Increase in the gibberellin response by low temperature pretreatment of azuki bean epicotyls

Epicotyl segments cut from azuki bean (Vigna angularis) seedlings grown at 27 C for 5 days and then treated at 15 C for 2 days were compared with those cut from seedlings not receiving the 15-C treatment, for their response to auxin and auxin plus gibberellin. The segments cut from 15C-treated seedlings showed greater elongation than the segments cut from untreated seedlings both in the absence and in the presence of gibberellin. The 15-C treatment increased the elongation caused by auxin plus gibberellin to a greater extent than it did the elongation caused by auxin alone; the gibberellin response of epicotyl was increased by the treatment. Diffusates from leaves and buds inhibited both the elongation caused by auxin and that caused by auxin plus gibberellin. The diffusates inhibited the latter more strongly than the former; the gibberellin response was decreased by the diffusates. Leaves or buds appear to supply epicotyls with a substance which decreases the gibberellin response. The supply of this substance was found to be temperature dependent. The diffusates obtained at 15 C caused no inhibition, while those obtained at 27 C decreased the gibberellin response. The lack of the supply of this substance at 15 C may account for the increase in the gibberellin response by the 15-C treatment.     

THE EFFECTS OF TEN PHENOLIC COMPOUNDS ON HYPOCOTYL GROWTH AND MITOCHONDRIAL METABOLISM OF MUNG BEAN

Ten phenolic compounds were examined for their effect on mung bean (Phaseolus aureus L.) hypocotyl growth and on respiration and coupling parameters of isolated mung bean hypocotyl mitochondria. Three compounds—tannic, gentisic, and p-coumaric acids—inhibited hypocotyl growth and when incubated with isolated hypocotyl mitochondria released respiratory control, inhibited respiration, and prevented substrate-supported Ca²⁺ and PO₄ transport. Vanillic acid also inhibited hypocotyl growth and reduced mitochondrial Ca²⁺ uptake but did not affect respiration or respiratory control of isolated mitochondria. This is the first compound reported to selectively inhibit Ca²⁺ uptake in plant mitochondria. Two other phenolic compounds—α, 3,5-resorcylic and protocatechuic acids—showed no significant effect on hypocotyl growth and did not affect mitochondrial oxidative phosphorylation either separately or in various combinations. Four phenolic compounds—ferulic, caffeic, p-hydroxybenzoic, and syringic acids—showed a significant reduction in mung bean hypocotyl growth but did not inhibit any of the mitochondrial processes examined. The results show that phenolic compounds which alter respiration or coupling responses in isolated mitochondria also inhibit hypocotyl growth and may reflect a mechanism of action for these natural growth inhibitors.     

Isolation and identification of a light-induced growth inhibitor in diffusates from blue light-illuminated oat (Avena sativa L.) coleoptile tips

The amounts of two growth inhibitors in diffusates from illuminatedhalves of phototropically stimulated oat (Avena sativa L.)coleoptile tips were larger than those from shaded halves. The less polarinhibitor was isolated from diffusates from oat coleoptile tips illuminatedwithblue light, and identified as uridine from ¹H NMR spectrum. Thedistribution of endogenous uridine in diffusates from the illuminated andshadedsides of coleoptile tips unilaterally exposed to blue light for 3, causing a first positive phototropic curvature, and fromdark-control tips, was determined using a physicochemical assay. The uridineconcentration was significantly higher in the diffusates from the illuminatedside than in those from the shaded side and the dark-control. Uridine inhibitedthe growth of etiolated oat coleoptile tips at concentrations of 30 and above. These results suggest that uridine plays a role inthe phototropism of oat coleoptiles.     

INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS. III. INHIBITORS OTHER THAN TANNINS

We obtained considerable evidence in earlier work that inhibition of nitrification begins during old-field succession and increases to a maximum in the climax (Rice and Pancholy, 1972, 1973). Moreover, we found that tannins and tannin derivatives appear to be important inhibitors of nitrification. In the present project, other potential phenolic inhibitors of nitrification were identified in acetone extracts of entire plants of most herbaceous species and leaves of tree species important in an intermediate stage of succession and the climax in three vegetation types in Oklahoma. Attempts were made also to identify potential inhibitors in acetone extracts of soil from the top 15 cm of the oak-pine climax. Seventeen potential inhibitors were identified from the eleven important species of plants surveyed. These were mostly phenolic acids and flavonoids, but one coumarin compound, scopolin, was found in high amounts in several species. The potential inhibitors were most common in green tops or green leaves, but roots, dead tops (of previous year), and dead leaves had high amounts of some compounds. Caffeic and ferulic acids were prominent in dead leaves or dead tops, and one flavonoid, myricetin, occurred in sizeable amounts in dead tops of Sorghastrum nutans. The aglycones of most of the compounds were tested against nitrification in soil suspensions, and all completely inhibited oxidation of NH⁺₄ to NO⁻₂ by Nitrosomonas at concentrations as low as 10⁻⁶ to 10⁻⁸ M. Oxidation of NO⁻₂ to NO⁻₃ by Nitrobacter, however, was affected much less severely by these inhibitors. The greater resistance of Nitrobacter is not significant biologically because inhibition of the first step carried out by Nitrosomonas effectively inhibits the entire process of nitrification. The 3-glucoside of quercetin, isoquercitrin, inhibited the activity of Nitrosomonas completely at the same concentration as quercetin. We found a compound in large quantities in the oak-pine climax soil which appeared in all tests to be a flavonoid aglycone, but we were never able to identify it to our satisfaction. This substance was extremely inhibitory to germination and seedling growth of ‘Crimson Giant’ radish seeds. These have hard seed coats and germinate very rapidly so most inhibitors do not affect their germination at all. It is likely that some, if not all, of the nitrification inhibitors identified may be important in inhibition of nitrification in the later stages of succession and in the climax along with the tannins.     

Changes in Phenolic Acids in Groundnut Leaves Infected with Rust

Quantitative changes of individual phenolic acids in rust-infected groundnut leaves were studied at various stages of disease development. There was no qualitative change in the phenolic acids. However, the concentration of the phenolic compounds increased due to infection more particularly of chlorogenic and trans and cis caffeic acids.     

Continuous exposure to the deterrents cis‐jasmone and methyl jasmonate does not alter the behavioural responses of Frankliniella occidentalis

Behavioural responses of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), a generalist, cell sap‐feeding insect species with piercing‐sucking mouthparts, after continuous exposure to two deterrent secondary plant compounds are investigated. We compared in choice assays on bean leaf discs, the settling, feeding, and oviposition preferences of F. occidentalis females that had no experience with the two fatty acid derivatives methyl jasmonate and cis‐jasmone before testing (naïve thrips) vs. females that had been exposed to the deterrent compounds before testing (experienced thrips). The thrips were exposed to the deterrents at low or high concentrations for varied time periods and subsequently tested on bean leaf discs treated with the respective deterrent at either a low or a high concentration. Frankliniella occidentalis females avoided settling on the deterrent‐treated bean leaf discs for an observation period of 6 h, independent of their previous experience. Our results demonstrate that feeding and oviposition deterrence of the jasmonates to the thrips were not altered by continuous exposure of the thrips to the jasmonates. Habituation was not induced, neither by exposure to the low concentration of the deterrents nor by exposure to the high concentration. These results indicate that the risk of habituation to two volatile deterrent compounds after repeated exposure is not evident in F. occidentalis. This makes the two compounds potential candidates to be integrated in pest management strategies.     

Behaviour of the Phenolic Compounds on Capsicum annuum Leaves Infected with Phytophthora capsici

In Capsicum annuum leaves, some phenolic compounds, such as chlorogenic acid and various apigenin or luteolin glycosides, can be separated by HPLC technique. During infection with Phytophthora capsici (the agent of pepper mildew), the concentrations of these compounds decreased. A fungal glucosidasic activity may be implicated, producing apigenin aglycon in the necrotic areas. Some of the phenolic compounds were only present in intercellular spaces, where their concentration increasedduring fungal infection, mostly in the resistant pepper cultivar. The involvement of phenolics in C. annuum resistance is discussed in relation to oxidative metabolism.     

