Effects of low concentrations of vapour of the phenoxyalkanoic herbicide 2,4-D-butyl on growth of tomato plants

Tomato plants (5–7 weeks old)were exposed to a range of concentrations of vapour of 2,4-D-butyl (0.12–2.4 ng litre^?;1), for periods of 6 or 24 h, using an air-flow system. Net carbon dioxide exchange of the whole plant was measured for up to 2 days after exposure and was found to decrease in treated plants approximately in proportion to vapour concentration. Six weeks after exposure, shoot dry-weights of plants exposed to herbicide vapour were less than control plants in all cases, by about 20 % or more. All characteristics measured were affected more by a 24-h exposure period than 6 h, at the same vapour concentration. The amount of herbicide vapour, expressed as the product of exposure period and vapour concentration, gave a similar effect at a low range of vapour concentrations (≤1.0 ng litre^?;1)and air-flow rates of about 200 litre min^?;1, but not at higher concentrations at a flow rate of about 120 litre min ^?;1. Better agreement between the experiments carried out at the two concentration ranges was obtained by expressing the herbicide vapour as the total amount to which the plants were exposed (i.e. the product of air-flow rate, vapour concentration and duration of exposure)instead of concentration alone.     

Uptake by tomato plants of the herbicide [14C] 2,4-D-butyl in the vapour phase

Uptake of [¹⁴C-phenyl]2,4-D-butyl by 4- to 6-week-old tomato plants was measured for vapour concentrations in the range 0.3–19 ng litre^?1, for an exposure period of 4 h. Calculation of boundary layer thicknesses at the surface of the leaves, and depletion of the vapour concentration due to uptake by the plants, suggested that the plants experienced concentrations very close to the nominal values. Relationships between external vapour concentration and plant uptake, expressed in terms of fresh weight, leaf area, or on a whole plant basis, were linear in all cases. Twenty-four hours after the commencement of exposure, leaves contained 63–93% of the total herbicide in the plant; the proportion retained by the leaves was greater at low vapour concentrations. The largest amount of herbicide was present in leaves from the mid-position on the stem, but in terms of leaf area, the amount was greatest in leaves at the apex and decreased basipetally. It is not known whether this was due to a greater uptake rate per leaf area at the apex, or to translocation. As visible symptoms of phytotoxicity usually develop at the apex, both of these processes, together with the preferential retention of herbicide in leaves at low vapour concentrations, may all contribute to the development of vapour damage.     

Long- and short-term effects of vapour of the herbicide 2,4-D butyl on the growth of tomato plants

An airflow system has been used to expose tomato plants to a range of concentrations of vapour of the herbicide 2,4-D butyl, from 5 to 50 ng l^?1. Experiments carried out at an air temperature of 20°C indicate that only short periods (less than 2.5 h) are required to produce symptoms of phytotoxicity at concentrations less than 5 ng l^?1, or approximately 2.5% of the saturated vapour pressure of the herbicide. A 5-h period of exposure to approximately 5 ng l^?1 reduced the dry weight and dry matter content of the tomato plants after 7 weeks by 18% and 9%, respectively, compared with the control. Phytotoxicity symptoms were shown by the plants in proportion to the vapour concentration during the period of exposure to herbicide. Rates of photosynthesis of treated plants had begun to decline within an hour of the commencement of exposure, slightly after leaf movement was first observed.     

Fate of fluroxypyr in soil

Batch adsorption K_oc values of fluroxypyr-methylheptyl ester (20000 1kg^?1) and fluroxypyr (74 1kg^?1) indicate increased mobility after hydrolysis of the ester to fluroxypyr. After 1 to 2 weeks incubation time in four soils, desorption K_oc values of fluroxypyr were 100-200 1kg^?1 but increased to 400-700 1kg^?1 after 8 weeks. The increase in desorption K_oc was related to incubation time and not to concentration, and it was interpreted as an entrapment of the fluroxypyr within the soil organic matter. Similar increases in desorption K_oc with incubation time were noticed for pyridinol and methoxypyridine metabolites of fluroxypyr. K_oc values also increased along the metabolic sequence fluroxypyr/pyridinol/methoxypyridine, with maximum K_oc values of 3000-4000 1 kg^?1 for the methoxypyridine metabolite. Hence mobility of the fluroxypyr aromatic ring strongly decreases with increased residence time in the soil.     

