Some physiological abnormalities induced by aflatoxin B1 in mung seeds (Vigna radiata variety Pusa Baishakhi)

Physiological processes of mung seeds (Vigna radiata variety Pusa Baishakhi) and their germination were found to be affected by different concentrations of aflatoxin B₁. Inhibition in seed germination, seedling growth, chlorophyll, protein and nucleic acid syntheses was found to be due to aflatoxin B₁. The range of inhibition varied with the concentration of the toxin added.     

Mechanism of action of aflatoxin B1

The inhibitory effects of aflatoxin B₁ were found to be related to the gram character in procaryotes, used in this study. Ethylene diamine tetra chloroacetic acid (0.05% w/v) or Tween-80 (0.05 % v/v) addition accentuated the aflatoxin B₁ growth inhibition inSalmonella typhi andEscherichia coli at different pH values. The inhibition of lipase production was only 5–20 % inPseudomonas fluorescence ca. 25–48% inStaphylococcus aureus andBacillus cereus at different aflatoxin B₁ concentrations (4–16μg/ml).However, inhibition of α-amylase induction was complete in1Bacillus megaterium whereas the inhibition was partial inPseudomonas fluorescence (27–40%) at 32μg aflatoxin B₁ concentration. An increase in leakage of cell contents and decreased inulin uptake were observed in toxin incubated sheep red blood cell suspension (1 %) with increased aflatoxin B₁ concentration     

Influence of aflatoxin B1 on seed germination, seedling growth, chlorophyll and carotenoid contents of mustard (brassica juncea L. var. pusa bold) seeds

Five different concentrations (100, 250, 500, 1000 and 2000 μg/L of aflatoxin B₁ were found to be inhibitory to seed germination and seedling growth (root and shoot lengths) of mustard seeds (variety Pusa bold). These also lowered the levels of chlorophyll and carotenoids in the emerging leaves during seedling growth. The inhibitory effect was correlated with the concentration of applied toxin.     

Effect of aflatoxin B1 on germination index and seedling growth in wheat varieties

The effect of different concentrations of aflatoxin B₁ (100, 250, 500, 1000, 2000 µg/l) was studied on germination index and seedling growth in three varieties of wheat seeds. Inhibition in the above process was directly influenced by the concentration of toxin. Concentration of toxin had highly significant effect (p<0.001) for seed germination rate and radicle and plumule development. Inhibition dose for 50% reduction in germination rate (ID₅₀) determined by probit analysis was maximum for the variety HP-129 (895 µg/l).     

Metabolism of aflatoxin B1 by Petroselinum crispum (parsley)

On administration of aflatoxin B₁ to whole parsley (Petroselinum crispum) plants, a derivative was formed, which was shown to be aflatoxicol by its chromatographic properties and mass spectrometry. Optimum conditions for the production of the derivative was on the second day after administration of the toxin to the plants, which were 90 days old after germination. Cell-free preparations of parsley were found not to produce aflatoxicol A from added aflatoxin B₁; instead they formed two new derivatives, which from chromatographic properties, were shown to be more polar than either aflatoxin B₁ or aflatoxicol A.     

Effects of Aflatoxin on Seeding Growth and Ultrastructure in Plants

Nineteen plants belonging to 11 species of the cruciferae were studied to determine the effects of aflatoxin B₁ on seed germination and seedling development. Germination was not inhibited in any test organism at a concentration of 100 μg of aflatoxin per ml of agar substrate. Inhibition of elongation of the hypocotyls and roots in the species studied varied from 29 to 93% and from 22 to 91% in the respective tissues. Lepidium sativum was the most susceptible plant studied and exhibited the maximal inhibitory response noted above at concentrations of 8 μg of aflatoxin per ml. The ultrastructure of Lepidium root cells treated with crystalline aflatoxin B₁ exhibited morphological changes characteristic of those found in aflatoxin-treated animal cells. In addition to changes in the cytoplasmic organelles, numerous ring-shaped nucleoli with prominent nucleolar caps were produced. The effect of aflatoxin on plant cells is compared with similar effects induced by actinomycin D. Seed germination and seedling development is discussed in relation to the effects of both compounds on deoxyribonucleic acid-dependent ribonucleic acid biosynthesis.     

X-ray irradiation of excised embryos of mesta (Hibiscus cannabinus L. and H. sabdariffa L.)

