Search

Amaranthus, Sesamum indicum, and Linum usitatissimum are the most popular oilseed grains worldwide. Protein-rich Amaranthus contains bioactive peptides, is nutritious, and exhibits anti-allergic properties. Sesamum indicum is a primary trigger of anaphylaxis. Linum usitatissimum also displays allergenic properties. A DNA marker assessable using quantitative real-time PCR was developed to detect S. indicum and L. usitatissimum as allergenic contaminants of anti-allergenic Amaranthus. The efficiency of each primer set ranged from 90–98%, and high linear correlation (R2 > 0.99) was obtained between crossover values and the log DNA concentration. We established a Ct value of 0.1% of the binary as a cutoff. The practical application of the designed marker was confirmed by analyzing 20 commercial products. The qPCR system developed for detecting flaxseed and sesame can be applied for regulatory monitoring of allergenic substances in commercial amaranth-containing foods, thus contributing to protecting public health and safety. [ABSTRACT FROM AUTHOR]

For invasion biologists, the key question as to why only some alien species emerge as successful invaders as against a majority of other alien introduced species is still unclear. One of the best ways to resolve this question is to compare phylogenetically related alien invasive vs alien non-invasive species. Here we compared the allelopathic potential and phytochemical profiling of two congeneric species of Amaranthus (Amaranthus caudatus—invasive alien and non-invasive alien Amaranthus blitum. Petri dish bioassay followed by a pot experiment was used to evaluate the allelopathic effects of aqueous leaf and root extracts (1:10 w/v) of the said alien congeners on the germination and shoot length of Raphanus sativus. Petri dish bioassay results revealed that both species exhibited comparable levels of allelopathic activity; however, leaf extracts of both species showed significantly stronger inhibitory effects than root extracts, a trend corroborated by phenolic content assessments. However, no allelopathic effects on seed germination were observed in the pot culture bioassay. Comparative phytochemical profiling of these Amaranthus species, utilizing Gas Chromatography–Mass Spectrometry (GC–MS) and High-resolution liquid chromatography and mass spectrometry (HR-LC-MS) identified diverse array of compounds including methyl 8,9-octadecadienoate, n-hexadecanoic acid, phytol, loliolide, stigmasta-7,16-dien-3-ol, catechol borane, ellagic acid etc. which are known for their role in allelopathic interactions and invasiveness of the alien plants. Phytochemical analysis unveiled comparable levels of phytochemicals in both the invasive alien and non-invasive alien species of Amaranthus. In conclusion, our study revealed that while allelopathy may contribute to the invasiveness of the Amaranthus species, it does not seem to be a unique characteristic feature for the invasiveness of invasive alien species (Amaranthus caudatus) in comparison with its non-invasive alien congener. The present study recommends that more congeneric comparisons are needed to understand the role of high chemical diversity in alien plant invasions, and whether it is linked to the origin of the plant species. [ABSTRACT FROM AUTHOR]

Amaranthus (Amaranthus spp.) is one of the crops considered superfoods, given that this grain is enriched for minerals, protein, and vitamins. Most cultivars of this species exhibit seed-shattering, resulting in a reduction in seed yield, but it is expected that this undesirable trait can be improved by further breeding. However, the genetic mechanism of seed-shattering in this organism remains largely unknown. In the present study, we compared two amaranthus isolates, the A. cruentus grain cultivar 'New Aztec' (NA) (which exhibits seed-shattering) and Amaranthus spp. Accession DB9350 (DB) (which lacks seed-shattering). In initial experiments, we conducted morphological observations of the spikelets and utricles in these two strains. NA, and not DB, showed a horizontal dehiscence line on the utricle, resulting in easy detachment of the upper part of the pericarp and seed release. Next, we investigated the presence or absence of seed-shattering in the F1 and F2 progeny of an NA×DB cross. Notably, all F1 plants (n=10) showed shattering traits. In contrast, F2 plants (n = 106) exhibited segregation, yielding 82 and 24 plants showing shattering and non-shattering traits (respectively), consistent with the segregation ratio expected for Mendelian inheritance (3:1, χ2 = 0.314, p = 0.575). To elucidate the genetics of this trait, we performed bulked segregant analysis and linkage analysis in the F2 progeny. This analysis identified a locus, designated Acsh, in the 15.2–16.0 Mbp range of Chromosome 2B; the genotype at this locus co-segregated with the seed-shattering phenotype. Together, these data demonstrated that the seed-shattering trait in A. cruentus is a dominant, single-gene, qualitative trait regulated by Acsh. These results are expected to facilitate the breeding of non-shattering cultivars in grain amaranthus. [ABSTRACT FROM AUTHOR]

The adverse impact of climate change on crop yield has accelerated the need for identification of crop cultivars resistant to abiotic stress. In the present study, a cultivar assortment index (CAI) was generated for the evaluation of forty Amaranthus hypochondriacus cultivars response to elevated ozone (EO) concentrations (AO + 30 ppb) in Free Air Ozone Enrichment (FAOE) facility using the parameters viz. foliar injury, gaseous exchange attributes, namely, net photosynthetic rate, stomatal conductance, transpiration rate, intercellular carbon dioxide, and water use efficiency along with above ground biomass and grain yield attributes. The dataset was used to identify key indicator parameters responsive to EO through principal component analysis (PCA) and further transformed to obtain linear score and weighted score. The CAI varied from 70.49 to 193.43. Cultivars having CAI value less than 151 were ozone tolerant (OT) whereas cultivars with CAI values between 150 and 170 were moderately tolerant (MOT). The cultivars exhibiting CAI values above 170 were ozone sensitive (OS). The cultivars exhibited differential sensitivity to EO with IC-5994 (CAI = 187.26) being the most affected cultivar whereas IC-5576 (CAI = 83.38) and IC-5916 (CAI = 70.49) being the least affected ones. The CAI, based on linear score and weighted score, offers easy identification of ozone sensitive (OS) and ozone tolerant (OT) cultivars. This index could help researchers to define a clear and strong basis for identification of OT cultivars which will reduce the time required for preliminary screening and further evaluation of crop cultivars for the development of climate smart crops. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) were devised with the sensitizers prepared from the leaves and flowers of Amaranthus cruentus. Fresh and dried leaves were employed for extracting the dye sensitizers. Acetone, ethanol, and deionized water were used as solvents for the extraction process. A sum of nine dyes was prepared. For all the extracted dyes, spectroscopic studies (UV–visible & FTIR) were performed to ensure that the dyes are suitable to be used as sensitizers for DSSC. XRD and SEM were recorded for the TiO2 paste used. Nine DSSCs were fabricated with the extracted dyes as sensitizers, TiO2 as semiconductor oxide, I−/I3− as electrolyte, and graphene-coated FTO as counter electrode. J-V characterization study was done for each cell showed that the cell with dye taken from the fresh leaves using acetone exhibited the highest efficiency of 0.816%. It was noted that these cells recorded higher efficiency than the previously reported works with dyes taken from Amaranthus red. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the chemical composition, mineral content and report the effect of gastrointestinal digestion on the proteins, phenolics, flavonoids and antioxidant activity of morphological parts of Amaranthus viridis (AV). The macronutrients found in the greatest quantity were proteins (leave, inflorescence and seeds) and fiber (roots and stem). The main minerals were calcium, potassium, iron and zinc. All the plant parts showed total phenolic (TPC) and total flavonoid (TFC) compounds that were correlated with antioxidant capacity (DPPH, ABTS and FRAP); the leaves and inflorescence presented the greatest potential. The antioxidant compounds from the leaves, inflorescence and roots decreased after static in vitro digestion, while the TPC and TFC of the digested seeds increased by more than 55%. Approximately 90% of the protein content was bioaccessible. To the best of our knowledge, for the first time, the bioaccessibility of proteins, phenolics, flavonoids and antioxidant activity of the leave, inflorescence, seeds, roots and stem from AV were reported. Taking into consideration the excellent nutritional properties, the morphological parts of the plant can be potentially explored as a source of protein, fiber, minerals and antioxidant compounds. [ABSTRACT FROM AUTHOR]

