Search results for "botany"
showing 10 items of 4586 documents
Growth increase of birch seedlings under the influence of earthworms—a laboratory study
1992
The effects of the earthworm Lumbricus rubellus (Hoffm.) on net production and nitrogen content of birch seedlings were studied in laboratory microcosms. Coniferous forest floors with litter, humus and mineral horizons were simulated in transparent plastic cylinders. The materials were partially sterilized by microwaving, and re-inoculated with microflora and -fauna. A young (9 cm) birch seedling (Betula pendula Roth) was planted in each container. Earthworms were added to half of the replicates. The microcosms, through which a constant air flow was maintained, were incubated in a climate chamber. After two growth periods, leaf and stem biomasses of birch in treatments with earthworms incre…
Responses of soil decomposer animals to wood-ash fertilisation and burning in a coniferous forest stand
2000
Abstract Responses of soil decomposer animals (enchytraeids and microarthropods) to wood-ash fertilisation (1000 and 5000 kg ha−1) and a fire treatment mimicking prescribed burning were studied in a Scots pine stand in central Finland. The experiment was conducted on 30 × 30 m2 plots, each treatment being replicated four times. Soil animals were sampled throughout the growing season in the third year after the treatments. As a rule, numbers of soil animals increased during the study period. Numbers of the only enchytraeid worm species found at the study site, Cognettia sphagnetorum, were lower in the plots with higher ash level and plots which have been burned. In the plots having these tre…
Effects of endogeic earthworms on soil processes and plant growth in coniferous forest soil
1992
The effects of the endogeic earthworm, Aporrectodea caliginosa tuberculata (Eisen) on decomposition processes in moist coniferous forest soil were studied in the laboratory. The pH preference of this species and its effects on microbial activity, N and P mineralization, and the growth of birch seedlings were determined in separate pot experiments. Homogenized humus from a spruce stand was shown to be too acid for A. c. tuberculata. After liming, the earthworms thrived in the humus and their biomass increased (at pH above 4.8). In later experiments in which the humus was limed, the earthworms positively influenced the biological activity in humus and also increased the rate of N mineralizati…
Effects of environmental factors on seed germination ofAnthyllis barba-jovisL
2008
Abstract The influence of the main environmental factors on seed germination of Anthyllis barba-jovis L. were analysed. This work is part of a broader investigation aimed at the reintroduction of this species on Mount Conero, Ancona (central Italy), where it is at present extinct. The seeds were collected from the Gargano headland (southern Adriatic coast). Experimental analyses were carried out to determine: (i) dormancy levels of seeds collected in successive years, and also collected from the soil seed bank; (ii) effects of usual pre-treatments for overriding the physical dormancy of the seeds; (iii) optimal temperature range for maximum germination; (iv) effects of fire on seed germinat…
Micropropagation of juvenile and adultDigitalis obscura and cardenolide content of clonally propagated plants
1991
Cultures ofDigitalis obscura L. were established from axillary buds of mature plants or leaves of seedlings obtained under aseptic conditions. Explants were cultured on Murashige and Skoog medium containing benzyladenine and/or naphthaleneacetic acid. Shoot proliferation from axillary buds was not affected by seasonal fluctuations in the stock plants and increased relative to the cytokinin concentration, but auxin reduced the multiplication rate. Differentiation of somatic embryos and adventitious buds from cultured leaves required naphthaleneacetic acid alone or combined with benzyladenine, respectively. Cardenolide pattern and content of the regenerated plants were determined by high perf…
An Analysis of the Process of Fertilization and Activation of the Egg
1957
Publisher Summary Fertilization consists fundamentally in the release of a chain of metabolic reactions by virtue of which morphogenesis is started. The result of fertilization is the activation of the egg. This can be achieved also by several agents other than the spermatozoon and it is then spoken of as “artificial activation.” This chapter discusses the structural, physiological, and chemical changes that occur in the egg at fertilization that are significant in the understanding of the mechanisms of the activation. The chapter presents the hypothesis that in the cortex of the unfertilized sea urchin egg an inhibitor–enzyme complex is present. By reacting with some substance introduced b…
Free and conjugated polyamine content in Citrus sinensis Osbeck, cultivar Brasiliano N.L.92, a Navel orange, at different maturation stages
2004
Biogenic amines, synthesized during physiological metabolic processes of all living organisms, are present in food. At low concentrations, polyamines are essential for cell renewal and growth, but they can be detrimental when consumed in high amount through the diet as they could support abnormal cell growth pathologies. The daily human diet contains more putrescine than spermidine or spermine, mostly derived from fruits. In general, orange fruits contain high levels of put, a fact that could limit their utilization in the daily diet besides the benefits contributed by their strong antioxidant properties. There is therefore an increasing interest in finding plant foods with low polyamine co…
Phytophthora palmivora a New Pathogen of Lavender in Italy
2019
Root rot caused by Phytophthora nicotianae is considered the most serious disease of lavender in commercial cultivations in Italy. In summer 2001, in the Gela area (Sicily), ≈60% of 34,000 2-year-old landscape shrubs of English lavender (L. angustifolia) grown in a clay loam soil showed symptoms of dieback associated with root rot. Plants had been transplanted from pots in May and watered using a trickle irrigation system. A species of Phytophthora was isolated consistently from roots of symptomatic plants using potato dextrose agar (PDA) containing benomyl, nystatin, pentachloronitrobenzene, rifampicin, ampicillin, and hymexazol. The species was identified as P. palmivora on the basis of …
A new species ofPythiumisolated from burgundian vineyards and its antagonism towardsBotrytis cinerea, the causative agent of the grey mould disease
2004
During the course of an investigation on the pythiaceous fungi occurring in burgundian vineyards, three isolates of Pythium were found, all of which were characterised by spherical to lemoniform, proliferating sporangia. Only one out of these three isolates produced sexual characters (S-12) after prolonged incubation, but their asexual structures, temperature growth relationship and molecular characteristics were identical. Saprolegnia-type internal proliferation of the sporangia, and Phytophthora-type lemoniform, papillate sporangia were characteristic of all the three isolates. The type specimen is S-12 which is a medium slow growing saprophyte. The sequence of its ITS region of the rDNA …
The compound internal pyrenoid in cultured cells of the green algaMonoraphidium griffithii (Berkel.) Komar.-Legner.
1979
The chloroplast ultrastructure ofMonoraphidium griffithii (Berkel.) Komar.-Legner. has been studied in axenic cultures of various ages. The algae have grown in a complete nutrient solution (illumination about 3,000 lx) and on its agar medium (illumination about 600 lx). The large parietal cup-shaped chloroplast of the cells includes a multiformed compound internal pyrenoid that is situated, especially in older cells, in the central part of the chloroplast opposite to the dictyosome and the nucleus. The chloroplast thylakoids either reach the edge of the pyrenoid or penetrate its matrix and run there parallel in more or less long bits. Starch grains were not found to form any sheath around t…