Epilobium Ciliatum Research Articles

An association between triazine resistance and powdery mildew resistance inEpilobium ciliatumandSenecio vulgaris

AbstractThe response of four naturally occurring biotypes ofEpilobium ciliatumand four sources of Senecio vulgaris to the herbicide atrazine were compared with their susceptibility to the powdery mildewsSphaerotheca epilobiiand Erysiphe cichoracearum. Biotypes that were resistant to atrazine were also resistant to mildew. Mechanisms that might explain the association between atrazine resistance and mildew resistance are discussed, along with possible implications of these findings for farmland ecology and for the production of herbicide‐ and mildew‐resistant crop plants.

Photoacoustic study of the photochemical energy conversion in Epilobium plants grown under very low light conditions

Epilobium ciliatum plants were grown under extreme shade conditions ( ca 20 μmol m −2 sec −1). The photosynthetic characteristics of these low-light-grown (LL) leaves were measured using the photoacoustic technique and were compared to those of control (HL) leaves grown at a higher (5x) photon flux density (100 μmol m −2 sec −1). Adaptation to very low light was not associated with a significant change in the maximal efficiency of photochemical energy storage (value extrapolated to the zero photon density) which was around 16% in both types of leaves. The most salient characteristic of LL leaves was the very rapid saturation of the photochemistry with increasing light irradiance. This latter effect was particularly pronounced when photochemical energy storage was measured at modulation frequencies of between 450 and 600 Hz, suggesting that the rate-limiting step responsible for the rapid light-saturation of the photosynthetic electron flux in LL leaves had a time constant decay of about 3000 sec −1. The high-frequency data were confirmed by photoacoustic measurements of oxygen evolution at low modulation frequencies, which indicated that the reduction of the relative quantum yield of oxygen evolution Φ with increasing photon flux densities was considerably faster in shade-adapted adapted leaves than in control leaves. When compared to HL leaves, LL leaves had a lower Φ except, however, at very low photon flux densities (below about 10–15 μmol m −2 sec −1), where Φ drastically decreased in control Epilobium leaves (“low light state”) but not in LL leaves. The preservation of a high oxygen yield at low photon flux densities could partially explain the ability of Epilobium ciliatum to grow under extreme shade conditions.

Photoacoustic characteristics of leaves of atrazine-resistant weed mutants

The photosynthetic characteristics of leaves of atrazine-resistant and-susceptible biotypes of several weed species (Solanum nigrum, Senecio vulgaris, Epilobium ciliatum and Chenopodium album) were compared using the photoacoustic method. Analysis of the dependence of the photoacoustic signal of the modulation frequency indicated that, in Solanum, Epilobium and Senecio, the relative quantum yield of O2 evolution ϕ (estimated by the ratio of the amplitude of the O2 signal, AOX, to that of the photothermal signal, APT) was substantially reduced in the atrazine-resistant mutant, without any changes in the O2 diffusion characteristics of the leaves. In contrast, in Chenopodium, atrazine-resistance was associated with a concomitant change in ϕ and in the leaf diffusion parameters. This latter change suggests that the leaf internal anatomy was modified in the resistant Chenopodium. Measurements of the Emerson enhancement indicated that the reduction of ϕ observed in the atrazine-resistant mutants was caused by a marked decrease in the photochemical potential of PS II (β). The study of the light intensity dependence of the AOX/APT ratio showed that saturation of O2 evolution occurred at the same light level (around 2000 μmol m(-2) s(-1)) in both types of plants. However, the relative maximal rate of O2 evolution was slightly lower (-10%) in the atrazine-resistant biotype as compared to the wild type. Reduced ϕ and light-saturated rate of O2 evolution were also measured in atrazine-resistant weed biotypes using a conventional Clark-type O2 electrode.

COMPARATIVE BIOLOGY OF TUSSILAGO FARFARA L., CHAMAFNFRION ANGUSTIFOLIUM (L.) SCOP., EPILOBIUM MONTANUM L., AND FPILOBIUM ADFNOCAULON HAUSSKN.

