1,720,986 research outputs found
The effects of phenolic compounds on soil properties
No full textPhenolic compounds are some of the most widespread molecules among plant secondary metabolites that play an important role in ecological processes in many plant communities through their effects on soil ecology. They are leached out from green foliage, decomposing litter, as well as by root exudates and thus reach the soil underneath the canopy. In terms of their abundance and primary productivity, the dominant species in plant communities have a great significance as the main source of phenolics, and therefore significant effect on plant-litter-soil interactions. Decomposition of plant litter as a crucial process in nutrient cycling in all terrestrial ecosystems is affected by phenolic compounds through effects on the composition and activity of the decomposer (soil microorganisms), on the rate of organic matter decomposition, and on soil C and N cycling. Phenolics can alter N availability by complexation with proteins from litter or with extracellular enzymes from microorganisms. The resulting decrease in the inorganic N availability for plant uptake may potentially affect plant growth. Therefore, soil fertility is influenced by phenolic compounds from plant or microbial sources not only because they are important precursors of soil stable humic substances, but also for their effects on soil nutrient dynamics (N, P, K, Mn, Fe, Cu, etc.), pH, ion-uptake, soil aggregation, etc. In addition, interaction between phenolics and different heavy metals through complexation and reduction reaction, affects their mobility and toxicity in soil. All above mentioned effects can influence natural regeneration of ecosystems.Muscolo A, Sidari M, editors. Soil Phenols. Nova Science Pub Inc; 2010. p. 31-62
The Auxin-like Activity of Humic Substances is Related to Membrane Interactions in Carrot Cell Cultures
No full textA detailed characterization of two humic fractions was performed: One with low relative molecular mass (LMr<3,500 Da) and one with high relative molecular mass (HMr >3,500 Da). Distinct 1H NMR spectroscopic patterns were observed for the two fractions.
HMr showed an aromatic proton region, an intense and broad region (3.0–5.0 ppm) attributed to sugar-like and polyether components, and an intense doublet at 1.33 ppm (identified as protons of the β-CH3 in lactate). In contrast, LMr did not show resonances due to aromatic protons and was characterized by a broad unresolved region, assigned to sugar-like components. The 13C NMR spectra showed that the LMr humic fraction was richer in carboxylic and aliphatic C groups compared to HMr fraction. These substances were fluorescein-labeled [fluorescein isothiocyanate (FITC)], and their interaction with carrot cells in culture was monitored for 10 d, and compared to FITC–indole-3-acetic acid
(IAA) to clarify their mechanisms of biological activity. After different incubation times, fluorescein staining of carrot cells and decrease of fluorescein concentration in the culture medium were evaluated. Fluorescent membrane staining was only present in IAA and the
LMr humic fraction treated cell cultures. A consequential decrease of fluorescein concentration in the culture media was also observed. Pretreatment of carrot cells with unconjugated IAA or LMr humic fraction markedly reduced fluorescein staining of both FITC–IAA and FITC–LMr humic fraction. Blocking tests gave indirect evidence of
possible binding of the LMr humic fraction to IAA cell membrane receptors. These results indicate that the two humic fractions behave differently. Only LMr humic fraction, like IAA, interacts with cellular membranes in carrot cell cultures
The effects of humic substances on pinus callus are reversed by 2,4-Dichlorophenoxy acetic acid
No full textThe reversal of humic matter-induced inhibition of callus growth
and metabolism by 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in
Pinus laricio. Two forest humic fractions (relative molecular mass (Mr) >
3500), derived from soil under Fagus sylvatica (Fs) and Abies alba (Aa) plantation,
were used. Pinus laricio calluswas grown for a subculture period (4 weeks)
on Basal Murashige and Skoog (MS) medium plus forest humic matters (Fs or
Aa), at a concentration of 1 mg C/l, and then was transferred, for an additional
four weeks, to a MS medium culture without humic matter, but with different
hormones: indole-3-acetic acid (IAA, 2 mg/1) or 2,4-dichlorophenoxyacetic
acid (2,4-D, 0.5 mg/1) and/or 6-benzylaminopurine (BAP, 0.25 mg/1). Growth
of calluse, glucose, fructose, and sucrose contents, and activities of soluble
and bound invertases, glucokinase, phosphoglucose isomerase, aldolase, and
pyruvate kinase were monitored. The results show a negative effect of humic
fractions on callus growth, due to decreased utilization of glucose and fructose,
and decreased activities of glycolytic enzymes. The effects are reversible.
Substitution of humic fractions with 2,4-D+BAP or 2,4-D is followed by an
increase of glycolytic enzyme activities and, consequently, by the utilization of
glucose and fructose that induces a restart of growth. In contrast, the inhibitory
effects of humic fractions persist when they are substituted with BAP alone,
indicating that only the auxin 2,4-D is capable of reversing the negative effects.
