Armenia is a small country situated in the Transcaucasus on the border of Europe and Asia. For visitors from Central Europe, the huge landscape variety from the perspective of geological, geomorfological and climatic factors is surprising, as well as the vegetation and floristic diversity. Here alpine vegetation, semideserts, phryganoid vegetations and mountain steppes occurre in the same area, together with interesting forest vegetation types. Beautiful country - side rich in ancient historical monuments is a great treasure for this small country lying at the crossroads of cultures, biogeo - graphical regions and migration routes. and Ester Ekrtová, Libor Ekrt.
Forest vegetation occupied some 20 % of this Armenian area, with forests of three types. Open forests consist of short, rather sparse trees (juniper/pistachio/oak). Alluvial vegetation occurs as a narrow belt of trees or scrub along rivers and streams. Deciduous forests usually develop in more humid places and may show interesting parallels to our lowland and upland forests. Traditional management (in Europe practi - sed in the past) is maintained, providing an inspiration for our nature conservation. and Ester Ekrtová, Libor Ekrt.
In Armenia, more than 50 % of the territory lies at an altitude of over 2 000 metres a. s. l. The overall landscape and the mountain flora and vegetation are determined by volcanic areas alternating with crystalline massif or limestone areas. and Ester Ekrtová, Libor Ekrt.
The extremely dry lower altitudes of Armenia are occupied by semi-desert and phryganoid xerophyte plant communities with many rare endemics, useful wild plant species and wild relatives of cultivated plants. The rather high proportion of semi- -desert vegetation was transformed to agricultural areas due to irrigation. At higher altitudes, steppes and meadow-steppes are abundant and thorn-cushion communities are rather widespread too. In regions with high annual precipitation, meadows represent species rich and ornamental forest-free vegetation. and Ester Ekrtová, Libor Ekrt.
Drought significantly constrains higher yield of alfalfa (Medicago sativa L.) in arid and semiarid areas all over the world. This study evaluated the responses of leaf cuticular wax constituents to drought treatment and their relations to gas-exchange indexes across six alfalfa cultivars widely grown in China. Water deficit was imposed by withholding water for 12 d during branching stage. Cuticular waxes on alfalfa leaves were dominated by primary alcohols (41.7-54.2%), alkanes (13.2-26.9%) and terpenes (17.5-28.9%), with small amount of aldehydes (1.4-3.4%) and unknown constituents (4.5-18.4%). Compared to total wax contents, the wax constituents were more sensitive to drought treatment. Drought decreased the contents of primary alcohol and increased alkanes in all cultivars. Alkane homologs, C25, C27, and C29, were all negatively correlated with photosynthetic rate, transpiration rate, stomatal conductance, and leaf water potential. Under drought conditions, both stomatal and nonstomatal factors were involved in controlling water loss from alfalfa leaves. No direct relationship was observed between wax contents and drought resistance among alfalfa cultivars. An increase in alkane content might be more important in improving drought tolerance of alfalfa under water deficit, which might be used as an index for selecting and breeding drought resistant cultivars of alfalfa., Y. Ni ... [et al.]., and Obsahuje bibliografii
The effects of water stress on leaf surface morphology (stomatal density, size, and trichome density of both adaxial and abaxial surfaces) and leaf ultrastructure (chloroplasts, mitochondria, and cell nuclei) of eggplant (Solanum melongena L.) were investigated in this study. Higher stomata and trichome densities were observed on abaxial surface compared with the adaxial surface. Compared with well watered (WW) plants, the stomata and trichome density of the abaxial surface increased by 20.39% and 26.23% under water-stress condition, respectively. The number of chloroplasts per cell profile was lesser, the chloroplasts became round in a shape with more damaged structure of membranes, the number of osmiophilic granules increased, and the number of starch grains decreased. The cristae in mitochondria were disintegrated. The cell nuclei were smaller and the agglomerated nucleoli were bigger than those of WW plants. Our results indicated that the morphological and anatomical responses enhanced the capability of plants to survive and grow during stress periods., Q. S. Fu ... [et al.]., and Obsahuje bibliografii
Nondestructive methods to estimate individual leaf area (LA) accurately, by leaf length (L) and/or width (W), is helpful for the in situ and successive LA measurements. However, leaf shape and size may covary with environment and thus alter the coefficients of LA estimation models. To test such hypothesis, we carried out an experiment by measuring Saussurea stoliczkai C. B. Clarke leaves along an altitudinal transect in Damxung county, central Tibet. In July 2011, we selected seven sites at about every 150 m in altitude from 4,350 m to 5,250 m a.s.l. A total of 1,389 leaves (182 to 203 leaves for each site) were measured. For each site, models developed by two leaf dimensions [LA = a (L×W) + b] could estimate LA more accurately than those by single dimension. L, W, LA and leaf shape index (L:W ratio) all decreased with increasing altitude, leading to significant differences in coefficients of two-dimension model between almost every two sites. Accordingly, a common
two-dimension model is unlikely to occur for S. stoliczkai across the whole altitudinal transect, indicating that the varying leaf shape may alter the coefficient of LA estimation models., Z. Wang, L. Zhang., and Obsahuje bibliografii
Water-lilies (the genus Nymphaea) are one of the most ancient groups of aquatic plants. Two species (N. alba and N. candida) are native to the flora of the Czech Republic, both are critically endangered. Morphological similarities, large phenotypic variation and putative interspecific hybridization pose difficulties for species identification. The amount of nuclear DNA was found to be a reliable characteristic that allows not only species but also their hybrids to be re - cognized. Native species are mainly threa - tened by the loss of suitable habitats and planting of garden cultivars in natural sites. and Klára Kabátová, Petr Vít, Jan Suda.