The Inhibition of Rust Fungus Growth in Allopurinol-Treated Bean Plants: Indirect Evidence for the Involvement of Xanthine Oxidoreductase in the Biotrophism of Uromyces phaseoli

Allopurinol [4-hydroxypyrazolo(3,4-d)pyrimidine], a specific, potent inhibitor of xanthine oxidoreductase, effective in vitro and in vivo, was applied to bean plants as soil drench at a 400 μM concentration 8–10 days before inoculation and strongly reduced the development of Uromyces phaseoli in bean leaves. Allopurinol was ineffective on uredospore germination, presumably due to the absence of any xanthine oxidoreductase activity in the extract of germinated uredospores. The concentration of allopurinol used for the treatment did not significantly influence the level of ureides in leaves mainly because low concentration of these compounds were found in leaves and also probably because allopurinol-insensitive biosynthetic route/s of these compounds are active in bean plants. This paper examines the possibility that host xanthine oxidase is in some way involved in the biotrophic nutritional process leading to the growth of bean rust fungus.     

Auxin-Synergists in the Rooting of Cuttings

Indole, α- and β-naphtol are synergistic with auxins in enhancing root production of cuttings of Phaseolus vulgaris. To find an explanation for this synergism the activity was compared with that of phenolic compounds which are known to be: a. inhibitors of the IAA oxidase system, b. cofactors of the conversion of tryptophane to IAA. Both processes appeared to occur in the bean cuttings (as estimated by root production), but none of the phenols bad an activity equally strong as the “synergists”. It is suggested that indole as well as α- and β-naphtol act as other injurious substances in “just sublethal” dose (Soekarjo 1966).     

Interaction of Cucumber mosaic virus and Bean yellow mosaic virus in co-infected plants of bean and broad bean

After evaluation of the responses of bean and broad bean common cultivars against an isolate of Cucumber mosaic virus (CMV-K) and Bean yellow mosaic virus (BYMV-K), interaction of isolates was statistically studied on co-infected plants of bean cv. Bountiful and broad bean cv. Lahijan at two trials. Based on viral relative concentration determined by quantitative enzyme-linked immunosorbent assay, BYMV interacts synergistically with CMV in bean at 14 days post inoculation, while in co-infection with BYMV, CMV interacts antagonistically in both host plants at least in one of the two trials. This suggests that CMV/BYMV interaction is dependent on host species and developmental stage of plant. Co-infection like single infection with CMV in bean plants led to significantly decrease in plants’ height and fresh weight than BYMV singly infected and healthy plants, while viral infection of broad bean plants did not significantly affect growth parameters. Decline effect of viral infection (especially co-infection) on chlorophyll and carotenoids value of bean plants was greater than those of broad bean. Viral infection (singly or doubly) caused irregular changes in nutrient elements values of both hosts compared with healthy ones.     

Root-promoting Substances in Salix alba

Root-promoting substances were extracted from softwood cuttings of Salix alba L. by centrifuging them with water or by shaking the ground freeze-dried stems with water. Rooting substances were partitioned by paper chromatography or chemical fractionation and their rooting activity was tested by mung bean cuttings. Both extracts indicated three major root -promoting fractions at Rf 0-0.1, 0.7-0.8, and 0.3-0.4 in a decreasing order of their activities when paper chromatographed with isopropanol:ammonia:water 8:1:1 v/v. The strongest one indicated an apparent synergistic rooting effect with indol-3yl-acetic acid (IAA) regardless of the extraction method. These results indicate that water can extract from freeze -dried sample the similar rooting substances found in the centrifugal diffusates. The Rf 0–0.1 fraction consisted of at least four fractions and the strongest one did not move from the starting line on the chromatogram when isopropanol:ammonia:water 8:1:1 was used. This starting line fraction was extremely strong in rooting activity and its highest concentration resulted in 8.7 times as many roots as controls. More thain additive rooting effect between IAA and the fraction was found only at the highest concentration. The fraction was very soluble in water but insoluble in chloroform or ethyl ether and only stimulated rooting of mung bean cuttings when it was applied within 3 days after cuttings were made. It had no effect in lengthening roots. The starting line fraction was further found to have four root-promoting subfractions at Rf 0.05, 0.35, 0.65, and 0.85 when it was chromatographed in 60 % isopropanol. Among these four, the subfractions at Rf 0.65 and 0.35 were strongly root promotive and displayed more than additive root promotion with IAA at the highest concentrations studied.     

