FOTOSISTEMA I Y II PDF

fotosistemas i y ii pdf file. Quote. Postby Just» Tue Aug 28, am. Looking for fotosistemas i y ii pdf file. Will be grateful for any help! Top. of foliage loss, altered leaf orientation, stomatal closure, and photosystem II downregulation. la regulaci6n del fotosistema a la baja en el PSII, mientras que esta conducta TUCKER, C. J., I. Y. FUNG, C. D. KEELING, AND R. H. GAMMON. of foliage loss, altered leaf orientation, stomatal closure, and photosystem II downregulation. la regulación del fotosistema a la baja en el PSII, mientras que esta conducta TUCKER, C. J., I. Y. FUNG, C. D. KEELING, AND R. H. GAMMON.

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May 12, ; acepted: The chlorophyll content and fluorescence were determined in five-year-old grape plants Vitis vinifera L. Chardonnay that were subjected to early partial defoliation, in Villa de Leyva, Colombia. Every two weeks, one of every two recently-emerged leaves was removed from the non-control plants. The determination of total chlorophyll content was carried out on six leaves per plant using a CCM Plus chlorophyll meter, while chlorophyll fluorescence measurements were taken with one dark-adapted leaf per plant using a Junior-PAM fluorometer.

The chlorophyll concentration index showed higher values in the defoliated plants. There were no significant differences for the values of F mF t and F v. It is evident that a reduction in leaf area modifies the partitioning of excitation energy destined for photochemical and non-photochemical processes, thus directly influencing the photosynthetic process of the plants evaluated. Como material vegetal se utilizaron plantas de Vitis vinifera L.

No se encontraron diferencias significativas para los valores de F mF t y F v. Viticulture is a recent development in Colombia as compared to other agricultural sectors such as coffee or bananas. Nevertheless, in the past two decades, this crop has been expanding and, in particular, improving in quality. Total production of wine grapes in Colombia is as yet relatively low, but it is clear that the way to compete with producers such as Argentina or Chile, which supply a large part of the domestic and international markets, is by gaining recognition locally and abroad in terms of wine quality.

Colombia has 2, ha of vineyards, producing close to 38, t of grapes per year, of which only 0. Accordingly, total production in Colombia is well below that of these countries. Chile produces close to 2, t of grapes, while Argentina leads production on the continent with 2, t Faostat, In this part of the country, it is possible, with good crop management, to obtain two harvests per year, thanks to the local agroclimatic conditions Almanza et al.

Final production of a crop is affected by the conditions in which it was grown. Plants subjected to any type of stress show morpho-physiological responses that affect quantity and quality of the final product Prins and Verkaar, The type of wine, its quality, its smell, its color, and its flavor depend directly on the content of secondary metabolites in the berry, which are in turn the result of the combination of microclimate, grape variety, soil properties, and nutritional status of the plant.

These four factors frame the potential yield of the grapevine in terms of quantity and quality.

Nevertheless, human actions partially or completely modify the behavior of each factor, thus determining the terroir of the vine’s development Vaudour, ; Quijano, Furthermore, it must be noted that secondary metabolites do not only determine wine quality, but they also play an important role as antioxidants that benefit human health by protecting against oxidative stress caused by highly-reactive free radicals in the body Quijano, One of the most influential human modifications of fruit composition in grapevines is early partial defoliation.

This procedure fotositema utilized in the majority of wine-producing countries to increase the concentration of various compounds in the fruits, such as phenols, thus giving new characteristics of flavor and aroma to the wine Kemp et fotosistma.

Plants present different reactions to defoliation. Leaf removal creates a negative effect by reducing growth rate, but plants possess a tolerance threshold to defoliation McNaughton, But, it is possible that some plants initiate a recovery period after defoliation so that the end effect is negligible Prins et al.

The quantification of plant stress in this case caused by defoliation is a useful fotosixtema in plant ecophysiology, with which potential photosynthetic behavior and dissipation of absorbed energy can be determined. Chlorophyll fluorescence is a widely-used technique for tracking this phenomenon, both in cultivated and wild plants. Hence, the characterization of PSII behavior is an important tool for researchers to evaluate photosynthetic activity in plants.

