Photosynthetic UV-B Response of Beech (Fagus sylvatica L.) Saplings (original) (raw)
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Acta Biol. …, 2005
Responses of beech seedlings to supplemental UV-B radiation were investigated during three consecutive seasons, in three repeated experiments. Our attention was paid on the alteration of the photosynthetic pigment composition -especially on the xanthophyll cycle pigments -chlorophyll fluorescence parameters, furthermore the accumulation of UV-B absorbing compounds in leaves, the specific leaf mass and leaf water content. The enhanced UV-B radiation generally affected significantly neither photochemical efficiency of PSII, nor photosynthetic pigment composition. UV-B radiation induced some protective mechanisms, thus VAZ-pool increased in beech leaves in every experiment, parallel with the enhancement of non-photochemical quenching. Amount of UV-B absorbing compounds in leaves increased under enhanced UV-B, but no significant changes were observed in the specific leaf mass. Sensitivity of plants to UV-B is largely influenced by other environmental factors and experimental conditions. Acta Biol Szeged 49(1-2):151-153 (2005) KEY WORDS UV-B photosynthetic pigments xanthophylls cycle UV-B absorbing compounds photochemical activity
Agricultural and Forest Meteorology, 2009
szö rményi ú t 128, H-4032, Hungary a g r i c u l t u r a l a n d f o r e s t m e t e o r o l o g y 1 4 9 ( 2 0 0 9 ) 7 4 5 -7 5 5 Specific leaf area UV-B absorbing compounds UV-B radiation Xanthophyll cycle a b s t r a c t This study describes the physiological responses of European beech saplings to varying levels of UV-B radiation under natural environmental conditions and in an outdoor pot experiment. In the field experiment, saplings at a forest site regenerating naturally in a clear-cut area were subjected to UV-B exclusion (UV-B exc ). In the outdoor pot experiment saplings were subjected to both exclusion of UV-B and enhanced UV-B (UV-B enh ). Three months after the start of the treatments, plants were monitored for photosynthetic pigment composition, chlorophyll fluorescence parameters, specific leaf mass (SLM, dry matter per unit leaf area) and UV-B absorbing pigments (flavonoids). In the forest site the leaves which developed under UV-B exclusion had significantly higher chlorophyll and water contents than under ambient UV-B (UV-B amb ). Both the total pool size of xanthophyll cycle pigments (violaxanthin + antheraxanthin + zeaxanthin: VAZ-pool) and the de-epoxidation state (DEEPS) of these pigments and the flavonoid content and specific leaf mass were significantly lower at midday under UV-B exc . UV-B exclusion moderated the changes in several leaf traits between morning and midday. In the pot experiment UV-B exc caused smaller, but significant, increase in chlorophyll content and decrease in flavonoid content as compared to UV-B amb than in forest site experiment. UV-B enh resulted in activation of photoprotective mechanisms (significant increases of total carotenoid content, VAZ-pool, DEEPS, flavonoid accumulation), but significantly lowered the concentration of chlorophylls and water content, while it slightly increased the Chl_a/ b ratio as compared to the UV-B amb . Larger midday reductions of potential photochemical activity of PSII assessed as F v /F m , ratio of variable chlorophyll fluorescence (F v , difference between maximum (F m ) and ground fluorescence F 0 ) to maximum fluorescence (F m ) in darkadapted leaves and leaf water content occurred under UV-B enh than under UV-B amb and (I. Mé szá ros).
Agricultural and Forest Meteorology, 2009
szö rményi ú t 128, H-4032, Hungary a g r i c u l t u r a l a n d f o r e s t m e t e o r o l o g y 1 4 9 ( 2 0 0 9 ) 7 4 5 -7 5 5 Specific leaf area UV-B absorbing compounds UV-B radiation Xanthophyll cycle a b s t r a c t This study describes the physiological responses of European beech saplings to varying levels of UV-B radiation under natural environmental conditions and in an outdoor pot experiment. In the field experiment, saplings at a forest site regenerating naturally in a clear-cut area were subjected to UV-B exclusion (UV-B exc ). In the outdoor pot experiment saplings were subjected to both exclusion of UV-B and enhanced UV-B (UV-B enh ). Three months after the start of the treatments, plants were monitored for photosynthetic pigment composition, chlorophyll fluorescence parameters, specific leaf mass (SLM, dry matter per unit leaf area) and UV-B absorbing pigments (flavonoids). In the forest site the leaves which developed under UV-B exclusion had significantly higher chlorophyll and water contents than under ambient UV-B (UV-B amb ). Both the total pool size of xanthophyll cycle pigments (violaxanthin + antheraxanthin + zeaxanthin: VAZ-pool) and the de-epoxidation state (DEEPS) of these pigments and the flavonoid content and specific leaf mass were significantly lower at midday under UV-B exc . UV-B exclusion moderated the changes in several leaf traits between morning and midday. In the pot experiment UV-B exc caused smaller, but significant, increase in chlorophyll content and decrease in flavonoid content as compared to UV-B amb than in forest site experiment. UV-B enh resulted in activation of photoprotective mechanisms (significant increases of total carotenoid content, VAZ-pool, DEEPS, flavonoid accumulation), but significantly lowered the concentration of chlorophylls and water content, while it slightly increased the Chl_a/ b ratio as compared to the UV-B amb . Larger midday reductions of potential photochemical activity of PSII assessed as F v /F m , ratio of variable chlorophyll fluorescence (F v , difference between maximum (F m ) and ground fluorescence F 0 ) to maximum fluorescence (F m ) in darkadapted leaves and leaf water content occurred under UV-B enh than under UV-B amb and (I. Mé szá ros).
