Dominik Tomaszewski

The wax layer and its morphological variability in four European Salix species

Summary The structure of the wax layer on leaves was analysed in four species of the genus Salix ( S. alba , S. fragilis , S. triandra and S. pentandra ). SEM observations showed that peculiar conical structures (named here ‘conicoids’) are present on the lower surface of the leaves in three species. In S. fragilis and S. triandra , conicoids are similar in size, whereas in S. alba , they are several times larger. In S. pentandra no such structures were found and the cuticle was covered only with an amorphous wax film. The observed differences between species can be used as identifying features in this group of plants. A comparison of conicoids on successive leaves on the shoot revealed differences and shed some light on the process of their formation.

Is Shape of a Fresh and Dried Leaf the Same

Plants kept as dried herbarium specimens share many characteristics with their living counterparts, but there are some substantial differences between them. Due to dehydration, leaves of herbarium specimens change not only their mass and colour, but in many cases change their dimensions, too. The present study aimed to determine whether leaf shape changes during the drying process. A total of 794 pairs of fresh and dried leaves or leaflets of 22 plant taxa were studied. The shape of the blades was quantified using elliptic Fourier analysis combined with principal component analysis. In addition, area and mass of the leaves were measured. Statistical tests were applied for comparing fresh and dried leaves. The results indicate that the preservation process of pressing and drying plants for herbarium purposes causes changes in leaf shape. In general, the shape changes were directional. As the shape of fresh and dried plants is different, it is strongly recommended that shape analyses should be performed on datasets containing either of the leaf types.

Salix anatolica (Salicaceae), a New Species from Turkey

Salix anatolica J. Zieliński & D. Tomaszewski sp. nova (Salicaceae) from central Turkey is described and illustrated. It is compared with the two morphologically closest species, S. pedicellata and S. pseudomedemii.

Stomata on the pericarp of species of the genus Rosa L. (Rosaceae)

Achenes of 36 species representing all subgenera and sections of the genus Rosa were studied. All have stomata on the pericarp that seem to be normal in appearance. They are usually few, scattered, mostly on the upper part of fruit, and open or closed. This is the first report of stomata on fruits of Rosa.

Changes in genomic 5-methylcytosine level mirror the response of orthodox (Acer platanoides L.) and recalcitrant (Acer pseudoplatanus L.) seeds to severe desiccation

Poor storability of recalcitrant seeds is due to their inability to tolerate low moisture content. Understanding the processes underlying their recalcitrance is a prerequisite to developing a maintenance strategy and prolonging their lifespan. Multiple studies have investigated the differences between orthodox (desiccation-tolerant) and recalcitrant (desiccation-sensitive) seeds. Information on epigenetic regulation, however, is lacking and thus limits our understanding of the processes defining the physiology of seeds. In the present comparative study, changes in the global levels of 5-methylcytosine (m5C) in orthodox and recalcitrant seeds of Acer platanoides L. and Acer pseudoplatanus L. were characterized during progressive stages of severe drying. Concomitant with their differential sensitivity to desiccation stress, we demonstrate variation in the response of embryonic axes and cotyledons to water deficit at the level of DNA methylation. Results indicate that desiccation-induced changes in m5C are both tissue- and seed category-specific and are highly correlated with recalcitrant seed viability. Moreover, we demonstrate that m5C global changes in response to desiccation are not retained in DNA isolated from seedlings, except in seedlings that are derived from strongly desiccated orthodox seeds (moisture content of 3.5%). Finally, the potential utilization of m5C status as a universal seed viability marker is discussed.

Sequences of epicuticular wax structures along stems in four selected tree species

Abstract Wax layer formation accompanies the processes of epidermis and cuticle formation. To examine these changes, observationsalong current-year long shoots of four woody species (Acer negundo, A. rufinerve, Gymnocladus dioica, and Gingko biloba) were made. Long shoots are suitable objects for such observations, because from the same stem, several samples can be obtained that represent a well-defined sequence of fragments of different ages. The data that were obtained from different and sometimes distant stem regions suggest that epicuticular wax crystals appear on the stems very early and quickly, since they are found near the stem apex during intensive plant growth. This was confirmed for the four examined species. Some differences, however, were noted. Very rapid production of prominent wax crystals was observed in stems. In an experiment involving mechanical wax removal from the A. negundo stem surface and subsequent analysis of the surface after several days via scanning electron microscopy (SEM), it was shown that wax regenerates very quickly. After only several hours, new emerging crystals were observed and their morphologies were essentially the same. Nearly full regeneration was observed several days after removal.