Topic
Embothrium coccineum
About: Embothrium coccineum is a research topic. Over the lifetime, 45 publications have been published within this topic receiving 991 citations.
Papers
TL;DR: Findings with Hakea prostrata (Proteaceae) indicate that P-toxicity symptoms result after the capacity of tissues to store P is exceeded, and the present review investigates cluster-root functioning in L. albus and native Proteaceae that have evolved in phosphate-impoverished environments.
Abstract: Cluster roots are an adaptation for nutrient acquisition from nutrient-poor soils. They develop on root systems of a range of species belonging to a number of different families (e.g., Proteaceae, Casuarinaceae, Fabaceae and Myricaceae) and are also found on root systems of some crop species (e.g., Lupinus albus, Macadamia integrifolia and Cucurbita pepo). Their morphology is variable but typically, large numbers of determinate branch roots develop over very short distances of main root axes. Root clusters are ephemeral, and continually replaced by extension of the main root axes. Carboxylates are released from cluster roots at very fast rates for only a few days during a brief developmental window termed an ‘exudative burst’. Most of the studies of cluster-root metabolism have been carried out using the crop plant L. albus, but results on native plants have provided important additional information on carbon metabolism and exudate composition. Cluster-root forming species are generally non-mycorrhizal, and rely upon their specialised roots for the acquisition of phosphorus and other scarcely available nutrients. Phosphorus is a key plant nutrient for altering cluster-root formation, but their formation is also influenced by N and Fe. The initiation and growth of cluster roots is enhanced when plants are grown at a very low phosphate supply (viz. ≤1 µM P), and cluster-root suppression occurs at relatively higher P supplies. An important feature of some Proteaceae is storage of phosphorus in stem tissues which is associated with the seasonality of cluster-root development and P uptake (winter) and shoot growth (summer), and also maintains low leaf [P]. Some species of Proteaceae develop symptoms of P toxicity at relatively low external P supply. Our findings with Hakea prostrata (Proteaceae) indicate that P-toxicity symptoms result after the capacity of tissues to store P is exceeded. P accumulation in H. prostrata is due to its strongly decreased capacity to down-regulate P uptake when the external P supply is supra-optimal. The present review investigates cluster-root functioning in (1) L. albus (white lupin), the model crop plant for cluster-root studies, and (2) native Proteaceae that have evolved in phosphate-impoverished environments.
437 citations
TL;DR: The hypothesis that pollinators can act as important biotic filters influencing plant distribution, and warn against predictions of geographical range shifts based solely on climatic variables, is supported.
Abstract: The limit of a species’ distribution can be determined biotically if an environmental gradient causes the loss of critical mutualists such as pollinators. We assessed this hypothesis for Embothrium coccineum, a self-incompatible red-flowered treelet growing along a strong west-east precipitation gradient from rainforest to forest-steppe ecotone in the rain shadow of the southern Andes in northwestern Patagonia. For 16 populations along this gradient, we quantified composition of the pollinator assemblage, pollination efficiency and limitation, and reproductive output. The treelet has a generalized pollination system, but the hummingbird Sephanoides sephaniodes was the most effective pollinator. The relative importance of this hummingbird as a flower visitor within populations influenced pollen transfer and fruit set more strongly than local precipitation. As hummingbirds and other pollinators, including passerine birds and nemestrinid flies, were replaced by bees towards the dry eastern range limit, pollen limitation increased and reproduction eventually failed. These results support the hypothesis that pollinators can act as important biotic filters influencing plant distribution, and warn against predictions of geographical range shifts based solely on climatic variables.
56 citations
TL;DR: The effects of forest fragmentation were detectable in E. coccineum, but these effects will probably not be detrimental to the viability of remnant populations because small, fragmented populations demonstrated higher levels of gene flow and lower inbreeding than larger stands.
