Viola banksii, the type species of section Erpetion, is endemic in eastern mainland Australia. In this paper we characterise morphological and anatomical features and assess genome size and genetic diversity in combination with the breeding system. V. banksii develops exclusively chasmogamous flowers. Ovules are anatropous, crassinucellate and bitegmic, the female gametophyte is of the Polygonum type, and the embryo is of Asterad type surrounded by nuclear endosperm. Pollen is non-heteromorphic, 3-aperturate, and highly viable. V. banksii grows in shade on moist, well drained, often sandy soils, and this is reflected in the anatomy of its organs, which includes a lack of subepidermal collenchyma in aerial parts, large leaf epidermal cells with thin cell walls, a narrow cuticle layer, and vascular bundles with xylem that are not rich in vessels. V. banksii is tolerant to zinc and lead based on phytotoxicity test. The high chromosome number (2n = 10x = 50) does not correspond to a small genome size (2C DNA = 1.27 pg). Low mean intra-populational gene diversity (HS = 0.077) detected by ISSR markers confirms the strong influence of selfing and clonal propagation by pseudostolons. Unique morphological traits of V. banksii include nyctinastic petal movement, the lack of a floral spur, the presence of gland-like protuberances on two stamens, and the presence of pseudostolons, which could be a synapomorphy for the whole section.
Flowering and nutritional status in Gladiolus hybridus L. ‘Black Velvet’ were assessed following gibberellic acid treatment (GA<sub>3</sub>). Treatment were applied to corm (12–14 diameter) by soaking for 30 min in water solutions of GA<sub>3</sub> at 100, 350 and 600 mg/dm<sup>3 </sup>with a control consisting of soaking-in water. All GA<sub>3</sub> treatments inhibited elongation of inflorescence shoots and stimulated spike elongation. None of the tested concentrations affected the number of developing flowers in the spike, except for the 100 mg/dm<sup>3</sup> in the 2nd year of the study. All GA<sub>3</sub> treatments stimulated calcium uptake, but had no effect on the uptake of other macronutrients. All the GA<sub>3</sub> treatments increased manganese content in leavesbud did not affect copper content. GA<sub>3</sub> at 600 mg/dm<sup>3</sup> stimulated uptake of iron and boron at 600 mg/dm<sup>3</sup> but inhibited both at lower concentrations. Zinc uptake was stimulated at 100 mg/dm<sup>3 </sup>but inhibited at higher concentration.
Background
Clearing methods allow relatively quick processing of plant material and examination of cellular structures by rendering tissues and organs translucent. They have been adapted for plant embryology, primarily to study ovule development, megasporogenesis, megagametogenesis and embryogenesis. Such clearing methods overcome several disadvantages of the conventional embedding-sectioning techniques that are arduous and time-consuming. Although numerous protocols with different clearing solutions have been described, there have been no reports to date proposing a reliable method to clear the crassinucellate ovules of the sugar beet (
Beta vulgaris
L.), an economically important crop. Therefore, this study aims to find a suitable approach to improve the tissue transparency of sugar beet ovules at different developmental stages.
Results
We established a methyl salicylate-based protocol that significantly improved the transparency of the
B. vulgaris
ovule structures, which allowed us to observe the megagameto- and embryogenesis of that species. This was achieved by (1) chemical softening of the tissues; (2) vacuum pump-assisted infiltration step; (3) shaking-assisted incubation with clearing mixtures; and (4) manual removal of the chemically softened seed coat.
Conclusions
The effectiveness of our method is due to the strategy combining various approaches at different stages of the procedure aiming at increasing the accessibility of the internal ovule structures to the clearing solution. The results of this study may be applied in sugar beet breeding programs, and it will provide a basis for further investigation of numerous aspects of the species’ embryology. Moreover, that unique approach may be easily adapted to other species developing crassinucellate ovules.
Electronic supplementary material
The online version of this article (10.1186/s13007-019-0452-6) contains supplementary material, which is available to authorized users.
Reproductive processes including male and female lines, embryo and endosperm development were studied in Cardaminopsis arenosa (syn. Arabidopsis arenosa) growing on two metalliferous sites (Bukowno and Bolesław, S. Poland), rich in Zn, Pb, Cd and other metals. Disturbances of developmental processes and necroses observed in anthers and ovules influenced plant fertility and seed set of plants from both metal-polluted sites. In anthers, disturbances and necrosis during male meiosis and pollen development occurred at low frequency (4-5%). Pollen grain viability was very high, reaching over 90%. In ovules the frequency of abnormal meiosis, female gametophyte developmental disturbances and necrosis was high, 23.5-28% depending on site. The polluted environment also affected embryo and endosperm. Necrosis of whole generative structures decreased plant fertility. This study indicates that the range of disturbances and necroses in embryological structures and processes (at gametophyte level) gives a set of useful characters to determine plant tolerance to stress, complementary to many tolerance characters at the sporophyte level of plant ontogenesis.
The costs of Biscutella laevigata adaptation, a facultative metallophyte, to an environment polluted with heavy metals were established by analyzing the differences in embryological processes between plants from two populations in Southern Poland (a mountain, in the Tatra Mountains and calamine, in Boles law). Disturbances in male and female lineage development and degeneration processes occurred in the anthers and ovules of plants from both populations, but with a higher frequency in the calamine population where A part of stamens/anthers and ovules in flowers were in a stage of degenertion. which could be interpreted as a strategy to save resources limited by the environment. The distribution of high-esterified homogalacturonan detected by LM20 antibody in the cell walls of embryos from the calamine population could be part of a resistance/defense system. The results from both populations indicate that B. laevigata has already developed adaptation/tolerance, enabling maintenance of the calamine population over time. Tolerant species could be an important source for revitalization and/or phytoremediation of polluted environments.
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