In most insect species, juvenile hormones regulate critical physiological processes such as metamorphosis and reproduction. In insects, these sesquiterpenoids are synthesized by retrocerebral endocrine organs, the corpora allata, via the classical mevalonate (MVA) pathway. One of these compounds, juvenile hormone III (JH III), has also been identified in the sedge Cyperus iria. In higher plants, biosynthesis of the sesquiterpenoid backbone may proceed through two distinct pathways: the MVA pathway or the 2C-methyl erythritol 4-phosphate pathway or through a combination of both pathways. Cell suspension cultures of C. iria were used to elucidate the biosynthetic pathway of JH III in the plant. Enzyme inhibition and labeling studies conclusively demonstrated that the biosynthesis of the sesquiterpenoid backbone of JH III proceeds via the MVA pathway. Inhibitor and precursor feeding studies also suggest that later steps of JH III biosynthesis in C. iria are similar to the insect pathway and that the final enzymatic reaction in JH III biosynthesis is catalyzed by a cytochrome P(450) monooxygenase. (+info)
(2/20) Oscillations of plants' stems and their damping: theory and experimentation.
Free oscillations of upright plants' stems, or in technical terms slender tapered rods with one end free, can be modelled by considering the equilibrium between bending moments and moments resulting from inertia. For stems with apical loads and negligible mass of the stem and for stems with finite mass but without top loading, analytical solutions of the differential equations with appropriate boundary conditions are available for a finite number of cases. For other cases approximations leading to an upper and a lower estimate of the frequency of oscillation omega can be derived. For the limiting case of omega = 0, the differential equations are identical with Greenhill's equations for the stability against Euler buckling of slender poles. To illustrate, the oscillation frequencies of 25 spruce trees (Picea sitchensis (Bong.) Carr.) were compared with those calculated on the basis of their morphology, their density and their static elasticity modulus. For Arundo donax L. and Cyperus alternifolius L. the observed oscillation frequency was used in turn to calculate the dynamic elasticity modulus, which was compared with that determined in three-point bending. Oscillation damping was observed for A. donax and C. alternifolius for plants' stems with and without leaves or inflorescence. In C. alternifolius the difference can be attributed to the aerodynamic resistance of the leaves, whereas in A. donax structural damping in addition plays a major role. (+info)
(3/20) Symptomatology and morphology of Claviceps cyperi on yellow nut sedge in South Africa.
Symptoms of ergot on yellow nut sedge, germination of sclerotia of the causal organism, Claviceps cyperi, and morphology of fresh specimens of the pathogen are described for the first time. The initial symptom of infection was a black sooty layer on inflorescences of infected plants due to colonization of the ergot honeydew by Cladosporium cladosporioides. Sclerotia of C. cyperi started to develop in March and April and could be discerned as small protuberances on inflorescences in the place of seed. Mature sclerotia were purplish-black. They generally remained viable for less than a year and germinated without prior cold treatment, although exposure for 21 d to 5 C before incubation significantly increased the germination rate. Under moist conditions at 24 C in the laboratory, germination commenced within 4-8 wk. Stromata took about 12 d to mature. Mature capitula were distinctly lobulate with a perithecium embedded in each lobe and a collar-like appendage around the base. Although dimensions of sclerotia, stipes, capitula, asci and ascospores were larger than in the original description, the general morphology supports treatment of C. cyperi as a distinct species. (+info)
(4/20) Adaptation to flooding in upland and lowland ecotypes of Cyperus rotundus, a troublesome sedge weed of rice: tuber morphology and carbohydrate metabolism.
(5/20) Norcyperone, a novel skeleton norsesquiterpene from Cyperus rotundus L.
(6/20) Chemical composition of the essential oils of Cyperus rotundus L. from South Africa.
(7/20) Evaluation of CNS activities of ethanol extract of roots and rhizomes of Cyperus rotundus in mice.
The ethanol extract of Cyperus rotundus (EECR) was tested for possible pharmacological effects on experimental animals. EECR significantly potentiated the sleeping time of mice induced by standard hypnotics, viz. pentobarbitone sodium, diazepam, and meprobamate in a dose dependent manner. EECR showed significant analgesic properties as evidenced by the significant reduction in the number of writhes and stretches induced in mice by 1.2% acetic acid solution. It also potentiated analgesia induced by morphine and pethidine in mice. Pretreatment with EECR caused significant protection against strychnine and leptazol-induced convulsions. The behavioral studies on mice indicate CNS depressant activity of the ethanol extract of C. rotundus. (+info)
(8/20) Polyphasic analysis of the bacterial community in the rhizosphere and roots of Cyperus rotundus L. grown in a petroleum-contaminated soil.
Cyperus rotundus L. is a perennial herb which was found prevailing in an area in the northeast of Brazil previously contaminated with petroleum. In order to enlarge the knowledge of microorganism-plant interaction in phytoremediation, the bacterial community present in the rhizosphere and roots of C. rotundus was evaluated by culture-dependent and molecular approaches. PCR-DGGE analyses based on the 16S rRNA gene showed that the profiles of bulk soil, rhizosphere and root samples had a high degree of similarity. A complex community of alkane utilizing-bacteria and a variable nitrogen-fixing community were observed when the PCR-DGGE analyses were based on the genes alkB and nifH, respectively. In addition, two clone libraries were generated from the alkB fragments of bulk and rhizosphere soils. Statistical analyses showed that the libraries were different concerning the alkB population composition. Using culture-dependent techniques, 209 bacterial strains were isolated from the rhizosphere and rhizoplane/roots of C. rotundus. Dot blotting analysis showed that the DNA from 17 strains hybridized, simultaneously, with the alkB and nifH probes. After partial 16S rRNA gene sequencing, these strains were affiliated with the genera Bosea, Cupriavidus, Enterobacter, Gordonia, Mycoplana, Pandoraea, Pseudomonas, Rhizobium and Rhodococcus. They can be considered of great potential for phytoremediation in this tropical soil area. (+info)