0000000000065893
AUTHOR
Riitta Julkunen-tiitto
Boron mobility in deciduous forest trees in relation to their polyols
Summary • Boron (B) has been found to be phloem mobile in species that translocate polyols, whereas it is almost immobile in other species. The objectives of the present study were to survey B mobility in deciduous trees, and to relate it to the presence of polyols. • The stable isotope 10B was applied as a tracer to mature leaves of seedlings, and growing leaves were subsequently harvested for B isotope analysis. • Extensive B mobility was found in Sorbus aucuparia and Prunus padus, species with high sorbitol content, but also in Ulmus glabra, with only trace amounts of B-complexing polyols. Alnus incana, Fraxinus excelsior, Betula pubescens and Larix sibirica also translocated 10B into ne…
Red : far-red light ratio and UV-B radiation: their effects on leaf phenolics and growth of silver birch seedlings
The natural variation in quantity and quality of light modifies plant morphology, growth rate and concentration of biochemicals. The aim of two growth-room experiments was to study the combined effects of red (R) and far-red (FR) light and ultraviolet-B (UV-B) radiation on the concentrations of leaf phenolics and growth and morphology of silver birch (Betula pendula Roth) seedlings. Analysis by high-performance liquid chromatography showed that the leaves exposed to supplemental FR relative to R contained higher concentrations of total chlorogenic acids and a cinnamic acid derivative than the leaves treated with supplemental R relative to FR. In contrast, concentration of a flavonoid, querc…
Metabolite specific effects of solar UV-A and UV-B on alder and birch leaf phenolics
We measured the concentrations of ultraviolet (UV)-absorbing phenolics varying in response to exclusion of either solar UV-B or both solar UV-A and UV-B radiations in leaves of grey alder (Ainus incana) and white birch (Betula pubescens) trees under field conditions. In alder leaves 20 and in birch leaves 13 different phenolic metabolites were identified. The response to UV exclusion varied between and within groups of phenolics in both tree species. The changes in concentration for some metabolites suggest effects of only UV-A or UV-B, which band being effective depending on the metabolite. For some other metabolites, the results indicate that UV-A and UV-B affect concentrations in the sam…
Interactions between willows and insect herbivores under enhanced ultraviolet-B radiation
We studied the effects of elevated ultraviolet-B radiation on interactions between insect herbivores and their host plants by exposing two species of phytochemically different willows, Salix myrsinifolia and S. phylicifolia, to a modulated increase in ultraviolet radiation in an outdoor experiment and monitoring the colonisation of insect herbivores on these willows. We examined the effect of increased ultraviolet-B (UV-B) radiation on (1) the quality of willow leaves, (2) the distribution and abundance of insect herbivores feeding on these willows, (3) the resulting amount of damage, and (4) the performance of insect larvae feeding on the exposed plant tissue. Six clones of each of the two…
Assessment of UV Biological Spectral Weighting Functions for Phenolic Metabolites and Growth Responses in Silver Birch Seedlings
In research concerning stratospheric ozone depletion, action spectra are used as biological spectral weighting functions (BSWFs) for describing the effects of UV radiation on plant responses. Our aim was to evaluate the appropriateness of six frequently used BSWFs that differ in effectiveness with increasing wavelength. The evaluation of action spectra was based on calculating the effective UV radiation doses according to 1-2) two formulations of the generalized plant action spectrum, 3) a spectrum for ultraviolet induced erythema in human skin, 4) a spectrum for the accumulation of a flavonol in Mesembryanthemum crystallinum, 5) a spectrum for DNA damage in alfalfa seedlings and 6) the pla…
Solar UV-B radiation affects leaf quality and insect herbivory in the southern beech tree Nothofagus antarctica
We examined the effects of solar ultraviolet-B (UV-B) radiation on plant-insect interactions in Tierra del Fuego (55°S), Argentina, an area strongly affected by ozone depletion because of its proximity to Antarctica. Solar UV-B under Nothofagus antarctica branches was manipulated using a polyester plastic film to attenuate UV-B (uvb-) and an Aclar film to provide near-ambient UV-B (uvb+). The plastic films were placed on both north-facing (i.e., high solar radiation in the Southern Hemisphere) and south-facing branches. Insects consumed 40% less leaf area from north- than from south-facing branches, and at least 30% less area from uvb+ branches than from uvb-branches. The reduced herbivory …
Carotenoid-based colour polyphenism in a moth species: search for fitness correlates
Carotenoid-based integumental coloration is often associated with individual performance in various animals. This is because the limited amount of the pigment has to be allocated to different vital functions. However, most of the evidence for the carotenoid-based trade-off comes from vertebrate studies, and it is unclear if this principle can be applied to insects. This possibility was investigated in Orgyia antiqua L. (Lepidoptera: Lymantriidae). The larvae of this species are polyphenic in their coloration, varying from a highly conspicuous combination of yellow hair tufts on black background to cryptic appearance with brown hair tufts. The conspicuous larvae are aposematic, advertising t…
Clonal differences in growth and phenolics of willows exposed to elevated ultraviolet-B radiation
Abstract In this study, the effects of elevated ultraviolet-B (UV-B, 280–320 nm) radiation on growth and leaf phenolics were evaluated in clones of dark-leaved willow ( Salix myrsinifolia Salisb.) and tea-leaved willow ( Salix phylicifolia L.). Willows were raised for one growing season in an irradiation field, where they were exposed either to a constant 50% increase in UV-B CIE radiation simulating 20–25% ozone depletion or to a small increase in UV-A radiation (320–400 nm). Control willows were grown in the irradiation field under solar radiation (ambient control). Despite the high constitutive concentrations of a UV-absorbing leaf flavonoid, dihydromyricetin, UV-treatments clearly reduc…
Seasonal fluctuations in leaf phenolic composition under UV manipulations reflect contrasting strategies of alder and birch trees
Seasonal variation in leaf phenolic composition may be important for acclimation of plants to seasonal changes in their biotic and abiotic environment. For a realistic assessment of how plants respond to solar UV-B (280-315 nm) and UV-A (315-400 nm) radiation, seasonal variation in both environment and plant responses needs to be taken into account. This also has implications for studies concerning stratospheric ozone depletion and resulting increased UV-B radiation, as other environmental variables and/or plant phenology could interact with UV radiation. To elucidate this, we established a field experiment using plastic films attenuating different parts of the solar UV spectrum. The concen…
Growth and defense in deciduous trees and shrubs under UV-B
Abstract Reflection by waxy or resinous surface structures and hairs, repair reactions of biomolecules and induction of different sheltering components provide the means of plant protection from harmful solar UV-B radiation. Secondary products, especially flavonoids and phenolic acids as defense components are also important in plant tolerance to UV-B, fulfilling the dual role as screens that reduce UV-B penetration in plant tissues, and as antioxidants protecting from damage by reactive oxidant species. Plants are sensitive to UV-B radiation, and this sensitivity can be even more clone-specific than species-specific. The results available in the literature for deciduous trees and shrubs in…