Variations in chlorophyll a/b and chlorophyll/carotenoid ratios are indicators of senescence, stress or damage to the photosynthetic apparatus and affect the normal course of plant biological processes. The aim of this work was to investigate the chlorophyll (a and b) and carotenoid content and ratios in the leaves of four Vitis vinifera L. table grape cultivars in the main phenophases of the annual biological cycle. During the annual cycle, the moisture content of the leaves decreased significantly (up to 21%), along with a reduction in leaf area and perimeter. Chlorophyll a and b showed a continuous accumulation until grape véraison, with lower values of the Chl a/b ratio at the beginning of the vegetative period. Carotenoids continued their biosynthesis until grape ripening (for another 30 days), at which stage there was a significant decrease in the chlorophyll/carotenoid ratio (2.62 ± 0.31). At véraison, peroxidase had the most intense activity (0.20 to 0.51 U/mg), possibly because of involvement in chlorophyll degradation, while total phenolic content started to decrease. Grape véraison could be regarded as the starting point of foliage senescence. Moreover, the relationship between total chlorophyll (by extraction) and chlorophyll content index (non-destructive method) was very significant (R 2 = 0.92). These results contribute to a better understanding of foliar pigment dynamics and the timing of their decline in order to define the behaviour of table grape cultivars during the annual biological cycle. INTRODUCTIONThe annual life cycle of grapevines is a process that takes place in the vineyard each year, beginning with bud burst in the spring and culminating with leaf fall in autumn, followed by winter dormancy (Creasy & Creasy, 2009). The annual life cycle comprises all morphological and biological changes with a periodic character through which the grapevine passes in a calendar year. These changes are called phenological stages (phenophases) and have a specific starting and ending time and a hereditary character (Wang et al., 2014). The occurrence and duration of phenological phases is influenced by climatic factors, and it should be noted that, under the same climatic conditions, the annual life cycle varies by cultivar (Jones & Davis, 2000). In the temperate continental climate, the annual cycle of grapevines lasts about 160 to 220 days.Chlorophylls (Chl) are probably the most important organic compounds on earth, as they are required for photosynthesis (Davies, 2004;Willows, 2004). Photosynthesis in plants is dependent upon capturing light energy in the pigment chlorophyll, and in particular chlorophyll a (Blankenship, 2014). Photosynthetic activity is a very intense process (5 to 11 μmol CO 2 /m 2 /s) that provides all the organic material needed for the growth and life activity of the plant (Popescu & Popescu, 2014). This is why photosynthesising cells have to contain large amounts of assimilatory pigments (up to 5% of total dry solids; Rabinowitch & Govindjee, 1969). In most species, the photos...
Botrytis cinerea is a necrotrophic fungus that affects over 200 plant species. In vineyards, this pathogen is responsible for one of the most important diseases, commonly known as botrytis bunch rot or grey mould. Keeping infection under control with synthetic fungicides leads to an increased biological resistance of pathogen populations. An alternative way to synthetic products is to obtain natural fungicides by using bioactive compounds of plants. This study focuses on the antifungal properties of a new bioproduct obtained from polymeric proanthocyanidins extracted from grape seeds of ‘Fetească neagră’ variety. The bioproduct in solid state presented a total content of polyphenols of 0.625 mg GAE mg-1, a polyphenolic index of 17.40 and an antioxidant activity of 91.27% scavenged DPPH. The bioproduct with polyphenolic structure showed a moderate effect on the radial growth of fungal mycelium, at EC50 values between 11.23 and 12.15 mg mL-1. Effective antifungal activity was showed in the inhibition of spore germination, where the EC50 values varied from 1.14 to 1.47 mg mL-1. These in vitro results sustain the possibility of including the bioproduct in the category of natural fungicides for biological control against Botrytis cinerea fungus.
The current work focuses on the effect of silica and titania nanotubes and their synthesis conditions on the potential antibacterial activity. Since most investigations are oriented towards carbon nanotubes, we focused on studying the biological activity of oxide nanotubes obtained under different synthesis and different thermal treatment conditions. The antibacterial activity against Bacillus sphericus, Bacillus subtilis, Escherichia coli and Virgibacillus halodenitrificans were examined by the plate counting method. The biological activity was evaluated as dehydrogenase activity. The results revealed that titania nanotubes exhibit a higher antibacterial activity as compared with silica. This activity could be correlated with differences in the structure and morphology of these two types of nanotubes investigated.
Malolactic fermentation (MLF) or biological decrease of wine acidity is defined as the enzymatic bioconversion of malic acid in lactic acid, a process performed by lactic acid bacteria (LAB). The procedures for the isolation of new indigenous LAB strains from the red wines produced in Copou Iasi wine center (NE of Romania) undergoing spontaneous malolactic fermentation, resulted in the obtaining of 67 catalase-negative and Gram-positive LAB strains. After testing in the malolactic fermentative process, application of specific screening procedures and identification (API 50 CH), two bacterial strains belonging to the species Oenococcus oeni (strain 13-7) and Lactobacillus plantarum (strain R1-1) with high yield of malolactic bioconversion, non-producing biogenic amines, and with active extracellular enzymes related to wine aroma, were retained and characterized. Tested in synthetic medium (MRS-TJ) for 10 days, the new isolated LAB strains metabolized over 98% of the malic acid at ethanol concentrations between 10 and 14 % (v/v), low pH (>3.0), total SO2 doses up to 70 mg/L and temperatures between 15 and 35 °C, showing high potential for future use in the winemaking process as bacterial starter cultures, in order to obtain high quality wines with increased typicity.
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