The Effects Of Humic Substances On Pinus Callus Are Reversed By 2,4-Dichlorophenoxyacetic Acid

The 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 (M_r) > 3500), derived from soil under Fagus sylvatica (Fs) and Abies alba (Aa) plantation, were used. Pinus laricio callus was 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.     

Assimilate transport in grapevines -effect of phloem disruption

Assimilate translocation in mature grapevines (cv. Gewürztraminer and cv. Harslevelü) under field conditions was investigated during the growth season by quantifying individual sugars and organic acids in mature leaves, shoot bark and berries, as affected by girdling the shoot just above the bunches. Tissue was sampled at berry set, pea size, veraison and ripeness stages of the vine. Invertase activity was determined in the shoot bark at ripeness. In the leaves, malic acid concentrations reached lowest levels at pea size, but increased thereafter. Tartaric acid decreased after peaking at pea size stage. Tartaric acid concentrations increased with girdling. Despite the increase in leaf age, sucrose concentrations remained virtually stable during the season, emphasising the importance of mature leaves for nourishing bunches. Girdling resulted in a build‐up of sucrose in the leaves. In the bark, malic and tartaric acid stayed more or less the same during the growth period, but increased above the girdle. As a result of phloem disruption, sucrose also increased. The increase in glucose and tartaric acid is believed to result from catabolic cleavage of sucrose by invertase. Invertase activity was evident in the bark (of mature Harslevelü vines) at ripeness, which may indicate involvement in osmotic adjustments and gradients in the bark/phloem structure. In the berries, malic and tartaric acids reached peak concentrations at pea size. The volume increase during the ripening period, and in the case of malic acid also respiratory loss, resulted in a decrease in organic acid concentration. Malic acid continued to decrease after the initial decline, whereas tartaric acid stayed virtually stable. Girdling had no marked effect on organic acid accumulation in the berries. Sucrose concentrations were low during the first part of the season, but increased thereafter. Sucrose concentrations during ripening increased with girdling, which may represent a concentration effect and/or import from the rest of the vine. Sucrose concentrations (in mature Harslevelü vines) were indeed lower below than above the girdle. Comparison of sucrose concentrations in the leaves, bark and berries showed the existence of a decreasing concentration gradient, in line with the source:sink transport concept. An equally prominent decrease in sucrose:glucose ratio in the berries from the start of the ripening period indicates that vacuolar integrity (compartmentation) was affected in the ripening berry, most probably allowing hydrolysis of sucrose by invertase and decreasing osmotic potential within the berry. The results provide further evidence for the hypothesis of an osmotic gradient driven transport to the berry.     

Production,thermal stability and immobilisation of inulinase from Fmarium oxysporum

Fusarium oxysporum produced maximum extracellular inulinase after 9 days of its growth at 25°C on a medium (pH 5.5) containing 3% fructan and 0.2% sodium nitrate. The level of this enzyme decreased on the addition of either glucose, fructose, galactose or sucrose to F. oxysporum already growing on a fructan-containing medium. A significant increase in invertase production which resulted in an increase of the invertase/inulinase (S/I) ratio, was observed on addition of inulin to this fungus growing on other carbon sources. Glycerol (10%) gave better protection to inulinase against thermal denaturation at 50°C compared to ethylene glycol and sorbitol. Inulinase immobilised in polyacrylamide gel retained 45% of its original activity. The immobilised enzyme showed a higher optimum temperature (45°C) compared to free enzyme (37°C). The immobilised enzyme after storage at 25°C for 96 h showed 58% activity. Thermal stability of entrapped inulinase increased in the presence of inulin.     

Sugar metabolism and involvement of enzymes in sugarcane (Saccharum officinarum L.) stems during storage

Sugarcane (Saccharum officinarum L. cv. Badila) was harvested at the mature stage and stored at 2, 10, and 20 °C for 30, 90, and 120 days, respectively. Metabolic changes in the contents of sucrose and reducing sugar in relation to the activities of soluble acid invertase (SAI), neutral invertase (NI) and sucrose-phosphate synthase (SPS), in sugarcane juice, were studied. Extractable juice, sucrose and vitamin C declined significantly with increasing storage temperatures, while respiration rate increased. There was a rapid increase in titratable acidity during storage, with a more rapid rate at higher temperatures. A sharp increase in reducing sugar was observed within 20 days at 20 °C and 70 days at 10 °C, followed by a rapid decrease. Both SAI and NI activities showed a sharp increase within 15 days at 20 °C, followed by a rapid decrease, while a moderate increase occurred within 40–60 days at 10 °C. Slight increases were observed in SPS activity within 20 days at 20 °C and 50 days at 10 °C. Enzyme activities remained steady or underwent a small change in canes stored at 2 °C. Enzyme activities were significantly correlated with reducing sugar content.     