Fate of fluroxypyr in soil

Fluroxypyr-MHE (methylheptyl ester) was added to four soils and incubated at 26 ± 1°C and approximately 0.1 MPa moisture. After initial rapid hydrolysis of the ester to fluroxypyr, fluroxypyr degraded with half-lives of 12, 12, 23, and 7 days in Barnes loam, Catlin silt loam, Hanford sandy loam, and Mhoon clay soils, respectively. Two metabolites (4-amino-3,5-dichloro-6-fluoro-pyridin-2-ol and 4-amino-3, 5-dichloro - 6 - fluoro - 2 -methoxypyridine) were identified, with the pyridinol at its maximum concentration after 2 to 4 weeks of incubation, and the methoxypyridine after 8 weeks. Degradation rates of fluroxypyr and its pyridinol were not significantly altered by diurnally varying soil temperature (21°C to 32°C) or moisture, nor by the presence of growing grass. Methoxypyridine dissipation was more rapid under greenhouse conditions, suggesting that laboratory studies underestimated the dissipation rate of this metabolite.     

Fate of fluroxypyr in water

Dissipation of fluroxypyr in North Dakota lake waters was examined in three laboratory studies: photolysis, aerobic metabolism, and anaerobic metabolism. Photolysis was negligible in sterilized water, with and without natural photosensitizers. In 1:10 sediment:water systems, 50% disappearance times of 0.5–2 weeks were observed in the metabolism studies (25°C). Major metabolites (>10%) included the dichloropyridinol and 3-chloropyridinol derivatives, while the 5-chloropyridinol derivative appeared (<7%) in anaerobic systems. The pyridinols disappeared readily in aerobic but more slowly in anaerobic systems. In typical pond and lake waters, fluroxypyr and pyridinols are expected to disappear by the end of the growing season. Devenir de fluroxypyr dans l'eau La dissipation du fluroxypyr dans les eaux de lac dans le Dakota Nord a étéétudiée dans 3 études de laboratoires: photolyse, métabolisme aérobique et métabolisme anaérobique. La photolyse était négligeable dans I'eau stérilisée, avec et sans photosensibilisants naturels. Dans des systémes sédiments/eau de 1/10 des temps de disparition 50% de 0-5-2 semaines ont été observées dans les études de meéabolisme (25°C). Les principaux metabolites (>10%) comprenaient les dérivés dichloropyridinol et 3-chloropyridinol, tandis que le dérivé 5-chloro-pyridinol apparaissait (<7%) dans les systemés anaérobiques. Les pyridinols disparaissent rapidement en aérobie mais lentement dans les systémes anaerobiques. Dans les eaux typiques de mares et d'étangs, le fluroxypyr et les pyridinols sont supposés avoir disparu à la fin de la saison de croissance. Verhalten von Fluroxypyr in Wasser Der Verlust an Rückständen von Fluroxypyr im Wasser aus Seen in North Dakota wurde hinsichtlich der Photolyse sowie des aeroben und anaeroben Metabolismus untersucht. Die Photolyse war in sterilisiertem Wasser mit und ohne natürlichen Photosensitizern vernachlässigbar. Bei den Metabolismusuntersuchungen bei 25°C in l:10-Sediment:Wasser-Systemen lagen die Zeiten für 50%igen Verlust bei 0,5.2 Wochen. Zu den Hauptmetaboliten (>10%) zählten Dichlorpyridinol und 3-Chlor-pyridinol-Derivate, während 5-Chlorpyridinol-Derivate in anaeroben Systemen unter 7% blieben. Die Pyridinole verschwanden rasch in aeroben, aber viel langsamer in anaerobischen Systemen. In solchen Gewässern werden Fluroxypyr und Pyridinole erwartungsgemäß zum Ende einer Vegetationsperiode verschwunden sein.     

Fate of fluroxypyr in soil

Fluroxypyr-MHE (methylheptyl ester) was applied to small field plots containing Londo sandy loam soil. After 30 days, fluroxypyr had degraded to about 60% of the initial concentration, but was still the main component, while after 120 and 366 days the methoxypyridine metabolite was the main component in the soil. At 30, 120, and 366 days, lettuce, turnips, green beans, soybeans, and wheat were planted and grown with no observed injury. Residues of ¹⁴C in the edible crop fractions were indistinguishable from ¹⁴C in control plants exposed to ¹⁴CO₂, while residues in plant greens and chaff were low (0.1–0.2 mg kg^?1), with little evidence of fluroxypyr and no evidence of metabolite uptake. These results indicate that the methoxypyridine metabolite, if present in the soil, does not harm and is not taken up into the plants.     

Zinc phosphate protects tomato plants against Pseudomonas syringae pv. tomato

Journal of Plant Diseases and Protection - The purpose of this study was to determine whether zinc phosphate treatments of tomato plants (Solanum lycopersicum L.) can attenuate bacterial speck...     

Lack of synergistic effects in tomato plants co-infected with tomato severe rugose virus and tomato chlorosis virus

The begomovirus Tomato severe rugose virus (ToSRV) and the crinivirus Tomato chlorosis virus (ToCV), in single and co-infections, are very common in tomato crops in Brazil. Both viruses are transmitted by the whitefly Bemisia tabaciMEAM1 (biotype B). The objective of this study was to analyse the interaction between ToSRV and ToCV in tomato plants of cultivars Santa Clara and Kada. Plants at 15, 30 and 45 days after emergence were inoculated with 30 viruliferous B. tabaci per plant. The following treatments were compared: plants inoculated with ToSRV, ToCV, ToSRV + ToCV, and healthy (control). The interaction between these viruses was analysed by measuring the virus titre by qPCR and the fresh and dry weights of the aerial parts of the tomato plants. Based on two independent assays, no significant effects for co-infection of ToSRV and ToCV on virus titres and plant development were observed compared to single infections. The dry weight of tomato plants of both cultivars infected with ToSRV, ToCV, or co-infected did not differ significantly. However, the dry weight of Santa Clara tomato plants infected with ToSRV, ToCV and ToSRV + ToCV showed mean reductions of 21.5%, 25.5% and 32%, respectively, compared to healthy plants, and mean reductions for Kada were 31.7%, 37.5% and 38%, respectively.     

Mobility of oxathiapiprolin in and between tomato plants

BACKGROUND

Oxathiapiprolin (OXPT; FRAC code 49) is a new piperidinyl-thiazole isooxazoline anti-oomycete fungicide that targets oxysterol-binding proteins. The fungicide is known to translocate acropetally from root to shoot to protect plants against fungal attack.

RESULTS

OXPT is ambimobile. It can also translocate basipetally from shoot to root. OXPT exhibits an unprecedented capacity for trans-plant protection. When two tomato plants are grown in one pot, and one is treated with OXPT (on the stem, leaves or apex), while the other plant and soil surface are adequately covered, both plants become protected against late blight caused by Phytophthora infestans.

CONCLUSION

Trans-plant systemic protection induced by OXPT involves translocation of the fungicide from the shoot of the treated plant to its root, exudation into the soil and uptake by the root of the neighboring untreated plant to protect it against the disease. Liquid chromatography–tandem mass spectrometry analyses confirmed the occurrence of OXPT in root exudates of OXPT-treated tomato plants in quantities sufficient to protect detached tomato leaves and intact plants against P. infestans. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Aspects of the selective phytotoxicity of methazole. II. Behaviour in plants following root exposure

The absorption, translocation and degradation of methazole were examined in onion, Stellaria media, Matricaria matricarioides and Veronica persica grown in culture solution. After a short period of initial rapid uptake, all four species absorbed herbicide and water in the same proportions. Translocation of herbicide to the shoots was directly proportional to transpiration, but the apparent solute concentration in the xylem was less than that in the external solution and varied between the species. A smaller percentage of the total absorbed herbicide was translocated to the shoot in V. persica, the most tolerant species. Methazole was relatively stable in M. matricariodes and was degraded slowly to 3-(3,4-dicnlorophenyl)-1-methylurea (DCPMU). It was degraded rapidly to DCPMU in the other three species and this accumulated in onion and S. media. In V. persica DCPMU was degraded further to 3-(3,4-dichlorophenyl) urea (DCPU). Methazole was not an active inhibitor of photosynthesis by isolated spinach chloroplasts. Both DCPMU and DCPU inhibited photosynthesis but DCPMU was 200-times more active than DCPU. Variations in the concentrations of DCPMU in the shoots of the different species largely accounted for the variations in their response to methazole applied pre-emergence.     

