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Jose Ignacio Garciaplazaola - One of the best experts on this subject based on the ideXlab platform.
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plasticity of photoprotective mechanisms of Buxus sempervirens l leaves in response to extreme temperatures
Plant Biology, 2007Co-Authors: Koldobika Hormaetxe, J M Becerril, Antonio Hernandez, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:Summer 2003 was unusually hot in Western Europe, with local droughts and an intense heatwave, that led to a massive damage in vegetation. Since high temperatures are supposed to generate photooxidative stress, we analysed photoprotective responses in leaves of the evergreen boxtree (Buxus sempervirens L.) during summer 2003. All the photoprotective compounds analysed (alpha-tocopherol, beta-carotene, and xanthophylls cycle pigments) were simultaneously induced in parallel with a reduction in photochemical efficiency (Fv/Fm). To characterise these responses, we compared these data with other data obtained during cold stress periods (2003, 2005) and with an unstressful summer (2002). Photoprotective responses observed during the heatwave were also induced by low temperature stress, and in both situations, this effect was exacerbated by light. In parallel with such induction the accumulation of red retro-carotenoids and xanthophyll esters was also observed under unfavourable conditions, suggesting a photoprotective role for both groups of carotenoids. This is the first report showing that in any species (Buxus sempervirens L.), the same retro-carotenoids can be induced in response to winter and summer stress. Present results demonstrate that the same mechanisms are induced as response to sub- and supraoptimal temperatures and the plasticity of such responses plays a critical role in plant acclimation to extreme temperatures, an ability that is specially important in the context of any future climate warming.
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dynamics of the α tocopherol pool as affected by external environmental and internal leaf age factors in Buxus sempervirens leaves
Physiologia Plantarum, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
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functional role of red retro carotenoids as passive light filters in the leaves of Buxus sempervirens l increased protection of photosynthetic tissues
Journal of Experimental Botany, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Isabel Fleck, Marta Pinto, Jose Ignacio GarciaplazaolaAbstract:Red (retro)-carotenoids accumulate in chloroplasts of Buxus sempervirens leaves during the process of winter leaf acclimation. As a result of their irregular presence, different leaf colour phenotypes can be found simultaneously in the same location. Five different colour phenotypes (green, brown, red, orange, and yellow), with a distinct pattern of pigment distribution and concentration, have been characterized. Leaf reddening due to the presence of anthocyanins or carotenoids, is a process frequently observed in plant species under photoinhibitory situations. Two main hypotheses have been proposed to explain the function of such colour change: antioxidative protection exerted by red-coloured molecules, and green light filtering. The potential photoprotective role of red (retro-) carotenoids as light filters was tested in Buxus sempervirens leaves. In shade leaves of this species the upper (adaxial) mesophyll of the lamina was replaced by the equivalent upper part of a different colour phenotype. These hybrid leaves were exposed to a photoinhibitory treatment in order to compare the photoprotective effect exerted by adaxial parts of phenotypes with a different proportion of red (retro)-carotenoids in the lower mesophyll of a shade leaf. The results indicated that the presence of red (retro)-carotenoids in the upper mesophyll did not increase photoprotection of the lower mesophyll when compared with chlorophyll, and the best protection was achieved by an upper green layer. This was due to the fact that the extent of photoinhibition was proportional to the amount of red light transmitted by the upper mesophyll and/or to the chlorophyll pool located above. These results do not exclude a protective function of carotenoids in the upper leaf layer, but imply that, at least under the conditions of this experiment, the accumulation of red pigments in the outer leaf layers does not increase photoprotection in the lower mesophyll.
