Common buckwheat is a valuable crop, mainly due to the beneficial chemical composition of its seeds. However, buckwheat cultivation is limited because of unstable seed yield. The most important reasons for the low yield include embryo and flower abortion. The aim of this work is to verify whether high temperature affects embryological development in this plant species. The experiment was conducted on plants of a Polish cultivar ‘Panda’ and strain PA15, in which the percentage of degenerating embryo sacs was previously determined and amounted to 32% and 10%, respectively. The plants were cultivated in phytotronic conditions at 20 °C (control), and 30 °C (thermal stress). The embryological processes and hormonal profiles in flowers at various developmental stages (buds, open flowers, and wilted flowers) and in donor leaves were analyzed in two-month-old plants. Significant effects of thermal stress on the defective development of female gametophytes and hormone content in flowers and leaves were observed. Ovules were much more sensitive to high temperature than pollen grains in both genotypes. Pollen viability remained unaffected at 30 °C in both genotypes. The effect of temperature on female gametophyte development was visible in cv. Panda but not in PA15 buds. A drastic reduction in the number of properly developed embryo sacs was clear in open flowers at 30 °C in both genotypes. A considerable increase in abscisic acid in open flowers ready for fertilization may serve as a signal inducing flower senescence observed in the next few days. Based on embryological analyses and hormone profiles in flowers, we conclude that cv. ‘Panda’ is more sensitive to thermal stress than strain PA15, mainly due to a much earlier response to thermal stress involving impairment of embryological processes already in the flower buds.

Programmed cell death (PCD) is a process that plays a fundamental role in plant development and responses to biotic and abiotic stresses. Knowledge of plant PCD mechanisms is still very scarce and is incomparable to the large number of studies on PCD mechanisms in animals. Quick and accurate assays, e.g., the TUNEL assay, comet assay, and analysis of caspase-like enzyme activity, enable the differentiation of PCD from necrosis. Two main types of plant PCD, developmental (dPCD) regulated by internal factors, and environmental (ePCD) induced by external stimuli, are distinguished based on the differences in the expression of the conserved PCD-inducing genes. Abiotic stress factors, including heavy metals, induce necrosis or ePCD. Heavy metals induce PCD by triggering oxidative stress via reactive oxygen species (ROS) overproduction. ROS that are mainly produced by mitochondria modulate phytotoxicity mechanisms induced by heavy metals. Complex crosstalk between ROS, hormones (ethylene), nitric oxide (NO), and calcium ions evokes PCD, with proteases with caspase-like activity executing PCD in plant cells exposed to heavy metals. This pathway leads to very similar cytological hallmarks of heavy metal induced PCD to PCD induced by other abiotic factors. The forms, hallmarks, mechanisms, and genetic regulation of plant ePCD induced by abiotic stress are reviewed here in detail, with an emphasis on plant cell culture as a suitable model for PCD studies. The similarities and differences between plant and animal PCD are also discussed.

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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.

In the current studies, heavy metal tolerance level, accumulation efficiency and sexual reproduction were determined in Viola × wittrockiana, a non-metallophytic ornamental cultivar in comparison to V. tricolor, a metallophyte, after zinc (Zn) or lead (Pb) treatment (0, 10, 100 and 1 000 ppm) in pot experiments. The seed germination frequency that was not reduced in comparison to the control, the effective Zn absorption from the soil and exclusion strategy for Pb, as well as the regular sexual reproduction of V. × wittrockiana treated with heavy metals all indicate the tolerance of this plant to heavy metals. The lack of a seed set under experimental conditions of V. × wittrockiana was due to the absence of pollinators, rather than the negative impact of heavy metals, as pollen viability and ovule  development were normal under the treatments. The results indicate that V. × wittrockiana represents similar tolerance to Viola metallophytes and could be considered as a good material for the reclamation of polluted areas. The exceptional tolerance to heavy metals, the ability to initiate new generations in heavy-metal-burdened soil, which are additionally coupled with the unique beauty, make the garden pansy a good candidate to be potentially used in the future for phytoremediation purposes.

Common buckwheat (Fagopyrum esculentum Moench) is a valuable crop plant with cereal-like seed chemical composition; however, it is susceptible to thermal stress. The aim of the study was to determine whether heat-shock proteins HSP-90 and HSP-70 can protect common buckwheat against thermal stress during development of microspores and embryo sacs. The study was performed on two accessions of common buckwheat, Panda and PA15, which differed in their tolerance to thermal stress. Accumulation of these proteins was determined in buds, open and wilted flowers, and donor leaves of plants grown at 20°C (control) and 30°C (thermal stress). Photochemical efficiency of donor leaves, closest to the inflorescences, based on chlorophyll a fluorescence (ChlF) was also analysed. All plants demonstrated higher values of ChlF at 30°C than at 20°C, which suggests that this 30°C temperature is more conducive to their vegetative growth. Pollen grains of both accessions demonstrated normal development at 30°C, whereas embryo sacs showed many developmental disturbances. Panda was more sensitive to thermal stress than PA15, as manifested in a higher percentage of degenerated embryo sacs at the flower bud phase. Moreover, a decrease in both HSPs in the studied organs of Panda was found relative to the control. At 30°C, both accessions accumulated more HSP-70 than HSP-90. These results suggest that, under heat stress, HSP-70 plays a protective role for flowers of common buckwheat. The analyses indicated that the donor leaf closest to the flower cluster may be a reliable indicator of temperature sensitivity in buckwheat flowers.

The study was designed to determine the proper conditions for suspension culture of Viola tricolor cells in toxicity studies of Pb at different concentrations (0, 200, 500, 1000, 2000 µM) and exposure times (24, 48, 72 h). By forming insoluble salts with ions from the medium, lead (II) nitrate added to the medium decreased the initial 5.7-5.8 pH of the medium, depending on the Pb salt concentration and light intensity.In alamarBlue assays, we found no dose-or time-dependent effect of Pb on cell viability when we did not adjust pH and did not standardize the illumination conditions to correct the effect of lead-salt-induced turbidity.When effective illumination was adjusted to correct for turbidity at the highest lead concentration and pH was adjusted to 5.7-5.8, cell viability decreased with the increase of Pb(NO 3 ) 2 concentration and with treatment time. These experiments demonstrate that the toxic action of lead on cells in suspension depends strongly on culture conditions, and not only on the metal concentration and duration of treatment.