27 research outputs found
Growth, photosynthetic responses and acclimaton of tree species to different light environments
A luz é um recurso primordial para o fluxo de energia nos sistemas biológicos sendo determinante para a vida das plantas. A grande variabilidade com que se apresenta em ambiente natural exige das plantas, em especial de árvores, que exibam grande capacidade de ajustar o metabolismo a variações espaciais e sazonais quanto a disponibilidade deste recurso visando não apenas a maximização na captura e utilização de luz, mas também o desenvolvimento de mecanismos eficiente na dissipação do excesso energia luminosa para evitar danos fotoinibitórios ao aparato fotossintético. Diante deste contexto, este estudo objetivou avaliar a plasticidade fotossintética e a capacidade de aclimatação de seis espécies arbóreas da Amazônia (Hymenea courbaril, Carapa guianensis, Hevea brasiliensis, Tabebuia serratifolia, Bellucia grossularioides e Ochroma
pyramidale) pertencentes a grupos sucessionais distintos (duas sucessionais tardias, duas
intermediárias e duas pioneiras , respectivamente) em reposta a diferentes condições de
luminosidade (pleno sol[FS – 100% da radiação solar, simulando ambientes abertos];
sombreamento moderado[MS–35% de FS, providenciado pelo uso de sombrites] - e
sombreamento intenso[DS – 5% de FS, sob a copa de árvores adultas, simulando ambiente de sub-bosque]). Foram avaliados o ritmo circadiano fotossintético e o acúmulo/turnover de CNE, as taxas de crescimento relativo e acúmulo de biomassa, a fotossíntese máxima e suas limitações, partição do N foliar, atividade do sistema antioxidante e as características da fluorescência da clorofila a. Independente do regime de luz as limitações ao curso diário
fotossintético foram preponderantemente difusivas. As espécies pioneiras e H. courbaril exibiram as maiores taxas fotossintéticas e maior acúmulo de biomassa em FS. Em DS B. grossularioides exibiu maior fotossíntese, mas isso não refletiu em acúmulo de biomassa. As alterações morfológicas mais relacionadas a aclimatação foram a área foliar em DS e o ganho de folhas em FS. A partição do nitrogênio foliar entre compostos fotossintéticos e estruturais foi mais determinante para a fotossíntese do que seu próprio conteúdo, sendo a capacidade de modular a alocação do N fundamental para o aumento ou diminuição da fotossíntese em função de alterações no ambiente de luz. Houve maior investimento de N foliar em Rubisco pelas plantas pioneiras em FS, que exibiram também maiores taxas fotossintéticas, transporte de elétrons e velocidade de carboxilação neste ambiente. Apesar do menor Vcmax em DS, as plantas exibiram maior estado de ativação da Rubisco sugerindo melhor capacidade de aproveitamento de sunflecks, especialmente pelas sucessionais tardias. Quanto ao sistema antioxidativo, a atividade da SOD foi fundamental para redução de danos celulares em FS, tendo menor participação com a diminuição da irradiância. Apenas a sucessional tardia C. guianensis exibiu fotoinibição em FS e a pioneira O. pyramidale não sobreviveu em DS, sugerindo que a aclimatação a alta irradiância é menos desafiadora do que o sombreamento intenso. Os resultados demonstraram que crescimento a sombra aparentemente é mais determinado por fatores relacionados ao acúmulo e turnover de amido do que da fotossíntese. Adicionalmente, pode-se concluir que a plasticidade para regular os ajustes fisiológicos e morfológicos na folha e a capacidade de aclimatação em resposta às mudanças no regime de luz do ambiente não estão necessariamente relacionadas ao grupo sucessional da espécie.Light is a fundamental resource for energy flow in biological systems and is highly determinant
for plant life. The great variability in the natural environment requires that plants, especially trees,
exhibit a great ability to adjust metabolism to spatial and seasonal variations in the availability of
this resource, aiming not only to maximize the capture and use of light, but also the development
of efficient mechanisms in the dissipation of excess light energy to avoid photoinhibitory damages
to photosynthetic apparatus. In this context, the objective of this study was to evaluate the
photosynthetic plasticity and light acclimation capacity of six Amazonian tree species (Hymenea
courbaril, Carapa guianensis, Hevea brasiliensis, Tabebuia serratifolia, Bellucia grossularioides
and Ochroma pyramidale) divided into different successional groups (two late successionals, two
mid-successional and two pioneers, respectively) in response to different light conditions (full
sunlight [FS - 100 % of solar radiation, which simulates a clearing area], moderate shade [MS -
provide by shade cloths reducing direct incident solar radiation] and deep shade [DS - provided
by adult tree canopies, which simulate an understory light environment]).The photosynthetic
circadian rhythm and NSC accumulation/turnover, relative growth and biomass accumulation
rates, maximum photosynthesis and their limitations, leaf N partition, antioxidant system activity
and transients of chlorophyll a fluorescence were evaluated in four individuals per species and
per environment using multivariate analyzes. Regardless of the light regime, the limitations to
daily photosynthetic course were preponderantly diffusive. The pioneer species and H. courbaril
