Ecogeomorfologia i drons com a eines de gestió dinàmica postincendi. El cas de la comarca del Pariatge, Mallorca

Ecogeomorphology and drones as dynamic tools for post-fire management. The experience in the Pariatge County, Mallorca Wildfires are one of the most significant driving factors in desertification processes. Furthermore, insular territories such Mallorca are more affected by human impacts due to their intrinsic socioecological fragility. The increase of burned surface area since 2011 in Balearic Islands involves a challenge in which forest management and research through interdisciplinary and technological advances should be joined. Ecogeomorphology is an emergent discipline which allows investigating the role of geomorphic processes in the vegetation recovery. Additionally, the introduction of unmanned aerial vehicles as remotesensing tools offers new and exciting opportunities for monitoring environmental processes. This paper pretends to elucidate the potential of ecogeomorphology and drones to implement more effective and dynamic post-fire management integrating both the resilience capacity of ecosystems with sediment connectivity for landscape restoration.Els incendis forestals són considerats un dels factors causals més importants en els processos de desertificació. Els territoris insulars com Mallorca són particularment sensibles als impactes antròpics, per la seva major fragilitat socioecològica. L?increment de superfície cremada a Mallorca d?ençà el 2011 esperoneja a vincular gestió forestal i recerca amb interdisciplinarietat i avenços tecnològics. L?ecogeomorfologia permet investigar el paper dels processos geomorfològics en la recuperació de la vegetació. Endemés, la introducció dels vehicles aeris no tripulats com a instruments de teledetecció presenta noves oportunitats en el monitoratge de processos ambientals. Aquest article pretén dilucidar el potencial de l?ecogeomorfologia i els drons per aplicar una gestió postincendi més efectiva i dinàmica, integrant la capacitat de resiliència dels ecosistemes amb la connectivitat dels sediments per restaurar el paisatge.Ecogeomorfología y drones como instrumentos de gestión dinámica post-incendio. El caso de la comarca del Pariatge, Mallorca Los incendios forestales son uno de los factores causales más importantes en los procesos de desertificación. Los territorios insulares como Mallorca son particularmente sensibles a los impactos antrópicos, a causa de su mayor fragilidad socioecológica. El incremento de superficie quemada en Mallorca desde el año 2011 incita vincular gestión forestal e investigación a través de interdisciplinariedad y avances tecnológicos. La ecogeomorfología permite investigar el papel de los procesos geomorfológicos en la recuperación de la vegetación. Además, la introducción de vehículos aéreos no tripulados como instrumentos de teledetección presenta nuevas oportunidades en la monitorización de procesos ambientales. Este artículo pretende dilucidar el potencial de la ecogeomorfología y de los drones para aplicar una gestión post-incendio más efectiva y dinámica, integrando la capacidad de resiliencia de los ecosistemas con la conectividad de los sedimentos para restaurar el paisaje

Different metabolic roles for alternative oxidase in leaves of palustrine and terrestrial species

The alternative oxidase pathway (AOP) is associated with excess energy dissipation in leaves of terrestrial plants. To address whether this association is less important in palustrine plants, we compared the role of AOP in balancing energy and carbon metabolism in palustrine and terrestrial environments by identifying metabolic relationships between primary carbon metabolites and AOP in each habitat. We measured oxygen isotope discrimination during respiration, gas exchange, and metabolite profiles in aerial leaves of ten fern and angiosperm species belonging to five families organized as pairs of palustrine and terrestrial species. We performed a partial least square model combined with variable importance for projection to reveal relationships between the electron partitioning to the AOP (τa) and metabolite levels. Terrestrial plants showed higher values of net photosynthesis (AN) and τa, together with stronger metabolic relationships between τa and sugars, important for water conservation. Palustrine plants showed relationships between τa and metabolites related to the shikimate pathway and the GABA shunt, to be important for heterophylly. Excess energy dissipation via AOX is less crucial in palustrine environments than on land. The basis of this difference resides in the contrasting photosynthetic performance observed in each environment, thus reinforcing the importance of AOP for photosynthesis.This work was mainly supported by Ministerio de Economía y Competitividad (MINECO, Spain) (project PGC2018-093824-B-C41) and the ERDF (FEDER). Others funding were provided by FONDECYT No. 1191118 from National Agency for Research and Development (ANID) and the Chilean Scholarship Program/Becas de doctorado nacional/2017–21180329, the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie grant agreement no. 753301, the ‘Ramon y Cajal’ contract RYC2019-027244-I/AEI/10.13039/501100011033 and the European Social Fund.Peer reviewe

