Main conclusion In this work, for the first time the activity of nitrate-permeable channels in the tonoplast of the moss Physcomitrella patens was recorded. The channels allowed nitrate flow in one direction-from the cytoplasm to the vacuole. Selectivity of nitrate over chloride of the channels was proved. The activity of the channels was dependent on cytoplasmic calcium, magnesium, and pH.A patch-clamp study carried out on the vacuolar membrane of the moss Physcomitrella patens has revealed that inhibition of cation-selective channels leads to disclosure of channels permeable to NO 3 -. These channels were inwardly rectifying and allowed anions to flow from the cytoplasm to the vacuole. After a decrease in the cytoplasmic NO 3 -concentration, the current density recorded in the whole-vacuole configuration and amplitude of the currents flowing through single channels were reduced. Application of the NO 3 -gradient caused a shift in the reversal potential (E rev ) towards E NO3-, indicating NO 3 -permeability. Research of the selectivity of the channels to Cl -and NO 3 -was also done; it indicated that Cl -is less permeable than NO 3 -(P NO3 /P Cl = 3.08). Measurements with different concentrations of cytoplasmic Ca 2? and Mg 2? revealed that the channel was activated by different concentrations of these ions-100 lM Ca 2? and 10 mM Mg 2? . Calcium dependence of the channels was also modulated by a redox agent-DTT (dithiothreitol), which added on the cytoplasmic side, caused a reduction in the threshold of channel activation with cytoplasmic Ca 2? . The NO 3 -permeable channel was also pH dependent. A decrease in the cytoplasmic pH reduced the open probability of the channel; in turn, an increase in the vacuolar pH did not decrease ion channel activity but lowered its conductance.

Flax (Linum usitatissimum L.) is an ancient crop that is widely cultivated as a source of oil, fiber, and bioactive compounds. Flax fiber is traditionally used in textile industry, linseed oil is processed for industrial oils, paints, varnishes and bio-petroleum. Flaxseeds are also rich in α-linolenic acid and phytochemicals such as lignans. In addition to the commercial aspects, this species has been used widely and readily in biotechnological, developmental, and plant-pathogen interaction studies. Differences in the levels of endogenous hormones in various cultivars of flax significantly affected the intensity of callogenesis and determined the type and concentration of growth regulators necessary for callus production. The aim of our investigation was to optimize the culture conditions for callus formation and cell proliferation in liquid medium of the Polish cultivar of fiber flax-Modran. In the first step, 4 combinations of phytohormones in the medium were tested to obtain established callus tissue suitable for initiation of suspension culture. Next, we investigated the effect of chosen plant growth regulators on cell divisions, fresh and dry weight, and dispersal of callus cells in liquid medium. Fast growing and friable callus was obtained in a modified MS medium supplemented with 0.5 mg/l BAP and 0.1 mg/l NAA. We determined that for the initiation of cell suspension supplementation with 0.5 mg/l BAP and 0.5 mg/l NAA is optimal. The results obtained indicated that high concentration of cytokinin (BAP) in liquid medium limited cell proliferation and decreased biomass formation.

The anatomical structure of the ovule of Larix kaempferi is typical for gymnosperms. During megasporogenesis, three megaspores arranged in one line are formed after incomplete meiotic division. Lipoxygenase occurrence in the Japanese larch ovules was shown by the Western-blotting method and confirmed using native PAGE. The localization of LOX in the young ovule of L. kaempferi during megasporogenesis was analysed by the immunogold labelling technique. The activity of the enzyme was measured spectrophotometrically at 234 nm using linoleic acid as a substrate. The location of LOX was rather random; however, clusters of immunogold particles were often observed in the vacuoles of integument cells. It was found in the cytoplasm, cell walls, vacuoles, starch grains, and nuclei. LOX activity in developing ovules of the Japanese larch was not correlated with the number of antibody-labelled molecules of the enzyme, which may indicate its non-enzymatic function. Two optima for LOX activity, at pH 8.0 and pH 7.0, were found in L. kaempferi developing ovules. The enzyme with a maximum activity at pH 8.0 appeared in ovules with a megaspore mother cell as well as with a triad of megaspores; the second maximum activity (at pH 7.0) was detected only at the stage with the triad of megaspores in the nucellus.