exhibited the highest photosynthetic rates and higher accumulation of biomass in FS. In DS,
greater photosynthesis was observed for B. grossularioides, however, this did not reflect in a
greater accumulation of biomass while in this environment. The morphological changes most
correlated to acclimation were leaf area in DS and leaf gain in FS. The leaf nitrogen partition
between photosynthetic and structural compounds was more determinant for photosynthesis than
its own content, since the ability to modulate the N allocation is fundamental for increasing or
decreasing photosynthesis as a consequence of changes in the light environment. There was
higher N foliar investment in Rubisco by the pioneers in FS, which also showed higher
photosynthetic rates, electron transport and carboxylation rate in this environment. Despite the
smaller Vcmax in DS, the plants exhibited a higher activation state of Rubisco suggesting a better
ability to take advantage of sunflecks, especially in late successional species. Regarding the
antixodative system, the SOD activity was fundamental for the reduction of cell damage in FS,
but this activity decreased n lower irradiances. Only the late successional C. guianensis exhibited
photoinhibition in FS and the pioneer O. pyramidale did not survive on DS, suggesting that
acclimation at high irradiance is less challenging than intense shading. The results suggest that
growth while in a shaded environment is apparently determined more by factors related to starch
accumulation and turnover than photosynthesis. Additionally, it can be concluded that the
plasticity to regulate the leaf’s physiological and morphological adjustments and the capacity of
acclimation in response to changes in light environment regime is not necessarily related to the
successional group of species
Identificação e Analise Comparativa das Propriedades Bioquímicas de Proteínas de Sementes de Leguminosas Arbóreas da Amazônia.
Energetic flux and performance index in copaiba (Copaifera multijuga Hayne) and mahogany (Swietenia macrophylla King) seedlings grown under two irradiance environments
Plant adaptation under conditions of limited irradiance can be investigated by their efficiency while using the available energy with a minimal thermodynamic energy loss. For this reason, we compared the energetic fluxes and the performance index (PIABS) in copaiba (Copaifera multijuga) and mahogany (Swietenia macrophyla) seedlings under both sunlight and shade. The experiment was carried out in Manaus (3°8′S, 59°52′W), Amazonas State, Brazil. The fluorescence transients were obtained in intact and healthy leaves using a Plant Efficiency Analyser (PEA) between 1200 h and 1300 h. Using the O-J-I-P test, the following parameters were calculated: 1) density of reaction centers per cross section (RC/CS), 2) maximum quantum yield for primary photochemistry of photosystem II (φPo), and 3) probability of energy excitation (ψo) or that of an absorbed photon (φEo) to move an electron further than quinone A, and 4) the performance index (PIABS). The highest PIABS was found in seedlings under shade for both species. Mahogany seedlings exhibited values of PIABS about three-fold and 14-fold higher than copaiba seedlings under shade and sunlight, respectively. For RC/CS, reaction centers were inactive under sunlight, 58% for mahogany and 78% for copaiba. The high irradiance induced a decrease of φPo in mahogany (36%) and in copaiba (69%) when compared to shaded seedlings. This likely was a result of need for excess energy dissipation under sunlight. In addition, it was verified that seedlings under sunlight presented a severe decrease in φEo, particularly in copaiba (23-fold), when compared to mahogany (9-fold). Therefore, mahogany seedlings showed the highest performance in energy use under low and high irradiance, thus it may be proposed that mahogany presented lower entropy than copaiba seedlings, as demonstrated by the higher plasticity in the use of energy
Efeito do ambiente de luz no crescimento de plantas jovens de mogno (Swietenia macrophylla King)
In the forest succession intermediate and climax tree species usually exhibit slow growth. The aim of this study was to investigate the biomass accumulation and photosynthetic traits in young S. macrophylla plants subjected to two light environments (1-open field and 2- natural shade). We investigated growth, biomass gain, chlorophyll contents and leaf gas exchange. In open field treatment, the increase photosynthetic performance reflected on the biomass accumulation of the plants, mainly due to the higher growth of the root system and stem diameter. This result happened due to the best use of photosynthetically active radiation, verified by increases in electron transport rate and quantum yield in plants grown in sunlight. This effect favors the carboxylation that was additionally induced by increased leaf gas exchange. On the other hand, the acclimation in the shade exposed seedlings was demonstrated by an increase in leaf area ratio and specific leaf area. We conclude that S. macrophylla seedlings showed physiological plasticity under high or low irradiance. But, above all, when exposed to high irradiance carbon, gain is optimized
Atividade de Proteínas Hemaglutinantes em Sementes de Leguminosas Arbóreas da Flora Amazônica.