SummaryThis paper describes the results of experiments on the growth of Tussilago farfara, Chamaenerion angustifolium, Epilobium montanum and E. adenocaulon in glasshouse conditions and also results of field experiments with Chamaenerion angustifolium and Epilobium adenocaulon. These results and results of work on germination, reported in the previous paper of this series, are discussed in relation to the ecology of the species.Glasshouse experiments showed that the growth forms of Epilobium montanum and E. adenocaulon are under the control of daylength but the growth form of Chamaenerion angustifolium is not controlled by it. All four species were found to make adequate growth under a range of shade conditions and nutrient supply. In all four species, plasticity of form of adaptative significance was shown to occur with respect to both light and mineral nutrient supply.Certain attributes of the species appear to be of high significance in determining, under natural selection, their ecological distributions. These include the longevity of dormant seed and the efficiency of dormancy mechanisms. Differences in these between the species appear to lead to differences in their occurrence in deciduous woodland and in their occurrence as weeds of cultivated ground.The small seed size of the species together with their commitments to large amounts of seedling growth relative to seed weight, operate to restrict seedling establishment to open sites in which supplies of light and mineral nutrients are adequate. The growth commitments of C angustifolium appear to be appreciably larger than in the other species and in C. angustifolium seedling establishment was found to be restricted by the nutritional status of certain experimental sites to a greater extent than in Epilobium adenocaulon.Differences between the species in growth form and pattern of vegetative reproduction appear, in part, to account for the differences in their occurrence in sites with mobile soil surfaces and in closed communities.The species differ in capacity for germination and viable growth on acid substrates. Also, between the species there are differences in their growth in regimes of high calcium/low potassium concentrations. Both these differences are considered to be of importance in determining respective differences of distribution of the species on acid and on lime‐rich soils.Finally, some assessment is made of the relative importance of genetic diversity and phenotypic plasticity to the survival of the species in the wide ranges of habitats in which they occur. The importance of differences in breeding system in maintaining different levels of diversity in the species is discussed.

COMPARATIVE BIOLOGY OF TUSSILAGO FARFARA L., CHAMAFNERION ANGUSTIFOLIUM (L.) SCOP., EPILOBIUM MONTANUM L. AND FPILOBIUM ADFNOCAULON HAUSSKN.

SummaryThe four species investigated occur in pioneer habitats but have different distributions. This study of their comparative biology is an attempt to account for these differences.The literature on the factors determining habitats and geographical distribution of each species is reviewed but this gives little or no evidence as to whether the species are causally related to, or merely associated with these factors in their ecological distribution. Experiments were therefore designed to test the causal relationship and mode of action of the factors, and this first paper describes those dealing with germination.It appeared from the literature that factors of probable importance in determining the ecological distributions of the species include mineral nutrients and light requirements. The mineral nutritional requirements of Chamaenerion angustifolium seemed to be particularly high. Tussilago farfara appeared to be the most calcicole and Chamaenerion angustifolium the most calcifuge of the species. Epilobium montanum seemed to be the most shade‐tolerant. Additional factors appeared likely to be involved at the limits of their geographical distributions; these include, along the southern limits, factors operating through the water relations of the species, and along the northern limits factors operating through the temperature relations and length of season of growth of the species.The wind‐dispersed seeds of the species are of low dry weight. Water culture experiments showed that, with regard to germination, Tussilago farfara is most successful and Chamaenerion angustifolium least successful in very low levels of mineral nutrient supply. The germination of Tussilago farfara in relation to increasing acidity is completely inhibited at a bigher pH (3.5) than it is in the other species (pH 3.0). In T. farfara germination is also restricted to the period mid‐April to mid‐June by the limited length of its seed viability and season of fruit dispersal. In the other species, though seed shedding is restricted to summer and autumn, the seed remains viable for at least a year and requires light to germinate. In Chamaenerion angustifolium this light requirement disappears as the temperature is raised to 30°C, but it remains in the two Epilobium species. At low temperatures (10°C) maximal percentage germination occurs under lower levels of illumination in E. adenocaulon than it does in Chamaenerion angustifolium, and this probably underlies the much greater percentage germination attained in Epilobium adenocaulon than in Chamaenerion angustifolium when the seeds are shallowly buried (2 mm). Germination in dry conditions also occurs more readily in Epilobium adenocaulon than in Chamaenerion angustifolium. Epilobium montanum is most similar to E. adenocaulon in germination requirements but differs in that its germination is inhibited at 30°C.

Natural Hybridization between Epilobium adenocaulon and E. brevistylum

Natural Hybridization between Epilobium adenocaulon and E. brevistylum