Phyllotactic patterns in capitula of Carlina acaulis L.

Phyllotaxis of inflorescences in Car/ina acaulis L. is spiral. In the majority of capitula it is represented by the main Fibo­nacci series. From the one thousand of specimens, thai were examined, thirty five new phyllotactic series were found: eighteen monojugies, for instance (2,17), (4, 11), (7,37) and seventeen multijugies, such as 2(8,9), 2(5,11), 8(2,3). The patterns had been identified on the basie of two or more consecutive num bers of phyllotaclic series. Both, the continuous and discontinous trans­formations of phyllotactic patterns, as well as 'deviations' from the parastichy group numbers were observed. The deviations were distinguished as the probable cases of the discontinuous transformations in which the sectorial change in the parastichy number occured, but the ultimate phyllotactic series could not be determined

The diagram for phyllotactic series

Many authors studying phyllotaxis in various plant species have reported the occurrence of many different numbers of contact parastichy pairs that are members of different Fibonacci-like series. On the basis of these reports a diagram was constructed in which any theoretically possible series was represented by the two first members of a given series

Various scenarios of the cell pattern formation in Arabidopsis lateral root

During lateral root (LR) development a coordinate sequence of cell divisions, accompanied by a change of the organ form takes place. Both the order of anatomical events and morphological features may vary for individual primordia. At early stages of LR primordia development oblique division walls are inserted in cells that are symmetrically located on both sides of the axis of the developing LR primordium, and thereby allow for the protrusion of the LR. We hypothesize that both oblique cell wall insertion and continuous changes in primordium form could be a consequence of a local change in stress distribution in the region of the LR initiation

The Pellicle - Another Strategy of the Root Apex Protection against Mechanical Stress?

In grasses, the apical part of the root is covered by a two-layered deposit of extracellular material, the pellicle, which together with the outer periclinal wall of protodermal cells forms the three-layered epidermal surface. In this study, the effect of mechanical stress on the pellicle was examined. An experiment was performed, in which maize roots were grown in narrow diameter plastic tubes with conical endings for 24 h. Two groups of experimental roots were included in the analysis: stressed (S) roots, whose tips did not grow out of the tubes, and recovering (R) roots, whose apices grew out of the tube. Control (C) roots grew freely between the layers of moist filter paper. Scanning electron microscopy and confocal microscopy analysis revealed microdamage in all the layers of the epidermal surface of S roots, however, protodermal cells in the meristematic zone remained viable. The outermost pellicle layer was twice as thick as in C roots. In R roots, large areas of dead cells were observed between the meristematic zone and the transition zone. The pellicle was defective with a discontinuous and irregular outermost layer. In the meristematic zone the pellicle was undamaged and the protodermal cells were intact. The results lead to the conclusion that the pellicle may prevent damage to protodermal cells, thus protecting the root apical meristem from the negative effects of mechano-stress

Dissecting the chromosomal composition of mutagen-induced micronuclei in Brachypodium distachyon using multicolour FISH

Background and Aims Brachypodium distachyon (Brachypodium) is a model species for temperate cereals and other economically important grasses. Its favourable cytogenetic features and advanced molecular infrastructure make it a good model for understanding the mechanisms of instability of plant genomes after mutagenic treatment. The aim of this study was to qualitatively and quantitatively assess the composition and origin of micronuclei arising from genomic fracture, and to detect possible ‘hot spots’ for mutagen-induced DNA breaks. • Methods Seeds of Brachypodium were treated with maleic hydrazide (MH) or X-rays. The structure of mutagen- induced micronuclei was analysed in root-tip meristematic cells using multicolour fluorescence in situ hybridization (mcFISH) with various repetitive (5S rDNA, 25S rDNA, telomeric, centromeric) and low-repeat [small and large pools of bacterial artificial chromosome (BAC) clones specific for chromosome Bd1] DNA sequences. • Key Results The majority of micronuclei derive from large, acentric fragments. X-rays caused more interstitial DNA breaks than MH. Double-strand breaks rarely occurred in distal chromosome regions. Bd1 contributed to the formation of more mutagen-induced micronuclei than expected from random chromosome involvement. • Conclusions mcFISH with chromosome-specific BAC clones offers insight into micronuclei composition, in so far as it allows their origin and formation to be determined more specifically. A reliable assay for micronuclei composition is crucial for the development of modern genotoxicity tests using plant cells. The combination of mutagenic treatments and well-developed cytomolecular resources in Brachypodium make this model species very promising for plant mutagenesis research

Detecting Brachypodium distachyon Chromosomes Bd4 and Bd5 in MH- and X-Ray-Induced Micronuclei Using mcFISH