Enhancement of adventitious root formation in mung bean cuttings by 3,5-dihalo-4-hydroxybenzoic acids and 2,4-dinitrophenol

3,5-Dihalo-4-hydroxybenzoic acids enhanced adventitious root formation in mung bean (Vigna radiata L.) cuttings. 3,5-Diiodo-4-hydroxybenzoic acid was more active than 3,5-dichloro-4-hydroxybenzoic acid, increasing the number of roots formed by about 4-fold. 2,4-Dinitrophenol also enhanced significantly adventitious root formation in mung bean cuttings. The phenolic compounds were active with or without indole-3-acetic acid. The possible mechanism by which these phenolic compounds enhance rooting is discussed.Abbreviations CCCP carbonyl cyanide 3-chlorophenylhydrazone - DIHB 3,5-diiodo-4-hydroxybenzoic acid - DNP 2,4-dinitrophenol     

Studies on the Browning Compounds of Broad Bean,Vicia fava L.

Browning of green broad bean appears only in the seed-coat, and not in cotyledon. This phenomenon coincides with the facts that phenolic compounds such as l-tyrosine and 3,4-dihydroxyphenylalanine are localized in the seed-coat tissues. But little is known about the browning mechanism of the seed-coat at present.

In this study, the presence of dopa-o-β-d-glucoside was confirmed in addition to those phenolic compounds mentioned above, and the distribution of this substance in tissues of green broad bean was examined by paper chromatography. A clear indication of the relationships between the mechanism of brown pigmentation and the biosynthesis of dopa-o-β-d-glucoside in vivo was also presented.     

The carbohydrate and water balance of beans (Vicia faba) attacked by broomrape (Orobanche crenata)

Orobanche crenata parasitizing beans maintained a slightly higher osmotic pressure than the bean roots, largely because of the higher concentration of sugars in the broomrape tissues. The sugar was withdrawn from the bean mainly as sucrose, which was hydrolysed to glucose and fructose by the Orobanche. These sugars were then rapidly translocated to the developing flower spike. As well as maintaining a high osmotic pressure this hydrolysis ensured a sucrose concentration gradient between host and parasite. In the field, bean plants showed wilt symptoms at about the time that the Orobanche flower spikes emerged. It was found that the higher the level of infection the lower was the water content of the host. This fall in water content was not due to increased water loss by the bean shoots and it seemed unlikely that it was due to water removal by the parasite. It was concluded that the death of the bean was due to desiccation brought about largely by the reduced ability of the carbohydrate-starved roots to extract water from the soil.     

Plant growth-promoting rhizobacteria-mediated induction of phenolics in pea ( Pisum sativum) after infection with Erysiphe pisi

Qualitative and quantitative estimation of phenolic compounds was done through high performance liquid chromatography (HPLC) in different parts of pea (Pisum sativum) after treatment with two plant growth-promoting rhizobacteria (PGPR), viz., Pseudomonas fluorescens (strain Pf4) and Pseudomonas aeruginosa (referred to here as Pag) and infection by Erysiphe pisi. The phenolic compounds detected were tannic, gallic, ferulic, and cinnamic acids on the basis of their retention time in HPLC. In all the treated plants, synthesis of phenolic compounds was enhanced. The induction of gallic, ferulic, and cinnamic acids was manyfold more than those in the control. Maximum accumulation of phenolic compounds was observed in plants raised from PGPR-treated seeds and infection with E. pisi. Under pathogenic stress, Pag performed better because a relatively higher amount of phenolics was induced compared with plants treated with Pf4. Received: 20 August 2001 / Accepted: 20 September 2001     

Inhibition of cellulose enzymatic hydrolysis by laccase‐derived compounds from phenols