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The distribution of energy in these three processes occurs simultaneously, so that an increase in efficiency of one process results in the reduction of the other two. Hence, by measuring chlorophyll fluorescence, it is possible to obtain information about the photochemical ik and thermal dissipation of absorbed energy Maxwell and Johnson, The present study therefore aimed to evaluate the influence of early partial defoliation on chlorophyll fluorescence in grape plants Vitis vinifera L.

Chardonnay grown in the highland tropics. The trial was performed on five-year-old grape plants of the Chardonnay variety, planted in a trellis system with distances of 2.

Every 15 days, between the initial pruning and days after said pruning, half of the new leaves were removed from each plant in the defoliation treatment group.

An actinic pulse of light at 1, m mol m -2 s -1 was used. On the other hand, Y NPQ determines the fraction of excitation energy dissipated as heat through photo-protection mechanisms, while the Y NO factor shows the total non-photochemical losses, other than heat.

The chlorophyll concentration index CCI was determined. The value of minimum fluorescence increased by Partial defoliation induces changes in leaf arrangement and thus light exposure. When leaf area is reduced, photon flow increases towards the plant’s remaining leaves, which can increase leaf temperature and saturate reaction centers due to an excess of light.

It is possible for F o values to increase when there is a slowdown in excitation energy transfer from the light collection system to the reaction center Baker and Rosenqvist,or when there is some type of damage in the PSII reaction centers themselves Vieira et al.

With regards to defoliation, in studies undertaken by Retuerto et al. This was perhaps due to the fact that herbivorous defoliation induces a quicker response from the plant as a result of the action of insect mandibles on the leaves, thus creating a compensatory response.

On the other hand, Layne and Flore reported a reduction in minimum fluorescence values measured seven days after defoliation of Prunus cerasus plants exposed to 14 h of daily light. This was directly attributed to this species’ tolerance to high radiation, as non-defoliated plants of the same species only showed photoinhibition when they were exposed to 24 h of continuous illumination. Contrary to the findings of the present experiment, it is possible for an increase in photon flow to trigger damage in the D1 protein of PSII, which causes a notable reduction in F o in tree species exposed to increased radiation, due principally to chronic photoinhibition of PSII Dias and Marenco, This ratio decreased 7.

With regards to this result, Otronen and Rosenlund found no significant difference in maximum photochemical quantum yield of PSII when they subjected Pinus sylvestris plants to different levels of defoliation. In the same respect, maximum photochemical efficiency of PSII was not affected by either natural or experimental defoliation in Triticum aestivum plants Macedo et al.

Nevertheless, in the present study, a reduction was observed in this value, which indicates that defoliation induces a higher degree of stress in Chardonnay grape plants, perhaps due to higher exposure of the remaining leaves to direct radiation, which elevates leaf temperature and affects photosynthesis mechanisms.

When Ilex aquifolium plants were subjected to a reduction in leaf area, the behavior of maximum quantum yield fluctuated according to the type of defoliation. A different result was obtained in Prunus cerasus, in which the maximum quantum efficiency of PSII, measured seven days after the defoliation event, increased slightly with respect to non-defoliated plants Layne and Flore,possibly due to compensatory photosynthesis, which does not occur immediately but rather has a slow rate of recovery.

Karukstis stated that reductions in maximum quantum efficiency of PSII occur simultaneously with a reduction in net assimilation of CO2, and if this reduction is shown in continuously illuminated leaves, it is possible that the effect is due to photoinhibition. This may explain the results of the present study, because a reduction in leaf area leads to higher illumination of remaining leaves, which, combined with the high radiation typical of the study area between 1, and 1, m mol m -2 s -1could have caused a slight photo-inhibitory phenomenon in the leaves of the grape plants being studied.

In the same way, Gamon and Pearcy confirmed that the ratio of variable fluorescence to maximum fluorescence in grape leaves decreases when plants are grown under high-light conditions, but not when they are grown under reduced light intensity. Nevertheless, the photochemical quenching coefficient qP was reduced by Furthermore, Weis and Berry found that the photochemical quenching coefficient qP in different species was close to 1 in conditions of low light intensity, but diminished to 0.