Micronuclei are biomarkers of genotoxic e ects and chromosomal instability. They are formed when chromosome fragments or whole chromosomes fail to disjoin into daughter nuclei. We present qualitative and quantitative analyses of the involvement of specific chromosome regions of chromosomes Bd4 and Bd5 in the formation of micronuclei of Brachypodium distachyon root tip cells following maleic hydrazide (MH) treatment and X-radiation. This is visualised by cytomolecular approaches using bacterial artificial chromosome (BAC)-based multicolour fluorescence in situ hybridisation (mcFISH) in combination with 5S and 25S rDNA probes. The results showed that the long arm of submetacentric chromosome Bd4 forms micronuclei at twice the frequency of its short arm, suggesting that the former is more prone to double-strand breaks (DSBs). In contrast, no di erence was observed in the frequency of micronuclei derived from the long and short arms of submetacentric chromosome Bd5. Interestingly, the proximal region of the short arm of Bd5 is more prone to DSBs than its distal part. This demonstrates that 5S rDNA and 35S rDNA loci are not “hot spots” for DNA breaks after the application of these mutagens

Topological traits of a cellular pattern versus growth rate anisotropy in radish roots

The topology of a cellular pattern, which means the spatial arrangement of cells, directly corresponds with cell packing, which is crucial for tissue and organ functioning. The topological features of cells that are typically analyzed are the number of their neighbors and the cell area. To date, the objects of most topological studies have been the growing cells of the surface tissues of plant and animal organs. Some of these researches also provide verification of Lewis’s Law concerning the linear correlation between the number of neighboring cells and the cell area. Our aim was to analyze the cellular topology and applicability of Lewis’s Lawto an anisotropically growing plant organ. The object of our study was the root apex of radish. Based on the tensor description of plant organ growth, we specified the level of anisotropy in specific zones (the root proper, the columella of the cap and the lateral parts of the cap) and in specific types of both external (epidermis) and internal tissues (stele and ground tissue) of the apex. The strongest anisotropy occurred in the root proper, while both zones of the cap showed an intermediate level of anisotropy of growth. Some differences in the topology of the cellular pattern in the zones were also detected; in the root proper, six-sided cells predominated, while in the root cap columella and in the lateral parts of the cap, most cells had five neighbors. The correlation coefficient rL between the number of neighboring cells and the cell area was high in the apex as a whole as well as in all of the zones except the root proper and in all of the tissue types except the ground tissue. In general, Lewis’s Law was fulfilled in the anisotropically growing radish root apex. However, the level of the applicability (rL value) of Lewis’s Lawwas negatively correlated with the level of the anisotropy of growth, which may suggest that in plant organs in the regions of anisotropic growth, the number of neighboring cells is less dependent on the cell size

Epigenetic chromatin modifications in barley after mutagenic treatment

In addition to their normal developmental processes, plants have evolved complex genetic and epigenetic regulatory mechanisms to cope with various environmental stresses. It has been shown that both DNA methylation and histone modifications are involved in DNA damage response to various types of stresses. In this study, we focused on the involvement of two mutagenic agents, chemical (maleic acid hydrazide; MH) and physical (gamma rays), on the global epigenetic modifications of chromatin in barley. Our results indicate that both mutagens strongly influence the level of histone methylation and acetylation. Moreover, we found that gamma irradiation, in contrast to MH, has a more robust influence on the DNA methylation level. This is the first study that brings together mutagenic treatment along with its impact at the level of epigenetic modifications examined using the immunohistochemical method

Silesian Botanical Garden : a proposal for agriculture and forestry

The Red List of endangered plant and anima] species has been enlarging alarmingly. Predictions are serious: within next twenty years about 20% of the world species will extinct. ln our industrial region almost 40% of vascular plant species is about to die out. For the past two hundred years 124 species of these plants have died out completely or vanished of the area of Poland. These are dramatic changes in agricultural methods that are responsible for this genetic erosion. First of all we are obliged to conserve biodiversity, not only in the natural environment, but also in agrocenoses. Another important task is to conserve gene recourses of the crops in order to provide a materiał for new varieties cultivation. One of the methods of gene recourses con­servation in a botanical gardens is the ex situ method meaning conservation of the genetic materiał of plants out of their natura] habitats. The ex situ conservation may be localized in: • seed storage, • in vitro tissues storage, • pollen storage, • field collections

Genome size variation in Chenopodium quinoa (Chenopodiaceae)

The extent and significance of intraspecific genome size variation were analysed in quinoa (Chenopodium quinoa Willd.), a pseudocereal important for human consumption in the Andean region of South America. Flow cytometry, with propidium iodide as the DNA stain, was used to estimate the genome size of 20 quinoa accessions from Ecuador, Peru, Bolivia, Argentina, Chile and the USA. Limited genome size variation was found among the analysed accessions. The differences between the accessions were statistically significant but the maximum inter-accession difference between the populations with the largest and the smallest genome reached only 5.9%. The largest genome was found in population C4 from Chile (mean 3.077 pg/2C) and the smallest in the Peruvian population P2 (mean 2.905 pg/2C). The variation was not correlated with collection site; however, the quinoa accessions analysed in this study belonged to three distinct geographical groups: northern highland, southern highland and lowland