Summary Excised embryos of Hibiscus spp. were treated with 1 kR to 6 kR of X-ray. Results indicate that germination was unaffected at this level of employed doses in both species, which in turn implies that the factors responsible for inhibition of germination are not present in the embryo. LD₅₀ values differed between varieties and species. Early varieties of both species were more sensitive to radiation than late varieties. Strikingly similar effects were observed for the varieties with smaller embryos over those with larger ones. Allopolyploid H. sabdariffa (2n=72) was more susceptible than diploid H. cannabinus (2n=36).Differences in mutation frequency exist between species with different levels of ploidy and between varieties within the same species. Most of the HC mesta varieties yielded higher mutation frequencies than those of HS mesta. Optimal dose for triggering mutations in all varieties (except the chlorophyll mutation variety of HC mesta) of the two species lies within a narrow range of 1 kR to 2 kR. Cent per cent seedling abnormalities is concomitant to LD₅₀; nevertheless, optimum dose for mutation frequency is independent of LD₅₀. Hence, the response should be viewed in terms of respective genotype. The advantages of the embryo irradiation technique are mentioned.     

Functional changes in rat liver tRNA following aflatoxin B1 administration

Administration of aflatoxin B₁ (3 mg/kg body wt) to rats leads to strong inhibition of the acceptor activity of liver tRNA as measured by charging with [¹⁴C]-chorella protein hydrolysate. The maximum inhibition occurs 2 h after treatment. At increasing intervals after treatment, the inhibition appears to be gradually relieved, till control values are restored by 72 h. The charging experiment using several [¹⁴C]-amino acids separately shows pronounced inhibition of acceptor activity of all tRNA species, although the degree of inhibition varies with individual species. Preliminary results seem to rule out the possibility of hypermethylation of tRNA or damage to the CCA terminus as probable causes. The resultant functional changes may be attributed to a covalent interaction of aflatoxin B₁-metabolite with tRNA.     

The effect of <Emphasis Type="Italic">Baccharis glutinosa</Emphasis> extract on the growth of mycotoxigenic fungi and fumonisin B<Subscript>1</Subscript> and aflatoxin B<Subscript>1</Subscript> production

The aim of this study was to evaluate the effect of Baccharis glutinosa isolated extract on the growth of Aspergillus flavus and Aspergillus parasiticus, and their aflatoxin B₁ production; and growth of Fusarium verticillioides, and their fumonisin B₁ production. The three fungi were exposed to an antifungal fraction, designated as fraction F6-1, isolated from B. glutinosa by methanolic extraction followed by silica gel chromatography. The growth of the fungi was evaluated in kinetics of radial extension growth, kinetics of spores germination, length and diameter of hyphae, spores diameter, as well as in aflatoxin B₁ and fumonisin B₁ production. Fraction F6-1 caused radial growth inhibition of the three fungi mainly F. verticillioides. Spores germination of A. flavus and A. parasiticus was delayed in the early stage of the incubation time, although they completely germinated at 27 h. In contrast, spore germination of F. verticillioides was inhibited 87.7% up to 96 h. The lengths and diameters of hyphae, and spore diameters of the three fungi, were significantly smaller in comparison with those of the controls, and several morphological alterations were observed. Concerning aflatoxin B₁ and fumonisin B₁, fraction F6-1 did not show any inhibition effect at the concentration used. Fraction F6-1 was able to significantly inhibit the development of the three fungi, mainly F. verticillioides. The strong inhibitory effect of F6-1 on hyphae and spores suggests that it interacted with the fungi cell walls, which caused severe deformities. Nevertheless, this fraction was unable in inhibiting mycotoxin production from the three fungi at the concentration tested.     

Hoary cress (Cardaria draba (L.) Desv.) seed germination ecology,longevity and seedling emergence

The effects of gibberellic acid (GA₃), potassium nitrate (KNO₃), prechilling, temperature, salt stress and osmotic potential on seed germination and sowing depth on seedling emergence and burial depth on seed viability of hoary cress (Cardaria draba (L.) Desv.), were studied in a series of laboratory, glasshouse and outdoor experiments. The optimal temperature for hoary cress seed germination was 20°C, both in light/dark and darkness regimes. Seed germination of hoary cress at 400 ppm concentration of GA₃ in a light/dark regime was maximal. Potassium nitrate concentrations increased the percentage of germination in comparison with the control treatment. Increasing the duration of dry prechilling to 30 and 45 days promoted the seed germination of hoary cress. Germination of hoary cress markedly decreased as salt and drought stress increased. Seed germination of hoary cress occurred at a range of pH from 3 to 11. Seedling emergence significantly decreased as planting depth increased. Total seed viability decreased with increasing burial depth. The maximum increase in mortality occurred in seeds that were buried at 5‐cm depth.     

