Physiological, biochemical and morpho-anatomical traits that determine the phenotypic plasticity of plants under drought were tested in two Arundinoideae with contrasting habitats, growth traits and metabolism: the fast-growing Arundo donax, which also is a strong isoprene emitter, and the slow-growing Hakonechloa macra that does not invest on isoprene biosynthesis. In control conditions, A. donax displayed not only higher photosynthesis but also higher concentration of carotenoids and lower phenylpropanoid content than H. macra. In drought-stressed plants, photosynthesis was similarly inhibited in both species, but substantially recovered only in A. donax after rewatering. Decline of photochemical and biochemical parameters, increased concentration of CO2 inside leaves, and impairment of chloroplast ultrastructure were only observed in H. macra indicating damage of photosynthetic machinery under drought. It is suggested that volatile and non-volatile isoprenoids produced by A. donax efficiently preserve the chloroplasts from transient drought damage, while H. macra invests on phenylpropanoids that are less efficient in preserving photosynthesis but likely offer better antioxidant protection under prolonged stress.

The leaf epidermis structure of Cydonia oblonga Mill. has been studied by light and scanning electron microscopy. Cuticle ornamentation and waxes have been observed. Simple single trichomes and cyclocytic stomatal type are determined. An attempt to estimate all features of taxonomic value is made and some relationships within subfamily Maloideae are discussed.ncentration 200 µM CdCl 2. Glutathione reductase (GR) activity was not detected in algal cells of the all experimental variants

The present work examined seven Hypericum species (Н. perforatum, Н. humifusum, Н. kalmianum, Н. annulatum, Н. tomentosum, Н. pulchrum, and H. rumeliacum) produced in vitro and regenerated after cryopreservation. The aim of the study was to assess, by means of light microscopy (LM) and transmission electron microscopy (TEM), the effect of freezing temperature on leaf histological organization and mesophyll chloroplast ultrastructure. Histological analysis showed a negative effect of ultralow temperatures on leaf tissue structure in Н. pulchrum and a positive effect in Н. perforatum. The TEM analysis showed that chloroplasts from ultralow temperature treated H. annulatum, H. tomentosum, and H. rumeliacum had a typically structured internal membrane system without destruction of thylakoid membranes, however, those of Н. humifusum had very high grana, and in Н. perforatum, chloroplast thylakoid destruction occurred. The chloroplast internal membrane system of in vitro cultured control plants and in vitro cultured cryopreserved plants of Н. kalmianum and Н. pulchrum had a specific spatial orientation without any destruction of the membranes. The results show a specific response of each species to these experimental conditions.Additional key words: chloroplast ultrastructure, in vitro culture, leaf histology.

ABSTRACT

Wax morphology and chemical composition are widely accepted to be important for the protective properties of the leaf’s surface and also valuable characteristics in plant systematics. The leaves of Sorbus domestica L. and Cotoneaster granatensis Boiss., species of two large genera with intricate taxonomy referred to subtribe Pyrinae, Rosaceae (formerly subfamily Maloideae), were studied by scanning electron microscope (SEM) and performing different methods of wax isolation. The aim of the study was to acquire a suitable, cost and time effective method for wax removal. Chloroform and methanol extractions and freeze-embedding method for direct isolation of the wax crystals were applied. Immersing the leaves for 3 minutes in chloroform was sufficient to extract the waxes whereas the efficiency of the methanol solvent was lower. Wax layers with wellpreserved structures of the crystals from both upper and lower epidermis were successfully transferred to artificial surfaces. The recrystallization experiment demonstrated that waxes from chloroform extracts could recrystallize in in vitro conditions on artificial surfaces. The crystals showed same micromorphology as on the intact leaves. Results of this study could be applied in further analytical researches of the waxes of S. domestica and C. granatensis or other species of the subtribe Pyrinae.