Melanins are a class of darkly pigmented biopolymers which are widely distributed among living organisms. the molecular and cellular mechanisms adopted by bacteria, fungi and animals to synthesize melanin, have been well described, but less is known regarding their production in plants. Here, a pair of barley near isogenic lines, bred to differ with respect to the pigmentation of the spike, was compared in order to understand the tissue and cellular location of melanin deposition. the melanic nature of the pigments purified from black spikes was confirmed by a series of solubility tests and Fourier transform infrared spectroscopy. An analysis of grains harvested at various stages of their development revealed that intracellular pigmented structures first appeared in the pericarp and the husk of black spike plants at early dough stage. The co-localization of these structures with red autofluorescence suggested that they form in chloroplast-derived plastids, here designated "melanoplasts". Differences in dynamics of plastid internal structure during grain ripening were detected between the lines by transmission electron microscopy. Both lines accumulated plastoglobuli inside plastids, which persisted in black grain pericarp tissue up to the hard dough stage, while neither plastoglobuli nor any plastids were observed in grain of the control line at this stage. the role of plastoglobuli in melanin synthesis is discussed.

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The migration of nuclei between plant cells (cytomixis) is a mysterious cellular phenomenon frequently observable in the male meiosis of higher plants. Cytomixis attracts attention because of unknown cellular mechanisms underlying migration of nuclei and its potential evolutionary significance, since the genetic material is transferred between the cells that form pollen. Although cytomixis was discovered over a century ago, the advance in our understanding of this process has been rather insignificant because of methodological difficulties. The data that allowed for a new insight into this phenomenon were obtained by examining the migrating nuclei with electron and confocal laser microscopy, immunostaining, and fluorescence in situ hybridization. As has been shown, the chromatin migrating between cells is surrounded by an undamaged nuclear membrane. Such chromatin does not undergo heterochromatization and contains normal euchromatin markers. The condensation degree of the migrating chromatin corresponds to the current meiotic stage, and normal structures of synaptonemal complex are present in the migrating part of the nucleus. The cells involved in cytomixis lack any detectable morphological and molecular markers of programmed cell death. It has been shown that individual chromosomes and genomes (in the case of allopolyploids) have no predisposition to the migration between cells, i.e., parts of the nucleus are involved in cytomixis in a random manner. However, the fate of migrating chromatin after it has entered the recipient cell is still vague. A huge amount of indirect data suggests that migrating chromatin is incorporated into the nucleus of the recipient cell; nonetheless, the corresponding direct evidences are still absent. No specific markers of cytomictic chromatin have been yet discovered. Thus, the causes and consequences of cytomixis are still disputable. This review briefs the recent data on the relevant issues, describes the classical and modern methodological approaches to analysis of the intercellular migration of nuclei, and discusses the problems in cytomixis research and its prospects.