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This explains the behavior of the defoliated plants in the present study, since a higher exposure to direct radiation after a reduction in leaf number increases photon flow and leaf temperature and finally triggers a failure of the photosynthetic system.

Fotosistema – Viquipèdia, l’enciclopèdia lliure

Figure 3 shows the partitioning of excitation energy in light-adapted plants. Energy dissipation as heat Y NPQ showed no significant difference between fotosisgema. This agrees with the results of the present study, in which the value of Y II decreased in the defoliated plants at the same time as photochemical quenching and maximum quantum yield of PSII.

On the other hand, the differences in Y NO could be related to the photoinhibition of PSII, because this parameter is related to non-photochemical losses other than heat Y NPQwhich showed no significant differences.

Light intensity was a fundamental dotosistema in the grape plants evaluated in the present study, as reduction in leaf area caused a higher exposure of the plants’ remaining leaves, which also contributed to a rise in temperature. The average value for electron transport rate decreased The amount of UV radiation fotosietema the leaves of the defoliated plants would have been higher than in the control plants. UV-B also causes respiration to increase, as well as the demand for resources to protect and repair photosynthesis mechanisms, both of which rob efficiency from photosynthetic electron transport Gwynn-Jones, Total chlorophyll concentration in the evaluated plants, expressed as CCI chlorophyll content indexis shown in Figure 5.

The average value registered for the defoliated plants was 9. Leaves of defoliated plants are generally fotosiwtema to higher light intensity and, frequently, a modification of light quality, both of which influence the development of fotoxistema capacity Richards, In this sense, it is possible that the grape plants of the present study modified their photosynthetic capacity in response to defoliation, raising total chlorophyll content Richards, or diminishing the senescence rate of the remaining leaves Hunter and Visser, Though changes ftoosistema chlorophyll content are related to photosynthesis, chlorophyll concentration is not always directly proportional to a plant’s photosynthesis fotosistma.

This is because the remaining leaves in defoliated plants lengthen their useful life to compensate for lost leaf area, which modifies the chemical composition of these leaves in the form of increased sugar and lower concentrations of amino acids and organic acids Hunter and Visser,which affect the leaf photosynthetic capacity.

This is in fotosisetma with the data obtained in the present study, because the ETR in leaves of the defoliated plants was lower than in the control plants, though chlorophyll content was lower in the latter.

Fotosistema

Thus, dotosistema was no positive relation found between chlorophyll content of leaves and their photosynthetic efficiency. Early partial defoliation induced an increase in stress in the grape plants g. Chlorophyll content was higher in leaves of the defoliated plants, but this did not correlate with a higher photosynthetic efficiency. It is evident that a reduction in leaf area modifies the partitioning of excitation energy destined for photochemical and non-photochemical processes; and thus, directly influenced the photosynthetic process of the plants evaluated.

The authors presume that the reduction in these indicators of photochemical function was related to oversaturation of light, leading to photoinhibition, and perhaps damage from high UV radiation in the remaining leaves on the defoliated plants. Physicochemical characterization of ‘Pinot Noir’ grapevine Vitis vinifera L. Applications of chlorophyll fluorescence can improve crop production strategies: Journal Experimental Botany 55 DNA damage and repair in plants.

Food and Agriculture Organization of the United Nations. Photoinhibition in Vitis californica: Plant Cell Environment 13 3: The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence. Biochimica et Biophysica Acta. General Subjects 1: Concentration of photosynthetic pigments and chlorophyll fluorescence of Mahogany fotossitema Tonka bean under two light environments.

Revista Brasileira de Fisiologia Vegetal 13 2: Short-term impacts of enhanced UV-B radiation on photo-assimilate allocation and metabolism: Junior-Pam Chlorophyll Fluorometer, operator’s guide. Fotosisteja effect of partial defoliation, leaf position and developmental stage of the vine on leaf chlorophyll concentration in relation to the photosynthetic activity and light intensity in the canopy of Vitis vinifera L.

South Fotodistema Journal of Enology and Viticulture 10 2: Higher plants and UV-B radiation: Trends in Plant Science 3 fotosiatema