas exchange parameters, while inclusion of ΨB in models resulted in a considerably better fit than those including ΨL, which supports the idea that stomatal openness is regulated to prevent stem rather than leaf xylem dysfunction. Under moderate water deficit (ΨL≥-1.55 MPa), leaf conductance to water vapour (gL), transpiration rate and leaf hydraulic conductance (KL) were higher (P < 0.05) and leaf temperature lower in trees grown in elevated air humidity (H treatment) than in control trees (C treatment). Under severe water deficit (ΨL<-1.55 MPa), the treatments showed no difference. The humidification manipulation influenced most of the studied characteristics, while the effect was to a great extent realized through changes in soil water availability, i.e. due to higher soil water potential in H treatment. Two functional characteristics (gL, KL) exhibited higher (P < 0.05) sensitivity to water deficit in trees grown under increased air humidity. CONCLUSIONS The experiment supported the hypothesis that physiological traits in trees acclimated to higher air humidity exhibit higher sensitivity to rapid water deficit with respect to two characteristics - leaf conductance to water vapour and leaf hydraulic conductance. Disproportionate changes in sensitivity of stomatal versus leaf hydraulic conductance to water deficit will impose greater risk of desiccation-induced hydraulic dysfunction on the plants, grown under high atmospheric humidity, in case of sudden weather fluctuations, and might represent a potential threat in hemiboreal forest ecosystems. There is no trade-off between plant hydraulic capacity and photosynthetic water-use efficiency on short time scale.
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Affiliation(s)
- Arne Sellin
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu 51005, Estonia
| | - Aigar Niglas
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu 51005, Estonia
| | - Eele Õunapuu-Pikas
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu 51005, Estonia
| | - Priit Kupper
- Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu 51005, Estonia
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Arve LE, Terfa MT, Gislerød HR, Olsen JE, Torre S. High relative air humidity and continuous light reduce stomata functionality by affecting the ABA regulation in rose leaves. PLANT, CELL & ENVIRONMENT 2013; 36:382-92. [PMID: 22812416 DOI: 10.1111/j.1365-3040.2012.02580.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Plants developed under high (90%) relative air humidity (RH) have previously been shown to have large, malfunctioning stomata, which results in high water loss during desiccation and reduced dark induced closure. Stomatal movement is to a large extent regulated by abscisic acid (ABA). It has therefore been proposed that low ABA levels contribute to the development of malfunctioning stomata. In this study, we investigated the regulation of ABA content in rose leaves, through hormone analysis and β-glucosidase quantification. Compared with high RH, rose plants developed in moderate RH (60%) and 20 h photoperiod contained higher levels of ABA and β-glucosidase activity. Also, the amount of ABA increased during darkness simultaneously as the ABA-glucose ester (GE) levels decreased. In contrast, plants developed under high RH with 20 h photoperiod showed no increase in ABA levels during darkness, and had low β-glucosidase activity converting ABA-GE to ABA. Continuous lighting (24 h) resulted in low levels of β-glucosidase activity irrespective of RH, indicating that a dark period is essential to activate β-glucosidase. Our results provide new insight into the regulation of ABA under different humidities and photoperiods, and clearly show that β-glucosidase is a key enzyme regulating the ABA pool in rose plants.
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Affiliation(s)
- Louise E Arve
- Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 Aas, Norway
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Abstract
When stomata first evolved they initiated the greening of terrestrial earth, and now more than 400 million years later these simple bi-cellular valves in the leaf surface regulate global fluxes of water and carbon. Despite their importance and superficial simplicity, the behaviour of stomata remains a great challenge to understand. Different approaches to studying stomatal control have yielded rather disparate models for how stomata respond to environmental stimuli. Much of this discord arises from the diversity of mechanisms apparently involved in changing guard cell turgor and hence the aperture of the stomatal pore. On the one hand, the physical tension produced by dragging water from the soil through the xylem to the leaves directly influences leaf and guard cell turgor, while on the other hand, phytohormone levels (most importantly abscisic acid), light, photosynthesis and atmospheric gases induce active changes in guard cell turgor by triggering ionic pumping. Each stomatal control mechanism has its own champion and no model has ever successfully integrated all components. In such an environment there is great value in examining how different parts of the stomatal control network interact, particularly the competition between 'hydraulic' signals related to leaf water content and 'metabolic' signals related to ambient photosynthetic conditions.
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Affiliation(s)
- T J Brodribb
- School of Plant Science, University of Tasmania, Bag 55, Hobart 7001, Australia.
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