Mesophyll conductance adaptation and acclimatization by anatomical adjustments

[eng] Mesophyll (internal) conductance to CO2 (gm) is a key photosynthetic trait. Despite it has been traditionally considered infinite, gm limits the diffusion of CO2 from the substomatal cavity to the sites of carboxylation in the chloroplast and varies in response to environmental factors, either in the short- (i.e. seconds to minutes) and long-term, along leaf ontogeny and differs between genotypes and phylogenetic groups. However, although several structural and biochemical determinants regulating gm have been identified, the mechanistic basis of gm variability are not fully understood. Among them, the mechanisms explaining the immediate changes of gm to environmental variations are unknown. Moreover, the extent of the effect of such variations on gm is reduced to a few species, notably crops and plant model species, being the information available on gm and its anatomical determinants in important groups of terrestrial plants (such as pteridophytes, lycophytes or bryophytes) very scarce. To determine these mechanistic bases and the different anatomical strategies that exist in photosynthetic organs is crucial for improving photosynthesis models and pinpointing targets for engineering leaf structure to enhance photosynthetic capacity in crops. The objectives of the present thesis are (1) to provide further insights on how the environment modulates the relationship between leaf anatomy and mesophyll conductance to CO2, and (2) to determine the main leaf anatomy traits influencing mesophyll conductance to CO2 across the land plant phylogeny. The results show that typically observed changes in gm in response to short-term variations in ambient CO2 concentrations or light intensity are not explained by anatomical mechanisms in tobacco. Instead, anatomical mechanisms largely explain the acclimation of gm to different light growth conditions in Arabidopsis. Leaves developed under higher irradiances present thicker leaves, allowing space for more mesophyll cells, which improves the mesophyll and chloroplast surface area exposed to intercellular airspaces per leaf area (Sm/S and Sc/S, respectively) and positively affecting gm. The role of cell walls on setting gm increases its relevance along Arabidopsis leaf ageing due to the increase of cell wall thickness (Tcw) regardless of the light intensity. Concerning different phylogenetic groups, the present PhD thesis represents the first exhaustive analysis of gm and the anatomical features that determines it in three of the most primitive embryophyte groups: pteridophytes, lycophytes and bryophytes. These land plant groups are distinguished by their low gm values, generally explained by their low Sc/S and their thick cell walls. These findings demonstrate a phylogenetic trend —whether due to evolutionary adaptation and/or adaptation to different habitats or life forms— towards decreased CO2 diffusion resistance inside photosynthetic organs mainly thanks to increased Sc/S and decreased Tcw along the land plant’s phylogeny. For a deeper understanding of the leaf structural strategies that allow to increase Sc/S, and therefore decrease total CO2 diffusion resistance in the mesophyll, the exceptional nature of Thuja plicata is investigated. T. plicata proves to be able to achieve the highest Sc/S ever reported by developing thick leaves and mesophyll cells, revealing another biologically viable target for manipulating the leaf structure in order to increase plants’ photosynthetic capacity. Finally, the study of physiological traits and cell wall properties in seven conifers reveals that, at least in species with thick cell walls, cell wall chemical properties are strong determinants of gm. Specifically, the pectin fraction content seems to have a crucial role in regulating gm.