The gases used: ethylene (C2H4), hydrogen cyanide (HCN) and nitric oxide (NO) showed a high activity as inductors of germination in primary dormant or non-dormant seeds exposed to stress or suboptimal temperatures. So far, research on the role of ethylene, hydrogen cyanide and nitric oxide has involved these gases during seed germination. This work describes gas-priming as a novel method for treating air dry seeds of the genus Amaranthus serving as a model. Effects of C2H4, HCN or NO applied to dry seeds were similar to those obtained when the gases were used during seed germination for an identical period of time. Application of the gases to air dry seeds presents a new opportunity to study the role of those gases in germination of dormant and non-dormant seeds and to constrain effects of the gases from time 0. The prolonged treatment time for dry seeds (24 h) is convenient because if the treatment is started in the morning, there is sufficient time the next day for further experiments to begin, e.g. germination test in water or in solutions of other compounds. Moreover, it is important that the gas-treated seeds can be stored or transported prior to use. The gas-priming method allows to prepare treated seed samples which can be used in experiments either immediately or after storage in open air or in a closed container. Gas-priming with C2H4, HCN and NO is a simple and useful treatment of air-dried seeds, which opens up new useful possibilities for basic research on the role of those gases in releasing dormancy and seed germination of various plant species. In addition, the method may prove very useful in horticulture and agriculture in improving germination of gas-sensitive seeds. [ABSTRACT FROM AUTHOR]

Several alien plant species have been introduced into Kashmir Himalaya from different regions of the world and subsequently some of these have been able to colonize and become invasive. Why only some species among the alien species pool establish as strong invaders represents a fundamental question for invasion ecologists. Trait comparisons of invasive with less/non-invasive congeners help in understanding the role of various trait differences in invasion success. In this study, we investigated the differences in various phenological, physiological and morphological traits in three alien plant congeners (Amaranthus blitum Linn., A. caudatus Linn. and A. spinosus Linn.) which differ in their invasion status, and attempted to relate the trait differences to their differential invasion potential in Kashmir Himalaya. The results revealed that the more aggressive behavior of A. caudatus in contrast to other two congeneric species is more likely explained by its early and longer germination period, shorter pre-reproductive period, early and extended flowering period, shorter generation time, early life cycle completion, fast growth, high reproductive allocation, more height, inflorescence length and higher seed production. We expect this knowledge to yield theoretical as well as practical information, about the possible adaptive traits employed by the three alien species, to target their long term management in the Kashmir Himalaya. [ABSTRACT FROM AUTHOR]

Amaranthus, a cosmopolitan genus including endangered species, restricted endemics and widespread weeds, is often difficult to characterize taxonomically and thus has generally been considered by systematists as a 'difficult' genus. Species in this genus have high genetic variability, with diversity in growth form, plant height, number of inflorescences, seed colour, protein content, seed yield, resistance to pests and diseases, and adaptation to soil type, pH, climate, rainfall and day-length. The combination of various anatomical characteristics of Amaranthus, such as Kranz anatomy, well developed root system, stomatal conductance, and maintenance of leaf area, results in increased efficiency of using CO under a wide range of temperatures, and higher light intensity and moisture stress environments which enables this plant to adapt under diverse geographic and environmental conditions. Buried seeds of Amaranthus constitute an important part of the soil seed bank and position, distribution and dormancy type of these seeds in the soil play an important role in their germination and subsequent emergence, which is further influenced by factors like temperature, soil moisture, and light availability. The current review highlights the positive as well as negative role of the various species of genus Amaranthus. Many species of the genus are medicinally important and bear antiallergic, anticancer, antihypertensive and antioxidant properties, thus being used in the treatment of several aliments. Amaranthus being a rich source of fatty acids, proteins, micronutrients, vitamins and squalene, are used as cereals, dye plants, forages, medicinal plants, ornamentals, and as vegetables. However some of the Amaranthus species are noxious weeds which are known to compete with many economic crops in different parts of the world and cause great yield losses. Thus, further research is warranted to strike a balance between the beneficial and harmful species of this Pseudocereal. Moreover, understanding the weedy behaviour of these plants would provide valuable information for improving our mechanistic models of crop-weed competition and weed population dynamics. [ABSTRACT FROM AUTHOR]

Full-length genomic DNA clones encoding starch branching enzymes (SBEs) from three cultivated grain amaranths were isolated and characterized. A sequence analysis showed that the SBE genes from Amaranthus caudatus, A. cruentus, and A. hypochondriacus, viz. SBE- ca, SBE- cr, and SBE- hy, respectively, contained the same exon and intron structure and consisted of 961 amino acids with molecular weights of approximately 108.4 kDa. The lengths of the genes were 7,446 ( SBE- ca), 7,453 ( SBE- cr), and 7,443 bp ( SBE- hy), and they are highly homologous. We also tested, for the first time, the potential use of SBE from diverse genetic sources to answer long-standing questions on the origin of grain amaranths. The maximum parsimony tree based on the SBE sequence data suggests that A. hybridus is the progenitor wild species of grain amaranths. The results could be summarized as follows: (1) the A. hybridus species comprise all grain amaranths, which can then be divided into two subgroups; (2) A. caudatus and A. hypochondriacus and/or A. caudatus and A. quitensis appear to be closely related to each other; (3) A. powellii was the most distantly related to the other five species in the A. hybridus complex. These results indicate that A. hybridus is the ancestor species in at least two separate domestication events, lending support to the theory of three separate, rather than one, domestication events involving A. hybridus as the common ancestor. A new approach to investigating the genetic diversity in Amaranthus using the nuclear gene SBE provided useful information on the evolutionary origin of three cultivated species. [ABSTRACT FROM AUTHOR]