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role of red carotenoids in photoprotection during winter acclimation in Buxus sempervirens leaves
Plant Biology, 2004Co-Authors: Koldobika Hormaetxe, J M Becerril, Antonio Hernandez, Jose Ignacio GarciaplazaolaAbstract:The red leaf coloration of several plant species during autumn and winter is due to the synthesis of phenolic compounds such as anthocyanins or red carotenoids. The latter occur very rarely and are non-ubiquitous and taxonomically restricted compounds. The present study shows that the leaves of common box ( Buxus sempervirens L.) accumulate red carotenoids (eschscholtzxanthin, monoanhydroeschscholtzxanthin, anhydroeschscholtzxanthin) as a response to photoinhibitory conditions during winter acclimation. These compounds are produced in a coordinated manner with the operation of other photoprotective systems: accumulation and sustained deepoxidation of VAZ pigments with a concomitant decrease in maximal photochemical efficiency, accumulation of alpha-tocopherol and a gradual decrease on chlorophyll content. All these processes were reversed when the photosynthetic tissues were transferred from photoinhibitory winter conditions to room temperature for 9 days. Buxus leaves showed a large degree of phenotype variation in the degree of reddening, ranging from green to orange. The differences in colour pattern were mainly due to differences in the accumulation of red carotenoids and xanthophyll esters. Red pigments were mainly anhydroeschscholtzxanthin and esters of eschscholtzxanthin. Conversely to fruit or petal chromoplasts, the plastids of red leaves in this species are not the terminal differentiated state but are able to redifferentiate again to chloroplasts. Their photoprotective role during winter as a light screen system or as antioxidants, in a similar way to other red pigments, and their implications on the wide ecological tolerance of this evergreen species are discussed.
Koldobika Hormaetxe - One of the best experts on this subject based on the ideXlab platform.
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Seasonal reversibility of acclimation to irradiance in leaves of common box (Buxus sempervirens L.) in a deciduous forest
Flora - Morphology Distribution Functional Ecology of Plants, 2008Co-Authors: José Ignacio García-plazaola, Koldobika Hormaetxe, Raquel Esteban, J M BecerrilAbstract:Abstract Understorey shade plants are seasonally exposed to dramatic changes in light conditions in deciduous forests related with the dynamics of the overstorey leaf phenology. These transitions are commonly followed by changes in herb plant communities, but shade-tolerant evergreen species must be able to adapt to changing light conditions. In this work we checked the photoprotective responses of evergreen species to acclimate to the shady summer environment and reversibly de-acclimate to a more illuminated environment after leaf fall on deciduous overstoreys. For that purpose we have followed the process of light acclimation in leaves of common box (Buxus sempervirens) during the winter to spring transition, which decrease irradiance in the understorey, and conversely during the transition from summer to autumn. Four parameters indicative of the structure and degree of acclimation of the photosynthetic apparatus have been studied: chlorophyll a/b ratio which is supposed to be inversely proportional to the antenna size, α/β-carotene which increases in shade acclimated leaves and the pools of α-tocopherol and xanthophyll cycle pigments (VAZ) which are two of the main photoprotection mechanisms in plants. Among these parameters, chlorophyll a/b ratio and VAZ pool responded finely to changes in irradiance indicating that modifications in the light harvesting size and photoprotective capacity contribute to the continuous acclimation and de-acclimation of long-lived evergreen leaves.
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plasticity of photoprotective mechanisms of Buxus sempervirens l leaves in response to extreme temperatures
Plant Biology, 2007Co-Authors: Koldobika Hormaetxe, J M Becerril, Antonio Hernandez, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:Summer 2003 was unusually hot in Western Europe, with local droughts and an intense heatwave, that led to a massive damage in vegetation. Since high temperatures are supposed to generate photooxidative stress, we analysed photoprotective responses in leaves of the evergreen boxtree (Buxus sempervirens L.) during summer 2003. All the photoprotective compounds analysed (alpha-tocopherol, beta-carotene, and xanthophylls cycle pigments) were simultaneously induced in parallel with a reduction in photochemical efficiency (Fv/Fm). To characterise these responses, we compared these data with other data obtained during cold stress periods (2003, 2005) and with an unstressful summer (2002). Photoprotective responses observed during the heatwave were also induced by low temperature stress, and in both situations, this effect was exacerbated by light. In parallel with such induction the accumulation of red retro-carotenoids and xanthophyll esters was also observed under unfavourable conditions, suggesting a photoprotective role for both groups of carotenoids. This is the first report showing that in any species (Buxus sempervirens L.), the same retro-carotenoids can be induced in response to winter and summer stress. Present results demonstrate that the same mechanisms are induced as response to sub- and supraoptimal temperatures and the plasticity of such responses plays a critical role in plant acclimation to extreme temperatures, an ability that is specially important in the context of any future climate warming.