Características fotossintéticas, nutricionais e hídricas de espécies arbóreas em diferentes estratos florestais de uma floresta primária do alto Rio Negro
Is average fact in the world scientific literature that tropical forests are important for the maintenance of the regional climate and, even global. In the context of the climatic changes, to know the dynamics of the gas changes in the inferior strata of the forest is very importance to understand the modifications in the participation of carbon in different forest environments and their contributions for the interaction between forest and climate. In that sense, this work had as objective Investigates the gas changes between plant -atmosphere in different forest strata. For so, six arboreal species were selected and marked with GPS in the experimental sites of the LBA inside of the National Park of the Pico da Neblina, in São Gabriel of the Cachoeira, to the northwest of the state of Amazon, distant 860 km of Manaus (0º 12' 44" N and 66º 45' 53" W). The studied species were Nephelium litchi and Lecythis idatimon of the canopy, Conceveiba guianensis and Protium macrophylum of the sub-canopy and Bocageopsis multiflora and Irynthera elliptica of the subforest. The Climatic data were obtained from LBA Project observation towers installed already at the place. The studied individuals were in ray of 200 m around of the tower. In the one what does tell respect the studied physiologic variables, were they appraised the specific leaf area (SLA), the potential of water in the leaf (ΨW), the gas exchanges, leaves nutrients, the content of chlorophylls (ICC) and the characteristics of the fluorescence of the chlorophyll a. The results demonstrate that N. Litchi (canopy) did it present the greatest photosynthesis t. However L. Idatimon, also of canopy it didn't present difference in relation to the other strata, with which the variables of gas exchanges were homogeneous. The studied species didn't differ as the efficiency in the use of the water, suggesting there not to be limitation of this resource in the soil-plant atmosphere sistem. As for the use of the nutrients, N. Litchi show largest efficiency. In what it concerns ICC, the great values were exhibited by the species of the sub-forest. As for the transient of the fluorescence of the chlorophyll the, the results show that the sub-forest species are more efficient in the capture of luminous energy. On the other hand, the efficiency of the species of the superior strata is larger. PIABS was better parameter to evaluate the acting of the species as the light use, and it demonstrated that so much the species of the canopy, with I. elliptica, of the sub-forest, it has larger efficiency photochemical that the others. Additionally, photoinhibition signs were not observed in none of the studied species, or evidences of smaller capacity photosynthetic in the species of the inferior strata. Therefore, in the conditions of experimental site estudied, suggest that the different forest strata show contribuition a homogeneous for the gas exchanges in the plant-atmosphere interactions.É fato corrente na literatura científica mundial que florestas tropicais são importantes para a manutenção do clima regional e, até global. No contexto das mudanças climáticas, conhecer a dinâmica das trocas gasosas nos estratos inferiores da floresta é de grande importância para entender as modificações na participação do carbono nos diferentes ambientes florestais e suas contribuições para a interação entre floresta e clima. Nesse sentido, este trabalho teve como objetivo investigar as trocas gasosas entre planta e atmosfera em diferentes estratos florestais. Para tanto, foram selecionadas e georreferenciadas seis espécies arbóreas de uma floresta primária no alto Rio Negro no sítio experimental do Projeto de Monitoramento de Grande Escala da Biosfera-Atmosfera na Amazônia LBA dentro do Parque Nacional do Pico da Neblina, no município de São Gabriel da Cachoeira, ao noroeste do estado do Amazonas, distante 