In the past 20 years, very little progress has been achieved in reducing food insecurity, child malnutrition and hunger in Africa. Under-nutrition and micronutrients deficiencies are widespread and affect mainly women and children. To address these problems, increased consumption of African leafy vegetables is promoted as sources of both micronutrients and bio-active compounds. Widely promoted African leafy vegetables include Amaranthus spp., a taxonomic group cultivated worldwide. Species of this genus are used as pseudo-cereals in Europe and America, and are mostly planted as vegetables in Africa. Amaranthus has been rediscovered as a promising food crop mainly due to its resistance to heat, drought, diseases and pests, and the high nutritional value of both seeds and leaves. Leaves are rich in proteins and micronutrients such as iron, calcium, zinc, vitamin C and vitamin A. All parts of the plant are used as medicine to heal many diseases in African communities. This paper focuses on leafy amaranths traditionally utilized on the continent. It briefly reviews the current knowledge on taxonomy, ecology, nutritional and nutraceutical value, production and cultivation systems, reproductive biology, genetic resources and breeding of amaranths. Species of interest include: A. blitum, A. caudatus, A. cruentus, A. dubius, A. hypochondriacus, A. spinosus, A. thunbergii, A. tricolor, and A. viridis. Research and development opportunities on nutritive and nutraceutical properties, production and commercialization, taxonomic evaluation and breeding perspectives were explored. [ABSTRACT FROM AUTHOR]

Amaranthus, collectively known as amaranth, is an annual or short-lived perennial plant used as leafy vegetables, cereals and for ornamental purposes in many countries including India. During 2011, leaf samples of Amaranthus plants displaying leaf curling, leaf distortion, leaf crinkling and yellow leaf margins were collected from Banswara district, Rajasthan in India. Full-length clones of a monopartite begomovirus, a betasatellite and an alphasatellite were characterized. The complete nucleotide sequence of the isolated begomovirus features as a typical 'Old World' begomovirus with the highest nucleotide per cent identity with Chilli leaf curl virus and hence, considered as an isolate of Chilli leaf curl virus. The complete nucleotide sequences of betasatellite and alphasatellite possess maximum nucleotide identity with Tomato yellow leaf curl Thailand betasatellite and Chilli leaf curl alphasatellite, respectively. This is the first report of the association of chilli-infecting begomovirus and satellite molecules infecting a new host, Amaranthus, causing leaf curl disease. [ABSTRACT FROM AUTHOR]

White-seeded cultivated amaranth [ Amaranthus caudatus L., A. cruentus L., and A. hypochondriacus L.] grain is less valuable if contaminated with brown off-type seeds from the hybrid weedy progeny of spontaneous crop–weed crossing. Crop–weed crossing frequency was estimated by using two grain amaranth cultivars. Both cultivars were planted at the same nine locations in the Midwest United States and exposed to pollen from local weedy Amaranthus species. Harvested seeds were grown in a greenhouse, and the frequency of crop–weed hybrids was determined by observing dominant weed traits in the progeny. The cultivar ‘Plainsman’ was approximately tenfold more likely to hybridize with weedy amaranths than was ‘D136-1’. These are the first amaranth cultivars to be evaluated in this way. The reduced hybridization potential of ‘D136-1’ or similar material can be exploited to reduce the occurrence of off-type seed contamination in grain amaranths. [ABSTRACT FROM AUTHOR]

The morphological variations (growth habit, leaf shape, leaf color, height, stem diameter, number of branches and internodes, leaf area, blade ratio, leaf thickness, number of leaves, and total leaf area) and protein content of 53 Indonesian amaranths ( Amaranthus spp.), consisting of weedy-, vegetable-, and ornamental-types, were assessed. The extent of variation in the Indonesian Amaranthus accessions were compared with the worldwide collection (26 accessions from United States Department of Agriculture (USDA) and 5 ornamentals from Nepal) in the experimental field of the University of Tsukuba, Japan. The variation in average values of most morphological traits and protein content in the Indonesian accessions were similar to those of the worldwide germplasm, but the important parameters that influence vegetable yield (e.g., number of leaves and stem diameter) were superior in the Indonesian accessions. Protein content showed a positive correlation with the number of leaves, whereas a negative correlation was observed with leaf thickness. The Indonesian accession of A. viridis and A. dubius showed a great potential to be further selected as parental lines for high protein content and number of leaves. The relatively high protein content of the leaves of Celosia may also potentially serve as an alternative protein source in the tropics. [ABSTRACT FROM AUTHOR]

Antioxidant properties of amaranth extracts isolated sequentially by acetone and methanol/water from defatted plant leaves, flowers, stems and seeds were assessed by ABTS, DPPH, ORAC and total phenols content (TPC) assays. In addition, antioxidant properties of solid plant material were evaluated by the direct QUENCHER method using the same assays. Leaves and flowers of amaranth as well as their extracts possessed the highest antioxidant activities. Radical scavenging capacity in ABTS assay for leaves, flowers, stems and seeds evaluated by QUENCHER method were 144.24 ± 2.41, 112.33 ± 7.45, 19.05 ± 1.13 and 21.82 ± 1.06 μmol trolox equivalents in 1 g of dry weight, respectively. On-line HPLC-DPPH assay was used to determine the activity of separated compounds and it was observed that rutin was the main radical scavenger in amaranth extracts. Preliminary screening of extract composition was performed by UPLC/ESI-QTOF-MS and rutin, nicotiflorin, isoquercitrin, 4-hydroxybenzoic and p-coumaric acids were identified by measuring their accurate mass and retention time. [ABSTRACT FROM AUTHOR]

The metabolic reasons associated with differential sensitivity of C and C plant species to enhanced UV-B under varying soil nutrient levels are not well understood. In the present study, spinach ( Spinacia oleracea L. var All Green), a C and amaranthus ( Amaranthus tricolor L. var Pusa Badi Chaulai), a C plant were subjected to enhanced UV-B (280-315 nm; 7.2 kJ m day) over ambient under varying soil nutrient levels. The nutrient amendments were recommended Nitrogen (N), Phosphorus (P), Potassium (K), 1.5× recommended NPK, 1.5× recommended N and 1.5× recommended K. Enhanced UV-B negatively affected both the species at all nutrient levels, but the reductions varied with nutrient concentration and combinations. Reductions in photosynthetic rate, stomatal conductance and chlorophyll content were significantly more in spinach compared with amaranthus. The reduction in photosynthetic rate was maximum at 1.5× recommended K and minimum in 1.5× NPK amended plants. The oxidative damage to membranes measured in terms of malondialdehyde content was significantly higher in spinach compared with amaranthus. Enhanced UV-B reduced SOD activity in both the plants except in amaranthus at 1.5× recommended K. POX activity increased under enhanced UV-B at all nutrient levels in amaranthus, but only at 1.5× K in spinach. Amaranthus had significantly higher UV-B-absorbing compounds than spinach even under UV-B stress. Lowest reductions in yield and total biomass under enhanced UV-B compared with ambient were observed in amaranthus grown at 1.5× recommended NPK. Enhanced UV-B did not significantly change the nitrogen use efficiency in amaranthus at all NPK levels, but reduced in spinach except at 1.5× K. These findings suggest that the differential sensitivity of the test species under enhanced UV-B at varying nutrient levels is due to varying antioxidative and UV-B screening capacity, and their ability to utilize nutrients. Amaranthus tolerated enhanced UV-B stress more than spinach at all nutrient levels and 1.5× recommended NPK lowered the sensitivity maximally to enhanced UV-B with respect to photosynthesis, biomass and yield. PCA score has also confirmed the lower sensitivity of amaranthus compared with spinach with respect to the measured physiological and biochemical parameters. [ABSTRACT FROM AUTHOR]