A transgenic RNAi approach for developing tomato plants immune to Pepino mosaic virus

RNA interference (RNAi) or gene silencing is a natural defence response of plants to invading viruses. Here, we applied this approach against pepino mosaic virus (PepMV) isolates in their natural host, tomato. PepMV isolates differ in their genetic sequences, the severity of the disease they induce, and their worldwide distribution. PepMV causes heavy crop losses, mainly due to impaired tomato fruit quality. Resistant varieties are not yet available, despite many years of resistance breeding efforts within the tomato seed industry. To generate broad resistance to PepMV strains, conserved sequences from three different strains of PepMV (US1, LP, and CH2) were synthesized as a single insert and cloned in a hairpin configuration into a binary vector, which was used to transform tomato plants. Transgenic tomato lines that expressed a high level of transgene-siRNA exhibited immunity to PepMV strains, including a new Israeli isolate. This immunity was maintained even after graft inoculation, in which a transgenic scion was grafted onto nontransgenic infected rootstocks. However, an immune transgenic rootstock was unable to induce resistance in a nontransformed scion. These results provide the first example of engineered immunity to diverse PepMV strains in transgenic tomato based on gene silencing.     

氟草烟防除水花生试验初报

水花生又名空心莲子草,是多年生宿根草本植物,它原产于巴西,于20世纪30年代末引种至我国,起先在上海郊区栽培用作养马饲料。20世纪50年代我国南方一些省市将水花生作为猪羊饲料推广,江苏省于20世纪60年代引进推广。由于水花生生命力强,适应于水生、湿生、旱生多种生态环境,生长繁殖非常迅速,故而逸生为杂草。目前,江苏省发生面积达80万hm2左右,危害面积30万hm2以上。水花生根系发达,地下部分生长繁茂,在农田生长会与作物争夺阳光、水分、肥料及生长空间,造成作物减产。为了探求对水花生的有效化学防除方法,我们开展了20%氟草烟EC防除畦畔水…     