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sistemas de fotoproteccion en respuesta al estres ambiental en Buxus sempervirens papel de los retro carotenoides
2006Co-Authors: Koldobika HormaetxeAbstract:Este trabajo caracteriza las respuestas de los mecanismos de fotoproteccion ante el estres ambiental, con especial interes en las respuestas a la temperatura y al doble estres invernal y estival. Para realizar este estudio se ha utilizado la planta perenne boj (Buxus sempervirens L.) como especie modelo, debido a la longevidad de sus hojas, a su gran amplitud ecologico y al elevado nivel de mecanismos de fotoproteccion, caracterizado por su alto contenido en pigmentos VAZ y en alfa-tocoferl. Ademas esta planta puede acumular tres retro-carotenoides que le confieren una coloracion rojiza a sus hojas. El boj es una planta tolerante al estres invernal y estival, debido a la plasticidad de los mecanismos de fotoproteccion que le permiten superar incluso periodos excepcionales de estres provocado durante las olas de frio o de calor. Entre los sistemas fotoprotectores, el VAZ es crucial, siendo una respuesta rapida y plastica a los proceso de la climatizacion y desaclimatacion. Por otro lado, el alfa-tocoferol esta constituido por dos pools, uno dinamico que responde al estres ambiental y otro dependiente de la edad que se acumula progresivamente durante la vida del tejido fotosintetico, independientemente de la luz. Este componente actua de forma general en todas las plantas B.sempervirens acumula retro-carotenoides y xantofilas esterificadas a acidos grasos de novo como resultado de la exposicion a un estres ambiental y a la intensidad luminica. Estos pigmentos se acumulan de forma coordinada con otros sistemas fotoprotectores, lo que le confiere una posible funcion fotoprotectora adicional. Ademas, existe una gran variabilidad fenotipica en boj debido a la diferentes composicion pigmentaria, la cual cambia la reflectancia foliar de cada fenotipo. Sin embargo, la atenuacion de la irradiancia por los fenotipos rojos se situa en un intermedio entre la atenuacion maxima de los fenotipos verdes y la atenuacion minima de los fenotipo
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dynamics of the α tocopherol pool as affected by external environmental and internal leaf age factors in Buxus sempervirens leaves
Physiologia Plantarum, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
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functional role of red retro carotenoids as passive light filters in the leaves of Buxus sempervirens l increased protection of photosynthetic tissues
Journal of Experimental Botany, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Isabel Fleck, Marta Pinto, Jose Ignacio GarciaplazaolaAbstract:Red (retro)-carotenoids accumulate in chloroplasts of Buxus sempervirens leaves during the process of winter leaf acclimation. As a result of their irregular presence, different leaf colour phenotypes can be found simultaneously in the same location. Five different colour phenotypes (green, brown, red, orange, and yellow), with a distinct pattern of pigment distribution and concentration, have been characterized. Leaf reddening due to the presence of anthocyanins or carotenoids, is a process frequently observed in plant species under photoinhibitory situations. Two main hypotheses have been proposed to explain the function of such colour change: antioxidative protection exerted by red-coloured molecules, and green light filtering. The potential photoprotective role of red (retro-) carotenoids as light filters was tested in Buxus sempervirens leaves. In shade leaves of this species the upper (adaxial) mesophyll of the lamina was replaced by the equivalent upper part of a different colour phenotype. These hybrid leaves were exposed to a photoinhibitory treatment in order to compare the photoprotective effect exerted by adaxial parts of phenotypes with a different proportion of red (retro)-carotenoids in the lower mesophyll of a shade leaf. The results indicated that the presence of red (retro)-carotenoids in the upper mesophyll did not increase photoprotection of the lower mesophyll when compared with chlorophyll, and the best protection was achieved by an upper green layer. This was due to the fact that the extent of photoinhibition was proportional to the amount of red light transmitted by the upper mesophyll and/or to the chlorophyll pool located above. These results do not exclude a protective function of carotenoids in the upper leaf layer, but imply that, at least under the conditions of this experiment, the accumulation of red pigments in the outer leaf layers does not increase photoprotection in the lower mesophyll.