Amaranthus is a cosmopolitan genus comprising large number of species with many morphotypes cultivars/accessions having diversified morphological features. The species, morphotypes within Amaranthus are very closely related requiring microclassification even revision in present taxonomic status. Most of the works have been done employing grain Amaranthus and their putative ancestors applying morphological and molecular data. In present study along with morphological features, phenolic compounds (secondary metabolites), isozyme profile of acid phosphatase were applied to get comprehensive reflection of interrelationship and relative closeness among the species, morphotypes/accessions of few vegetable, grain and weed Amaranthus. Both the vegetable and grain Amaranthus are supposed to have originated from respective weed progenitor through occasional outcrossing and gradual domestication. The study strongly vouched the previous interpretations regarding interrelationship of grain Amaranthus and their derivation from their putative progenitor also showed clear separate clustering of vegetable and grain Amaranthus with their close relatives. A sharp congruence in cluster pattern was achieved between morphological dendrogram and cumulative dendrogram computed on morphological and biochemical parameters, which is a rare event in systematics. [ABSTRACT FROM AUTHOR]

Due to an increasing demand of leaf vegetables, and hence their economic importance in the tropics, it is very common that excessive fertil izer N rates are applied to vegetable gardens and fields to attain high yield. This calls for more information on their nutrient requirements. In this study, we designed experiments to explore the effect of organic N levels on the yield and agronomic N use efficiency (ANE) by chinese cabbage (Brassica rapa) and amaranthus (Amaranthus cruentus). The experimental design was a randomized complete block design consisting of chinese cabbage (CC) and amaranthus (AM) with three replicates. Chicken manure (CHM) and cattle manure (CAM) were the source o f N . The treatments were 0, 200, 300 kg N ha-1 and 0, 170, 250 kg N ha-1 for CC and AM, respectively. Chicken manure resulted in increased fresh and dry matter yield of CC and AM compared to CAM. All treatments at first harvest induced higher marketable yield of vegetables than controls except with low levels of CAM N. At second harvest, only 300 kg CHM N ha·1 resulted in significantly (P<0.05) higher marketable yield of CC compared to control, while no significant difference observed in AM by 170 kg CAM N ha-1 · Agronomic N use efficiency was decreasing with increasing N levels. Nitrogen levels can be reduced to 200 and 170 kg N ha-1 for CC and AM without significantly affecting the yield. [ABSTRACT FROM AUTHOR]

Three amaranth hybrids ( Amaranthus paniculatus f. cruentus (Vishnevyi dzhem), A. paniculatus (Bronzovyi vek), and A. caudatus f. iridis (Izumrud) were grown in the climate-controlled chamber on Jonson nutrient medium supplemented with 2 μM Fe-EDTA. When plants developed 5-6 true leaves (six-week-old plants), NiCl was added to medium to final concentrations of 0 (control), 50, 100, 150, 200, and 250 μM. In 6 days, the increment in biomass of young and mature leaves, stems, and roots, and also the contents of Ni and Fe in them were measured. The red leaf amaranth hybrid Vishnevyi dzhem manifested the highest phytoremediation potential. i.e., the highest capacity for Ni accumulation in the shoots and the most pronounced symptoms of Fe deficit. In the presence of 150 and 250 μM NiCl in medium, the shoots of these plants contained about 2 and 4 mg Ni/g dry wt, respectively. In experiments with Fe deficit in plants grown for a week in the presence of NiCl (0, 25, 50, 75, and 100 μM), it was established that all tested nickel concentrations suppressed iron reduction in intact roots, which is catalyzed by ferric-chelate reductase, and this may underlie the antagonism between the two metals. In the presence of 50 μM NiCl in medium and 2 μM Fe (Fe deficit) and especially 100 μM Fe (Fe excess), the content of MDA and proline in leaves increased and superoxide dismutase was activated; this indicates a development of oxidative stress. Leaf treatment with polyamines (putrescine or spermidine) with aminoguanidine (the inhibitor of HO generation at polyamine oxidation) and with 1,3-diaminopropane led to the increase in nickel accumulation in leaves but did not result in the appearance of any signs of injury. This confirms our previous suggestion that polyamines manifest their protectory action as Ni chelators and detoxicants. [ABSTRACT FROM AUTHOR]

Plant growth responses to arbuscular mycorrhizal fungi (AMF) are highly variable, ranging from mutualism in a wide range of plants, to antagonism in some non-mycorrhizal plant species and plants characteristic of disturbed environments. Many agricultural weeds are non mycorrhizal or originate from ruderal environments where AMF are rare or absent. This led us to hypothesize that AMF may suppress weed growth, a mycorrhizal attribute which has hardly been considered. We investigated the impact of AMF and AMF diversity (three versus one AMF taxon) on weed growth in experimental microcosms where a crop (sunflower) was grown together with six widespread weed species. The presence of AMF reduced total weed biomass with 47% in microcosms where weeds were grown together with sunflower and with 25% in microcosms where weeds were grown alone. The biomass of two out of six weed species was significantly reduced by AMF (−66% & −59%) while the biomass of the four remaining weed species was only slightly reduced (−20% to −37%). Sunflower productivity was not influenced by AMF or AMF diversity. However, sunflower benefitted from AMF via enhanced phosphorus nutrition. The results indicate that the stimulation of arbuscular mycorrhizal fungi in agro-ecosystems may suppress some aggressive weeds. [ABSTRACT FROM AUTHOR]

The aim of the study was to confirm the presence of rutin, one of the most common quercetin glycosides, and other quercetin derivatives in plants of genus Amaranthus, to investigate the influence of the species and variety on rutin distribution in the plant and content changes during growing season. The rutin content was determined by micellar electrokinetic capillary chromatography in individual plant parts at the beginning of the growth, at the flowering stage and at the maturity stage of five Amaranthus species. The total quercetin content was determined by micellar electrokinetic capillary chromatography too. The rutin content in amaranth ranged from 0.08 (in seeds) to 24.5 g/kg dry matter (in leaves). Comparison of the determined total quercetin content and the calculated content of quercetin released from rutin did not prove important presence of quercetin or other quercetin derivatives than rutin. Only amaranth leaves sampled at the maturity stage probably contained quercetin or quercetin derivatives. Significant differences in the rutin content were established among species and as well varieties. Amaranthus hybrid and A. cruentus were the best sources of rutin. [ABSTRACT FROM AUTHOR]