The presence of inhibitors compounds after pretreatment of lignocellulosic materials affects the saccharification and fermentation steps in bioethanol production processes. Even though, external addition of laccases selectively removes the phenolic compounds from lignocellulosic prehydrolysates, when it is coupled to saccharification step, lower hydrolysis yields are attained. Vanillin, syringaldehyde and ferulic acid are phenolic compounds commonly found in wheat‐straw prehydrolysate after steam‐explosion pretreatment. These three phenolic compounds were used in this study to elucidate the inhibitory mechanisms of laccase‐derived compounds after laccase treatment. Reaction products derived from laccase oxidation of vanillin and syringaldehyde showed to be the strongest inhibitors. The presence of these products causes a decrement on enzymatic hydrolysis yield of a model cellulosic substrate (Sigmacell) of 46.6 and 32.6%, respectively at 24 h. Moreover, a decrease in more than 50% of cellulase and β‐glucosidase activities was observed in presence of laccase and vanillin. This effect was attributed to coupling reactions between phenoxyl radicals and enzymes. On the other hand, when the hydrolysis of Sigmacell was performed in presence of prehydrolysate from steam‐exploded wheat straw a significant inhibition on enzymatic hydrolysis was observed independently of laccase treatment. This result pointed out that the other components of wheat‐straw prehydrolysate are affecting the enzymatic hydrolysis to a higher extent than the possible laccase‐derived products. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:700–706, 2015     

Within-leaf differences in nutritive value and defence mechanism in chrysanthemum to the two-spotted spider mite (Tetranychus urticae)

Some chrysanthemum leaf characteristics were evaluated to determine their importance as nutrition for, and as factors of resistance to,Tetranychus urticae Koch. These characteristics were: leaf age and chemical composition, content of phenolic substances, total nitrogen, and soluble protein.Mite density was lower on young leaves than on mature ones. Young leaves appear to be protected againstT. urticae by a higher concentration of mono-and polyphenols, although they contained higher levels of nutrients than mature ones. After mite infestation, the most valuable young leaves were also the best-protected leaves on their shoots. Content of phenolic compounds increased only in young chrysanthemum leaves after mite feeding.     

Gibberellins in Diffusates from Shoots of Apple Trees

Excised shoot apices, leaves and internodes from shoots of apple trees (Malus×domestica) give off gibberellins by diffusion on agar. A methanol extract of the agar was prepared, the extract separated on thin layer plates, and the gibberellin activity estimated by means of Rumex and lettuce hypocotyl bioassays. The largest amounts of gibberellin are found in diffusates from the shoot apex, the two upper leaves and the two upper internodes. Several promotive fractions are found on the chromatograms as well as growth inhibitors. Removal of young leaves retards elongation of the internodes. Probably gibberellins produced in young leaves exercise some control over this process. The growth regulators Alar and CCC also retard internode elongation. Diffusates from shoots treated with these substances were also examined. Preliminary results suggest that the amount of diffusible gibberellins from treated shoots is not reduced.     

Seasonal variation in the nutritional value of woody plants along a natural gradient in Eastern Africa

Several hypotheses relate a negative relationship between foliar concentration of phenolic compounds and nitrogen to physiological processes such as leaf development, seasonal variation in allocation priorities, nutrient, light and water related growth limitation, as well as herbivore attack. We sampled four common deciduous woody species of central Tanzania monthly during the growing season to assess changes in this relation and their nutritional value to ruminants. We found a negative relationship between leaf N and phenolic compounds within and among species and sites that weakens during the course of the growing season that was consistent for total phenolics, but not for condensed tannins. Leaf N concentration decreased throughout the season, its withdrawal being positively related with leaf N at first sampling date. Secondary compounds concentration showed no consistent seasonal trend. Concentrations of leaf N and phenolics were correlated with ¹³C discrimination in the two shrub species and with soil P in the two tree species. Digestibility was positively correlated with foliar N and negatively correlated with secondary compounds. We conclude that phenolic compounds may serve as reliable clues for selecting foliage rich in N at site and species level only during the first months of the growing season.