J M Becerril - One of the best experts on this subject based on the ideXlab platform.
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Seasonal reversibility of acclimation to irradiance in leaves of common box (Buxus sempervirens L.) in a deciduous forest
Flora - Morphology Distribution Functional Ecology of Plants, 2008Co-Authors: José Ignacio García-plazaola, Koldobika Hormaetxe, Raquel Esteban, J M BecerrilAbstract:Abstract Understorey shade plants are seasonally exposed to dramatic changes in light conditions in deciduous forests related with the dynamics of the overstorey leaf phenology. These transitions are commonly followed by changes in herb plant communities, but shade-tolerant evergreen species must be able to adapt to changing light conditions. In this work we checked the photoprotective responses of evergreen species to acclimate to the shady summer environment and reversibly de-acclimate to a more illuminated environment after leaf fall on deciduous overstoreys. For that purpose we have followed the process of light acclimation in leaves of common box (Buxus sempervirens) during the winter to spring transition, which decrease irradiance in the understorey, and conversely during the transition from summer to autumn. Four parameters indicative of the structure and degree of acclimation of the photosynthetic apparatus have been studied: chlorophyll a/b ratio which is supposed to be inversely proportional to the antenna size, α/β-carotene which increases in shade acclimated leaves and the pools of α-tocopherol and xanthophyll cycle pigments (VAZ) which are two of the main photoprotection mechanisms in plants. Among these parameters, chlorophyll a/b ratio and VAZ pool responded finely to changes in irradiance indicating that modifications in the light harvesting size and photoprotective capacity contribute to the continuous acclimation and de-acclimation of long-lived evergreen leaves.
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plasticity of photoprotective mechanisms of Buxus sempervirens l leaves in response to extreme temperatures
Plant Biology, 2007Co-Authors: Koldobika Hormaetxe, J M Becerril, Antonio Hernandez, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:Summer 2003 was unusually hot in Western Europe, with local droughts and an intense heatwave, that led to a massive damage in vegetation. Since high temperatures are supposed to generate photooxidative stress, we analysed photoprotective responses in leaves of the evergreen boxtree (Buxus sempervirens L.) during summer 2003. All the photoprotective compounds analysed (alpha-tocopherol, beta-carotene, and xanthophylls cycle pigments) were simultaneously induced in parallel with a reduction in photochemical efficiency (Fv/Fm). To characterise these responses, we compared these data with other data obtained during cold stress periods (2003, 2005) and with an unstressful summer (2002). Photoprotective responses observed during the heatwave were also induced by low temperature stress, and in both situations, this effect was exacerbated by light. In parallel with such induction the accumulation of red retro-carotenoids and xanthophyll esters was also observed under unfavourable conditions, suggesting a photoprotective role for both groups of carotenoids. This is the first report showing that in any species (Buxus sempervirens L.), the same retro-carotenoids can be induced in response to winter and summer stress. Present results demonstrate that the same mechanisms are induced as response to sub- and supraoptimal temperatures and the plasticity of such responses plays a critical role in plant acclimation to extreme temperatures, an ability that is specially important in the context of any future climate warming.