The effects of Ni(NO3)2 and Pb(NO3)2 on Amaranthus sp. L. root growth and the effect of calcium on heavy metal (HM) accumulation in the growing root zone and root growth inhibition were studied. The seeds were germinated in the Pb(NO3)2 solutions at concentrations of 50, 100, 200, 500 and 700 μM or Ni(NO3)2 solutions at concentrations of 10, 50, 70, 100, and 500 μM in the presence of 100 μM Ca(NO3)2 or without it. HM toxicity was assesses in 7 days after seed sowing by the root length. Distribution of HM over the tissues of the growing root part was examined histochemically. Ni was more toxic to root growth than Pb. In the presence of Ca, Ni and Pb accumulation in the amaranth root growing part increased markedly, and this enhanced their growth-inhibitory of action. A comparison of results obtained in this work and available from the literature permitted a conclusion that the routes of HM penetration into the root differ in different plant species, and this determines ambiguity of protective Ca action. [ABSTRACT FROM AUTHOR]

Moving towards sustainable agriculture implies exploring the interconnections between farming and the environment, and soil is a key component of sustainability. Mulching is one of the methods to protect and enhance the productivity of the soil. We studied here the effect of mulching applied to mandarin tree rows for weed control in two localities near Tortosa, Spain, to compare its performance with the present chemical weed control system using the herbicide glyphosate. Three mulches were tested in each citrus orchard: rice straw, almond husk and black geotextile. Five plots per treatment, that is, three mulches, glyphosate application and control, were arranged following a randomized block design. Each plot was five trees long and its width was the distance between the two drip-lines. Just before mulch installation, bags containing non-dormant seeds of Amaranthus retroflexus and Diplotaxis erucoides were buried at three depths, and were exhumed one year later. After exhumation, sets of 250 seeds were placed in incubators and cumulative germination was obtained. Moreover, the weed flora was monitored at the two localities on four dates over one year and its total cover was evaluated. Seeds of A. retroflexus and D. erucoides showed the highest germination below almond husk, 90.9% and 96.2%, respectively. In total 74 species were recorded covering the mandarin tree rows. Our results indicated that black geotextile and almond husk controlled the presence of weeds as well as or better than the applications of glyphosate at least during the first year after their introduction. No significant differences were found between the mean weed cover of black geotextile (0.88%), almond husk (4.04%) and herbicide plots (2.04%). Altogether, our results show that mulching is one weed control strategy in mandarin orchards that also provides other benefits in terms of sustainable agriculture, such as soil protection or avoiding herbicide pollution. [ABSTRACT FROM AUTHOR]

Amaranthus blitoides S. Watson (prostrate pigweed) populations resistant to acetolactate synthase (ALS; EC 4.1.3.18)-inhibiting herbicides and triazines (SuR/TR) were found in Israel. The Ganot population was 6- to 790-fold more resistant to ALS inhibitors than the wild type due to an altered target site. Molecular analyses showed that the Ganot population was a mixture of two biotypes: (i) SuRA/TR in which domain A of the als gene differed in one nucleotide, resulting in substitution of Pro by Ser 188; (ii) SuRB/TR in which a mutation in domain B led to a substitution of Trp by Leu 569. The mutation in domain A resulted in resistance to all ALS inhibitors except imidazolinones, whereas the mutation in domain B led to resistance to all ALS inhibitors tested. SuRA/TR and SuRB/TR are multiple-resistant with an additional single mutation in the plastidic psbA gene that changes Ser 264 to Gly in the D1 protein, leading to triazine resistance. It is evident that plants within a population exposed to a similar selection pressure may show different patterns of cross-resistance due to three different point mutations. This unique phenomenon renders planning of rational weed management difficult or even impossible. [ABSTRACT FROM AUTHOR]

The genus Amaranthus includes several important monoecious and dioecious weed species, and several populations of these species have developed resistance to herbicides. These species are closely related and two or more species often coexist in agricultural settings. Collectively, these attributes raise the concern that herbicide resistance might transfer from one weedy Amaranthus species to another. We performed research to determine if a dominant allele encoding a herbicide-insensitive form of acetolactate synthase (ALS) could be transferred from a monoecious species, A. hybridus, to a dioecious species, A. rudis. Numerous F1 hybrids were obtained from controlled crosses in a greenhouse between A. rudis and herbicide-resistant A. hybridus, and most (85%) of these hybrids were herbicide-resistant. Molecular analysis of the ALS gene was used to verify that herbicide-resistant hybrids contained both an A. rudis and an A. hybridus ALS allele. Although hybrids had greatly reduced fertility, 42 BC1 plants were obtained by backcrossing 33 hybrids with male A. rudis. Fertility was greatly restored in BC1 progeny, and numerous BC2 progeny were obtained from a second backcross to A. rudis. The herbicide-resistance allele from A. hybridus was transmitted to 50% of the BC1 progeny. The resistance allele was subsequently transmitted to and conferred herbicide resistance in 39 of 110 plants analyzed from four BC2 families. Parental species, hybrids, and BC2 progeny were compared for 2C nuclear DNA contents. The mean hybrid 2C nuclear DNA content, 1.27 pg, was equal to the average between A. rudis and A. hybridus, which had 2C DNA contents of 1.42 and 1.12 pg, respectively. The mean 2C DNA content of BC2 plants, 1.40 pg, was significantly (α < 0.01) less than that of the recurring A. rudis parent and indicated that BC2 plants were not polyploid. This report demonstrates that herbicide resistance can be acquired by A. rudis through a hybridization event with A. hybridus. [ABSTRACT FROM AUTHOR]

The beet armyworm, Spodoptera exigua (Hübner), can utilize a number of different host plants for oviposition and larval development, but some host plants are preferred over others. This study, using cage choice tests and olfactometer assays, demonstrates the beet armyworm's preference for pigweed, Amaranthus hybridus L., over cotton, Gossypium hirsutum L. Cage and olfactometer choice assays indicated that olfaction plays an important role in host selection by ovipositing females. First instars exhibited no feeding preference, but the more mobile third instars showed a significant feeding preference for excised pigweed leaves. The higher quantities and more diverse accumulations of free amino acids in pigweed might, in conjunction with other physiochemical and mechanical attractant and deterrent factors in the two-plant species system, play roles in the tendency of the beet armyworm to select pigweed over cotton and in providing a superior array of easily absorbed amino acids as compared to cotton. [ABSTRACT FROM AUTHOR]

The methods of distinguishing Amaranthus species and cultivars and assessment of outcrossing rate in grain amaranths are proposed. The collection of 20 cultivars and accessions of 7 species ( A. tricolor, A. mantegazzianus, A. cruentus, A. caudatus, A. hypochondriacus, A. hypochondriacus × A. hybridum and A. paniculatus) was examined. Urea-soluble proteins both from bulked samples (20 seeds) of particular cultivars, and samples which were obtained by mixing together cultivars of each species were extracted. To estimate the outcrossing rate, the proteins were extracted from each of100 seeds of cultivar A10 ( A. caudatus). In this case seeds were collected both from isolated inflorescences and from flowers exposed to open-pollination. The electrophoretical separations of proteins (SDS-PAGE) were performed. The protein pattern of 56–64 bands was detected. The samples were classified to three groups: 1- A. caudatus and A. cruentus, 2- A. tricolor and A. mantegazzianus and 3- A. hypochondriacus, A. hypochondriacus × A. hybridus and A. paniculatus. All species can be distinguished from each other. The protein pattern of A. tricolor (leafy type of amaranths) is considerably different from other species. The present study suggests a closer similarity between A. caudatusand A. cruentus than between the pairs of species A.hypochondriacus / A. caudatus and A. hypochondriacus / A. cruentus. Only small differences were seen between cultivars, nevertheless they were sufficient for distinguishing all the cultivars. It is possible to detect outcrossing between cultivars, by observing that30% of ‘A10’ seeds performed other patterns of proteins. Electrophoretic analysis of seed proteins proved to be useful for distinguishing species and cultivars of Amaranth, for describing similarity between species and for estimation its outcrossing rate. [ABSTRACT FROM AUTHOR]

