Anatomia ecológica da folha e da raiz e aspectos ecofisiológicos de Orchidaceae epífitas de uma campina da Amazônia central

Root and leaf ecological anatomy of twenty-five Orchidaceae epiphytic species occurring in the Amazonian campina is related with C 3 and CAM type carbon fixation pathways, spatial distribution and orchid growing management. Furthermore, we propose a descriptive anatomical model for the absorbing roots as well as a classification for fibrovascular bundles, in addition to dividing these species leaf blades into categories and making ecological and evolutionary interpretations. Thereby, we see that Brassavola martiana, Bulbophyllum setigerum, Cattleya eldorado, Encyclia amicta, Encyclia tarumana, Encyclia vespa, Epidendrum compressum, Epidendrum huebneri, Epidendrum sculptum, Epidendrum strobiliferum, Maxillaria tarumaensis and Maxillaria uncata, adopt the CAM pathway in hot and dry periods alternately. They are capable of living in rich light radiation, xeric and/or oligotrophic environments, such as open grassland. In orchid growing, they can do without a rigorous irrigation regime. On the other hand, we see that Bifrenaria longicornis, Encyclia fragrans, Epidendrum nocturnum, Maxillaria sp, Maxillaria camaridii, Maxillaria pauciflora, Maxillaria pendens, Maxillaria rudolfi, Maxillaria villosa, Ornithidium parviflorum, Rudolfiella aurantiaca, Sobralia fragrans and Sobralia macrophylla only present the C 3 fixation pathway with no other alternative in hot and dry seasons. This is offset by the presence of pseudobulbs, varying succulence degrees or leaf strategic loss, and they are well adapted for colonising environments with little light radiation such as, shaded grassland and, in orchid growing they need a more rigorous irrigation regime. The species present several anatomical characters in common, yet, in a differentiated number, which is directly related to xeromorphism, oligotrophism and herbivoria, among others, which together, comprise an evolutionary adaptive syndrome for the Amazonian ecosystems.Relaciona-se a anatomia ecológica da folha e da raiz de vinte e cinco espécies epífitas de Orchidaceae ocorrentes na Campina amazônica com as vias de fixação do Carbono do tipo C 3 e CAM, com a distribuição espacial e com o manejo orquidiocultural. Adicionalmente, propõe-se um modelo anatômico descritivo para as raízes absorventes e uma classificação para os feixes fibrovasculares, além de se dividir as lâminas foliares destas espécies em categorias e se fazer interpretações ecológicas e evolutivas. Assim, temos que Brassavola martiana, Bulbophyllum setigerum, Cattleya eldorado, Encyclia amicta, Encyclia tarumana, Encyclia vespa, Epidendrum compressum, Epidendrum huebneri, Epidendrum sculptum, Epidendrum strobiliferum, Maxillaria tarumaensis e Maxillaria uncata, adotam, alternadamente, em períodos quentes e secos, a via CAM, estando aptas para vegetarem em ambientes com radiação abundante, xéricos e /ou oligotróficos, como os da campina aberta e, na orquidiocultura, podem dispensar um regime rigoroso de irrigação. Por outro lado, temos que Bifrenaria longicornis, Encyclia fragrans, Epidendrum nocturnum, Maxillaria sp, Maxillaria camaridii, Maxillaria pauciflora, Maxillaria pendens, Maxillaria rudolfi, Maxillaria villosa, Ornithidium parviflorum, Rudolfiela aurantiaca, Sobralia fragrans e Sobralia macrophylla possuem somente a via de fixação C 3 , não apresentando via alternativa para períodos quentes e secos, sendo que esta falta é compensada pela presença de pseudobulbos, graus variados de suculência ou por perda estratégica de folhas, estando bem adaptadas para a colonização de ambientes umbrófilos como os da Campina sombreada e, na orquidiocultura, necessitam de um regime mais rigoroso de irrigação. As espécies possuem em comum, porém com número diferenciado, vários caracteres anatômicos e que estão diretamente relacionados com o xeromorfismo, oligotrofismo e herbivoria, entre outros, que em conjunto, constituem uma síndrome adaptativa evolutiva para os ecossistemas amazônicos

Ecophysiological Studies of Orchidaceae in Amazonia. II - Ecology of Leaf Anatomy of Species with Cam Metabolism in a Central Amazonian White Sand Campina

This paper is the second in a series which discusses the leaf anatomy and mode of fixation of C02 in relation to the geographic of Orchidaceae, and specifically describes the occurence of succulence in the species studied, and classifies them according to the anatomical system of WITHNER et al.(1974). The anatomical characteristics which might related to behavioural and/or nutritional sclerophism and CAM photoshyntesis are examined, and these are found to form an adaptative syndrome for the control of water flow through the leaf surface, allowing these species to colonize the drier habitats such as the open campina. Succulence is a characteristic of plants with CAM metabolism, and the leaves were classified as being coriaceous.Este trabalho é o segundo de uma série que objetiva correlacionar a anatomia foliar e via de fixação de C02 com a distribuição geográfica de Orchidaceae e especificamente, detectar a existência de suculência nas espécies estudadas e também qualificá-las na classificação anatômica de WITHNER et al.(1974). Enfoca-se características anatômicas que possivelmente se relacionariam com o xeromorfismo habitacional e/ou escleromorfismo nutricional e via fotossintética CAM, e estas estabeleceriam uma sindrome adaptativa para o efetivo controle do fluxo hídrico no limbo foliar, dando para as espécies condições para a colonização de ambientes mais xéricos como os da Campina aberta. Detectou-se a presença de suculência anatômica propícia para a ocorrência do metabolismo CAM, sendo que as folhas foram classificadas como sendo do tipo Coriáceas