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dynamics of the α tocopherol pool as affected by external environmental and internal leaf age factors in Buxus sempervirens leaves
Physiologia Plantarum, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
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functional role of red retro carotenoids as passive light filters in the leaves of Buxus sempervirens l increased protection of photosynthetic tissues
Journal of Experimental Botany, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Isabel Fleck, Marta Pinto, Jose Ignacio GarciaplazaolaAbstract:Red (retro)-carotenoids accumulate in chloroplasts of Buxus sempervirens leaves during the process of winter leaf acclimation. As a result of their irregular presence, different leaf colour phenotypes can be found simultaneously in the same location. Five different colour phenotypes (green, brown, red, orange, and yellow), with a distinct pattern of pigment distribution and concentration, have been characterized. Leaf reddening due to the presence of anthocyanins or carotenoids, is a process frequently observed in plant species under photoinhibitory situations. Two main hypotheses have been proposed to explain the function of such colour change: antioxidative protection exerted by red-coloured molecules, and green light filtering. The potential photoprotective role of red (retro-) carotenoids as light filters was tested in Buxus sempervirens leaves. In shade leaves of this species the upper (adaxial) mesophyll of the lamina was replaced by the equivalent upper part of a different colour phenotype. These hybrid leaves were exposed to a photoinhibitory treatment in order to compare the photoprotective effect exerted by adaxial parts of phenotypes with a different proportion of red (retro)-carotenoids in the lower mesophyll of a shade leaf. The results indicated that the presence of red (retro)-carotenoids in the upper mesophyll did not increase photoprotection of the lower mesophyll when compared with chlorophyll, and the best protection was achieved by an upper green layer. This was due to the fact that the extent of photoinhibition was proportional to the amount of red light transmitted by the upper mesophyll and/or to the chlorophyll pool located above. These results do not exclude a protective function of carotenoids in the upper leaf layer, but imply that, at least under the conditions of this experiment, the accumulation of red pigments in the outer leaf layers does not increase photoprotection in the lower mesophyll.
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Dynamics of the α‐tocopherol pool as affected by external (environmental) and internal (leaf age) factors in Buxus sempervirens leaves
Physiologia Plantarum, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Raquel Esteban, José Ignacio García-plazaolaAbstract:The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
Raquel Esteban - One of the best experts on this subject based on the ideXlab platform.
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Seasonal reversibility of acclimation to irradiance in leaves of common box (Buxus sempervirens L.) in a deciduous forest
Flora - Morphology Distribution Functional Ecology of Plants, 2008Co-Authors: José Ignacio García-plazaola, Koldobika Hormaetxe, Raquel Esteban, J M BecerrilAbstract:Abstract Understorey shade plants are seasonally exposed to dramatic changes in light conditions in deciduous forests related with the dynamics of the overstorey leaf phenology. These transitions are commonly followed by changes in herb plant communities, but shade-tolerant evergreen species must be able to adapt to changing light conditions. In this work we checked the photoprotective responses of evergreen species to acclimate to the shady summer environment and reversibly de-acclimate to a more illuminated environment after leaf fall on deciduous overstoreys. For that purpose we have followed the process of light acclimation in leaves of common box (Buxus sempervirens) during the winter to spring transition, which decrease irradiance in the understorey, and conversely during the transition from summer to autumn. Four parameters indicative of the structure and degree of acclimation of the photosynthetic apparatus have been studied: chlorophyll a/b ratio which is supposed to be inversely proportional to the antenna size, α/β-carotene which increases in shade acclimated leaves and the pools of α-tocopherol and xanthophyll cycle pigments (VAZ) which are two of the main photoprotection mechanisms in plants. Among these parameters, chlorophyll a/b ratio and VAZ pool responded finely to changes in irradiance indicating that modifications in the light harvesting size and photoprotective capacity contribute to the continuous acclimation and de-acclimation of long-lived evergreen leaves.