A total of 229 genotypes of 20 Amaranthus species from the United States Department of Agriculture – Agricultural Research Service (USDA – ARS) National Plant Germplasm Amaranth Collection was evaluated in field experiments in Beijing and Wuhan, China, in 1994. Agronomic traits, including plant height, maturity, leaf number and color, stem color, seed color, branch number, 1000-grain-weight, yield per plant, and resistance to stresses (including diseases) were measured. The results indicated: 1. Many of the species were sensitive to daylength; 2. Cultivated genotypes generally had higher grain yield but were more seriously affected by diseases than non-cultivated species; 3. There was wide diversity in agronomic traits among Amaranthus species and among genotypes within the same species, and several genotypes were identified that appeared to carry favorable agronomic traits of immediate use in cultivar improvement; 4. For introduction of genotypes for use in plant breeding in China, selection should be partially based on matching the climates of the location of origin and the target area for production. [ABSTRACT FROM AUTHOR]

Changes in pH, titratable acidity and mineral content (Ca, Fe, Mg, Zn) were estimated in processed cassava products while the mineral content of raw and blanched amaranthus vegetable was determined. pH of fresh cassava (6.5) decreased as total organic acid (0.07%) increased with fermentation period. Fufu and lafun had the lowest pH and the highest total organic acids contents. Fermentation of cassava increased the total calcium and iron contents, reduced magnesium level while zinc remained fairly constant in grated cassava but was reduced when soaked in water (for the preparation of fufu and lafun). Fermentation also increased the availability of these selected minerals in both cassva products and simulated cassava-vegetable diets. Blanching reduced the mineral content of amaranthus vegetable but increased mineral availability. Fermentation of cassava and blanching of vegetables play an important role in making minerals more available and these processing methods should be encouraged to potentially ameliorate the disease states associated with mineral deficiency. [ABSTRACT FROM AUTHOR]

Meiotic studies were carried out in four accessions of three grain species, viz. Amaranthus cruentus, A. powellii and A. retroflexus and their F1 hybrids to elucidate the genome relationships between the cultivated and wild types and the cytogenetical mechanisms involved in speciation. All the three species were morphologically distinct and cytologically uniform with 17 bivalents at metaphase I. Morphologically the interspecific hybrids were either intermediate or had an overall dominance of wild parents. Chromosome analysis at meiotic metaphase I in the F1 interspecific hybrids of A. powellii with the Indian and Mexican accessions of A. cruentus showed an average of chromosome association of 1.0 IV + 0.10 III + 14.78 II + 0.14 I and 1.0 IV + 0.45 III + 14.20 II + 0.25 I and 5.81% in the former and 8.44% in the later pollen grain fertility, respectively and that of A. retroflexus with A. cruentus (Indian and Mexican) showed almost similar chromosomal associations. These studies show close genomic homology amongst all these three species involving certain chromosomal aberrations resulting in their evolution. [ABSTRACT FROM AUTHOR]

Photosynthesis was studied in relation to the carbohydrate status in intact leaves of the C plant Amaranthus edulis. The rate of leaf net CO assimilation, stomatal conductance and intercellular partial pressure of CO remained constant or showed little decline towards the end of an 8-h period of illumination in ambient air (340 μbar CO, 21% O). When sucrose export from the leaf was inhibited by applying a 4-h cold-block treatment (1°C) to the petiole, the rate of photosynthesis rapidly decreased with time. After the removal of the cold block from the petiole, further reduction in photosynthetic rate occurred, and there was no recovery in the subsequent light period. Although stomatal conductance declined with time, intercellular CO partial pressure remained relatively constant, indicating that the inhibition of photosynthesis was not primarily caused by changes in stomatal aperture. Analysis of the leaf carbohydrate status showed a five- to sixfold increase in the soluble sugar fraction (mainly sucrose) in comparison with the untreated controls, whereas the starch content was the same. Leaf osmotic potential increased significantly with the accumulation of soluble sugars upon petiole chilling, and leaf water potential became slightly more negative. After 14 h recovery in the dark, photosynthesis returned to its initial maximum value within 1 h of illumination, and this was associated with a decline in leaf carbohydrate levels overnight. These data show that, in Amaranthus edulis, depression in photosynthesis when translocation is impaired is closely related to the accumulation of soluble sugars (sucrose) in source leaves, indicating feedback control of C photosynthesis. Possible mechanisms by which sucrose accumulation in the leaf may affect the rate of photosynthesis are discussed with regard to the leaf anatomy of C plants. [ABSTRACT FROM AUTHOR]

Phosphoenolpyruvate carboxylase (EC 4.1.1.31) was purified 43-fold from Amaranthus viridis leaves by using a combination of ammonium-sulphate fractionation, chromatography on O-(diethylaminoethyl)-cellulose and hydroxylapatite, and filtration through Sepharose 6B. The purified enzyme had a specific activity of 17.1 μmol·(mg protein)·min and migrated as a single band of relative molecular weight 100000 on sodium dodecyl sulphate-polyacrylamide gel electrophoresis. A homotetrameric structure was determined for the native enzyme. Phosphoenolpyruvate carboxylase from Zea mays L. and A. viridis showed partial identity in Ouchterlony two-dimensional diffusion. Isoelectric focusing showed a band at pI 6.2. K values for phosphoenolpyruvate and bicarbonate were 0.29 and 0.17 mM, respectively, at pH 8.0. The activation constant (K) for Mg was 0.87 mM at the same pH. The carboxylase was activated by glucose-6-phosphate and inhibited by several organic acids of three to five carbon atoms. The kinetic and structural properties of phosphoenolpyruvate carboxylase from A. viridis leaves are similar to those of the enzyme from Zea mays leaves. [ABSTRACT FROM AUTHOR]

