Detroit Dark Red Research Articles

Bioavailability, Acceptability and Contribution of Beetroot Powder Processed Under Different Conditions to The Iron Intake of Adolescent Girls Aged 10 To 19 Years

ABSTRACT Iron deficiency anemia (IDA) is a prevalent issue among adolescent schoolgirls, significantly affecting their cognitive development and school performance. Beetroot, known for its high iron content, presents a potential solution for mitigating IDA. This study investigated the bioavailability, acceptability, and contribution of beetroot powder, processed under different conditions, to the iron intake of adolescent schoolgirls aged 10-19 years. Two beetroot varieties, Detroit Dark Red and Crimson Globe, were subjected to different processing methods, including boiling, sun drying, oven drying, and freeze drying. The bioavailability of iron was assessed through oxalate-to-iron molar ratios, while sensory acceptability was evaluated using a 9-point hedonic scale. The results revealed that the oxalate-to-iron molar ratios were below 1.0, indicating favorable iron bioavailability. Additionally, beetroot powder contributed between 9.24 mg and 9.5 mg of iron per 100g, equating to more than 50% of the recommended daily allowance (RDA) for adolescent schoolgirls. Sensory evaluation indicated moderate acceptability, with scores ranging from "like slightly" to "like moderately." These findings suggest that beetroot powder, particularly when processed by boiling and sun drying, can serve as a valuable dietary supplement to address IDA in adolescent girls.

Effect of Preparation and Drying Techniques on the Physicochemical, Functional and Nutritional Properties of products from Beetroot (Beta Vulgaris L.) varieties

Beetroot (Beta vulgaris L.) is rich in biologically active compounds. This study aimed to assess how different methods of preparation and drying affect the physical, chemical, functional, and nutritional properties of iron-rich beetroot powder. Two beetroot varieties, Detroit Dark Red (DetR) and Crimson Globe (CrimG), were processed using three drying techniques: sun drying (SD), oven drying (OD), and freeze drying (FD), with both boiled and fresh beetroots. The properties evaluated in the study included water activity, color, total phenolics and flavonoids, oxalate content, and mineral content. The results showed significant (p<0.05) differences in these properties between the dried and fresh samples. Notably, drying increased calcium, zinc, and phosphorus levels while decreasing the iron content. Boiling followed by sun drying was the best method for retaining iron, particularly for the CrimG variety. The study suggests that drying can help preserve or even enhance the physicochemical properties and micronutrient content, especially iron while reducing phytochemical levels affecting iron absorption. These findings are important for developing iron-rich beetroot products to improve dietary iron intake, especially for adolescent children.

Biochemical and Mineral Evaluation of Four Exotic Beetroot Varieties Grown in Bangladesh

In Bangladesh beetroot is getting attention in recent years due to its high food value and potential industrial use. The present study was conducted to assess the food value in terms of biochemical and mineral nutritional constituents of four exotic beetroot varieties (viz. Chioggia, Detroit Dark Red, Early Wonder Tall Top, and Red Ace) of Bangladesh. The pH, brix and dry matter (DM%) levels of the four beetroot varieties ranges between 5.52 to 6.51, 8.9 to 10.5, and 8.8 to 11.0%, respectively; and Detroit Dark Red had the highest DM%. the protein, fibre, ash, and total sugar contents were also significantly varied in the four varieties and the values ranged between 10.80-12.50, 5.10-6.20, 7.65-8.86, 2.62-6.06%DM, respectively. The vitamin C was found highest in Chioggia (6.20 mg/100g). Among the micro and macronutrient elements tested, all parameters were significantly varied and Detroit Dark Red contained the highest amount of N (1904 mg 100 g−1 DM), Fe (53 mg 100 g−1 DM), Zn (26 mg 100 g−1 DM) and Mn (17 mg 100 g−1 DM); while Chioggia contained the highest amount of K (3331 mg 100 g−1 DM), Ca (151 mg 100 g−1 DM) and B (21 mg 100 g−1 DM). Total anthocyanin and total phenolic contents also varied among the varieties and the highest values were observed in Chioggia and Early Wonder Tall Top, respectively. Based on the observed parameters, Chioggia and Detroit Dark Red seemed to be the better performers among the four beetroot cultivars.
 Vol. 9, No. 3, December 2022: 279-287