Acta Biologica …, 2005
Responses of beech seedlings to supplemental UV-B radiation were investigated during three consecutive seasons, in three repeated experiments. Our attention was paid on the alteration of the photosynthetic pigment composition -especially on the xanthophyll cycle pigments -chlorophyll fluorescence parameters, furthermore the accumulation of UV-B absorbing compounds in leaves, the specific leaf mass and leaf water content. The enhanced UV-B radiation generally affected significantly neither photochemical efficiency of PSII, nor photosynthetic pigment composition. UV-B radiation induced some protective mechanisms, thus VAZ-pool increased in beech leaves in every experiment, parallel with the enhancement of non-photochemical quenching. Amount of UV-B absorbing compounds in leaves increased under enhanced UV-B, but no significant changes were observed in the specific leaf mass. Sensitivity of plants to UV-B is largely influenced by other environmental factors and experimental conditions. Acta Biol Szeged 49(1-2):151-153 (2005) KEY WORDS UV-B photosynthetic pigments xanthophylls cycle UV-B absorbing compounds photochemical activity
Agricultural and Forest Meteorology, 2003
Quantitative changes in foliar chemistry in response to UV-B radiation are frequently reported but less is known about the qualitative changes in putative UV-screening compounds. It has also not been conclusively shown whether qualitative differences in screening compounds or differences in localization patterns influence the sensitivity of plants to damage from UV-B radiation and there is some question as to whether differences in the amounts of soluble screening compounds correlate with physiological sensitivity to UV-B radiation. This study represents the first part of a multiple-year study designed to answer the above questions. In this study we evaluated whether differences in soluble UV-screening compounds were linked with possible effects on gas exchange and photosynthetic carbon assimilation. Branches of mature trees of sweet gum (Liquidambar styraciflua), tulip poplar (Liriodendron tulipifera) and red maple (Acer rubrum) were exposed to supplemental levels of UV-B radiation over three growing seasons. Controls for UV-A were also measured by exposing branches to supplemental UV-A only and additional branches not irradiated were also used for controls. These species demonstrated differing levels of screening compounds with poplar being the most responsive in terms of epidermal accumulation of phenolics. These were separately identified as flavonols, chlorogenic acid and hydroxycinnamates (HCAs). Red maple had the highest levels of constitutive UV-absorbing compounds but these showed little response to supplemental UV-B radiation. Leaf area was marginally influenced by UV exposure level with both UV-A and UV-B tending to reduce leaf area in red maple and poplar and increase it in sweet gum, when averaged over the 3-year period. Assimilation was generally not reduced by UV-B radiation in these species and was enhanced in red maple by both UV-B and UV-A and by UV-A in sweet gum. These findings are consistent with a hypothesis that epidermal attenuation of UV-B would only be reduced in poplar, which accumulated the additional epidermal screening compounds. It is possible that photosynthetic efficiency was enhanced in red maple by the increased absorption of blue light within the mesophyll due to elevated levels of HCAs. Stomatal conductance was generally reduced and this led to an increase in water use efficiency (WUE) in red maple and poplar. Since few detrimental effects of supplemental UV-B were observed, these results suggest that these tree species utilized a range of UV-screening compounds and deposition patterns to achieve UV-B tolerance and further, that subtle responses to UV-B could have ecological significance in the absence of reduced productivity or photosynthetic efficiency.
