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The significance of micro-morphologica1 leaf surface characters of plants in indication and mitigation of auto-exhaust pollution has been investigated. For the purpose of the study, the following plant species growing along roadsides in low and high traffic density areas have been selected: Asparagus racemosus, Azadirachta indica, Bougainvillea spectabilis, Cassia fistula, Ficus religiosa, Nerium...
The germination responses of Discopodium penninervium were tested at different constant and alternating temperature regimes as well as under various light conditions both in the laboratory and glasshouse. Seeds incubated at 10, 15, 20, 25 and 30 °C failed to germinate. When the seeds were incubated at alternating temperatures of 20/12 °C and 30/12 °C under continuous light, germination was 89 and...
In the present paper NH 4+ -, NO 3− and both (NH 4 NO 3 )-N nutrition is compared in 5 Carex species that are native to wet-acidic oligotrophic (C. limosa, C. rostrata), moist-eutrophic (C. gracilis), saline (C. distans) and flysh habitats (C. pilosa). Water-soluble inorganic ions, organic acids, low molecular weight carbohydrates (LMWC), amino acids, total...
Draba chionophila, a small rosette-plant that reaches the highest elevation of vascular species in the Venezuelan Andes, grows in frost-disturbed areas where miniature sorted stripes develop. A 100-plant population examined at 4480–4525 m showed preferential establishment in pebble-filled troughs, where 85% of the rosettes were rooted. Only 11 plants grew in adjacent fine-soil ridges, and 4 rosettes...
In a greenhouse experiment, single ramets of Ajuga reptans, a stoloniferous herb, were planted on the divider of two halves of trays. The two halves of a tray had the same or different nutrient supply. The aim was to study root and shoot plasticity and the placement of ramets and roots in response to the heterogeneous nutrient environment. Number of primary stolons, number of secondary stolons, stolon...
Structural and functional traits of Quercus ilex L. were monitored in plants growing in the climax area (Castelporziano, Rome; site A) and at the northern distribution limit (Nago, Trento; site B) in Italy. The most distinctive climatic differences between the two sites were duration and frequency of drought, heat spells in summer at site A, and the occurrence of frost and sub-zero temperatures in...
Odyssea paucinervis is a rhizomatous, perennial, C 4 grass, which is widely distributed in southern Africa on saline or alkaline soils. Salt glands are uniformly localised within grooves on both surfaces of the lamina as well as the leaf sheath. The glands are typically bicellular, consisting of a large, flask-shaped, subtending basal cell and a smaller, dome-shaped or hemispherical cap cell...
This study using light, transmission and scanning electron microscopy, describes the structure of Pinus halepensis primary needles collected from seedlings 22 and 24 weeks after emergence. P. halepensis is a circum-mediterranean pine of high importance for ecosystem maintenance and reforestation, in which primary needles are formed three to four years before being replaced by secondary needles. The...
In natural forest communities of Central Europe, Fagus sylvatica predominates in the tree layer under a wide range of site conditions due to a remarkable competitive ability. An exception are skeleton-rich soils such as screes where several other broad-leaved tree species co-exist with, or even replace, F. sylvatica. Little is known about the mechanisms that lead to the stable co-existence of 4–6...
Eucalyptus camaldulensis Dehnh., considered as a drought tolerant species, was examined in relation to some mechanisms linked to drought tolerance (cell-wall elastic adjustment and osmotic adjustment) and to the intraspecific variation related to those features. Rooted cuttings of five clones obtained from three different provenances from Australia (Gilgandra: 106, 109; Lake Albacutya: 119, 125; Condamine:...
The secretory nodule of Hypericum perforatum represents a very interesting gland. In fact, many of its active compounds, such as hypericin and hyperforin, are therapeutic agents. We observed, by transmission electron microscopy, the development of the structures, which appeared different from most plant glands, in leaves of H. perforatum. As observed by several authors, they appeared as a solid black...
Cryptobiotic crusts (biological soil crusts) are a dominant component of a unique system of dunes and intermittently inundated pans and playas situated on Pleistocene Lake Thompson bed at Edwards Air Force Base, California. Previous work reported on basic ecological parameters including distribution, abundance, and species composition of these algal (cyanobacterial)-dominated crusts.As a step toward...
The leaf epicuticular exudate of the Mediterranean ruderal Dittrichia viscosa is water soluble and easily drained to the soil by rain. As a result, soil enriched with this material is inhibitory for seed germination of lettuce, while germination of Malcolmia maritima, (a species co-occurring with D. viscosa in the same habitat) is considerably delayed. We investigated the possible mode of action of...
Nutrient relations in two spring wheat cultivars differing in salinity tolerance (Sarsabz, salt tolerant and Barani-83, salt sensitive) under sub-optimal and supra-optimal levels of nitrogen were examined in a glasshouse experiment. Twenty eight-day old plants of both the cultivars were subjected to five concentrations of 56, 112, 224, 336, and 448 mg N kg −1 soil for 42 days. Both cultivars...
Semiarid calcareous grasslands adjacent to agricultural land are often subject to eutrophication in the border zones. Depending on the extent of the nutrient input, a more or less strongly pronounced nutrient gradient develops in the semiarid grassland, and a change in structure of the plant community occurs. In this study, changes in above-ground energy fixation along nutrient gradients in four semiarid...
Selaginella lepidophylla is a pteridophyte resurrection plant from Central America deserts that has been studied hitherto only for microphyll ultrastructure and photosynthetic activity during rehydration. With the present work the anatomy and cell ultrastructures have been examined during progressive rehydration. Light microscope observations clearly showed the maintenance in the dry condition of...
In this study we focus on four particular aspects in the field of ecological studies of woody tissue respiration: 1) the application of the non-destructive soda lime technique to the in situ measurement of CO 2 efflux rates from branches or stems of standing trees all year round; 2) the investigation of respiration rates of branches of similar diameter but different positions in the canopy;...
We studied the species composition of vegetation and seed bank in an experiment with grassland and oldfield plots in an eutrophic alluvial wetland (called “Marais de Redon”) of Western France. In this wetland, artificial disturbances (mowing) and natural disturbances (cattle, roebucks, boars, voles…) are very frequent. In order to mime these natural disturbances, experimental disturbances were generated...
The special features of the endothecial thickenings in 59 species of 44 Solanaceae genera were studied and four different thickening types were distinguished: annular, helical, and reticulate ribs, and palmate baseplate. Some variations can be observed due to the presence of branched ribs and differences in the ribs width and number per cell. In general, each species shows a single thickening type,...
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