Screening Table Beet and Swiss Chard for Resistance to Pseudomonas syringae pathovar aptata

Bacterial leaf spot (BLS) has emerged in the last few decades as an economically important disease of both table beet (Beta vulgaris ssp. vulgaris) and Swiss chard (Beta vulgaris ssp. cicla). BLS is caused by Pseudomonas syringae pv. aptata, which is spread readily on infected seeds. Symptoms appear as circular to irregular shaped, with a tan to dark brown center and a very dark border. Disease incidence and severity is dependent on cool, humid conditions and can vary widely year to year depending on the environment. Both the vegetative and reproductive phases of these biennial crops are susceptible to the pathogen. Table beet and Swiss chard commercial cultivars (n = 21), table beet breeding lines (n = 5), and table beet plant introductions (PIs) (n = 26) were screened for response to spray inoculation with P. syringae pv. aptata in a controlled greenhouse setting. Plants were rated for severity of symptoms using percent of the area of each pair of leaves (leaf set) with symptoms and an overall plant score assigned based on the scores for each leaf pair. Accessions varied in BLS susceptibility. PI accessions were most variable, with the area under the disease progress curve (AUDPC) ranging from 1.33 to 8.75. Highly significant differences among PIs were detected for disease scores in the vegetative stage, beginning 21 days after inoculation. Screens during the reproductive growth stage showed the least variation in AUDPC among PIs. Although cultivars varied less than PIs, good BLS resistance (low disease scores) was noted for ‘Touchstone Gold’, ‘Kestrel’, ‘Bull’s Blood’, ‘Rainbow’ chard, as well as PIs 222234 and NSL 28026. Accessions W451C, Red Cloud, Detroit Dark Red, and NSL 28020 were highly susceptible. There was no consistent association between disease score in the vegetative and reproductive phases, suggesting that breeders may need to screen for BLS in both phases of the biennial life cycle. The more resistant PIs or cultivars identified in this study can be used in future efforts to breed for host resistance to BLS and to establish mapping populations to better understand the genetic control of resistance, to aid in breeding efforts.

Effect of Different Spacing and Nitrogen Levels on of Beetroot cv. Detroit Dark Red Quality Parameters under Telangana State Conditions

The aim of this paper was to establish the effect of different spacing and nitrogen levels on quality parameters of beetroot cv. Detroit Dark Red under Telangana state conditions. It was carried out during rabi season of 2020-21 at SKLTSHU, College of Horticulture, Rajendranagar, Hyderabad, India. The experiment was laid out in Factorial Randomized Block Design with sixteen treatments replicated thrice. Treatment consisted of four levels of spacing S1 (45cm ×15cm), S2 (30cm×15cm), S3 (30cm×10cm) and S4 (15cm ×15cm) and four levels of nitrogen N1 (70 Kg ha-1), N2 (87.5 Kg ha-1), N3 (105 Kg ha-1) and N4 (122.5 Kg ha-1). The effects of the spacing and nitrogen levels was observed for quality characters. Highest total soluble solids (TSS) (9.93 oBrix), reducing sugars (1.64%), total sugars (7.31%) and chlorophyll content 45.50 (SPAD value) were recorded in wider spacing S1- 45 cm x 15 cm and highest ascorbic acid content (10.09 mg 100g-1) was recorded in closer spacing S4-15 cm x 15 cm, whereas pH and titrable acidity were found to be non-significant. Highest pH (6.20), reducing sugars (1.52%), total sugars (7.29%), ascorbic acid content (10.06 mg 100g-1) were recorded in nitrogen level N1-70 Kg N ha-1, whereas highest TSS (9.79 oBrix), chlorophyll content 45.70 (SPAD value) were observed in nitrogen level N4-122.5 Kg N ha-1. The interaction effect on quality parameters was found to be non-significant.