Pruned source-sink transport systems from predarkened plants of Amaranthus caudatus L. and Gomphrena globosa L. were used to study the localization of C-labeled photosynthate imported into experimentally induced sink leaves by microautoradiography. During a 6-h ( Amaranthus) or a 4-h ( Gomphrena) transport period, C-assimilates were translocated acropetally from a mature source leaf provided with CO, into a younger induced sink leaf (dark/-CO). In addition, a young still-expanding source leaf exposed to CO exported C-assimilates basipetally into a mature induced sink leaf (dark/-CO). Microautoradiographs showed that imported C-photosynthate was strongly accumulated in the sieve element/companion cell complexes of midveins, secondary veins, and minor veins of both the mature and the expanding sink leaf. Some label was also present in the vascular parenchyma and bundlesheath cells. In petioles, C-label was concentrated in the sieve element/companion cell complexes of all bundles indicating that assimilates were imported and distributed via the phloem. Moreover, a considerable amount of radioactivity unloaded from the sieve element/companion cell complexes of petiolar bundles, was densely located at sites of secondary wall thickenings of differen-tiating metaxylem vessels, and at sites of chloroplasts of the vascular parenchyma and bundle-sheath cells. These observations were more striking in petioles of Gomphrena than Amaranthus. [ABSTRACT FROM AUTHOR]

Simultaneous measurements of CO uptake, transpiration rate, and chlorophyll a fluorescence in leaf strips of C plants during the induction phase of photosynthesis are described. The timecourse of CO fixation is biphasic with the initial phase occurring within the first 1 to 5 min and the secondary phase consisting of a slow rise to the steady-state rate of photosynthesis. Transpiration rate follows the CO-fixation timecourse closely but the intercellular CO concentration never falls below saturation for C plants. Chlorophyll a fluorescence quenching occurs exclusively during the initial fast phase of the CO-fixation timecourse. The effect of duration of dark pretreatment of leaves on these parameters and the effects of light intensity and CO concentration are examined. These results are discussed with respect to the C cycle and photochemical and non-photochemical chlorophyll fluorescence quenching. [ABSTRACT FROM AUTHOR]

Acyl lipids and their constituent fatty acids were studied in leaves, chloroplasts and bundle-sheath strands of the C plant Amaranthus paniculatus L. grown under normal and 4%-oxygen-containing atmospheres. In all fractions the major lipids were found to be monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulphoquinovo-syldiacylglycerol and phosphatidylglycerol. Significant quantities of phosphatidylcholine and phosphatidylethanolamine were restricted to leaves and bundle-sheath strands. All lipids, except phosphatidylglycerol where 3- trans-hexadecenoic acid was also present, contained palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. On a chlorophyll basis and compared with whole leaves, the amounts of phosphatidylcholine and phosphatidylethanolamine in bundle-sheath strands were considerably reduced. Three weeks after the change from a normal to a 4% atmospheric O level, the galactolipid content, particularly in the bundlesheath strands, was enhanced. There were no significant differences in the degrees of saturationunsaturation of total acyl lipid for the plants grown in the low oxygen and normal atmospheres, although under 4% O the phosphatidylglycerol contained an increased proportion of 3- trans-hexadecenoic acid at the expense of palmitic acid. [ABSTRACT FROM AUTHOR]

In this paper we make comparisons between the observed oxygen and hydrogen stable isotope composition of leaf water and the predictions of the Craig-Gordon model of evaporative isotopic enrichment. Comparisons were made among two C species ( Chenopodium album and Helianthus annuus) and two C species ( Amaranthus retroflexus and Kochia scoparia), when plants were exposed to natural environmental conditions in the field. There were significant differences among the species for the hydrogen and oxygen isotopic composition of leaf water at mid-day. The Amaranthus and Helianthus plants had lower leaf water δD and δO values than did Kochia and Chenopodium. The observed leaf water δ values were significantly lower than those predicted by the evaporative enrichment model for all the species. The degree of discrepancy between the observed and modelled leaf water isotopic compositions differed among species. There was a strong linear relationship between the oxygen and hydrogen isotopic compositions of stem water, observed leaf water and the modelled leaf water for all species. The observed leaf water isotopic composition for the different species occurred at different points along the line connecting the stem water isotopic composition and the modelled leaf water isotopic composition in a plot of δD and δO. We interpret these linear relationships as mixing lines between the unfractionated source or stem water isotopic composition and the isotopic composition of water at the evaporation sites within leaves (as defined by the evaporative enrichment model). [ABSTRACT FROM AUTHOR]

Fifteen fungal species were found to be associated with seeds of three cultivars of Amaranthus cruentus L. There was a seasonal variability in the frequency of isolation, distribution and quantity of these seed-borne fungi among cultivars. The wetness, high temperature and air humidity that accompanied harvests of the first and second seasons greatly increased the number and amount of seed-borne fungi. Least number and mean percentage seed infection were recorded for NHAc while NHAc and NHAc carried highest percentage inoculum of these pathogens. The seed testa of all cultivars was found to harbour the highest number and amount of some of these pathogens also in the second season. These seed-borne fungi, Choanephora cucurbitarum, Rhizoctonia solani and Pythium aphanidermatum were highly pathogenic on seedlings of NHAc and NHAc. Five of these seed-borne mycoflora have not been recorded on Amaranthus in Nigeria. [ABSTRACT FROM AUTHOR]

Amaranthus includes approximately 60 species, of which three are cultivated as a grain source. Many wild Amaranthus species possess agriculturally desirable traits such as drought and salt tolerance, and pathogen resistance. We examined relationships among wild and cultivated Amaranthus species based upon restriction-site variation in two chloroplast DNA regions and in a nuclear DNA region. The chloroplast regions consisted of (1) an intergenic spacer in transfer RNA genes and (2) the ribulose-1,5-bisphosphate carboxylase gene with a flanking open reading frame. The nuclear region was the internal transcribed spacers ITS-1 and ITS-2 flanking the 5.8S gene in the ribosomal DNA. These regions were amplified by the polymerase chain reaction and digested with a total of 38 restriction endonucleases. We detected 11 potentially informative restriction-site mutations and seven length-polymorphisms among the 28 Amaranthus species. Parsimony analysis was used to find the shortest tree for each separate data set (chloroplast, nuclear, and length) and for two combined matrices (chloroplast/nuclear and all data sets). Overall, there was a low level of variation which generated poorly resolved trees among the 28 species. Congruence analyses revealed that the chloroplast and nuclear data sets were congruent with each other but not to the length data set. The congruence of the chloroplast and nuclear data sets suggested that cytoplasmic gene flow may not be a confounding factor in our analyses. The phylogeny also suggested that drought tolerance evolved independently several times. The molecular phylogeny provides a basis for selection of species pairs for crop development. [ABSTRACT FROM AUTHOR]

Both the mesophyll and bundle-sheath cells associated with the minor veins in the leaf of Amaranthus retroflexus L. contain abundant tubular endoplasmic reticulum, which is continuous between the two cell types via numerous plasmodesmata in their common walls. In bundle-sheath cells, the tubular endoplasmic reticulum forms an extensive network that permeates the cytoplasm, and is closely associated, if not continuous, with the delimiting membranes of the chloroplasts, mitochondria, and microbodies. Both the number and frequency of plasmodesmata between various cell types decrease markedly from the bundle-sheath - vascular-parenchyma cell interface to the sicve-tube member - companion-cell interface. For plants taken directly from lighted growth chambers, a stronger mannitol solution (1.4 M) was required to plasmolyze the companion cells and sieve-tube members than that (0.6 M) necessary to plasmolyze the mesophyll, bundle-sheath, and vascular-parenchyma cells. Placing plants in the dark for 48 h reduced the solute concentration in all cell types. Judging from the frequency of plasmodesmata between the various cell types of the vascular bundles, and from the solute concentrations of the various cell types, it appears that assimilates are actively accumulated by the sieve-tube - companion-cell complex from the apoplast. [ABSTRACT FROM AUTHOR]