Acta Physiologiae Plantarum, 1999
The effect of UV-B on the photosynthetic apparatus of conife> ous trees: Picea abies (L) Karst~, Picea pzmge,s (Engehn.), Pmus sytvestris (L.), Pimts cerebra (L.) and Abies albo (Mill.) was investigated. Three and four-year-old plantlets coming from different Iatitudes, longitudes and altitudes were used. The experiment was carried out in greenhouse. Two doses of ultraviolet-B irradiation were applied: control = 0, tow dose = 2 1 11.32 and high dose = 22.64 kJ-m-. d UV-B}m (biologically effective irradiance of UV-B). Measurements of chlorophyll fluorescence, gas exchange, chlorophyll and flavonoids content were carried out. Response of forest trees to an increased UV-B radiation depends on species, location of place of pantalets collecting and UV-B dose. Pinus cerebra, Picea abies and Pinus sylvestris from high altitude (1000 m a.s.l.) were less sensi6ve to UV-B than these from plain location. The altitude determined adaptation of forest coniferous trees to an enhanced UV-B radiation much more than the latitudinal gradient. Permanent discoloration was observed only on the young needles of the fir plantlets that were grown in light limiting conditions. Photosynthetic parameters were af fected by the UV-B radiation. Both maximal and the steady state fluorescence of chlorophyll were reduced as a conse
Antioxidant system response on action of UVB radiation on plant systems
2015
The plants’ development process is regulated by genetic and environmental factors, which affect the biosynthesis, metabolism, transport and signaling pathway of the auxins. The phytohormones play a complex role, exerting direct effects – which influence the cellular division or growth – or indirect effects – interacting with other molecules or phytohormones. In dicotyledonous plants, in the absence of light, the stalks elongate and the leaves remain small, sometimes being reduced to scales, whilst in monocotyledonous plants the stalks remain short and the leaves are elongated. The low light intensity causes the discoloring of the etiolated plants, which lose their green color and turn to a pale yellow color, because the biosynthesis of chlorophyll is favored stimulated by light. The light’s action is positively correlated with that of the temperature and the CO2 concentration.
Plant Science, 2011
The effects of ultraviolet-B (UV-B: 280-320 nm) radiation on the photosynthetic pigments, primary photochemical reactions of thylakoids and the rate of carbon assimilation (P n) in the cotyledons of clusterbean (Cyamopsis tetragonoloba) seedlings have been examined. The radiation induces an imbalance between the energy absorbed through the photophysical process of photosystem (PS) II and the energy consumed for carbon assimilation. Decline in the primary photochemistry of PS II induced by UV-B in the background of relatively stable P n , has been implicated in the creation of the energy imbalance. The radiation induced damage of PS II hinders the flow of electron from Q A to Q B resulting in a loss in the redox homeostasis between the Q A to Q B leading to an accumulation of Q A −. The accumulation of Q A − generates an excitation pressure that diminishes the PS II-mediated O 2 evolution, maximal photochemical potential (F v /F m) and PS II quantum yield (˚P S II). While UV-B radiation inactivates the carotenoid-mediated protective mechanisms, the accumulation of flavonoids seems to have a small role in protecting the photosynthetic apparatus from UV-B onslaught. The failure of protective mechanisms makes PS II further vulnerable to the radiation and facilitates the accumulation of malondialdehyde (MDA) indicating the involvement of reactive oxygen species (ROS) metabolism in UV-B-induced damage of photosynthetic apparatus of clusterbean cotyledons.
Journal of plant physiology, 2003
The effect of acclimation to high irradiance stress (HIS, 250 W m-2) in wheat leaves grown under three different irradiances was investigated by HPLC analyses of pigments, chlorophyll a fluorescence parameters and photochemical activities of chloroplasts. Significant loss of β-carotene was observed compared to the xanthophylls in all three types of seedlings exposed to HIS. However, the effect of HIS on neoxanthin and lutein contents was not significant. The loss of partial electron transport (Asc-DCPIP to MV, PS I activity) was less than the whole chain (H 2 O to MV) and PS II activity (H 2 O to DCPIP) suggesting that PS I is less susceptible to HIS compared to PS II. The percent of reductions in Fv/Fm and Φ PS II were less in plants grown under high irradiance (HI-1, 30 W m-2 and HI-2, 45 W m-2) compared to those grown under moderate irradiance (MI, 15 W m-2). On the other hand, the percent of NPQ increased more in the leaves of HI plants compared to the leaves of MI when exposed to HIS which suggests a more efficient non-radiative dissipation of excess excitation energy in HI plants compared to MI. These observations suggest that plants grown under relatively high irradiance are better adapted to HIS condition.