[cat] La conductància del mesòfil (interna) al CO2 (gm) és un tret fotosintètic clau. La gm, malgrat haver estat considerada tradicionalment com a infinita, limita la difusió del CO2 des de la cavitat subestomàtica fins als llocs de carboxilació en el cloroplast i, a més, varia en resposta de factors ambientals, tant a curt (és a dir, de segons a minuts) com a llarg termini, durant l’ontogènia foliar, i entre genotips i grups filogenètics. No obstant això, tot i que s’han identificat diversos determinants estructurals i bioquímics que regulen la gm, les bases mecanicistes de la variabilitat de la gm no són completament compreses. Entre aquestes bases, es desconeixen els mecanismes que expliquen els canvis immediats de la gm a variacions ambientals. A més, l’abast de l’efecte d’aquestes variacions sobre la gm es redueix a unes poques espècies, principalment a cultius i espècies de plantes model, de tal manera que és molt escassa la informació disponible sobre la gm i els seus determinants anatòmics en grups importants de plantes terrestres (com els pteridòfits, els licòfits o els briòfits). Determinar aquestes bases mecanicistes i les diferents estratègies anatòmiques que existeixen en els òrgans fotosintètics és crucial per millorar els models fotosintètics i per identificar les dianes per a redissenyar l’estructura de les fulles i millorar la capacitat fotosintètica dels cultius. Els objectius d’aquesta tesi són (1) proporcionar més informació sobre com l’ambient modula la relació entre l’anatomia de les fulles i la conductància del mesòfil al CO2, i (2) determinar els principals trets anatòmics foliars que influencien la conductància del mesòfil al CO2 al llarg de la filogènia de les plantes terrestres. Els resultats mostren que els canvis típicament observats en gm en resposta a variacions a curt termini de les concentracions ambientals de CO2 o de la intensitat lumínica no s’expliquen per mecanismes anatòmics en el tabac. En canvi, els mecanismes anatòmics expliquen en gran mesura l’aclimatació de la gm a diferents condicions lumíniques de creixement en el cas de l’Arabidopsis. Les fulles desenvolupades sota irradiacions superiors presenten fulles més gruixudes, fet que permet més espai per a cèl•lules del mesòfil i augmenta l’àrea de superfície del mesòfil i cloroplàstica exposada als espais aeris intercel•lulars per unitat d’àrea foliar (Sm/S i Sc/S, respectivament). Conseqüentment, això afecta positivament a la gm. El paper de les parets cel•lulars en la determinació de la gm augmenta en rellevància durant l’envelliment de les fulles de l’Arabidopsis a causa de l’augment de la gruixa de la paret cel•lular (Tcw), independentment de la intensitat lumínica de creixement. Pel que fa als diferents grups filogenètics, aquesta tesi doctoral representa el primer anàlisi exhaustiu de la gm i les característiques anatòmiques que la determinen en tres dels grups més primitius d’embriòfits: pteridòfits, licòfits i briòfits. Aquests grups de plantes terrestres es distingeixen per una gm baixa, generalment explicada per la baixa Sc/S i les gruixudes parets cel•lulars. Aquests resultats demostren una tendència filogenètica —ja sigui com a resultat d’una adaptació evolutiva i/o una adaptació a diferents hàbitats o formes de vida— cap a la disminució de la resistència a la difusió del CO2 dins els òrgans fotosintètics al llarg de la diversificació de les plantes terrestres. Això és possible principalment gràcies a l’augment de Sc/S i la disminució de la Tcw. Per tal de comprendre més profundament les estratègies estructurals que permeten assolir majors Sc/S a les fulles i que, per tant, disminueixen la resistència total a la difusió del CO2 en el mesòfil, s’ha investigat el caràcter excepcional de Thuja plicata. Aquesta espècie demostra la capacitat d’aconseguir la Sc/S més elevada que s’ha reportat mai gràcies al desenvolupament de fulles gruixudes i cèl•lules del mesòfil de gran mida, el que identifica una nova estratègia biològicament viable per manipular l’estructura de les fulles i així augmentar la capacitat fotosintètica. Finalment, l’estudi dels característiques fisiològiques i de les propietats de la paret cel•lular a set coníferes demostra que, almenys en espècies amb parets cel•lulars gruixudes, les propietats químiques de la paret cel•lular determinen de forma important la gm. Específicament, la fracció de pectines sembla tenir un rol crucial en la regulació de gm.