Showing papers on "Amaranthus hypochondriacus published in 1999"

Low-Cot DNA sequences for fingerprinting analysis of germplasm diversity and relationships in Amaranthus.

Abstract: We examined genetic diversity and relationships among 24 cultivated and wild Amaranthus accessions using the total low-Cot DNA and five individual repetitive sequences as probes. These low-Cot DNA probes were obtained by the isolation of various classes of repetitive-DNA sequences, including satellites, minisatellites, microsatellites, rDNA, retrotransposon-like sequences, and other unidentified novel repetitive sequences. DNA fingerprints generated by different types of repetitive-DNA probes revealed different levels of polymorphism in the Amaranthus genomes. A repetitive sequence containing microsatellites was found to be a suitable probe for characterizing intraspecific accessions, whereas more conservative sequences (e.g. rDNA) were informative for resolving phylogenetic relationships among distantly related species.Genetic diversity, measured as restriction fragment length polymorphism (RFLP) and the similarity index at the low-Cot DNA level, was equally high among intraspecific accessions between the two species groups: grain amaranths (A. caudatus, A. cruentus, and A. hypochondriacus) and their putative wild progenitors (A. hybridus, A. powellii, and A. quitensis). At the interspecific level, however, the grain amaranth species are less divergent from each other than their wild progenitors. With the rare exceptions of certain A. caudatus accessions, grain amaranths were found to be closely related to A. hybridus. The results based on low-Cot DNA were comparable with previous RAPD and isozyme studies of the same set of species/accessions of Amaranthus, indicating that low-Cot DNA sequences are suitable probes for a fingerprinting analysis of plant germplasm diversity and for determining phylogenetic relationships.

Effect of elevated carbon dioxide concentration at night on the growth and gas exchange of selected C4 species

Abstract: Biomass of certain C4 species is increased when plants are grown at elevated CO2 concentrations. Experiments using four C4 species (Amaranthus retroflexus L., Amaranthus hypochondriacus L., Sorghum bicolor (L.) Moench and Zea mays L.) exposed both day and night from sowing to carbon dioxide concentrations of 370 (ambient) or 700 µmol mol-1 (elevated) or to 370 µmol mol-1 during the day and 700 µmol mol-1 at night, determined whether any biomass increase at elevated CO2 concentrations was related to a reduction in the night-time rate of CO2 efflux at high night-time CO2 concentrations. Of the four species tested, only A. retroflexus significantly increased both CO2 assimilation (+13%) and plant biomass (+21%) at continuous elevated relative to continuous ambient concentrations of CO2. This increase was not associated with improvement in leaf water potential during dark or light periods. In contrast, high CO2 only during the night significantly reduced plant biomass compared to the 24 h ambient CO2 treatment for both A. retroflexus and Z. mays. This indicates that the observed increase in biomass at elevated CO2 for A. retroflexus was not caused by a reduction of carbon loss at night (i.e. increased carbon conservation), but rather a direct stimulation of daytime CO2 assimilation, independent of any improvement in leaf water potential.

Plastic responses to clipping in two species of Amaranthus from the Sierra Norte de Puebla, Mexico.

Abstract: This study investigates the plastic responses after shoot removal of Amaranthus cruentus L. and A. hypochondriacus L. This practice is common in the Sierra Norte de Puebla, Mexico, where both species are cultivated and used as a food source during the vegetative stage. Empirical observations indicate that biomass increases in clipped plants. The experimental study carried out on both species of Amaranthus imitated local farm management. Three levels of shoot removal were applied to plants of both species: Control, 10% and 40%. In A. cruentus plants with 10% of the shoot removed produced more stalk biomass, more leaves, greater leaf area, greater length of primary branches and a larger number of secondary branches than the control plants. In A. hypochondriacus, there were no differences among levels of shoot removal in stem biomass; in general, the number of primary and secondary branches in control plants was greater than that in clipped plants. Patterns of biomass allocation revealed important differences between species, as clipped plants allocated more biomass to seeds in A. cruentus, while control plants allocated more to leaves in A. hypochondriacus. Furthermore, changes in response at the primary branch (secondary branches, leaf biomass, and area) level were observed between species. In general, clipped plants of A. cruentus overcompensate for the damage, while this response was not evident in clipped plants of A. hypochondriacus. Instead, this species showed high tolerance to damage. The phenotypically plastic responses expressed for both species can be used as a guide to improve management of these plants by local farmers from the Sierra.

Phytotoxic Compounds from Esenbeckia yaxhoob.

Abstract: Investigation of the aerial parts of Esenbeckia yaxhoob Lundell (Rutaceae) led to the isolation of a new dammarane-type of triterpene which was characterized by spectral means as (24S)-24-methyl-dammara-20,25-diene-3β-yl-acetate. In addition, 2-tridecanone, asarinin, imperatorin, lupeol and hesperidin were obtained. (24S)-24-Methyl-dammara-20,25-diene-3β-yl-acetate, 2-tridecanone, asarinin and imperatorin caused significant inhibition of the radicle growth and\or germination of seedlings of Amaranthus hypochondriacus, Echinochloa crusgalli, Lactuca sativa and Lycopersicum esculentum. Also, it has been found that imperatorin inhibited ATP synthesis and both phosphorylating and uncoupled electron flow from H2O to K3[Fe(CN)6]. On the other hand, this coumarin stimulated the basal electron flow from H2O to K3[Fe(CN)6] and the activity of the light-activated Mg2-ATPase. These effects were measured in freshly lysed illuminated spinach chloroplasts and allowed to determine that imperatorin acts as an uncoupler and as a Hill reaction inhibitor.

Cloning and characterization of a trypsin inhibitor cDNA from amaranth (Amaranthus hypochondriacus) seeds.

Abstract: We previously isolated and sequenced the major trypsin inhibitor from Amaranthus hypochondriacus seeds. This amaranth trypsin inhibitor (AmTI) is a 69 amino acid protein with high homology to members of the potato-1 inhibitor family. This paper describes the cloning and expression of a cDNA encoding this trypsin inhibitor in various vegetative tissues of the amaranth plant during seed development and imbibition, and investigates the possible induction of AmTI expression by wounding.

Selection of acid tolerant strains of phosphate-solubilizing bacteria in soils of Uttar Pradesh Himalaya

Abstract: An experiment was conducted during 1993 to isolate and enumerate phosphate-solubilizing bacteria in 64 soil samples of various land use classes in soils of Uttar Pradesh Himalaya. Counts of potential indigenous phosphatesolubilizing bacteria ranged from 32-99 x 10 3 /g soil and significantly correlated with organic matter, available phosphate, water-holding capacity and bulk density Of the 23 bacterial isolates, 14 were gram positive and 9 gram negative. An isolate (PAS 2) of pasture and waste land (PH 4.8) had higest phosphate-solubilizing capacity (63%) which tolerated a wide range of soil acidity (PH 4.5 -6.1). Seed inoculation of this isolate increased most probable number counts in rhizosphere and non-rhizosphtere soil samples of crops like maize (Zea mays L.), amaranth (Amaranthus hypochondriacus L.) and soybean (Glycine mex (L.) Merr.) and also available soil phosphorus. The isolate belonged to Bacillus sp.