Características fisiológicas e anatômicas de folhas de dois clones de guaraná

The objective of this work was to analyze gas exchange, photosynthetic characteristics, photochemical efficiency of photosystem II and anatomical characteristics of young plant leaves of two guarana (Paullinia cupana) clones (BRS-CG372RC and BRS-CG611RL) growing under open field. The variables of gas exchange and fluorescence of chlorophyll a were evaluated in mature leaves. The values of photosynthesis and transpiration found for BRS-CG372RC were 27% greater and 80% lesser than values found for BRS-CG611RL, respectively. The values of stomatal conductance found for the clones BRS-CG372RC and BRS-CG611RL were in the order of 224 and 614 mmol mm-2 s-1, respectively. The values of photorespiration, rate of carboxylation and rate electron transport were greater in BRS-CG372RC. The clone BRS-CG372RC exhibited stomatal density 26% greater than BRS-CG611RL. However, the area of ostiolar opening was 42% greater in BRS-CG611RL. The values of the water use efficiency in BRS-CG372RC were 134% greater than in BRS-CG611RL. High stomatal density and low stomatal conductance can be important characteristics in the selection of the clones with a good ability to assimilate carbon and optimize the use of water.O objetivo deste trabalho foi analisar as trocas gasosas, as características fotossintéticas, a eficiência fotoquímica do fotossistema II e as características anatômicas foliares de plantas jovens de dois clones de guaraná desenvolvidas a pleno sol. As variáveis de trocas gasosas e fluorescência da clorofila a foram determinadas em folhas maduras. Os valores de fotossíntese e transpiração encontrados para BRS-CG372RC foram 27% maiores e 80% menores que os valores encontrados para BRS-CG611RL, respectivamente. Os valores de condutância estomática dos clones BRS-CG372RC e BRS-CG611RL foram de aproximadamente 224 e 614 mmol m-2 s-1, respectivamente. Os valores de fotorrespiração, taxa de carboxilação e taxa de transporte de elétrons foram maiores em BRS-CG372RC. O clone BRS-CG372RC apresentou densidade estomática 26% maior que BRS-CG611RL. A área de abertura do ostíolo foi 42% maior em BRS-CG611RL. O valor da eficiência no uso da água em BRS-CG372RC foi 134% maior que em BRS-CG611RL. Alta densidade estomática e baixa condutância estomática são características importantes para a seleção de clones com boa capacidade para assimilar carbono e que sejam eficientes no uso da água

Physiological and anatomical characteristics of leaves of two clones of guarana

The objective of this work was to analyze gas exchange, photosynthetic characteristics, photochemical efficiency of photosystem II and anatomical characteristics of young plant leaves of two guarana (Paullinia cupana) clones (BRS-CG372RC and BRS-CG611RL) growing under open field. The variables of gas exchange and fluorescence of chlorophyll a were evaluated in mature leaves. The values of photosynthesis and transpiration found for BRS-CG372RC were 27% greater and 80% lesser than values found for BRS-CG611RL, respectively. The values of stomatal conductance found for the clones BRS-CG372RC and BRS-CG611RL were in the order of 224 and 614 mmol mm-2 s-1, respectively. The values of photorespiration, rate of carboxylation and rate electron transport were greater in BRS-CG372RC. The clone BRS-CG372RC exhibited stomatal density 26% greater than BRS-CG611RL. However, the area of ostiolar opening was 42% greater in BRS-CG611RL. The values of the water use efficiency in BRS-CG372RC were 134% greater than in BRS-CG611RL. High stomatal density and low stomatal conductance can be important characteristics in the selection of the clones with a good ability to assimilate carbon and optimize the use of water

Local hydrological conditions influence tree diversity and composition across the Amazon basin

Tree diversity and composition in Amazonia are known to be strongly determined by the water supplied by precipitation. Nevertheless, within the same climatic regime, water availability is modulated by local topography and soil characteristics (hereafter referred to as local hydrological conditions), varying from saturated and poorly drained to well-drained and potentially dry areas. While these conditions may be expected to influence species distribution, the impacts of local hydrological conditions on tree diversity and composition remain poorly understood at the whole Amazon basin scale. Using a dataset of 443 1-ha non-flooded forest plots distributed across the basin, we investigate how local hydrological conditions influence 1) tree alpha diversity, 2) the community-weighted wood density mean (CWM-wd) – a proxy for hydraulic resistance and 3) tree species composition. We find that the effect of local hydrological conditions on tree diversity depends on climate, being more evident in wetter forests, where diversity increases towards locations with well-drained soils. CWM-wd increased towards better drained soils in Southern and Western Amazonia. Tree species composition changed along local soil hydrological gradients in Central-Eastern, Western and Southern Amazonia, and those changes were correlated with changes in the mean wood density of plots. Our results suggest that local hydrological gradients filter species, influencing the diversity and composition of Amazonian forests. Overall, this study shows that the effect of local hydrological conditions is pervasive, extending over wide Amazonian regions, and reinforces the importance of accounting for local topography and hydrology to better understand the likely response and resilience of forests to increased frequency of extreme climate events and rising temperatures

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran\u27s eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R$^{2}$ = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R$^{2}$ = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions

Estimating the global conservation status of more than 15,000 Amazonian tree species

Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict thatmost of the world’s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

AimAmazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.LocationAmazonia.TaxonAngiosperms (Magnoliids; Monocots; Eudicots).MethodsData for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.ResultsIn the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.Main ConclusionNumerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions