Onion roots

Green vegetables, cabbage, onions Root vegetables... 

Pentachlorothiophenol was formed Iji vitro from S-(PCP)Cys by a C-S lyase enzyme from onion root. This enzyme was active with S-(PCP)Cys, S-(2,M-dinitrophenyl)cysteine, and the cysteine conjugate of propachlor. A C-S lyase from Alblzzla lophanta was previously shown to utilize a broad range of cysteine derivatives (2U). 

Table I. ACTIVITY OF VARIOUS SUBSTRATES FOR THE METHYL TRANSFERASE SYSTEM FROM ONION ROOT /...

APase in onion roots. Enzyme activity was mainly extracellular with the heaviest concentration in corner spaces between the epidermal and hypo-dermal layers. He suggested the possibility of a subcutaneous pore through which the enzyme could be released to the root surface. Bieleski and co-workers (Reid Bieleski, 1970 Bieleski Johnson, 1972) studied the psi induction and location of APase in duckweed (Spirodela oligorrhiza). APase in control plants was located primarily in and around the vascular strands. In P-deficient plants psi-APase activity was 10-20 times the control value. Enzyme activity was primarily located in the epidermis of the root and undersurface of the frond, the tissue locations most likely to provide access to phosphate esters in the medium. These workers further demonstrated that hydrolysis of organic phosphates occurred in the external medium and/or the apoplast followed by Pi uptake into the cell. 

De Jong, D.W. (1965). Histochemical demonstration of extracellular distribution of acid phosphatase in onion roots. Phyton 22, 141-6. 

Micrographs of (A) control, (B) 1,4-cineole-, and (C) 1,8-cineole-treated onion root tip cells, p = prophase, m = metaphase, a = anaphase, and t = telophase. Asterisk indicates formation of a cell plate. (From Romagni, J. G. et al. 2000, J. Chem. Ecol. 23, 303-313. With permission). 

Stiles et al.43 found artemisinin to inhibit respiration in Lemna minor, but the compound strongly stimulates oxygen uptake by lettuce root tips.6 All mitotic phases of onion root tips are inhibited by the compound, and it induces a low level of abnormal mitotic figures.6 Dayan et al.6 conducted a battery of simple physiological tests with several artemisinin analogues. All phytotoxic compounds had similar effects, indicating a common mode of action. In summary, the mode of action results with artemisinin as a phytotoxin are not definitive. 

Owusu-Bennoah, E. Wild, A. (1979). Autoradiography of the depletion zone of phosphate around onion roots in the presence of vesicular arbuscular mycorrhiza. New Phytologist, 82, 133-40. 

Colchicine-like mitosis in onion root tip Narcosis of barnacle larvae Narcosis of 2.5-day tadpoles Narcosis of 12-day tadpoles I5o guinea pig ileum 100% inhibition tadpole movement Narcosis of 83-day tadpoles... 

Holotoxin Ai inhibits the RNA biosynthesis in Candida albicans and Saccharomyces carlsbergensis, as indicated by the decrease in incorporation of C-uridine to the acid-insoluble fraction of the cells. Similar results were obtained for glycoside fractions of 14 species of Pacific sea cucumbers [132]. Apparently the inhibition of RNA biosynthesis in Saccharomyces carlsbergensis is related to nucleotide loss from yeast cells after treatment with glycosides. Holotoxin Ai also inhibits biosyntheses of squalene, lanosterol and ergosterol in S. carlsbergensis [133]. Mitosis is arrested and DNA synthesis inhibited in onion root bulbs by crude holothurin [134]. 

The deamination of xenobiotic cysteine conjugates can lead to thlo-acetlc acid conjugates, as observed with PCNB In peanut (100). or thlo-lactlc acid conjugates, as observed with EPTC In corn and cotton (106) or PCNB In peanut (WO). Cysteine conjugates can also undergo 8-lyase cleavage to thioalcohols, as observed with PCNB In peanut (WO). The thioalcohols can be methylated by an S-adenosyl-methlonlne methyltransferase system, as demonstrated with an In vitro enzyme system derived from onion root (J01 ). Pentachloro-... 

The action of these active substances on plant cells has been studied by Richmond and Phillips (1975) using onion (Allium cepa) as test object. Benomyl and carbendazim induce identical aberrations in the cells of onion root. Benomyl acts considerably more rapidly than carbendazim. However, the proportion of abnormal mitosis caused by them is presumably insufficient to cause irregular plant growth. On the other hand, a property of benomyl and MBC similar to that of cytoquinine has been noted (Skene, 1972 Thomas, 1973 and 1974). 