Extraction procedure of betalains pigments from hardy beetroot matrix and its stabilization

Beetroot betalains (E162) as natural colorants, extracted by physical means, are permitted by the European Union for use as a natural colorant in foods. Like other natural colorants, betalains have limitations due to the lack of standardized extraction protocols and reduced stability. An experiment was conducted for the process optimization of betalains extraction from a competent variety and subsequently its stabilization through acidulants. Results revealed that the Crimson Globe cultivar was a feasible matrix for betalains extraction over Detroit Dark Red. Box Behnken Design of Response Surface Methodology (RSM) optimized that at 70°C, 4.0 min extraction time and 1:3 solid to solvent ratio, maximum betalains and phenolics could be extracted. Betalains were found to be more related to color expression (r = .962) than the antioxidant activity (r = .688). Among various acidulants, betalains was maximally retained by 1% (w/v) ascorbic acid with t1/2 = 155.17 h followed by citric (92.36 h), tartaric (85.20 h), succinic (83.96 h), and malic acid (75.72 h). Novelty impact statement Beetroot betalains, designated as GRAS, are known for their antioxidant and coloring potential. Detailed extraction methodology for betalains was optimized with pure aqueous solvent so that the extracted betalains, when used as a food colorant are devoid of any solvent residue. Further, the study concluded that among various acidulants, the performance of ascorbic acid was best in terms of better color and antioxidant stability. The betalains acidified with ascorbic acid could be stored up to 9 months at 10°C. This is the first detailed report on aqueous extraction protocol standardization from beetroot cv. Crimson Globe and its stabilization using acidulant/s.

Effects of Cattle Manure on the Growth, Yield, Quality and Shelf Life of Beetroot (Beta vulgaris L. cv. Detroit Dark Red)

Beetroot (Beta vulgaris L.) is one of the widely and popularly used salad vegetable in the Kingdom of Eswatini: However, there is scarcity of information pertaining to its organic production. A field study laid out in a Randomised Complete Block Design (RCBD) was conducted at the Horticulture Farm, Faculty of Agriculture, Luyengo Campus, at the University of Eswatini to determine the effects of cattle manure on growth, yield, quality and shelf-life of beetroot. Five treatments were applied in this experiment, and included cattle manure applied at 20, 40, 60, and 80 t/ha and a control of inorganic fertilizer, NPK [2:3:2 (22)] applied at 100 kg/ha as basal dressing and limestone ammonium nitrate (LAN) (28) applied at 80 kg as a top dressing. The treatments were replicated four times. The results obtained showed that beetroot grown under the application rate of 80 t/ha exhibited higher values in plant height (32.5 cm), number of leaves (9), leaf area (206 cm2), root diameter (5.1 cm), root length (11.7 cm), root fresh mass/plant (10.8 g), root dry mass/plant (9.2 g), marketable yield/plant (9.2 g) and quality [(aroma (33.5%), flavour (34%), texture (35%)] of the edible part. Plants supplied with 20 t/ha of cattle manure and inorganic fertiliser (control) gave the lowest vegetative growth parameters, quality parameters and marketable yield.