Abstract: Deforestation of temperate forests has created landscapes of forest remnants in matrices of intense human use. We studied the genetic effects of fragmentation in southern Chile on Embothrium coccineum J.R. et G. Forster, an early colonizing, bird-pollinated tree. We tested the hypothesis that, because of its self-incompatibility and life-history strategy, E. coccineum is less strongly affected by fragmentation. We studied the effects of reduced population size and increased isolation on population genetic structure and early performance of progeny. Samples were collected from spatially isolated trees and six fragments of differing sizes (small, 1 ha; medium, 20 ha; large, >150 ha). Based on isozyme polymorphisms we estimated parameters of genetic diversity, divergence, and inbreeding for adults and greenhouse-grown progeny. We also measured germination, seedling growth, and outcrossing rates on progeny arrays. Genetic variation of adults did not correlate significantly with population size, as expected, given that fragmentation occurred relatively recently. Weak effects of fragmentation were measured on progeny. Only adults yielded significant inbreeding. Similar total genetic diversity was found in adults and progeny. Low but significant genetic differentiation existed among adult and progeny populations. Seedling growth correlated positively with the effective number of alleles, showing deleterious effects of inbreeding on progeny. Seeds from small fragments had the highest outcrossing rates and germination success, indicating that higher pollinator activity in such fragments reduced selfing, thereby buffering genetic erosion and maintaining adaptive variation. The effects of forest fragmentation were detectable in E. coccineum, but these effects will probably not be detrimental to the viability of remnant populations because small, fragmented populations demonstrated higher levels of gene flow and lower inbreeding than larger stands. Pioneer species that are insensitive to forest clearing may be crucial in recovery plans to facilitate the establishment of species intolerant to such disturbance.
54 citations
TL;DR: The results are consistent with the proposal that the costs of obtaining enough N for crown maintenance and expansion may constrain the fitness of shade-tolerant angiosperm trees in late successional stages on infertile sites, when soil nutrient availability is reduced by increased uptake and sequestration in biomass and litter.
Abstract: Summary
1 Shade-tolerant angiosperm trees are reported to require relatively fertile soils in temperate forests. We explored the possibility that high foliage allocation in shade-tolerant species could result in higher whole-plant nitrogen demands than in light-demanding trees of comparable diameters. We measured foliage mass and area, leaf life span, and nitrogen (N) content of fresh foliage and leaf litter for juveniles of 11 evergreen angiosperms in a Chilean temperate rain forest. This permitted estimation of annual nitrogen losses in leaf litter fall by individuals of a given diameter.
2 Leaf life spans were longest in shade-tolerant species. The highest leaf N levels were found in small short-lived early successional trees, whereas among longer-lived species there was no general relationship of leaf N with shade tolerance level. Shade-tolerant species had lower N resorption efficiencies, and therefore higher leaf litter N concentrations on an area basis, than light-demanding associates.
3 Foliage mass, foliage area and total crown N pool were strongly positively related to shade tolerance level.
4 Interspecific variation in annual N losses in leaf litter fall was more closely related to foliage area (R2 = 0.52) than to N concentration of leaf litter (R2 = 0.31) or leaf lifetimes (R2 = 0.01). Although the short-lived early successional species Embothrium coccineum had the highest annual crown N losses of the 11 species, shade-tolerant species had higher annual losses than light-demanding overstorey dominants of comparable longevities.
5 The results are consistent with the proposal that the costs of obtaining enough N for crown maintenance and expansion may constrain the fitness of shade-tolerant angiosperm trees in late successional stages on infertile sites, when soil nutrient availability is reduced by increased uptake and sequestration in biomass and litter. On the other hand, high N loss rates may be more sustainable for short-lived early colonists that complete their life cycles in the initial stages of secondary succession, when nutrient availabilities are often relatively high.
54 citations
TL;DR: It was found that pollinator visiting rates were negatively correlated with forest patch area and were highest for pasture trees, and this trend was largely due a decline in the number of visits by E. albiceps, the main flower visitor, in larger patches.
Abstract: We investigated the effects of forest patch size on the behaviour of birds feeding on the flower nectar of the proteaceous tree Embothrium coccineum J R et G Forster, which is typically restricted to forest edges in agricultural landscapes in southern Chile We quantified reproductive parameters of trees (no inflorescences per branch, total and open flowers per inflorescence) in forest fragments varying from 1 ha (small), to 20 ha (medium) and to >150 ha (large), and in remnant trees in pastures Visits to flowers by nectar-feeding birds were recorded during 30-min observation periods, spread throughout the day during two flowering seasons, November 1992 and 1993 (n = 242 periods overall) Aggressive encounters among flower visitors were recorded in 1992 We expected less visits to trees in pastures and small forest patches because abundances of Embothrium's main pollinators, the flycatcher Elaenia albiceps and the hummingbird Sephanoides sephaniodes, decreased in smaller patches We found, however, that pollinator visiting rates were negatively correlated with forest patch area and were highest for pasture trees This trend was largely due a decline in the number of visits by E albiceps, the main flower visitor, in larger patches Hummingbird visits did not change with forest patch size Lower visitation rates to flowering trees in larger forest fragments seemed to be a consequence of territorial defence by E albiceps and were unrelated to differences in floral display
45 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 2 |
| 2020 | 2 |
| 2019 | 5 |
| 2018 | 3 |
| 2017 | 1 |
| 2016 | 2 |