Prediction of signal peptide functional properties: a study of the orientation and angle of insertion of yeast invertase mutants and human apolipoprotein B signal peptide variants

A number of studies have introduced mutations into the yeastinvertase signal peptide, using it as a model system to elucidatefeatures for targeting, translocation and intracellular transportUsing molecular modelling of the invertase signal peptide wehave analysed the hydrophobicity potential and the change inthe dielectric constant of the energy transfer, when the moleculemoves from a hydrophobic to a hydrophilic phase at the simulatedhydrophobic-hydrophilic interface. This modelling has been carriedout on wild type and mutant invertase signal peptides of alteredfunction, previously reported in the literature. While the predictedangle of insertion correlates with the measured extent of invertasesecretion, with an optimum angle of 45, mutations that changethe angle of orientation reduce the extent of invertase secretion.We have applied these same molecular modelling principles tothe naturally occurring variants of the human apolipo-proteinB (apoB) signal peptide, that confer a secretion defective phenotypewhen fused to yeast invertase and expressed in yeast. Our modellingthus identifies a strong correlation between the predicted angleof insertion of the signal peptide into the membrane and itsability to direct secretion.     

Enzymes as Potential Markers of Wine Aging

There is no analytical method currently available in Spain to determine elapsed time in wine aging. The only control used is based on the levels of esters and other secondary metabolites as important indicators related to wine quality. The main goal of this work was to establish a useful method to differentiate among young, “crianza”, “reserva” and “gran reserva” wines based on the study of the enzymatic decay of different hydrolases present in the wines and also to determine which enzyme(s) may be applicable in fraud detection as regards time and storage conditions of the wine. We elaborated red wine based on “Tempranillo” grapes from the Rioja Alta Alavesa and fermented with Saccharomyces cerevisiae USC 013, followed by malolactic fermentation by Oenococcus oeni CECT 630 in order to evaluate the different enzymes. One of the enzymes present, i.e., invertase, which is resistant to inactivation, could be a useful marker of wine aging.     

Isolation and identification of galactinol from castor oilseed meal

Galactinol, 1-O-α-D-galactopyranosyl-D-myo-inositol, is an essential intermediate in the biosynthesis of raffinose saccharides in plant tissues. The unavailability of a commercial source for this metabolite has hindered research on raffinose saccharide metabolism to date. The objective of this study was to develop a facile method for obtaining highly purified galactinol from a readily available source. Defatted castor oilseed meal was found to exhibit a simple soluble carbohydrate profile that included galactinol. Purification of galactinol from castor meal was achieved by enzymatic treatment and a series of liquid chromatography steps, including ion-exchange and carbon adsorption. The isolation procedure was reliable with a yield of 278 mg of galactinol from 150 g of defatted meal. The purity of galactinol was estimated at 96.4% by high-performance liquid chromatography. The identity of the purified galactinol was confirmed by enzymatic analysis, identical relative retention times on high-performance liquid chromatography and gas chromatography, and comparison of its mass spectrum to that of authentic galactinol. Presented at the AOCS Annual Meeting in Chicago in May 1991 [INFORM 2:334 (1991)].     

钛营养对烤烟生长过程中生理特性的影响

研究了不同浓度钛溶液灌根对烤烟生长过程中各种生理特性的影响.结果表明:在伸根期用适量的钛肥灌根,能增加烤烟叶片中叶绿素、类胡萝卜素含量和转化酶活性,可以促进烤烟的光合作用,有利于烟草同化产物的转化和利用,同时也能够提高烤烟叶片中SOD和POD活性,降低MDA含量,明显降低烟叶中细胞膜脂过氧化程度,提高烤烟抗衰老能力和抗逆性.上述作用,在钛肥灌根的短期内,效果尤为明显,其中富钛增效剂稀释600倍灌根效果最好.