Accumulation of betalain (amaranthin) in the seedling of Amaranthus caudatus, var. viridis, is inducible by light. Since the apparent lag-phase of amaranthin accumulation after the onset of light is of the order of 3 h, light induction experiments could be performed up to 3 h after the onset of light without interference with actual synthesis. The intricate induction phenomena can be explained as follows: The inductive light operates through phytochrome and through a blue/UV photoreceptor ('cryptochrome'). A phytochrome-dependent 'High Irradiance Reaction' is of minor importance. However, there is a strong, specific interaction between the light effects mediated through phytochrome and cryptochrome in the sense that the 'extent of the reversible response' - (response obtained with a particular light treatment terminated with a saturating red light pulse) minus (response obtained with the same light treatment when terminated with a saturating 756 nm light pulse) -increases with increasing P level and total fluence rate during the induction period. It is concluded that light induced amaranthin synthesis is, in fact, a convenient biochemical model system of photomorphogenesis in the case when phytochrome and cryptochrome operate simultaneously in mediating photomorphogenesis. [ABSTRACT FROM AUTHOR]

Seedlings of Amaranthus caudatus L. var. Pendula were used to study the influence of several treatment: white light, 3,4-dihydroxyphenylalanine (DOPA), kinetin, gibberellic acid (GA) on betalains biosynthesis. The pigments, betacyanins and betaxanthins, were separated using a Sephadex G-15 column chromatography. Qualitative as well as quantitative differences were observed according to the treatments applied. The amaranthin biosynthesis seemed to be favored in the absence of DOPA. Under the combined effect of kinetin and white light a small quantity of betanin was also synthesized. Adding exogenous DOPA led to a more diversified production which included betacyanins (amaranthin and betanin), betaxanthins (vulgaxanthin and miraxanthin), and even dopachrome. As a general rule, kinetin activated the betalains biosynthesis whereas GA inhibited it. The stimulating effect of white light was always much greater than that of kinetin. [ABSTRACT FROM AUTHOR]

In the C plant, Amaranthus graecizans, increasing [O] from 2% up to 100% inhibited photosynthesis, quantum yield, and the carboxylation efficiency, and increased the CO compensation point (Γ) from 2 to about 12 μl/l. The O inhibition of photosynthesis was fully reversible. When changing from 2.5 to 40% O and vice versa, about 1 h was required for full equilibration with an O inhibition of 18%; whereas in wheat, a C species, inhibition of photosynthesis and its reversal occurs within minutes after changing [O], resulting in 63% inhibition of photosynthesis by 45% O. These differences in O inhibition between a C and C species can be explained by high diffusive resistance across bundle-sheath cells of C plants and the increased CO/O ratio in bundle-sheath cells which is the consequence of the C cycle. In A. graecizans, Γ increased with increasing [O] but tended to reach a maximum at relatively high O levels. The lack of a linear increase in Γ as previously observed for C species indicates that a considerable amount of photorespired CO may be re-fixed with increasing levels of O. In comparison to previous reports with other C species, photosynthesis of A. graecizans shows greater sensitivity to O, with a noticeable inhibition occurring with shifts from 2 to 21% O. A. graecizans has characteristics of other C species with respect to Kranz anatomy, localization of PEP carboxylase in mesophyll cells and RuBP carboxylase in bundle-sheath cells, and little fractionation among carbon isotopes during CO fixation. The basis for the higher sensitivity of photosynthesis of A. graecizans to O may be based upon a lower diffusive resistance of gases across bundle-sheath cells than in some other C species. [ABSTRACT FROM AUTHOR]

The cytokinin activities of cis and trans ribosylzeatin isomers and that of N-(Δ-isopentenyl)adenosine were compared in four bioassays. The trans isomer was found to be more active than the cis isomer in stimulation of cucumber cotyledon expansion (100x), retention of chlorophyll in detached leaf pieces (7x), induction and stimulation of chlorophyll synthesis in cucumber cotyledons (20x) and of betacyanin synthesis in Amaranthus caudatus seedlings grown in the dark (60x). The N-(Δ-isopentenyl)adenosine adenosine was less active than the trans ribosylzeatin in all four bioassays and more active than the cis ribosylzeatin in induction and stimulation of betacyanin and chlorophyll synthesis. These results show that the hydroxylation of the trans methyl group in the N side chain of N-(Δ-isopentenyl)adenosine increases the biological activity and that this activity is either decreased or not significantly changed when the cis methyl group is hydroxylated. [ABSTRACT FROM AUTHOR]

The first inductive (short-day; SD) cycle advanced the initiation of reproductive development, while additional SD cycles progressively reduced the lag phase between the start of induction and initiation. The sensitivity to SD increased during ontogeny in long-days (LD) until even the requirement for the first SD cycle disappeared at the onset of 'autonomous' flowering. In photo-induced plants, the postinitiation rate of elongation of the apex was accelerated as the SD dose was increased, but was progressively slower as the start of induction was delayed closer to autonomous flowering, approaching asymptotically the rate of non-induced controls. The inflorescences were branched in plants growing continuously in LD and unbranched in those growing continously in SD. The subsequent branching of the inflorescence could be repressed by SD at any time prior to autonomous flowering, and the degree of repression increased with the induction dose. After the initial SD cycle, 1-2 additional SD could induce the loss of apical dominance, causing excessive elongation and leaf production in the subjacent branches. Further increase in the SD dose inhibited this elongation by accelerating the transformation of the apices of these branches to the reproductive state. [ABSTRACT FROM AUTHOR]

The ontogenetic change taking place in the facultative photoperiodic response of A. retroflexus to inductive short-day (SD) conditions was studied by exposing plants to continuous induction after different initial exposures to long-days (LD), and comparing the kinetics of their developmental responses (cumulative number of plants with reproductive apices, flowering stage, and height of the apical dome). As the plants progressed from emergence to 'autonomous' flowering (i.e., in non-inductive conditions), their response to continuous induction became progressively more rapid. Reproductive development was initiated following a progressively shorter lag-phase after the start of induction, but its subsequent rate remained unchanged. Until the onset of reproductive development, the undifferentiated upper part of the shoot apex (apical dome) elongated much more rapidly in SD than in LD. However, in both cases reproductive development was initiated when the apex had elongated to about the same extent, after which its elongation accelerated considerably, but to similar rates in both photoperiods. The data indicate that progress towards reproductive development takes place in inductive (SD), as well as in non-inductive (LD) photoperiods, but one cycle of the latter is as effective as 0.20-0.25 of a cycle of the former. -Plants induced at different stages in ontogeny started to change their subsequent branching pattern (ratio of leafy to leafless branches) as soon as induction was delayed beyond 'autonomous' flowering. [ABSTRACT FROM AUTHOR]