Use of propolis and ultragriseofulvin to inhibit aflatoxigenic fungi

Propolis ethanolic extract (PEE) at 3 and 4 g/L and ultragriseofulvin (UG) at 0.75 and 1 g/L reduced the percentage of conidia germination in twoAspergillus flavus isolates. PEE at 1–4 g/L decreased the mycelial dry mass ofA. flavus isolates by 11–80%, and aflatoxin B₁ production by 34–100%. UG concentrations of 0.25–1 g/L reduced the growth and aflatoxin B₁ production of the isolates by 16–88 and 48–98%, respectively. Any increase in PEE and UG concentration was accompanied by a clear decrease in the per cent conidia germination, growth and aflatoxin B₁ production. At equal concentration, UG was about 4-times more effective than PEE.     

The action of penicillin in mungbean (Phaseolus aureus L.) seedlings and wheat (Triticum vulgare L.) coleoptile sections

Penicillin caused elongation inhibition of mungbean (Phaseolus aureus L.) seedlings at concentrations above 100 mgl^-1. Inhibition of hypocotyl could be reduced to different degrees by manganese, pyruvate, succinate, fumarate, malate, GA₃, purines, pyrimidines and nucleosides, whereas the amino acids except cysteine were not effective. Penicillin inhibited neither elongation of wheat coleoptile sections nor the cell enlargement induced by IAA in this tissue. Thus penioillin inhibits intact seedling elongation probably through an Effect on cell division apparently without inhibiting cell enlargement.     

The effects of aflatoxin B1 and palmotoxins B0 and G0 on the germination and leaf colour of the cowpea (vigna sinensis)

Aflatoxin B₁, crude aflatoxins and palmotoxins B₀ and G₀ were tested for seed germination and chlorophyll formation using the cowpea. It was found that aflatoxin B and crude aflatoxins inhibited both chlorophyll formation and seed germination and palmotoxins inhibited these processes to a lesser extent. 3 — Indolylacetic acid reduced the inhibitory effects of the aflatoxins in seed germination and chlorophyll formation in the cowpea.     

Effect of Vanadium on Testa,Seed Germination,and Subsequent Seedling Growth of Alfalfa (Medicago sativa L.)

Seed germination is the critical initial phase in the life cycle of plant and it is affected by various exogenous factors, including heavy metals. Seed germination and subsequent seedling growth of alfalfa (Medicago sativa L.) incubated in glass Petri dish in presence of elevated concentrations of pentavalent vanadium V(V) solution (0, 0.1, 0.5, 2, 4, 10, 50 mg L⁻¹ V, supplied as NaVO₃·2H₂O) were evaluated. Results showed that vanadium did not (P > 0.05) affect seed germination, final survival rate, and seedling height of alfalfa when exogenously treated dosages were ≤ 10 mg L⁻¹ V, whereas the root vitality and root elongation were distinctly inhibited at ≥ 0.5 mg L⁻¹ V treatments. A progressively deepened testa color at increasing vanadium concentrations during germination and an apparent modified structure of the seed coat at 50 mg L⁻¹ V compared to control in alfalfa were noted. Alfalfa seeds showed rapid and almost synchronous radicle emergence, independently of the vanadium concentration in the medium. The accumulation of vanadium in testa is beneficial to alleviate its toxicity to the seed germination of alfalfa. Leaf proline content was dramatically increased at ≥ 0.5 mg L⁻¹ V treatments compared with the control. Emerged seedlings displayed enough vigor and health to potentially colonize in the vanadium-contained matrix. Thus, alfalfa represents a good candidate for phytoremediation approach aimed at decontaminating environments when vanadium concentrations are within the determined thresholds.

     

The potential value of silage in detoxifying aflatoxin B1

Serial concentrations of aflatoxin B₁ ranging from 200 to 1500 p.p.b. in 2% lactic acid solution (which is the aimed concentration of lactic acid in fresh silage) were assayed for detoxification. Thin-layer chromatography analysis, revealed a complete transformation of 1 000 p.p.b. of aflatoxin B₁ to a new fluorescing compount corresponding to aflatoxin B_2a which is referred to as hydroxydihydro-aflatoxin B₁ toxicity test on chickens confirmed Ciegler's findings (4). The results confirm that the chemical changes taken place in the silo can detoxify aflatoxin B₁ to aflatoxin B_2a.     

The action of 1-alkyl-1-nitrosoureas and 1-alkyl-3-nitro-1-nitrosoguanidines on the M1 generation of barley andArabidopsis thaliana (L.) heynh.

The activity of 1-methyl-1-nitrosourea (MNH), 1-ethyl-1-nitrosourea (ENH), 1-methyl-3-nitro-1-nitrosoguanidine (MNG) and 1-ethyl-3-nitro-1-nitrosoguanidine (ENG) was tested on seeds of barley andArabidopsis. The activity of nitrosoamides tested was expressed by the germination and M₁ seedling height reduction of barley and M₁ root length reduction ofArabidopsis.