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plasticity of photoprotective mechanisms of Buxus sempervirens l leaves in response to extreme temperatures
Plant Biology, 2007Co-Authors: Koldobika Hormaetxe, J M Becerril, Antonio Hernandez, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:Summer 2003 was unusually hot in Western Europe, with local droughts and an intense heatwave, that led to a massive damage in vegetation. Since high temperatures are supposed to generate photooxidative stress, we analysed photoprotective responses in leaves of the evergreen boxtree (Buxus sempervirens L.) during summer 2003. All the photoprotective compounds analysed (alpha-tocopherol, beta-carotene, and xanthophylls cycle pigments) were simultaneously induced in parallel with a reduction in photochemical efficiency (Fv/Fm). To characterise these responses, we compared these data with other data obtained during cold stress periods (2003, 2005) and with an unstressful summer (2002). Photoprotective responses observed during the heatwave were also induced by low temperature stress, and in both situations, this effect was exacerbated by light. In parallel with such induction the accumulation of red retro-carotenoids and xanthophyll esters was also observed under unfavourable conditions, suggesting a photoprotective role for both groups of carotenoids. This is the first report showing that in any species (Buxus sempervirens L.), the same retro-carotenoids can be induced in response to winter and summer stress. Present results demonstrate that the same mechanisms are induced as response to sub- and supraoptimal temperatures and the plasticity of such responses plays a critical role in plant acclimation to extreme temperatures, an ability that is specially important in the context of any future climate warming.
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dynamics of the α tocopherol pool as affected by external environmental and internal leaf age factors in Buxus sempervirens leaves
Physiologia Plantarum, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Raquel Esteban, Jose Ignacio GarciaplazaolaAbstract:The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
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Dynamics of the α‐tocopherol pool as affected by external (environmental) and internal (leaf age) factors in Buxus sempervirens leaves
Physiologia Plantarum, 2005Co-Authors: Koldobika Hormaetxe, J M Becerril, Raquel Esteban, José Ignacio García-plazaolaAbstract:The pools of photoprotective molecules respond to changes in the environmental conditions and sometimes to leaf ageing. We asked to what extent both factors contribute to the contents of α-tocopherol and xanthophyll cycle [V + A + Z (VAZ)] pigments. To address this question, we used boxtree (Buxus sempervirens) as model species because its leaves are long-lived and evergreen and are subjected to a succession of different stress conditions during their lifespan. In three age classes of sun and shade leaves of this species, seasonal changes in photoprotective compounds were followed during 15 months and a leaf age interval of 40 months was covered. As could be expected, VAZ and α-tocopherol pools increased in parallel during stress periods (summer and winter), but only VAZ recovered to the initial pools once stress disappeared. As a result, the basal α-tocopherol level increased linearly in a time-dependent manner that was also higher in sun leaves of this species when compared with shade leaves, and in fact, the rate of tocopherol increase was directly proportional to irradiance in another evergreen (Laurus nobilis). To study whether light dependency of tocopherol accumulation is observed in other species, we performed a literature survey that revealed that this age-dependent tocopherol increase was significant in sun leaves from 65% of the species for which age-dependent tocopherol changes have been reported, and it was on average 2.2-fold higher in sun leaves as compared with shade leaves. We conclude that there are two components in the α-tocopherol pool, one dynamic that responds to environmental changes and one age-related which increases linearly with time in a light-dependent manner. The physiological meaning of the latter remains obscure.
Wiebe Nijland - One of the best experts on this subject based on the ideXlab platform.
