Solar radiation as a factor in the evolution of scleromorphic leaf anatomy in Proteaceae

Jordan, Gregory J.; Dillon, Rebecca; Weston, Peter H.

doi:10.3732/ajb.92.5.789

Cited by 144 publications

(93 citation statements)

References 36 publications

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“…S27-S30)]. The remainder could not be placed into groups, because the Australian sclerophyll flora shows high levels of morphological convergence and apart from Proteaceae and Ericaceae (26)(27)(28)(29), has poorly known anatomy. For example, superficially similar small, linear entire leaves with tightly revolute margins occur within Proteaceae, Fabaceae, Asteraceae, Lamiaceae, Euphorbiaceae, Ericaceae, Dilleniaceae, Tremandraceae, Frankeniaceae, Rhamnaceae, and Polygalaceae.…”

Section: Resultsmentioning

confidence: 99%

Fossil evidence for a hyperdiverse sclerophyll flora under a non–Mediterranean-type climate

Sniderman

Jordan

Cowling

2013

Proc. Natl. Acad. Sci. U.S.A.

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The spectacular diversity of sclerophyll plants in the Cape Floristic Region in South Africa and Australia's Southwest Floristic Region has been attributed to either explosive radiation on infertile soils under fire-prone, summer-dry climates or sustained accretion of species under inferred stable climate regimes. However, the very poor fossil record of these regions has made these ideas difficult to test. Here, we reconstruct ecological-scale plant species richness from an exceptionally well-preserved fossil flora. We show that a hyperdiverse sclerophyll flora existed under high-rainfall, summerwet climates in the Early Pleistocene in southeastern Australia. The sclerophyll flora of this region must, therefore, have suffered subsequent extinctions to result in its current relatively low diversity. This regional loss of sclerophyll diversity occurred at the same time as a loss of rainforest diversity and cannot be explained by ecological substitution of species of one ecological type by another type. We show that sclerophyll hyperdiversity has developed in distinctly non-Mediterranean climates, and this diversity is, therefore, more likely a response to long-term climate stability. Climate stability may have both reduced the intensity of extinctions associated with the Pleistocene climate cycles and promoted the accumulation of species richness by encouraging genetic divergence between populations and discouraging plant dispersal.macrofossil flora | species diversity | species-area curve | glacial-interglacial cycles M editerranean climate regions support ∼20% of vascular plant species on 5% of Earth's surface (1) and show positive anomalies in the latitudinal plant species diversity gradient. Researchers have used two approaches to explain this gradient. The first approach emphasizes the importance of contemporary environmental processes. For example, some models use energy and water availability to explain global patterns of diversity (2, 3). Alternatively, historical models focus on geological-scale processes and often invoke the contrasting antiquity of tropical vs. temperate climates. For example, the tropical conservatism hypothesis (4) argues that the high diversity of tropical floras accumulated over tens of millions of years during warm, ever-wet, early-middle Cenozoic climates. This model infers that temperate floras are depauperate because they were derived relatively recently from a small number of thermophilic lineages that were able to colonize novel temperate climates during the late Cenozoic.

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Section: Resultsmentioning

confidence: 99%

Fossil evidence for a hyperdiverse sclerophyll flora under a non–Mediterranean-type climate

Sniderman

Jordan

Cowling

2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Tais substâncias são frequentes em xerófitas e provavelmente reduzem a passagem de luz através das células epidérmicas, protegendo contra o excesso de radiação solar (IZAGUIRRE et al, 2007) que pode ter efeitos deletérios sobre as plantas como danos por radiação ultravioleta, estresse induzido por aquecimento das folhas e fotoinibição resultante da exposição a níveis altos de luz que danificam o sistema fotossintético (JORDAN; DILLON;WESTON., 2005). A falta de água causa perda de turgor nas células-guarda, o fechamento dos estômatos e, por sua vez, diminui o dióxido de carbono disponível limitando a fotossíntese; isto aumenta o estresse oxidativo e pode induzir o acúmulo de compostos fenólicos (CLOSE;MCARTUR, 2002).…”

Section: Resultsunclassified

Adaptações anatômicas em folhas de marmeleiro e velame da caatinga brasileira

Barros¹,

Soares²

2013

Rev. Ciênc. Agron.