Basis for the selective action of fluroxypyr

The dose-response, foliar uptake, translocation and metabolism of the methylheptyl ester (MHE) of fluroxypyr were examined in lambs-quarters (Chenopodium album L.), wild buckwheat (Polygonum convolvulus L.), Canada thistle (Cirsium arvense L. Scop.) and field bindweed (Convolvulus arvensis L.). Under controlled environment growth room conditions, E₅₀ values, determined from shoot dry weights of the susceptible species, wild buckwheat (16 g ha^?1) and field bindweed (40 g ha^?1), were markedly different than those of the tolerant species, lambsquarters (331 g ha^?1) and Canada thistle (800 g ha^?1). Regardless of species, more than 80% of applied [¹⁴C]fluroxypyr-MHE was absorbed by foliar surfaces 120 h after treatment. Translocation of radioactivity out of the treated leaves of susceptible species was significantly greater than that of tolerant species. For example, 120 h after treatment with [¹⁴C]-fluroxypyr-MHE, the proportion of applied radioactivity translocated in tolerant Canada thistle and lambsquarters was 15 and 10%, respectively, whereas in susceptible wild buckwheat and field bindweed it was 41 and 40% of applied radioactivity, respectively. High-performance liquid chromatography (HPLC) of plant extracts indicated four distinct chroma-tographic peaks common to all four species. More fluroxypyr was recovered in the susceptible species (70%) than in the tolerant species (30%), 120 h after application. Selectivity differences between the tolerant and susceptible species may be the result of enhanced metabolic transformation of the herbicide to more polar, non-phytotoxic compounds with limited mobility within the tolerant species. Les bases de la sélectivité du fluroxypyr La courbe dose effet, la pénétration foliaire, la migration et le métabolisme de Tester méthyle-heptyle (MHE) du fluroxypyr ont étéétudiés chez le chénopode blanc (Chenopodium album L.), la renouée faux-liseron (Polygonum con-vulvulus L.), le chardon des champs (Cirsium arvense L. Scop.) et le liseron des champs (Convolvulus arvensis L.). En conditions de crois-sance contrôlées, les valeurs ED₅₀, déterminées à partir du poids de matière sèche des parties aériennes étaient nettement différentes chez les plantes sensibles et chez les plantes résistan-tes:renouée faux-liseron, 16 g ha^?1; liseron des champs, 40 g ha^?1; chénopode blanc, 331 g ha^?1; chardon des champs, 800 g ha^?1. Quelle que soit 1'espèce, plus de 80% du [¹⁴C]fluroxypyr-MHE pénétrait dans les feuilles en 120 h. La migration de la radioactivité hors des feuilles traitérs était significativement plus importante chez les plantes sensibles que chez les plantes tolérantes. Par exemple, 120 h après le traite-ment avec du [¹⁴C]fluroxypyr-MHE, la proportion de radioactivité appliquée qui avait migré dans le chardon des champs et le chénopode, tolérants, était respectivement 15 et 10%, alors que chez la renouée faux-liseron et le liseron des champs, sensibles, elle était respectivement 41 et 40%. Des analyses par HPLC des extraits de plantes montraient quatre pics chro-matographiques distincts dans chacune des quatre espèces. Davantage de fluroxypyr était retrouvé 120 h après 1'application chez les plantes sensibles que chez les plantes résistantes (70% contre 30%). Les différences de sensibilité entre espèces pourraient être dues chez les plantes tolérantes à un métabolisme plus important de l'herbicide en composés plus polaires, non phytotoxiques et peu mobiles. Grundlagen für die selektive Wirkung von Fluroxypyr Die Dosis/Wirkungs-Beziehung, Blattaufnahme, Translokation und Metabolismus des Methylheptyl-Esters (MHE) von Fluroxypyr wurden bei Weißem Gänsefuß (Chenopodium album L.), Gemeinem Windenknöterich (Polygonum convolvulus L.), Acker-Kratzdistel (Cirsium arvense (L.) Scop.) und Gemeiner Ackerwinde (Convolvulus arvensis L.) untersucht. Unter den kontrollierten Umweltbedingungen eines Phytotrons wurden anhand des Trockengewichts die ED₅₀-Werte bestimmt, die bei den empfindlichen Arten Polygonum convolvulus mit 16 g ha^?1 und Convolvulus arvensis mit 40 g ha^?1 sich deutlich von denen der toleranten Arten Chenopodium album mit 331 g ha^?1 und Cirsium arvense mit 800 g ha^?1 unterschieden. Unabhängig von der Art waren mehr als 80 % der Aufwandmenge von [¹⁴C]-Fluroxypyr-MHE durch die Blattoberflächen 120 h nach der Behandlung aufgenommen. Die Translokation der Radioaktivität aus den behandelten Blättern war bei den empfindlichen Arten signifikant größer als bei den toleranten. Z. B. waren 120 h nach der Behandlung bei den toleranten Arten Cirsium arvense und Chenopodium album 15 bzw. 10 % der Radioaktivität transloziert, während es bei den empfindlichen Arten Polygonum convolvulus und Convolvulus arvensis 41 bzw. 40 % waren. Bei allen 4 Arten ergab eine HPLC-Untersuchung der Pflanzenextrakte 4 distinkte Peaks. Bei den empfindlichen Arten wurde 120 h nach der Anwendung mit 70 % mehr Fluroxypyr wiedergefunden als bei den toleranten (30 %). Die Selektivitätsunterschiede zwischen den toleranten und empfindlichen Arten könnten auf einen beschleunigten Metabolismus des Herbizids zu stärker polaren, nichphytotoxischen Stoffen mit eingeschränkter Mobilität bei den toleranten Arten zurückgeführt werden.     

Persistence and translocation of a benzothiadiazole derivative in tomato plants in relation to systemic acquired resistance against Pseudomonas syringae pv tomato

A reproducible and accurate procedure, based on HPLC analysis, has been developed to determine simultaneously acibenzolar‐S‐methyl (CGA 245 704) and its acid derivative (CGA 210 007) in tomato leaves. The limit of detection and quantification of the method are 0.015 and 0.15 mg litre^?1 for CGA 245 704 and 0.030 and 0.30 mg litre^?1 for CGA 210 007. In tomato plants treated with 250 µM CGA 245 704, it was found that the inducer rapidly translocates from treated leaves (cotyledons, 1st and 2nd) to untreated leaves (3rd to 5th), with the maximum translocation (40% of the total quantity found) occurring 8 h after the treatment. CGA 245 704 residues decreased as time elapsed in both treated and untreated tomato leaves, reaching negligible values 72 h after treatment. The acid derivative, CGA 210 007, was formed in tomato plants as early as 2 h after CGA 245 704 treatment, albeit only in the treated leaves. CGA 210 007 residues decreased in treated tomato leaves with a trend similar to that observed for CGA 245 704. Treatment of tomato plants with CGA 245 704 or CGA 210 007 at 250 µM systemically protected the plants against Pseudomonas syringae pv tomato attacks, the causal agent of bacterial speak disease. Evidence of this were reductions in the degree of infection, the bacterial lesion diameter and the bacterial growth in planta. Since neither CGA 245 704 nor CGA 210 007 inhibited bacterial growth in vitro and the protection against bacterial speak of tomato was observed when the two compounds were completely degraded, the protection must be due to the activation of the plant's defence mechanisms. © 2001 Society of Chemical Industry     