1. 1)
   After the action of both nitrosoureas (MNH and ENH) the germination of barley is at the same level as that of controls, even at concentrations, leading to a maximal reduction in the height of seedlings. After the action of both nitrosoguanidines (MNG and ENG) germination decreases in parallel with the decreasing seedling height. InArabidopsis no such differences in the relation germination to root length reduction were observed after nitrosoureas and nitrosoguanidines treatment. The differences in the M₁ generation of barley andArabidopsis after nitrosoguanidines treatment may be the reason for the non-mutagenic action of MNG and ENG in barley.     
   
   

Gamma rays induced genetic variability in tomato (Solanum lycopersicum L.) germplasm

The present study assessed the effectiveness of gamma radiation in inducing favorable genetic variability in tomato (Solanum lycopersicum L.). An experiment was conducted in a randomized complete block design to produce M₁ generation. Significant differences were observed among the genotypes as well as between the treatments at individual plant level based on observed traits (seed germination percentage, seedling survival, plant height, number of flower clusters plant^?1, number of flowers and fruits plant^?1). All observed characters in the mutagenized population were adversely affected with increasing radiation dose. Results identified 450 Gy as the most damaging radiation dose followed by 300 Gy and 150 Gy. Moreover, 300 Gy treatment was identified as lethal dose (LD₅₀) as it caused a 50% germination inhibition in almost all the evaluated genotypes. The 150 Gy treatment showed the least damaging impact and induced maximum genetic variability in almost all the genotypes under study. Character association studies were also conducted which could be utilized in the selection of desirable mutants. Correlation studies revealed an altered association among the observed parameters from positive to negative direction in 300 Gy and 450 Gy treatments as compared to control. These deviations in correlation coefficients proved that mutagenesis can break the linkage among specific loci. Furthermore, path coefficient analysis identified the growth attributes with an effective direct and indirect contribution in yield.     

Germination stimulation in wild oats (Avena fatua L.) by synthetic strigol analogs and gibberellic acid

At concentrations of 0.01–1 mM, five synthetic multiring analogs of strigol were effective germination stimulants of intact and dehulled wild oat (Avena fatua L.) seeds. The effect was concentration-dependent and equaled or exceeded that produced by equimolar gibberellic acid (GA₃). The most effective strigol analog treatments induced 55–80% germination within 7 days in intact wild oat seeds and resulted in 63–86% germination and normal seedling growth over 14 days. Intact wild oat controls germinated 14% after 14 days. The stimulation of wild oat germination by these synthetic strigol analogs demonstrates that these compounds, initially developed as germination stimulants for the seeds of the parasitic weed, witchweed (Striga asiatica L. Kuntz.), have bioregulatory activity in dormant seeds of monocots, as well as dicots. None of the compounds tested significantly affected the germination of nondormant cultivated oat seeds (Avena sativa L.). The commonly used dispersal agent, Tween 20 (0.1%), was found to inhibit germination of cultivated oats, alone and in the presence of 2% acetone.     

Development of Aspergillus parasiticus and formation of aflatoxin B1 under the influence of conidiogenesis affecting compounds

The influence of various inhibitors of hyphal growth, sporulation and biosynthesis of aflatoxin B₁ in Aspergillus parasiticus NRRL 2999 was studied. 6-Thioguanine, dl-ethionine, fluoroacetic acid and phenylboric acid, inhibitors of maturation of fungal conidiophores and of conidiogenesis, were added at various concentrations to malt extract agar. Lower concentrations of 6-thioguanine and dl-ethionine did not inhibit the growth of hyphae and the sporulation. Phenylboric acid reduced conidiogenesis more than hyphal growth. The yields of aflatoxin B₁ were significantly reduced. Additions of fluoroacetic acid did not greatly affect the growth of hyphae but totally inhibited the production of conidia and concurrently significantly reduced the formation of aflatoxin B₁. An interrelation between conidiogenesis and onset of secondary metabolism in A. parasiticus is evident.     

The effects of methyl jasmonate on sunflower (Helianthus annuus L.) seed germination and seedling development

Some effects of methyl jasmonate (Me-Ja) on sunflower (Helianthus annuus L.) seed germination and seedling development are described and compared with those of ABA. Both growth regulators have very similar action. They inhibit germination, but high concentrations of O₂ in the atmosphere suppress this inhibitory action. Depending on the concentration, Me-Ja inhibits root and hypcotyl growth, however the root is more sensitive to Me-Ja than to ABA. Me-Ja also strongly reduces oxygen uptake during germination and inhibits chlorophyll biosynthesis in isolated cotyledons.