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Adaptações anatômicas em folhas de marmeleiro e velame da caatinga brasileira 1Anatomical adaptations in leaves of the quince and velame of the Brazilian caatinga Ileane Oliveira Barros 2 e Arlete Aparecida Soares 3 * RESUMO -A disponibilidade de água é o principal fator limitante para as espécies vegetais em ambientes áridos e semiáridos. Nessas plantas, uma combinação de características contribui para a economia hídrica, entre elas as anatômicas. Assim, estudos em folhas de marmeleiro (Croton blanchetianus) e velame (Croton heliotropiifolius), duas espécies comuns na caatinga e de importância apícola, foram realizados para verificar as características anatômicas adaptativas relacionadas à maior eficiência na utilização de água. As folhas de ambas as espécies possuem indumento denso, parede das células basais dos tricomas impregnadas com lipídios e compostos fenólicos nas células epidérmicas e parenquimáticas. Em plantas de ambientes áridos, os tricomas podem ajudar a reduzir o aquecimento e a transpiração foliar e também impedir o fluxo apoplástico da água devido à presença de lipídios nas paredes das células basais. Estas características anatômicas podem atuar na economia hídrica e ser, desta maneira, consideradas adaptações às condições de semiaridez da caatinga. Palavras-chave:Marmeleiro. Croton. Plantas e água. Plantas da caatinga.ABSTRACT -Water availability is the main limiting factor for plants in arid and semi-arid environments. In these plants, a combination of characteristics contributes to water economy, among them being anatomical features. Thus, studies in leaves of the quince (Croton blanchetianus) and the velame (Croton heliotropiifolius), two common species in the caatinga and of importance in beekeeping, were performed to verify adaptive anatomical characteristics which are related to a greater efficiency in water usage. The leaves of both species have a dense indumentum, the basal-cell walls of the trichomes are impregnated with lipids, and phenolic compounds are found in the epidermal and parenchymal cells. In plants from arid environments, the trichomes can help reduce heating and leaf transpiration and also prevent the apoplastic flow of water due to the presence of lipids in the walls of the basal cells. These anatomical features may act on the water economy, and can thus be considered as adaptations to the semi-arid conditions of the caatinga.

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“…Cuticle thickness was measured microscopically on transverse sections approximately 0.05 mm thick, cut approximately half way along the leaves as described in Jordan et al (2005). Measurements were made on three separate sections from one leaf, for each leaf age class of five plants, for each nutrient treatment.…”

Section: Leaf Anatomymentioning

confidence: 99%

How do soil nutrients affect within-plant patterns of herbivory in seedlings of Eucalyptus nitens?

et al. 2006

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This study assessed how the palatability of leaves of different age classes (young, intermediate and older) of Eucalyptus nitens seedlings varied with plant nutrient status, based on captive feeding trials with two mammalian herbivores, Red-bellied Pademelons (Thylogale billardierii), and Common Brushtail Possums (Trichosurus vulpecula). Seedlings were grown under three nutrient treatments (low, medium and high) and we determined how palatability was related to chemical and physical characteristics of the leaves. Pademelons ate more older leaves than young and intermediate leaves for all treatments. This pattern was best explained by sideroxylonals (formylated pholoroglucinol compounds known to deter herbivory by other marsupials), and/or essential oil compounds that were in lower concentrations in older leaves. In the low nutrient treatment, possums also ate more of the older leaves. However, in the medium and high nutrient treatments, possums ate more intermediate leaves than older leaves and showed a behavioural preference for young leaves (consuming younger leaves first) over intermediate and older leaves, in spite of high levels of sideroxylonals and essential oils. The young leaves did, however, have the highest nitrogen concentration of the leaf age classes. Thus, either sideroxylonals and essential oils provided little or no deterrent to possums, or the deterrent was outweighed by other factors such as high nitrogen. This study indicates that mammalian herbivores show different levels of relative use and damage to leaf age classes at varying levels of plant nutrient status and, therefore, their impact on plant fitness may vary with environment.

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Solar radiation as a factor in the evolution of scleromorphic leaf anatomy in Proteaceae

Cited by 144 publications

References 36 publications

Fossil evidence for a hyperdiverse sclerophyll flora under a non–Mediterranean-type climate

Fossil evidence for a hyperdiverse sclerophyll flora under a non–Mediterranean-type climate

Adaptações anatômicas em folhas de marmeleiro e velame da caatinga brasileira

How do soil nutrients affect within-plant patterns of herbivory in seedlings of Eucalyptus nitens?

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