[spa] La conductancia del mesófilo (interna) al CO2 (gm) es un rasgo fotosintético clave. La gm, a pesar de haber sido considerada tradicionalmente como infinita, limita la difusión del CO2 desde la cavidad subestomática hasta los sitios de carboxilación en el cloroplasto i, además, varía en respuesta a factores ambientales, tanto a corto (es decir, de segundos a minutos) cómo a largo termino, durante la ontogenia foliar, y entre genotipos y grupos filogenéticos. Sin embargo, pese a que se han identificado diversos determinantes estructurales y bioquímicos que regulan la gm, las bases mecanicistas de la variabilidad de la gm no son completamente comprendidas. Entre estas bases, se desconocen los mecanismos que explican os cambios inmediatos de la gm a variaciones ambientales. Además, el alcance del efecto de estas variaciones sobre la gm se reduce a unas pocas especies, principalmente a cultivos y especies de plantas modelo, de tal manera que es muy escasa la información disponible sobre la gm y sus determinantes anatómicos en grupos importantes de plantas terrestres (cómo los pteridófitos, los licófitos o los briófitos). Determinar estas bases mecanicistas y las diferentes estrategias anatómicas que existen en los órganos fotosintéticos es crucial para mejorar los modelos fotosintéticos y para identificar las dianas para rediseñar la estructura de las hojas y mejorar la capacidad fotosintética de los cultivos. Los objetivos de esta tesis son (1) proporcionar más información sobre cómo el ambiente modula la relación entre la anatomía de las hojas y la conductancia del mesófilo al CO2, y (2) determinar los principales rasgos anatómicos foliares que influencian la conductancia del mesófilo al CO2 a lo largo de la filogenia de las plantas terrestres. Los resultados muestran que los cambios típicamente observados en gm en respuesta a variaciones a corto término de las concentraciones ambientales de CO2 o de la intensidad lumínica no se explican por mecanismos anatómicos en el tabaco. En cambio, los mecanismos anatómicos explican en gran medida la aclimatación de la gm a diferentes condiciones lumínicas de crecimientos en el caso de la Arabidopsis. Las hojas desarrolladas bajo irradiaciones superiores presentan hojas más gruesas, hecho que permite más espacio para células del mesófilo y aumenta el área de superficie del mesófilo y cloroplástica expuesta a los espacios aéreos intercelulares por unidad de área foliar (Sm/S y Sc/S, respectivamente). En consecuencia, esto afecta positivamente a la gm. El papel de las paredes celulares en la determinación de la gm aumenta en relevancia durante el envejecimiento de las hojas de la Arabidopsis a causa del aumento del grosor de la pared celular (Tcw), independientemente de la intensidad lumínica de crecimiento. Por lo que se refiere a los diferentes grupos filogenéticos, esta tesis doctoral representa el primer análisis exhaustivo de la gm y las características anatómicas que la determinan en tres de los grupos de embriófitos más primitivos: pteridofitos, licófitos y briófitos. Estos grupos de plantas terrestres se distinguen por una gm baja, generalmente explicada por la baja Sc/S y las gruesas paredes celulares. Estos resultados demuestran una tendencia filogenética —ya sea cómo resultado de una adaptación evolutiva y/o una adaptación a diferentes hábitats o formas de vida— hacia la disminución de la resistencia a la difusión del CO2 dentro de los órganos fotosintéticos a lo largo de la diversificación de las plantas terrestres. Esto es posible principalmente gracias al aumento de Sc/S y la disminución del Tcw. Para comprender más profundamente las estrategias estructurales que permiten alcanzar mayores Sc/S a las hojas y que, por tanto, disminuyen la resistencia total a la difusión del CO2 en el mesófilo, se ha investigado el carácter excepcional de Thuja plicata. Esta especie demuestra la capacidad de conseguir la Sc/S más elevada que se ha reportado nunca gracias al desarrollo de hojas gruesas y células del mesófilo de gran tamaño, lo que identifica una nueva estrategia biológicamente viable para manipular la estructura de las hojas y así aumentar la capacidad fotosintética. Finalmente, el estudio de las características fisiológicas y de las propiedades de la pared celular en siete coníferas demuestra que, al menos en especies con paredes celulares gruesas, las propiedades químicas de la pared celular determinan de forma importante la gm. Específicamente, la fracción de pectinas parece tener un rol crucial en la regulación de gm