A possible competitive action on the auxin-binding site between 2,4-D and the
chemical structures in the forest humic fractions is suggested
The ascorbate system during the early stage of germination in Pinus laricio seeds treated with extracts from two different sources of humus
No full textThe aims of the paper was to study how the AA biosynthetic capacity, as well as the activities of REDOX enzymes of the ascorbate systems during the early stage of pinus laricio germination, were affected by humus from two forestry sites
Coumarin inhibits the growth of carrot (Daucus carota L. cv. Saint Valery) cells in suspension culture
No full textWe used a carrot (Daucus carota L. cv. Saint Valery) cell suspension culture as a simplified model system to study the effects of the allelochemical compound coumarin (1,2 benzopyrone) on cell growth and utilisation of exogenous nitrate, ammonium and carbohydrates. Exposure to micromolar levels of coumarin caused severe inhibition of cell growth starting from the second day of culture onwards. At the same time, the presence of 50μmol/L coumarin caused accumulation of free amino acids and of ammonium in the cultured cells, and stimulated their glutamine synthetase, glutamate dehydrogenase, glucose-6-phosphate dehydrogenase and phosphoenolpyruvate carboxylase activities. Malate dehydrogenase, on the other hand, was inhibited under the same conditions. These effects were interpreted in terms of the stimulation of protein catabolism and/or interference with protein biosynthesis induced by coumarin. This could have led to a series of compensatory changes in the activities of enzymes linking nitrogen and carbon metabolism. Because coumarin seemed to abolish the exponential phase and to accelerate the onset of the stationary phase of cell growth, we hypothesise that such allelochemical compounds may act in nature as an inhibitor of the cell cycle and/or as a senescence-promoting substance
Rootstock influences seasonal dry matter and carbohydrate content and partitioning in aboveground components of 'Flordaprince' peach trees
No full textSeasonal development of leaf area, leaf area index (LAI), dry matter, and carbohydrate content were measured from harvest 1992 to harvest 1993 in above-ground components of 'Flordaprince' peach [Prunus persica (L.) Batsch] trees grafted on GF 677 (Prunus persica x Prunus amygdalus) and MrS 2/5 (Prunus cerasifera free pollinated) rootstocks, which widely differ in vigor. Whole trees were separated in to fruit, leaves, shoots, 1-year-old wood an d >1-year-old wood. Sampling dates were coincident with key fruit and tree developmental stages: dormancy, fruit set, pit hardening, and fruit harvest. Rootstock modified the vegetative vigor of the tree, the seasonal partitioning of dry matter, and starch content in above-ground components. Leaf area, LAI, and total above-ground dry matter were twice as high in the most vigorous combination ('Flordaprince'/GF 677), which gave the highest yield, but had the lowest harvest index. Rootstock vigor did not affect soluble sugar concentration in any of the canopy components. Starch content was greatest during dormancy and in the oldest wood of GF 677 trees. During fruit development, starch content rapidly decreased in 1-year-old wood and perennial components; at pit hardening it was four times greater in MrS 2/5 than in GF 677 trees. The vegetative-to-fruit dry mass ratio by pit hardening was 3:1 for MrS 2/5 and 9:1 for GF 677 trees. Competition with shoot growth apparently reduced fruit growth, particularly during Stage I and Stage II, as fruit size at harvest was significantly lower (17%) in G-F 677 than in MrS 2/5 trees
Alteration of aminoacid metabolism by humic substances during germination of Pinus laricio seeds
No full textThe results suggest that HS inhibit seed germination by affecting metabolic processes, in particular the krebses cycle that provides the carbon skeleton necessary to synthesize aminoacids
Effect of imazamethabenz-methyl on nitrate uptake in wheat (Triticum durum L.)
No full textThe effect of the herbicide imazamethabenz-methyl (IMZM), a mixture of the two isomers methyl (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-4-methylbenzoate (para isomer) and methyl (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxa-1H-imidazol-2-yl]-5-methylbenzoate (meta isomer), on the uptake of nitrate by wheat grown hydroponically was studied. IMZM stimulates the nitrate uptake in both "induced" (NO3--pretreated) and "uninduced" (NO3--starved) seedlings, most likely as a response to a plant stress. The decrease in acetohydroxy acid synthase (AHAS; EC 4.1.3.18) activity and in protein content of IMZM-treated roots supports this hypothesis. The presence of valine, leucine, isoleucine, and IMZM prevents the effects of the herbicide treatment in both induced and uninduced plants. The addition of IMZM to humic acid enhances the nitrate uptake, although to a lower extent than with the herbicide alone. Possible traces of imazamethabenz acid (IMZA) in growing units do not seem to be responsible for the greater N demand observed
The auxin-like activity of humic substances is related to membrane interactions in carrot cell cultures
No full textA detailed characterization of two humic fractions was performed: One with low
relative molecular mass (LMr<3,500 Da) and one with high relative molecular mass (HMr
>3,500 Da). Distinct 1H NMR spectroscopic patterns were observed for the two fractions.
HMr showed an aromatic proton region, an intense and broad region (3.0–5.0 ppm)
attributed to sugar-like and polyether components, and an intense doublet at 1.33 ppm
(identified as protons of the β-CH3 in lactate). In contrast, LMr did not show resonances
due to aromatic protons and was characterized by a broad unresolved region, assigned to
sugar-like components. The 13C NMR spectra showed that the LMr humic fraction was
richer in carboxylic and aliphatic C groups compared to HMr fraction. These substances
were fluorescein-labeled [fluorescein isothiocyanate (FITC)], and their interaction with
carrot cells in culture was monitored for 10 d, and compared to FITC–indole-3-acetic acid
(IAA) to clarify their mechanisms of biological activity. After different incubation times,
fluorescein staining of carrot cells and decrease of fluorescein concentration in the culture
medium were evaluated. Fluorescent membrane staining was only present in IAA and the
LMr humic fraction treated cell cultures. A consequential decrease of fluorescein
concentration in the culture media was also observed. Pretreatment of carrot cells with
unconjugated IAA or LMr humic fraction markedly reduced fluorescein staining of both
FITC–IAA and FITC–LMr humic fraction. Blocking tests gave indirect evidence ofpossible binding of the LMr humic fraction to IAA cell membrane receptors. These results
indicate that the two humic fractions behave differently. Only LMr humic fraction, like
IAA, interacts with cellular membranes in carrot cell cultures
- …