Levels of Organochlorinated Pesticide Residues in Vegetables

ABSTRACTContamination of soil and crops with organochlorine pesticide (OCP) residues is a public health problem. This study was conducted to assess residue levels of dichlorodiphenyltrichloroethane (DDT), hexachloro-cyclohexane (HCH), endosulfan, aldrin, and dieldrin in tissues of eggplant (Solanum melongena L., cv. GJB-3), potato (S. tuberosum L., cv. Kufri Chandramukhi), tomato (S. lycopersicum L., cv. Gujarat Tomato-2), onion (Allium cepa L., cv. Pusa White Round), beet (Beta vulgaris L., cv. Detroit dark red), spinach (Spinacia oleracea L., cv. Pusa Bharati), and cabbage (Brassica oleracea L., cv. Pusa Ageti). Total concentrations of OCP residues ranged from 0.31 to 109.03 μg·kg−1 (wet weight). All samples had some contamination of 1, or more, OCP residues. Mean concentrations of ΣDDT, ΣHCH, Σendosulfan, Aldrin, and dieldrin over all vegetables were 27.01 ± 2.67, 23.13 ± 3.92, 9.97 ± 1.83, 1.43 ± 0.79, and 1.06 ± 0.37 μg·kg−1 (wet weight), respectively. The maximum OCP residue accumulation was in root vegetables, followed by leafy and fruit vegetables. Levels of OCP residues were below the recommended maximum residue limits set by the European Commission and Indian government except for levels for dieldrin, making the vegetables unsafe for human consumption.

Function of sodium and potassium in growth of sodium-loving Amaranthaceae species

We observed that the growth of three Amaranthaceae species was promoted by sodium (Na), in the order dwarf glasswort (Salicornia bigelovii Torr.) >> Swiss chard (Beta Burgaris L. spp. cicla cv. Seiyou Shirokuki) > table beet (Beta vulgaris L. spp. vulgaris cv. Detroit Dark Red). In the present study, these Na-loving plants were grown in solutions containing 4 mol m−3 nitrate nitrogen (NO3-N) and 100 mol m−3 sodium chloride (NaCl) and potassium chloride (KCl) under six Na to potassium (K) ratios, 0:100, 20:80, 40:60, 60:40, 80:20 and 100:0, to elucidate the function of Na and K on specific characteristics of Na-loving plants. The growth of dwarf glasswort increased with increasing Na concentration of the shoot, and the shoot dry weight of plants grown in 100:0 Na:K was 214% that of plants grown at 0:100. In Swiss chard and table beet, growth was unchanged by the external ratio of Na to K. The water content was not changed in Swiss chard or table beet by the external Na to K ratio. These observations indicate that both Na and K have a function in osmotic regulation. However, dwarf glasswort could not maintain succulence at 0:100; therefore, Na has a specific function in dwarf glasswort for osmotic regulation to maintain a favorable water status, and the contribution of K to osmotic regulation is low. NO3-N uptake was promoted by Na uptake in dwarf glasswort and Swiss chard. NO3-N uptake and transport to shoots was optimal at 100:0 in dwarf glasswort and at 80:20 in Swiss chard. These functions are very important for the Na-loving mechanism, and the contribution of K was lower in dwarf glasswort than in Swiss chard.

Antioxidant Activity and Phenolic Content of Betalain Extracts from Intact Plants and Hairy Root Cultures of the Red Beetroot Beta vulgaris cv. Detroit Dark Red

Betalains are water-soluble plant pigments that are widely used as food colorants, and have a wide range of desirable biological activities, including antioxidant, anti-inflammatory, hepatoprotective, anti-cancer properties. They can be produced from various plants, notably beetroot, but betalain products obtained in this way also have some undesirable properties and are difficult to standardize. A potentially attractive alternative is to use hairy root cultures. In the study reported here, we found that betalain extracts obtained from hairy root cultures of the red beetroot B. vulgaris cv. Detroit Dark Red also had higher antioxidant activity than extracts obtained from mature beetroots: six-fold higher 2,2-dyphenyl-1-picrylhydrazyl radical scavenging ability (90.7% inhibition, EC(50) = 0.11 mg, vs 14.2% inhibition, EC(50) = 0.70 mg) and 3.28-fold higher oxygen radical absorbance capacity (4,100 microM TE/g dry extract, vs 1,250 microM TE/g dry extract). The high antioxidant activity of the hairy root extracts was associated with increased concentrations (more than 20-fold) of total phenolic concomitant compounds, which may have synergistic effects with betalains. The presence of 4-hydroxybenzoic acid, caffeic acid, catechin hydrate, and epicatechin were detected in both types of extract, but at different concentrations. Rutin was only present at high concentration (1.096 mg.g(-1) dry extract) in betalain extracts from the hairy root cultures, whereas chlorogenic acid was only detected at measurable concentrations in extracts from intact plants.