Cell wall composition strongly influences mesophyll conductance in gymnosperms

14 Pág.Cell wall thickness is widely recognized as one of the main determinants of mesophyll conductance to CO2 (gm). However, little is known about the components that regulate effective CO2 diffusivity in the cell wall (i.e. the ratio between actual porosity and tortuosity, the other two biophysical diffusion properties of cell walls). The aim of this study was to assess, at the interspecific level, potential relationships between cell wall composition, cell wall thickness (Tcw) and gm. Gymnosperms constitute an ideal group to deepen these relationships, as they present, on average, the thickest cell walls within spermatophytes. We characterized the foliar gas exchange, the morphoanatomical traits related with gm, the leaf fraction constituted by cell walls and three main components of primary cell walls (hemicelluloses, cellulose and pectins) in seven gymnosperm species. We found that, although the relatively low gm of gymnosperms was mainly determined by their elevated Tcw, gm was also strongly correlated with cell wall composition, which presumably sets the final effective CO2 diffusivity. The data presented here suggest that (i) differences in gm are strongly correlated to the pectins to hemicelluloses and cellulose ratio in gymnosperms, and (ii) variations in cell wall composition may modify effective CO2 diffusivity in the cell wall to compensate the negative impact of thickened walls. We speculate that higher relative pectin content allows higher gm because pectins increase cell wall hydrophilicity and CO2 molecules cross the wall dissolved in water.This work was supported by the project CTM2014-53902-C2-1-P from the Ministerio de Economía y Competitividad (MINECO, Spain) and the ERDF (FEDER). MC acknowledges the predoctoral fellowship FPI/1700/2014 by Conselleria d’Educació, Cultura i Universitats (Govern de les Illes Balears) and European Social Fund, and MN acknowledges predoctoral fellowship BES-2015-072578 by Ministerio de Economía y Competitividad (MINECO, Spain) and European Social Fund.Peer reviewe

Linking xylem network failure with leaf tissue death

12 págs.- 5 figuras.- referenciasGlobal warming is expected to dramatically accelerate forest mortality as temperature and drought intensity increase. Predicting the magnitude of this impact urgently requires an understanding of the process connecting atmospheric drying to plant tissue damage. Recent episodes of forest mortality worldwide have been widely attributed to dry conditions causing acute damage to plant vascular systems. Under this scenario vascular embolisms produced by water stress are thought to cause plant death, yet this hypothetical trajectory has never been empirically demonstrated. Here we provide foundational evidence connecting failure in the vascular network of leaves with tissue damage caused during water stress. We observe a catastrophic sequence initiated by water column breakage under tension in leaf veins which severs local leaf tissue water supply, immediately causing acute cellular dehydration and irreversible damage. By highlighting the primacy of vascular network failure in the death of leaves exposed to drought or evaporative stress our results provide a strong mechanistic foundation upon which models of plant damage in response to dehydration can be confidently structured.This study was supported by funds from the Australian Research Council (DP190101552) to TB; a visiting research fellowship from University of Tasmania (UTAS) to CRB; Individual Fellowship from the European Union’sHorizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 751918 -AgroPHYS to CRD.Peer reviewe

Stomatal and mesophyll conductances to CO2 in different plant groups: Underrated factors for predicting leaf photosynthesis responses to climate change?