On the other hand, protected edible parts of plants like seeds, tubers (potatoes), bulbs (onions), roots (radish and carrots) show hardly any increase in lead. It s an evidence that lead salts are immobile in the soil and largely unavailable to plant s roots. 

Synchronized cultures of Chlorella ellipsoidea were used as a model system to identify biochemical modes of action of two herbicides/ butamiphos (0-ethyl--0-(3-methyl-6-nitropheny1)-N-sec-buty1-phosphorothioamidate, formerly coded S-2846), and chlorpropham (isopropyl inch lorocarban il ate). Cell cycle studies showed that butamiphos inhibited cell division, whereas its effects on respiration and general biosynthesis were slight. Confirmatory experiments with onion root apices showed that mitosis was blocked at the metaphase and that the spindle apparatus was disrupted. 

Onion root tip tissue was selected for this purpose,... 

Chlorpropham is isopropyl jm-chlorocarbanilate as shown in Figure 4, A number of reports have appeared concerning biochemical responses of higher plants to chlorpropham, Chlorpropham was reported to inhibit mitosis in onion root ( ), Mann e t al. reported that chlorpropham inhibited protein synthesis in barley coleoptiles and sesbania hypocotyls (9 ), Moreland e t observed that chlorpropham inhibited the biosynthesis of RNA and protein in soybean hypocotyls and RNA synthesis by corn mesocotyls (10),... 

Mountain ash berries parasorbic acid onion, roots ... 

TABLE 6, Types and Frequencies of Chromosomal Aberrations Produced by 2-hr Treatments with Caffeine in Onion Root Tips and in Cell Cultures of the Chinese Hamster ... 

FIGURE 7. Percentages of labeled(L) and unlabeled(U) metaphases with aberrations obtained in onion root tips and in cell cultures of the Chinese hamster various times after 2-hr treatments with 2 X 10 M caffeine and tritiated thymidine. 

Thus, our experiments have shown that the stages sensitive to caffeine are prophase and Gg in onion root tips, and S (and possibly G ) in cell cultures of the Chinese hamster. The aberrations produced are of the... 

Although the types of effects produced by caffeine in hamster cells and in onion root tips are very different, the concentrations needed to produce these effects are about the same in both materials i.e., onion root tips and hamster cells appear to be about equally sensitive to caffeine. On the other hand, we have found that 8-ethoxycaffeine, which is much more active than caffeine in plant roots (e.g., Kihlman, 1952), has about the same activity as caffeine in hamster cells. 

In repeated studies in vitro, cycasin was nonmutagenic. In addition to being carcinogenic, methylazoxymethanol, the metabolite of cycasin, was found to be mutagenic for S, typhimurium (Smith, 1966), to cause chromosome aberrations in onion root tip cells, and to increase sex-linked recessive lethal mutations in Drosophila (Smith, 1966 Teas and Sax, 1966). In studies with G-46, cycasin was not active in vitro, while the metabolite MAM was mutagenic (Gabridge et aL, 19696). 

In Europe tests with rotifers, cysts from aquatic invertebrates (Calleja et al., 1994), development of onion roots have been tried but none have been accepted (Persoone et al., 1994 Snell and Persoone, 1989 Fresjog, 1985 Gaggi et al. 1995). Jaffe (1995) has proposed a method using the survival of a protozoan. Toxic chemicals kill the protozoa. The test requires a Coulter particle counter to determine the numbers of viable protozoa. 

It is this latter hypothesis as to the biological function of M-rays that has remained controversial to the present day. Gurwitsch used onion root tips and later yeast cells and measured an increase in mitotic figures in the former and an increased rate of growth in the latter (Gurvitsch, 1932 ... 

Chromosome aberrations CHO cells Onion root tips Simple phenols phenolic acids cinnamic acids Chlorogenic acid Several phenolics Stich et al. (1981a) Stich et al. (1981b) Levan and Tjio (1948)... 

Gianinazzi-Pearson V, Gianinazzi S (1978) Enzymatic studies on the metabolism of vesicular arbuscular mycorrhiza n. Soluble alkaline phosphatase specific to mycorrhizal infection in onion roots. Physiol Plant Pathol 12 45-53... 

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