Betalain biosynthesis by red beet ( Beta vulgaris L.) hairy root culture

The time course of growth and betalains biosynthesis by Beta vulgaris L. (cv. Detroit Dark Red) hairy root culture were investigated. It was established that hairy root culture produced 42.2 mg/flasks betalains (26.2 mg/flasks betaxanthins and 16.0 betacyanins) between 6th and 15th days of cultivation. The uptake of sucrose, nitrate and phosphate ions were followed during the cultivation and data on the physiology of the B. vulgaris hairy root culture are presented.

Biosynthesis and radical scavenging activity of betalains during the cultivation of red beet (Beta vulgaris) hairy root cultures.

Betalains biosynthesis and antiradical scavenging activity were investigated during cultivation of four hairy root cultures of Beta vulgaris, obtained from different cultivars (Bordo, Egyptian, Detroit 2 and Detroit Dark Red). The best producer of betalains was a hairy root culture from Beta vulgaris cv. Detroit Dark Red (13.27 mg/g dry weight total pigment production). The ethanol extract, derived from roots of the same culture grown for 15 days under submerged conditions, showed a high antiradical activity (83% of inhibition of the stable DPPH.).

Influence of Chloride and Nitrogen Form on Rhizoctonia Root and Crown Rot of Table Beets.

The effect of NaCl combined with Ca(NO3)2 or (NH4)2SO4 was examined on table beets (Beta vulgaris) in the presence and absence of Rhizoctonia solani (anastomosis group 2-2), the cause of Rhizoctonia root and crown rot. Transplants of cvs. Detroit Dark Red and Early Wonder grown in the greenhouse in infested soils and fertilized with Ca(NO3)2 (10 mmol of N) were 32% larger in dry weight than plants treated with (NH4)2SO4 (10 mmol of N). In noninfested soils, a 17% increase in dry weights was observed for plants treated with Ca(NO3)2 compared to plants that were fed (NH4)2SO4. When NaCl (0.17 mmol) was applied, the mean dry weight sincreased 40% in noninfested soil and 12% in infested soil compared to plants that received no NaCl. No significant interaction occurred between N fertilizer and NaCl in greenhouse trials. However, in field soils infested with R. solani, NaCl (560 kg/ha) combined with (NH4)2SO4 (112kg of N per ha) produced 26 to 47% more root yield than when (NH4)2SO4 was used alone. Inthe absence of NaCl, Ca(NO3)2 suppressed disease more than (NH4)2SO4, but adding NaCl to Ca(NO3)2 did not increase yield more than Ca(NO3)2 alone. The Cl salts KCl, CaCl2, and MgCl2did not significantly differ from NaCl in their ability to increase the dry weight of beets grownin infested soils. Leaf and root analyses revealed that (NH4)2SO4 applications increased N, P, S, and Mn in tissue more than Ca(NO3)2 applications. Applying NaCl increased tissue levels of Na, Cl, and Mn more than in plants that were not fed NaCl. All of the Cl salts had the effect of increasing concentrations of Cl and Mn in the plant. There was no evidence that the Na ion was disease suppressive. Chloride, however, may be of use in disease management of Rhizoctonia root and crown rot of table beets.

Target molecular size suggesting a dimeric structure for the red beet plasma membrane Ca 2+-ATPase

The target molecular size of the red beet ( Beta vulgaris L. var. Detroit Dark Red) plasma membrane Ca 2+-ATPase was determined by radiation inactivation analysis involving γ-rays from a 60Co source. The Ca 2+ transport activity associated with the Ca 2+-ATPase in native plasma membrane vesicles declined in an exponential manner with radiation dose and the target molecular size was estimated to be about 245 000 ± 5000. As the catalytic subunit (phosphorylated intermediate) of the red beet plasma membrane Ca 2+-ATPase has been shown to be about 100 000 to 120 000, these results suggest that the enzyme exists as a dimer in the native membrane.

