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| 2. |
- Aguirre, A., et al.
(author)
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Morphological variation in the flowers of Jacaratia mexicana A. DC. (Caricaceae), a subdioecious tree
- 2009
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In: Plant Biology. - 1435-8603 .- 1438-8677. ; 11:3, s. 417-424
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Journal article (peer-reviewed)abstract
- The Caricaceae is a small family of tropical trees and herbs in which most species are dioecious. In the present study, we extend our previous work on dioecy in the Caricaceae, characterising the morphological variation in sexual expression in flowers of the dioecious tree Jacaratia mexicana. We found that, in J. mexicana, female plants produce only pistillate flowers, while male plants are sexually variable and can bear three different types of flowers: staminate, pistillate and perfect. To characterise the distinct types of flowers, we measured 26 morphological variables. Our results indicate that: (i) pistillate flowers from male trees carry healthy-looking ovules and are morphologically similar, although smaller than, pistillate flowers on female plants; (ii) staminate flowers have a rudimentary, non-functional pistil and are the only flowers capable of producing nectar; and (iii) perfect flowers produce healthy-looking ovules and pollen, but have smaller ovaries than pistillate flowers and fewer anthers than staminate flowers, and do not produce nectar. The restriction of sexual variation to male trees is consistent with the evolutionary path of dioecy from hermaphrodite ancestors through the initial invasion of male-sterile plants and a subsequent gradual reduction in female fertility in cosexual individuals (gynodioecy pathway), but further work is needed to confirm this hypothesis.
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| 4. |
- Lazaro, A., et al.
(author)
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Variation in sexual expression in the monoecious shrub Buxus balearica at different scales
- 2007
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In: Plant Biology. - : Wiley. - 1435-8603 .- 1438-8677. ; 9:6, s. 736-744
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Journal article (peer-reviewed)abstract
- Monoecy allows high plasticity in gender expression because the production of separate female and male flowers increases the ability to respond to specific environmental circumstances. We studied variation in sexual expression and its correlates in the monoecious shrub Buxus balearica, for two years, in six populations in the Balearic Islands and four in the Iberian Peninsula. Phenotypic gender varied among populations; while island populations showed slight variations around an average gender, mainland populations showed a broad range of variation in gender among individuals, always biased towards increasing maleness compared with the other populations. Within populations, gender was not related to plant size. Between-year changes were slight and mainly consisted of an increase in relative maleness in the mast year. Reproduction did not affect gender in the next year, as assessed by either observational or experimental methods. Most variation in gender expression occurred among individuals within populations (83.6%), followed by variation among populations (13.6%) and years (2.8%). Our results suggest that male-biased gender at population and plant levels was related to stressful conditions and resource limitation, because: (1) maleness was higher in mainland populations, where summer drought was stronger; (2) maleness increased with elevation; (3) fruit set was positively correlated with femaleness; (4) the percentage of male inflorescences increased over the flowering period; and (5) male inflorescences were preferentially in lower parts of the branch nodes. Higher maleness in mast years, however, could be related to increased male success under synchronic flowering.
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| 5. |
- Méndez, M., et al.
(author)
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Equivalence of three allocation currencies as estimates of reproductive allocation and somatic cost of reproduction in Pinguicula vulgaris
- 2007
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In: Plant Biology. - : Wiley. - 1435-8603 .- 1438-8677. ; 9:4, s. 462-468
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Journal article (peer-reviewed)abstract
- Which is the most appropriate currency (biomass, energy, water, or some mineral nutrient) for expressing resource allocation in plants has been repeatedly discussed. Researchers need to assess to which extent interindividual, interpopulational, or interspecific comparisons of resource allocation could be affected by the allocation currency chosen. The ""currency issue"" is relevant to at least three related aspects of resource allocation to reproduction: (a) reproductive allocation (RA), (b) size-dependence of reproductive allocation, and (c) somatic cost of reproduction (SCR). Empirical tests have mostly dealt with the first aspect only. We examined the equivalence of estimates for the three aspects above across three different allocation currencies (dry mass, N, P) in 11 populations of Pinguicula vulgaris. For RA we studied the equivalence of allocation currencies at three scales: among individuals of the same population, between populations of the same species, and among species. Equivalence of currencies in the ranking of RA for individuals within populations was high (R-s >= 0.43) and did not strongly decrease when comparing populations or species. Excepting for size-dependence of RA, ranking of RA, or SCR between populations was equivalent for biomass and N, but not for P. Our study gives two positive guidelines for empirical plant reproductive ecologists facing the ""currency issue"": (1) become increasingly concerned about the ""currency issue"" as you increase the scale of your comparison from individuals to populations to species, and (2) avoid estimating allocation in redundant currencies (biomass and N in our case) and choose preferentially ""complementary"" currencies that provide a broader view of allocation patterns (biomass and P in our case).
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| 6. |
- Oksanen, E., et al.
(author)
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Northern environment predisposes birches to ozone damage
- 2007
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In: Plant Biology. - : Wiley. - 1435-8603 .- 1438-8677. ; 9:2, s. 191-196
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Journal article (peer-reviewed)abstract
- Ozone sensitivity of silver birch (Betula pendula Roth) has been thoroughly investigated since early 1990's in Finland. in our long-term open-field experiments the annual percentage reduction in basal diameter and stem volume increment were the best non-destructive growth indicators for ozone impact when plotted against AOTX. Remarkable differences in defence strategies, stomatal conductance, and defence compounds (phenolics), clearly indicate that external exposure indices are ineffective for accurate risk assessment for birch. For flux-based approaches, site-specific values for g(max) and g(dark) are necessary, and determinants for cletoxification capacity, ageing of leaves, and cumulative ozone impact would be needed for further model development. increasing CO2 seems to counteract negative ozone responses in birch, whereas exposure to springtime frost may seriously exacerbate ozone damage in northern conditions. Therefore, we need to proceed towards incorporating the most important climate change factors in any attempts for ozone risk assessment.
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| 7. |
- Pawlowski, Katharina, et al.
(author)
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Truncated Hemoglobins in Actinorhizal Nodules of Datisca glomerata.
- 2007
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In: Plant Biol (Stuttg). - 1435-8603. ; 9:6, s. 776-785
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Journal article (other academic/artistic)abstract
- Three types of hemoglobins exist in higher plants, symbiotic, non-symbiotic, and truncated hemoglobins. Symbiotic (class II) hemoglobins play a role in oxygen supply to intracellular nitrogen-fixing symbionts in legume root nodules, and in one case (Parasponia sp.), a non-symbiotic (class I) hemoglobin has been recruited for this function. Here we report the induction of a host gene, Dgtrhb1, encoding a truncated hemoglobin in Frankia-induced nodules of the actinorhizal plant Datisca glomerata Induction takes place specifically in cells infected by the microsymbiont, prior to the onset of bacterial nitrogen fixation. A bacterial gene (Frankia trHbO) encoding a truncated hemoglobin with O (2)-binding kinetics suitable for the facilitation of O (2) diffusion ( ) is also expressed in symbiosis. Nodule oximetry confirms the presence of a molecule that binds oxygen reversibly in D. glomerata nodules, but indicates a low overall hemoglobin concentration suggesting a local function. Frankia TrHbO is likely to be responsible for this activity. The function of the D. glomerata truncated hemoglobin is unknown; a possible role in nitric oxide detoxification is suggested.
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