Kazimierz Marciniak

Presowing seed treatment with melatonin protects red cabbage seedlings against toxic copper ion concentrations

Abstract:  One of the targets of modern plant physiology is to identify tools for improving seed germination and plant growth under unfavorable environmental conditions. Seeds of Brassica oleracea rubrum were pretreated with melatonin at concentrations: 1, 10, and 100 μm using a hydropriming method. Air‐dried seeds of each experimental variants that were nonpretreated (control), hydroprimed (H) or hydroprimed with melatonin (HM1, HM10, and HM100) were germinated in darkness for 3 days at 25°C. Young seedlings were then transferred to the light and grown for an additional 5 days. Both germination and growth tests were performed in water and in CuSO4 water solutions in concentrations of 0.5 and 1 mm. H, HM1 and HM10 improved seed germination both in water and in the presence of Cu2+. One or 10 μm melatonin eliminated the inhibitory effect of the 0.5 mm metal concentration on the fresh weight of seedlings. HM100 had a negative effect; thus seed germination was lower and seedlings had poor establishment. The toxic effect of Cu2+ manifested by membrane peroxidation and DNA endoreplication blocking in the seedlings grown from nontreated (control) and H seeds was not observed in the seedlings grown from HM1 and HM10 seeds; in contrast, HM100 enhanced the toxic effect of Cu2+.

Transport of rRNA into cytoplasm required for initiation of S phase in root meristem cells inHelianthus annuus L.

SummaryCold treatment (10‡C) of root meristem during a period longer than duration of the cell cycle in 20‡C causes a blocking of most cells in G1. One of the causes of cell cycle blockade is the decrease of rRNA synthesis and inhibition of rRNA transport into cytoplasm. Transfer of seedlings to 20‡C results in increase of rRNA synthesis and its transport to cytoplasm as well as transition of almost all cells from G1 to S during 3 hours. Synchronization of DNA replication, comprising cells within rows of cells, is preceded by similar transport patter of rRNA to cytoplasm.

Analysis of mitotic synchrony induced by cold treatment in root meristems of Vicia faba L.

Abstract In cold-pretreated seedlings (24 hr at 4°C), 3 hr after transfer to 20°C 50% of the cells were in S phase. After 13 hr of postincubation at 20°C the mitotic index rapidly increased from 1 to 19% and through 3 H-thymidine incorporation, 60% of mitotic cells became radioactive. A comparison of cytoplasmic protein content in 3 H-labelled and unlabelled prophase cells indicated that the cells containing more cytoplasmic protein entered mitosis earlier. Synchronization of mitotic divisions occurred within cell packets. The number of plasmodesmata in transverse cell walls between cells in mitosis was greater than that between interphase cells.

Relationship between resumption of rRNA transport into cytoplasm after cold treatment and progression through the cell cycle in root meristem cells

Abstract Experiments with 3 H-uridine incorporation have shown that cold treatment inhibits rRNA transport from nucleoli to the cytoplasm. The rate of rRNA transport during recovery after cold treatment has been investigated in root meristems of Secale cereale, Vicia faba and Allium cepa . Results obtained by use of autoradiographic and cytophotometric methods indicate that in each species nucleoli lose half their radioactivity after the first 2.5–3.0 hr postincubation at 20°C. Concomitantly the number of cells entering the S phase and mitosis increases.

Changes in Nuclear, Nucleolar, and Cytoplasmic Protein Contents during Differentiation of Root Parenchyma Cells in Species with Different Dynamics of DNA Endoreplication

Summary In order to determine the relation between DNA content and nuclear, nucleolar and cytoplasmic protein amounts during parenchyma cell differentiation, double cytophotometry enabling simultaneous measurements of DNA (Feulgen) and protein (dinitrofluorobenzene) was used. 4 species with different 2 C values and characterized by different dynamics of nuclear DNA endoreplication were chosen. The quantities of nuclear protein were correlated with DNA content at each stage of differentiation. Nucleolar protein amounts decrease less rapidly in species with high dynamics of DNA endoreplication. Cytoplasmic protein contents are higher in endopolyploid than in diploid cells, but the highest increase in cytoplasmic protein amounts during cell differentiation takes place in the species with the highest value of 2 C DNA, in which DNA endoreplication does not occur. It is concluded that the nucleotypic effect is realized by DNA endoreplication which recompensates the low amount of 2 C DNA.