Search results for "Perennial"
showing 10 items of 82 documents
Carbon dynamics of soil organic matter in bulk soil and aggregate fraction during secondary succession in a Mediterranean environment.
2013
Clarifying which factors cause an increase or decrease in soil organic carbon (SOC) after agricultural abandonment requires integration of data on the temporal dynamics of the plant community and SOC. A chronosequence of abandoned vineyards was studied on a volcanic island (Pantelleria, Italy). Vegetation in the abandoned fields was initially dominated by annual and perennial herbs, then by Hyparrhenia hirta (L.) Stapf, and finally by woody communities. As a consequence, the dominant photosynthetic pathway changed from C3 to C4 and then back to C3. Conversion of a plant community dominated by one photosynthetic pathway to another changes the 13C/12C ratio of inputs to SOC. Using the time si…
Characterization of Leaf Essential Oil Composition of Homozygous and HeterozygousCitrus clementinaHort. Extan. and its Ancestors
2013
Clementine is a natural tangor, resulting from an interspecific cross between mandarin and sweet orange. Gametic embryogenesis, allowing the single-step development of complete homozygous line from the heterozygous parents, increases the efficiency of perennial crop breeding programs. Tri-haploids have been regenerated through pollen embryogenesis (specifically, by anther culture) of Citrus clementina Hort. ex Tan., cv. Nules. Two of them (HOMO1 and HOMO2) have been acclimatized and grafted in vivo in 2000. Research regarding the chemical characteristics of plant regenerated by pollen embryogenesis or gynogenesis are useful to study the “gametoclonal variation”, as well as for further appli…
What are the biological determinants of regeneration of perennial weeds? Effect of fragment weight and bud number on the regrowth of five perennial w…
2022
Perennial weeds have become an increasing problem with the reduction of herbicide use andtillage. Because of their capacity to regenerate from vegetative organs, such as roots andrhizomes, they must be controlled with different management techniques than annuals. Todate, few studies exist on this topic and farmers often lack solutions to control perennials intheir cropping systems. Management strategies must focus on the depletion of theregenerative organ reserves to hamper the production of new shoots. However, there is aneed for a better understanding of below-ground organs physiology and the determiningfactors of their regrowth capacities.Our aim was to assess the number of shoots and th…
Riflessioni critiche sul collegamento fra autotutela sostitutiva e principio di perennità’ dell’azione impositiva
2023
Con opinabile orientamento, la Suprema Corte ha esteso i confini dell’autotutela c.d. sostitutiva fino a ricomprendervi un principio di “perennità” dell’azione amministrativa, che mal si raccorda, laddove non ne nega addirittura la ratio sottostante, con la disciplina positiva che regola i presupposti per l’esercizio della funzione impositiva e per la sua rinnovazione. Siffatto principio, peraltro, appare in contrasto con quello della “buona amministrazione” (diretta declinazione dell’art. 97 Cost.) nella misura in cui essa trova la sua moderna dimensione nell’essere anche strumento di tutela dell’amministrato dall’esercizio (extra ordinem) dei pubblici poteri. The Italian Supreme Court has…
Effects of intensity and duration of infection by a hemiparasitic plant, Rhinanthus serotinus, on growth and reproduction of a perennial grass, Agros…
1999
Arising from annual variation in parasitic plant population densities, substantial yearly changes may occur in the parasitic load of an individual perennial host. We conducted two two-year greenhouse pot experiments to examine the effects of varying intensities and duration of infection by an annual root hemiparasitic plant, Rhinanthus serotinus, on the growth and reproduction of its perennial host grass, Agrostis capillaris. In the first experiment, one host plant was growing either alone or under a load of 1 or 3 root hemiparasitic plants for one growing season, and during the next season all hosts continued their life free of hemiparasites. In the second experiment, the host plants eithe…
Digitalis spp.: In Vitro Production of Haploids
1990
Digitalis, a member of the Scrophulariaceae, is composed of biennial or perennial herbs and occasionally of small shrubs. Several Digitalis species are used therapeutically, as they are a source of cardiac glycosides. The importance and distribution of these species are summarized below, with special attention to D. purpurea, D. lanata and D. obscura. For a detailed review see Thtin et al. (1972), Morton (1977), and Font Quer (1978).
Pollination biology in an endangered rocky mountain toadflax (Linaria cavanillesii)
2013
Knowledge about the reproductive system of species inhabiting rocky habitats is scarce. The reproductive biology (floral biology, experimental pollination, insect visits, inbreeding depression, and seed predation) of the rupicolous Linaria cavanillesii was analyzed under field and experimental conditions. Self-compatibility was revealed by the high fruit set, seed set, and seed mass in the pollination experiment. Furthermore, results disclose that this species does not need insect visitors for seed production since fruit set after autonomous self-pollination was similar to that by hand cross-pollination. Self-offsprings were not affected by a strong degree of inbreeding depression in early …
Relationships among soil characteristics, plant macronutrients, and cardenolide accumulation in natural populations of Digitalis obscura
2005
In the present study, we have investigated relationships among several soil parameters (pH, organic matter, total carbonate, macronutrients, electrical conductivity, cation-exchange capacity) and macronutrient and cardenolide contents in leaves of wild Digitalis obscura plants. Young and mature leaves and soil samples were collected in ten different areas, corresponding to three Mediterranean bioclimatic belts (thermo-, meso-, and supramediterranean belts). Soil and leaf macronutrient (N, P, K, Ca, and Mg) contents and leaf cardenolide contents were determined. Bioclimatic conditions influenced the development of D. obscura, biomass being lowest in plant populations of the supramediterranea…
Effects of defoliation on male and female reproductive traits of a perennial orchid, Dactylorhiza maculata
2000
1The effects of defoliation on male reproductive traits of plants have received little attention. We conducted two field experiments with Dactylorhiza maculata (L.) Soo to examine the effects of defoliation on both male and female reproductive traits. We removed 0, 50 or 100% of leaves prior to flowering. The quality of pollen was tested by transferring pollen from the differently treated plants to untreated plants of the same population. 2The non-defoliated plants did not differ from the defoliated plants in mass of pollinia. No differences were found in the weight of seed capsules or in the proportion of embryonic seeds raised by flowers receiving pollen from differently treated pollen do…
Brassica trichocarpa (Brassicaceae), a new species from Sicily
2013
A new species of Brassica from Sicily, namely B. trichocarpa, is described and illustrated. This suffrutex was found on a calcareous peak of a mount near Palermo, where it is represented by a single population occupying a really small surface. It is well differentiated from the other perennial species belonging to B. sect. Brassica mainly in having hairy ovary and very short, thickened, hairy, not torulose fruits. Its relationships and taxonomical position within this group are examined too. An analytical key of the current taxa belonging to the genus Brassica sect. Brassica is also provided.