8 Pág., 4 Fig., 1 Tabl. Available online 20 June 2014. The definitive version is available at: http://www.sciencedirect.com/science/article/pii/S0168945214001459The climate change conditions predicted for the end of the current century are expected to have an impact on the performance of plants under natural conditions. The variables which are foreseen to have a larger effect are increased CO2 concentration and temperature. Although it is generally considered CO2 assimilation rate could be increased by the increasing levels of CO2, it has been reported in previous studies that acclimation to high CO2 results in reductions of physiological parameters involved in photosynthesis, like the maximum carboxylation rate (Vc,max), stomatal conductance (gs) and mesophyll conductance to CO2 (gm). On the one hand, most of the previous modeling efforts have neglected the potential role played by the acclimation of gm to high CO2 and temperature. On the other hand, the effect of climate change on plant clades other than angiosperms, like ferns, has received little attention, and there are no studies evaluating the potential impact of increasing CO2 and temperature on these species. In this study we predicted responses of several representative species among angiosperms, gymnosperms and ferns to increasing CO2 and temperature. Our results show that species with lower photosynthetic capacity – such as some ferns and gymnosperms – would be proportionally more favored under these foreseen environmental conditions. The main reason for this difference is the lower diffusion limitation imposed by gs and gm in plants having high capacity for photosynthesis among the angiosperms, which reduces the positive effect of increasing CO2. However, this apparent advantage of low-diffusion species would be canceled if the two conductances – gs and gm – acclimate and are down regulated to high CO2, which is basically unknown, especially for gymnosperms and ferns. Hence, for a better understanding of different plant responses to future climate, studies are urged in which the actual photosynthetic response/acclimation to increased CO2 and temperature of ferns, gymnosperms and other under-evaluated plant groups is assessed.This work was partly supported by the Plan Nacional, Spain, contracts AGL2009-11310 (A. Díaz-Espejo), BFU2011-23294 (J. Flexas and J. Gago), contracts AGL2009-07999 (J. Galmés), BFU2011-26989 (F. Morales), FPI grant from AGL2008-04525-C02-01, AGL2011-30408-C04-01, (S. Martorell), the FONDECYT N 1120965 (R.E Coopman) UE Innovine Project (Combining innovation in vineyard management and genetic diversity for a sustainable European viticulture (Call FP7-KBBE-2012-6, Proposal N° 311775-INNOVINE)) (F. Morales) and Gobierno de Aragón (A03 research group) (F. Morales).Peer reviewe

Ecogeomorfología y drones como instrumentos de gestión dinámica post-incendio. El caso de la comarca del Pariatge, Mallorca

Els incendis forestals són considerats un dels factors causals més importants en els processos de desertificació. Els territoris insulars com Mallorca són particularment sensibles als impactes antròpics, per la seva major fragilitat socioecològica. L’increment de superfície cremada a Mallorca d’ençà el 2011 esperoneja a vincular gestió forestal i recerca amb interdisciplinarietat i avenços tecnològics. L’ecogeomorfologia permet investigar el paper dels processos geomorfològics en la recuperació de la vegetació. Endemés, la introducció dels vehicles aeris no tripulats com a instruments de teledetecció presenta noves oportunitats en el monitoratge de processos ambientals. Aquest article pretén dilucidar el potencial de l’ecogeomorfologia i els drons per aplicar una gestió postincendi més efectiva i dinàmica, integrant la capacitat de resiliència dels ecosistemes amb la connectivitat dels sediments per restaurar el paisatge.Paraules clau: gestió postincendi, connectivitat dels sediments, ecofisiologia vegetal, UAV, ecosistemes mediterranis.Ecogeomorphology and drones as dynamic tools for post-fire management. The experience in the Pariatge County, Mallorca Wildfires are one of the most significant driving factors in desertification processes. Furthermore, insular territories such Mallorca are more affected by human impacts due to their intrinsic socioecological fragility. The increase of burned surface area since 2011in Balearic Islands involves a challenge in which forest management and research through interdisciplinary and technological advances should be joined. Ecogeomorphology is an emergent discipline which allows investigating the role of geomorphic processes in the vegetation recovery. Additionally, the introduction of unmanned aerial vehicles as remotesensing tools offers new and exciting opportunities for monitoring environmental processes. This paper pretends to elucidate the potential of ecogeomorphology and drones to implement more effective and dynamic post-fire management integrating both the resilience capacity of ecosystems with sediment connectivity for landscape restoration.Keywords: post-fire management, sediment connectivity, vegetal ecophysiology, UAVs, Mediterranean ecosystems.Los incendios forestales son uno de los factores causales más importantes en los procesos de desertificación. Los territorios insulares como Mallorca son particularmente sensibles a los impactos antrópicos, a causa de su mayor fragilidad socioecológica. El incremento de superficie quemada en Mallorca desde el año 2011 incita vincular gestión forestal e investigación a través de interdisciplinariedad y avances tecnológicos. La ecogeomorfología permite investigar el papel de los procesos geomorfológicos en la recuperación de lavegetación. Además, la introducción de vehículos aéreos no tripulados como instrumentos de teledetección presenta nuevas oportunidades en la monitorización de procesos ambientales. Este artículo pretende dilucidar el potencial de la ecogeomorfología y de los drones para aplicar una gestión post-incendio más efectiva y dinámica, integrando la capacidad de resiliencia de los ecosistemas con la conectividad de los sedimentos para restaurar el paisaje.Palabras clave: gestión post-incendio, conectividad de sedimentos, ecofisiologíavegetal, UAVs, ecosistemas mediterráneos