Calcium Stimulation of Ammonium Absorption and Growth by Beet

AbstractInefficiency in N use by plants contributes to environmental degradation. We examined the use of Ca2+ as a means of increasing NH+4 absorption in beet (Beta vulgaris cv. Detroit dark red). Ammonium absorption was measured in greenhouse and field studies. In the greenhouse, beet plants received full‐strength nutrient solutions with Ca2+: NH+4 molar ratios (MR) of 0, 0.25, 0.5 and 1.0 (Ca2+:NH+4) and a NO‐3 check. Absorption of 15NH+4 was monitored over a 30‐h period. The field production trials occurred over 3 yr on a calcareous Saneli silty clay loam [clayey over sandy or sandy‐skeletal, montmorillonitic (calcareous), thermic Vertic Torrifluvent]. The 15NH+4 absorption study showed the greatest plant weight at the molar ratio (MR) of 1.0 in tops (except in seedlings) and at 0.5 in bulbs. In seedlings, a biomass reallocation occurred in the root‐bulbs from the tops. In both the intermediate and mature growth stages the weight of roots, tops and bulbs greatly increased. In the 15NH+4 absorption studies N concentrations were unchanged or decreased as the Ca2+ concentrations increased, but total N increased. Seedling bulb‐root weight increases were apparenlly metabolite transfer from tops. The intermediate and mature beet plants showed increases in total N. In the greenhouse growth test, vegetative matter increased in excess of 300% at the MR of 0.5 over the check (MR:0). Growth of beet in the 0.5 MR treatment exceeded that on the NO‐3 comparison by 14%. In field testing at a MR of 0.25 (CaCl2:urea), yields increases averaged 26% over 3 yr when compared with urea alone.

Non-lethal secondary product release from transformed root cultures of Beta vulgaris

Transformed root tissue of Beta vulgaris (Detroit Dark Red) was permeabilized to stimulate the release of intracellularly stored betanin without adverse affects on tissue viability as measured by biomass accumulation. Product release of up to 15% (w/w) was achieved by heat treatment at 42°C for 45 min with minimal effect on viability. Higher levels of product release were obtained with increasing temperature and exposure, but at the expense of viability. Viability was measured by comparing dry weight increases of permeabilized tissue 3 days after treatment vs non-permeabilized tissue over the same time interval. Recovery of heat-treated tissue was improved by addition of CaCl2 (20 mm for 10 min) post-heat treatment. Betanin release up to 15% was also obtained at ambient temperature (25°C) by addition of up to 20 mm (NH4)2SO4 in the presence of 1 mm ethylenediaminetetraacetic acid (EDTA).

Production and release of pigments by culture of transformed hairy root of red beet

Adventitious roots were induced from red beet ( Beta vulgaris L. cv. Detroit dark red) by infecting the plant with a soil bacterium, Agrobacterium rhizogenes . Based on analysis of opines which are uniquely produced in transformed hairy roots, the established clone was proved to be a transformed hairy root. In a shake culture of the beet hairy root clone with a liquid medium, it was found that significant amounts of pigments, mainly betanin and vulgaxanthin-I, were released into the medium by the cessation of culture shaking (temporary limitation of oxygen supply). The hairy root cells were capable of propagation even after the cells were subjected to shaking cessation. Repeated-batch culture of the beet hairy root was performed with the cell growth phases for 9 or 10 d and with pigment leakage phases during shaking cessation for 2 d, and more than 20% of the total intracellular pigments were recovered from the culture broth at a culture time of 35 d. The released pigments were confirmed to be substantially identical to those extracted from the hairy root and original plant cells of red beet.