Growth inhibitors associated with fusarium wilt of tomato

The localization of vascular infections by a process of vascular occlusion is a primary basis for single dominant gene resistance of tomato to fusarium wilt. Failure of this response process to prevent systemic spread of fusarium in susceptible tomato plants is associated with an inhibition of tylose development, a key factor in the overall walling off process. This research was designed to detect, isolate and characterize inhibitory metabolites that accumulate during the course of the tomato/ Fusarium interaction which could inhibit tylose development. Isolation of inhibitors from chloroform extracts of systemically infected tissues was achieved by a series of successive chromatographic separations and bioassays. R_FValues of inhibitors in the several solvent systems employed and their respective colour reactions with chromogenic reagents were recorded. The accumulation of a highly inhibitory compound in chloroform extracts during the early stages of Fusarium infection was determined quantitatively by colourimetric assay in a subsequent experiment. This compound, tentatively identified as rishitin, was isolated from the region of initial infection in stem vascular tissues 1–11 days after inoculation. This inhibitor accumulated rapidly in near-isolines of both resistant and susceptible tomato cultivars in 1–4 days and then continued to accumulate in susceptible, but declined in resistant, plants from 5 to 11 days. The relative phytotoxicity of this compound at low concentrations was determined by assessing its effects on the viability of cultured tomato cells. These data, together with measurements of its accumulation and determinations of its distribution in infected tissues, indicates that rishitin, a host product that accumulates in response to infection, could account for the inhibition of tylose development observed in susceptible tomato plants following infection by Fusarium. Thus we are faced with a paradox in that a substance that presumably functions in defence can, under certain circumstances, interfere with the defence process. A likely resolution of this paradox is discussed.     

Induced resistance in tomato plants to the toxin-dependent necrotrophic pathogen Alternaria alternata

A necrotrophic pathogen, the tomato pathotype of Alternaria alternata (Aa) causes Alternaria stem canker on tomato. Its pathogenicity depends on the production of host-specific AAL-toxin. Pre-inoculation with nonpathogenic Aa or pretreatment an elicitor prepared from Aa reduced disease symptoms by the pathogen. Salicylic acid (SA)- and jasmonic acid (JA)-dependent defense responses in tomato are not involved in the resistance to the pathogen induced by nonpathogenic Aa. The results suggest that an alternative and unknown signaling pathway independent of SA- and JA-signaling might modulate the induced resistance by activating the expression of the multiple defense genes.     

Uptake of some volatile alkyl methylphosphonofluoridates from the vapour phase by wheat plants

The uptake of cyclohexyl, isopropyl and 1,2,2-trimethylpropyl methylphosphonofluoridates from the vapour phase by growing wheat plants was studied. The compounds were absorbed through the leaves of the plants and were degraded in a manner similar to that following their uptake through the roots from hydroponic culture solution. The levels of the methylphosphonic acid derivatives in the plant extracts were influenced by the vapour concentration of the methylphosphonofluoridate, the period of exposure to the vapour and the state of illumination of the plants, but were not markedly influenced by the chemical nature of the compounds. Likely mechanisms for the uptake are discussed and it is concluded that the main route of absorption involves the stomata. The studies suggest that growing plants can absorb and possibly have a “sink effect” for atmospheric organophosphorus contamination.     

The relation between polyphenoloxidase activity and ability to produce indoleacetic acid in Fusarium-infected tomato plants

Different protein fractions precipitated with ammonium sulphate from extracts of healthy andFusarium-infected tomato plants showed a linear relationship between polyphenoloxidase activity and ability to form indoleacetic acid (IAA) from tryptophan in the presence of chlorogenic acid. Dialysis slightly reduced polyphenoloxidase activity of as well as IAA formation by crude and purified extracts.Polyphenoloxidase as well as IAA production were partially inhibited by DIECA, EDTA, cystein and ascorbic acid. The inhibition was shown to occur in crude and purified extracts and stem slices of both healthy and diseased plants, but was consistently higher in material from diseased plants.The reported results may be considered to further confirm the strict interdependence between polyphenoloxidase activity and ability to form IAA in tomato plants. The different sensitivity to some inhibitors shown by material from healthy and from diseased plants is emphasized.