Different Metabolic Roles for Alternative Oxidase in Leaves of Palustrine and Terrestrial Species

The alternative oxidase pathway (AOP) is associated with excess energy dissipation in leaves of terrestrial plants. To address whether this association is less important in palustrine plants, we compared the role of AOP in balancing energy and carbon metabolism in palustrine and terrestrial environments by identifying metabolic relationships between primary carbon metabolites and AOP in each habitat. We measured oxygen isotope discrimination during respiration, gas exchange, and metabolite profiles in aerial leaves of ten fern and angiosperm species belonging to five families organized as pairs of palustrine and terrestrial species. We performed a partial least square model combined with variable importance for projection to reveal relationships between the electron partitioning to the AOP (ta) and metabolite levels. Terrestrial plants showed higher values of net photosynthesis (AN) and ta, together with stronger metabolic relationships between ta and sugars, important for water conservation. Palustrine plants showed relationships between ta and metabolites related to the shikimate pathway and the GABA shunt, to be important for heterophylly. Excess energy dissipation via AOX is less crucial in palustrine environments than on land. The basis of this difference resides in the contrasting photosynthetic performance observed in each environment, thus reinforcing the importance of AOP for photosynthesis.info:eu-repo/semantics/publishedVersio

Cell wall thickness and composition are involved in photosynthetic limitation

[eng] The key role of cell walls in setting mesophyll conductance to CO2 (gm) and, consequently, photosynthesis is reviewed. First, the theoretical properties of cell walls that can affect gm are presented. Then, we focus on cell wall thickness (Tcw) reviewing empirical evidence showing that Tcw varies strongly among species and phylogenetic groups in a way that correlates with gm and photosynthesis; that is, the thicker the mesophyll cell walls, the lower the gm and photosynthesis. Potential interplays of gm, Tcw, dehydration tolerance, and hydraulic properties of leaves are also discussed. Dynamic variations of Tcw in response to the environment and their implications in the regulation of photosynthesis are discussed, and recent evidence suggesting an influence of cell wall composition on gm is presented. We then propose a hypothetical mechanism for the influence of cell walls on photosynthesis, combining the effects of thickness and composition, particularly pectins. Finally, we discuss the prospects for using biotechnology for enhancing photosynthesis by altering cell wall-related genes

Mesophyll diffusion conductance to CO 2: An unappreciated central player in photosynthesis

Mesophyll diffusion conductance to CO 2 is a key photosynthetic trait that has been studied intensively in the past years. The intention of the present review is to update knowledge of g m, and highlight the important unknown and controversial aspects that require future work. The photosynthetic limitation imposed by mesophyll conductance is large, and under certain conditions can be the most significant photosynthetic limitation. New evidence shows that anatomical traits, such as cell wall thickness and chloroplast distribution are amongst the stronger determinants of mesophyll conductance, although rapid variations in response to environmental changes might be regulated by other factors such as aquaporin conductance.Gaps in knowledge that should be research priorities for the near future include: how different is mesophyll conductance among phylogenetically distant groups and how has it evolved? Can mesophyll conductance be uncoupled from regulation of the water path? What are the main drivers of mesophyll conductance? The need for mechanistic and phenomenological models of mesophyll conductance and its incorporation in process-based photosynthesis models is also highlighted