Osmotic Adjustment and the Growth Response of Seven Vegetable Crops following Water-deficit Stress

Growth-chamber studies were conducted to examine the ability of seven vegetable crops-`Blue Lake' bean (Phaseolus vulgaris L.), `Detroit Dark Red' beet (Beta vulgaris L.), `Burgundy' okra (Abelmoschus esculentus (Moench), `Little Marvel' pea (Pisum sativum L.), `California Wonder' bell pepper (Capsicum annuum L.), `New Zealand' spinach (Spinacia oleracea L.), and `Beefsteak' tomato (Lycopersicon esculentum Mill.)–to adjust osmotically in response to water-deficit stress. Water stress was imposed by withholding water for 3 days, and the adjustment of leaf and root osmotic potentials upon relief of the stress and rehydration were monitored with thermocouple psychrometers. Despite similar reductions in leaf water potential and stomata1 conductance among the species studied, crop-specific differences were observed in leaf and root osmotic adjustment. Leaf osmotic adjustment was observed for bean, pepper, and tomato following water-deficit stress. Root osmotic adjustment was significant in bean, okra, pea, and tomato. Furthermore, differences in leaf and root osmotic adjustment were also observed among five tomato cultivars. Leaf osmotic adjustment was not associated with the maintenance of leaf growth following water-deficit stress, since leaf expansion of water-stressed bean and pepper, two species capable of osmotic adjustment, was similar to that of spinach, which exhibited no leaf osmotic adjustment.

Determination of H+/ATP Stoichiometry for the Plasma Membrane H+-ATPase from Red Beet (Beta vulgaris L.) Storage Tissue

The H(+)/ATP stoichiometry was determined for the plasma membrane H(+)-ATPase from red beet (Beta vulgaris L., var Detroit Dark Red) storage tissue associated with native vesicles. The determination of H(+)/ATP stoichiometry utilized a kinetic approach where rates of H(+) influx, estimated by three different methods, were compared to rates of ATP hydrolysis measured by the coupled enzyme assay under identical conditions. These methods for estimating H(+) influx were based upon either determining the initial rate of alkalinization of the external medium from pH 6.13, measuring the rate of vesicle H(+) leakage from a steadystate pH gradient after stopping the H(+)-ATPase or utilizing a mathematical model which describes the net transport of H(+) at any given point in time. When the rate of H(+) influx estimated by each of these methods was compared to the rate of ATP hydrolysis, a H(+)/ATP stoichiometry of about 1 was observed. In consideration of the maximum free energy available from ATP hydrolysis (DeltaG(atp)), this value for H(+)/ATP stoichiometry is sufficient to account for the magnitude of the proton electrochemical gradient observed across the plasma membrane in vivo.

Chlorate transport in isolated tonoplast vesicles from red beet ( Beta vulgaris L.) storage tissue

There is strong evidence that 36ClO 3 − can serve as a suitable radiotracer for nitrate in transport experiments with plant tissue. In this study, 36ClO 3 − was used to investigate the mechanism of nitrate influx and efflux in sealed tonoplast membrane vesicles isolated from red beet ( Beta vulgaris L. cv. Detroit Dark Red) storage tissue. Uptake of 36ClO 3 − into red beet tonoplast vesicles was ATP-dependent, inhibited by carbonylcyanide m-chlorophenylhydrazone and demonstrated saturation kinetics with a K m of about 5 mM. While ATP-driven 36ClO 3 − uptake was inhibited by the collapse of the membrane electrical potential (ΔΨ) and an artificially imposed pH gradient could not drive radiolabel uptake, radiolabel uptake could be driven by an artificially imposed, positive-interior ΔΨ. These results suggest that ATP-driven 36ClO 3 − influx at the tonoplast may be mediated by a uniport system which responds to the positive interior membrane potential. When 36ClO 3 − was pre-loaded into the vesicles and radiolabel efflux was examined, no evidence could be found for the existence of an ATP-driven H +/ 36ClO 3 − symport for efflux. Overall, this study demonstrates the feasibility of using 36ClO 3 − as a radiotracer with isolated membrane vesicles and sets the stage for further research on the mechanism of NO 3 − transport systems.