860 km de Manaus (0º 12 44 N e 66º 45 53 W). As espécies estudadas foram Nephelium litchi e Lecythis idatimon do dossel, Conceveiba guianensis e Protium macrophylum do sub-dossel e Bocageopsis multiflora e Irynthera elliptica do subbosque. Dados climatológicos foram obtidos a partir da torre de observação do Projeto LBA já instalada no local. Os indivíduos estudados estavam situados em raio de 200 m ao redor da torre. No que diz respeito às variáveis fisiológicas estudadas, foram avaliadas: a área foliar específica (AFE), o potencial de água na folha (ΨW), as trocas gasosas, os teores de nutrientes foliares, o índice de conteúdo de clorofilas (ICC) e as características da fluorescência da clorofila a. Os resultados demonstraram que N. Litchi (dossel) apresentou a maior taxa de fotossíntese. Contudo L. Idatimon, também de dossel não apresentou diferença em relação aos demais estratos, com os quais as variáveis de trocas gasosas foram bastante homogêneas. As espécies estudadas não diferiram quanto à eficiência no uso da água, sugerindo não haver limitação deste recurso no sistema solo-planta-atmosfera. Quanto ao uso dos nutrientes, destaca-se a maior eficiência de N. Litchi. No que diz respeito ao ICC, os maiores valores foram exibidos pelas espécies do sub-bosque. Quanto aos transientes da fluorescência da clorofila a, os resultados demontraram que as espécies de sub-bosque são mais eficientes no que diz respeito à captura de energia luminosa. Por outro lado, a eficiência das espécies dos estratos superiores é maior. O PIABS demonstrou ser melhor parâmetro para avaliar o desempenho das espécies quanto a utilização de luz, e demonstrou que não apenas as duas espécies do dossel, mas também I. elliptica, do sub-bosque, tiveram alta eficiência fotoquímica. Adicionalmente, não foram observados sinais de fotoinibição em nehuma das espécies estudadas, nem evidências de menor capacidade fotossintética nas espécies dos estratos inferiores. Portanto, nas condições do sítio florestal estudado, sugere-se que os diferentes estratos florestais exibiram contribuição homogênea para as trocas gasosas na interface planta-atmosfera
Efeito do ambiente de luz no crescimento de plantas jovens de mogno (Swietenia macrophylla King)
Indicadores de estresse emn plantas jovens de mogno Swietenia macrophylla submetidas a diferentes condições de disponibilidade hídrica.
Photochemical Efficiency and Oxidative Metabolism of Tree Species during Acclimation to High and Low Irradiance
The balance between efficiency of absorption and use of light energy is fundamental for plant metabolism and to avoid photoinhibition. Here, we investigated the effects of light environments on the photosynthetic apparatus of tropical tree species of three successional groups (pioneer, mid-, and late successional) subjected to different light conditions: full sunlight (FS), moderate shade (MS), and deep shade (DS). Twenty-nine ecophysiological parameters were correlated with each other. The pioneer species exhibited better photochemical performance and a more efficient antioxidant enzymatic system in comparison with the other successional groups. Plants in FS showed higher intensity of lipid peroxidation, with superoxide dismutase having a prominent role in the antioxidant system. At lower irradiance the enzymatic activity was reduced, and the photochemical efficiency was the preferred way to reduce oxidative damages. P was highly related to photochemical yield, and the N modulation amplified the light harvesting complex in DS to the detriment of the antioxidant system. Despite evidence of cell damage, most species exhibited the ability to adjust to high irradiance. Contrary to expectations, Hymenea courbaril (late-successional) exhibited higher plasticity to fluorescence, nutritional, and antioxidant parameters. Only Carapa guianensis (late-successional) displayed photoinhibitory damage in FS, and Ochroma pyramidale (pioneer) did not survive in DS, suggesting that acclimation to shade is more challenging than to high irradiance