Aims: Cabraleadiol (1), Ocotilone (2) and Odoratone (3) are three triterpenes isolated from Cabralea canjerana (Vell.) Mart. (Meliaceae). They were chemically characterized, and their effect was tested on the light re...Aims: Cabraleadiol (1), Ocotilone (2) and Odoratone (3) are three triterpenes isolated from Cabralea canjerana (Vell.) Mart. (Meliaceae). They were chemically characterized, and their effect was tested on the light reaction of photosynthesis. Study Design: Natural products were used as models to find new models for inhibitors of photosynthesis. Place and Duration of Study: Departmento de Química, Universidade Federal de São Carlos and Departmento de Bioquímica, Facultad de Química, Universidad Nacional Autonoma de México, between May 2013 and January 2014. Methodology: The natural products had their effect on the light reaction of photosynthesis studied by pollarography and Chlorophyll a (Chl a) fluorescence transients. Results: The compounds inhibited ATP synthesis and electron transport rate (basal, phosphorylating and uncoupled). Therefore, they act as Hill reactions inhibitors. Their inhibition site were located in the range of electron flow from OEC complex and between P680 to QA of PS II, and inhibited the photosystem II (PS II) by inducing the appearance of a K-band which is an indicative that the photochemical apparatus is failing at the donor side of PS II interacting at the OEC complex and by transforming active reaction centers to “heat sinks” or the formation of silent reaction centers unable to reduce QA. Conclusion: Furthermore, these triterpenes inhibit PS II and induce the appearance of small G band which is related with the decreased plastoquinone (PQ) pool reduction.展开更多
Forest disturbances at gap levels are one of the most important events for the regeneration and establishment of intermediate tree species.Abrupt canopy openings expose plants to high light intensity and high evaporat...Forest disturbances at gap levels are one of the most important events for the regeneration and establishment of intermediate tree species.Abrupt canopy openings expose plants to high light intensity and high evaporative demands that stress shade-acclimated plants.Later,the slow closure of gaps reduces light availability to plants established when the incident irradiation was higher.This work evaluated the morphological and physiological acclimation of Cabralea canjerana(Vell)Mart.regeneration to sudden and to gradual changes in canopy cover.A pot experiment was carried out with plants exposed to a sudden opening.A few days after the light shock,plants rapidly increased photosynthetic rates and decreased leaf water potential.After two months,plants activated physiological responses at leaf and whole plant levels to high light and water stresses,e.g.,increased stoma-tal conductance,stomatal index and reduction of leaf:fine roots ratio and chlorophyll.After seven months,hydraulic conductivity of petioles and the whole leaf increased,and growth was much higher than plants that remained under the canopy.In a field experiment in gaps in the rainforest,plants acclimated to all canopy covers.Seven years after planting,growth was maximum in open environments within the gaps,even if the canopy closed during the first 20 months after planting.In conclusion,if this species is planted to enrich the rainforest,positions within gaps with lower canopy cover should be chosen and gap closure will not affect growth.To manage C.canjerana natural regeneration,the opening of gaps and removal of understory will increase survival and growth without the risk that the stress caused by these sudden openings could lead to the death of seedlings.Com-bining pot and field experiments helps to understand the autecology of trees with particular ecological interest,and to build sound restoration practices.展开更多
基金financial support of the DGAPA-UNAM IT102012-3#FAPESP(Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)+1 种基金#CNPq(Conselho Nacional de Pesquisa e Desenvolvimento)CAPES(Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior).
文摘Aims: Cabraleadiol (1), Ocotilone (2) and Odoratone (3) are three triterpenes isolated from Cabralea canjerana (Vell.) Mart. (Meliaceae). They were chemically characterized, and their effect was tested on the light reaction of photosynthesis. Study Design: Natural products were used as models to find new models for inhibitors of photosynthesis. Place and Duration of Study: Departmento de Química, Universidade Federal de São Carlos and Departmento de Bioquímica, Facultad de Química, Universidad Nacional Autonoma de México, between May 2013 and January 2014. Methodology: The natural products had their effect on the light reaction of photosynthesis studied by pollarography and Chlorophyll a (Chl a) fluorescence transients. Results: The compounds inhibited ATP synthesis and electron transport rate (basal, phosphorylating and uncoupled). Therefore, they act as Hill reactions inhibitors. Their inhibition site were located in the range of electron flow from OEC complex and between P680 to QA of PS II, and inhibited the photosystem II (PS II) by inducing the appearance of a K-band which is an indicative that the photochemical apparatus is failing at the donor side of PS II interacting at the OEC complex and by transforming active reaction centers to “heat sinks” or the formation of silent reaction centers unable to reduce QA. Conclusion: Furthermore, these triterpenes inhibit PS II and induce the appearance of small G band which is related with the decreased plastoquinone (PQ) pool reduction.
基金supported by UCAR,Ministerio de Agricultura,Ganadería y Pesca de la Nación,Argentina(PIA 12010 and 14,031)ANPCyT-MINCyT,Argentina(PUE INFIVE:10520180101142CO).
文摘Forest disturbances at gap levels are one of the most important events for the regeneration and establishment of intermediate tree species.Abrupt canopy openings expose plants to high light intensity and high evaporative demands that stress shade-acclimated plants.Later,the slow closure of gaps reduces light availability to plants established when the incident irradiation was higher.This work evaluated the morphological and physiological acclimation of Cabralea canjerana(Vell)Mart.regeneration to sudden and to gradual changes in canopy cover.A pot experiment was carried out with plants exposed to a sudden opening.A few days after the light shock,plants rapidly increased photosynthetic rates and decreased leaf water potential.After two months,plants activated physiological responses at leaf and whole plant levels to high light and water stresses,e.g.,increased stoma-tal conductance,stomatal index and reduction of leaf:fine roots ratio and chlorophyll.After seven months,hydraulic conductivity of petioles and the whole leaf increased,and growth was much higher than plants that remained under the canopy.In a field experiment in gaps in the rainforest,plants acclimated to all canopy covers.Seven years after planting,growth was maximum in open environments within the gaps,even if the canopy closed during the first 20 months after planting.In conclusion,if this species is planted to enrich the rainforest,positions within gaps with lower canopy cover should be chosen and gap closure will not affect growth.To manage C.canjerana natural regeneration,the opening of gaps and removal of understory will increase survival and growth without the risk that the stress caused by these sudden openings could lead to the death of seedlings.Com-bining pot and field experiments helps to understand the autecology of trees with particular ecological interest,and to build sound restoration practices.