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the spectral response of Buxus sempervirens to different types of environmental stress a laboratory experiment
Isprs Journal of Photogrammetry and Remote Sensing, 2012Co-Authors: Steven M De Jong, E A Addink, Priscilla Hoogenboom, Wiebe NijlandAbstract:Abstract The European Mediterranean regions are expected to encounter drier summer conditions and warmer temperatures for the winter of +2 °C and of +5 °C for the summer in the next six decennia. As a result the natural vegetation will face harsher conditions due to lower water availability, longer summer droughts and higher temperatures resulting in plant stress conditions. To monitor vegetation conditions like stress and leaf area index dynamics in our study area in Mediterranean France we use earth observation techniques like imaging spectroscopy. To assist image analysis interpretation we carried out a laboratory experiment to investigate the spectral and visible response of Buxus sempervirens , a common Mediterranean species, to five different types of stress: drought, drought-and-heat, light deprivation, total saturation and chlorine poisoning. For 52 days plants were subjected to stress. We collected data on the visible and spectral signs, and calculated thirteen vegetation indices. The plant’s response time to different stress types varied from 10 to 32 days. Spectroscopic techniques revealed plant stress up to 15 days earlier than visual inspection. Visible signs of stress of the plants included curling and shrinking of the leaves, de-colouring of the leaves, leaves becoming breakable, opening up of the plant’s canopy and sagging of the branches. Spectral signs of stress occurred first in the water absorption bands at 1450 and 1940 nm, followed by reduced absorption in the visible wavelengths, and next by reduced reflectance in near infrared. Light deprivation did not result in any stress signs, while drought, drought and heat and chlorine poisoning resulted in significant stress. The spectral response did not show differences for different stress types. Analysis of the vegetation indices identified the Carter-2 ( R 695 / R 760 ), the Red–Green Index ( R 690 / R 550 ) and the Vogelman-2 ( R 734 − R 747 )/( R 715 + R 726 ) as the best performing ones to identify stress. The lab experiment shows that spectroscopic techniques are useful to detect stress status of plants and in an earlier stage than visible signs of stress become apparent, but that spectroscopy does not reveal the type of plant stress.
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The spectral response of Buxus sempervirens to different types of environmental stress – A laboratory experiment
ISPRS Journal of Photogrammetry and Remote Sensing, 2012Co-Authors: Steven M De Jong, E A Addink, Priscilla Hoogenboom, Wiebe NijlandAbstract:Abstract The European Mediterranean regions are expected to encounter drier summer conditions and warmer temperatures for the winter of +2 °C and of +5 °C for the summer in the next six decennia. As a result the natural vegetation will face harsher conditions due to lower water availability, longer summer droughts and higher temperatures resulting in plant stress conditions. To monitor vegetation conditions like stress and leaf area index dynamics in our study area in Mediterranean France we use earth observation techniques like imaging spectroscopy. To assist image analysis interpretation we carried out a laboratory experiment to investigate the spectral and visible response of Buxus sempervirens , a common Mediterranean species, to five different types of stress: drought, drought-and-heat, light deprivation, total saturation and chlorine poisoning. For 52 days plants were subjected to stress. We collected data on the visible and spectral signs, and calculated thirteen vegetation indices. The plant’s response time to different stress types varied from 10 to 32 days. Spectroscopic techniques revealed plant stress up to 15 days earlier than visual inspection. Visible signs of stress of the plants included curling and shrinking of the leaves, de-colouring of the leaves, leaves becoming breakable, opening up of the plant’s canopy and sagging of the branches. Spectral signs of stress occurred first in the water absorption bands at 1450 and 1940 nm, followed by reduced absorption in the visible wavelengths, and next by reduced reflectance in near infrared. Light deprivation did not result in any stress signs, while drought, drought and heat and chlorine poisoning resulted in significant stress. The spectral response did not show differences for different stress types. Analysis of the vegetation indices identified the Carter-2 ( R 695 / R 760 ), the Red–Green Index ( R 690 / R 550 ) and the Vogelman-2 ( R 734 − R 747 )/( R 715 + R 726 ) as the best performing ones to identify stress. The lab experiment shows that spectroscopic techniques are useful to detect stress status of plants and in an earlier stage than visible signs of stress become apparent, but that spectroscopy does not reveal the type of plant stress.
