40 research outputs found
Developmental stage is an important factor that determines the antioxidant responses of young and old grapevine leaves under UV irradiation in a green-house.
The impact of UV irradiation was studied on photosynthesis, photosystem II photochemical
yields and antioxidant responses using green-house grown grapevine (Vitis vinifera L. cv. Chardonnay)
leaves. Supplemental UV irradiation (290-400 nm) was centred in the UV-B region, and corresponded
to 8.95 kJ m-2 d-1 global (280-400 nm) or 8.04 kJ m-2 d-1 UV-B (280-315 nm) biologically effective
dose. UV irradiation was applied daily and its effects were evaluated after 4-days. Younger (1-3 weeksold)
leaves (YL) and older (4-6 weeks-old) leaves (OL) were affected differently, UV irradiation
decreased their photochemical yields to 78% and 56%, respectively. Unlike OL, YL responded by an
increase in UV-B absorbing pigment, anthocyanin and total phenolics contents. UV irradiation
increased total antioxidant capacities in YL but not in OL. YL were also different in their ability to
increase speciıic hydroxyl radical and singlet oxygen neutralizing capacities in response to the
supplemental UV irradiation, which is reported here for the ıirst time. Our results suggest that the
ability of maintaining photosynthesis under supplemental UV is not necessarily determined by base
levels of antioxidants but rather by their inducibilities in response to the irradiation and emphasise the
importance of comparing leaves of the same age in UV studies. Correlations between various
antioxidant capacities, pigment contents and photosynthesis parameters were also examined.
However, no single element of the defence system can be picked up as decisive factor of sensitivity to
UV
Developmental stage is an important factor that determines the antioxidant responses of young and old grapevine leaves under UV irradiation in a green-house.
The impact of UV irradiation was studied on photosynthesis, photosystem II photochemical
yields and antioxidant responses using green-house grown grapevine (Vitis vinifera L. cv. Chardonnay)
leaves. Supplemental UV irradiation (290-400 nm) was centred in the UV-B region, and corresponded
to 8.95 kJ m-2 d-1 global (280-400 nm) or 8.04 kJ m-2 d-1 UV-B (280-315 nm) biologically effective
dose. UV irradiation was applied daily and its effects were evaluated after 4-days. Younger (1-3 weeksold)
leaves (YL) and older (4-6 weeks-old) leaves (OL) were affected differently, UV irradiation
decreased their photochemical yields to 78% and 56%, respectively. Unlike OL, YL responded by an
increase in UV-B absorbing pigment, anthocyanin and total phenolics contents. UV irradiation
increased total antioxidant capacities in YL but not in OL. YL were also different in their ability to
increase speciıic hydroxyl radical and singlet oxygen neutralizing capacities in response to the
supplemental UV irradiation, which is reported here for the ıirst time. Our results suggest that the
ability of maintaining photosynthesis under supplemental UV is not necessarily determined by base
levels of antioxidants but rather by their inducibilities in response to the irradiation and emphasise the
importance of comparing leaves of the same age in UV studies. Correlations between various
antioxidant capacities, pigment contents and photosynthesis parameters were also examined.
However, no single element of the defence system can be picked up as decisive factor of sensitivity to
UV
Existing antioxidant levels are more important in acclimation to supplemental UV-B irradiation than inducible ones: Studies with high light pretreated tobacco leaves
Greenhouse grown tobacco plants were exposed to supplemental ultraviolet irradiation (280-400 nm, UV-B
centered) for 6 days and changes in their photosynthesis (gas exchange and electron transport) and general and
specific antioxidant activities were measured. UV irradiation corresponded to 8.95 kJ m-2 d-1 biologically
effective dose and was supplemented to below ambient (200 μmol m-2 s-1 photon flux density) photosynthetic
photon flux density (PPFD, 400-700 nm). Two groups of plants, which were different in their leaf antioxidant
capacities due to one of them having been acclimated to high irradiance (1000 μmol m-2 s-1 PPFD) before the
UV treatment, responded differently. High light pretreated leaves lost approximately 25% of photosynthetic
activity during the UV exposure and showed no change either in the amounts of UV-absorbing pigments or
antioxidant levels. On the other hand, leaves which were exposed to UV irradiation without the preceding high
light acclimation had 60% lower photosynthesis by the end of the treatment, and increased antioxidant
activities. Our results emphasize the importance of base antioxidant levels over inducible pools in leaf responses
to low doses of UV irradiation and may also contribute to hypotheses on acclimation under field conditions
Testing drought tolerance of wheat by a complex stress diagnostic system installed in greenhouse
Drought is one of the most important abiotic stress factors and depending on the season it can seriously limit wheat production. Breeding for drought tolerance is becoming a more and more important challenge in case of crop plants, notably in wheat. The breeding process includes the characterization of the basic breeding materials in aspect of performance under well-watered and drought stressed conditions. In our experiments we set up a complex stress diagnostic system in the greenhouse of the Cereal Research Non-profit Company where we could analyze the responses of different winter and spring wheat cultivars to drought. Wheat plants were grown under ideal water regime (watering to 60% of the 100% soil water capacity) and under drought stress conditions (watering to 20% of the 100% soil water capacity). The effect of water withholding on plant growing was tracked by a digital imaging system on the basis of number of plant pixels. After harvesting, plant heights, spike lengths, grain numbers and total grain weights were measured and values of well-watered and stressed plants were compared. Here the measured parameters of two drought tolerant (Sardari, GK 11-05) and two drought sensitive (Kärtner Früh, Jing 411) wheat genotypes are presented to prove the competence of our system in characterizing drought tolerance of wheat plants
Antioxidant defence in UV-irradiated tobacco leaves is centred on hydrogen-peroxide neutralization
Greenhouse grown tobacco (Nicotiana tabacum L. cv. Petit Havana) plants were exposed to supplemental UV centred at 318 nm and corresponding to 13.6 kJ m-2 d-1 biologically effective UV-B (280-315 nm) radiation. After 6 days this treatment decreased photosynthesis by 30%. Leaves responded by a large increase in UV-absorbing pigment content and antioxidant capacities. UV-stimulated defence against ROS was strongest in chloroplasts, since activities of plastid enzymes FeSOD and APX had larger relative increases than other, non-plastid specific SODs or peroxidases. In addition, non-enzymatic defence against hydroxyl radicals was doubled in UV treated leaves as compared to controls. In UV treated leaves, the extent of activation of ROS neutralizing capacities followed a peroxidases > hydroxyl-radical neutralization > SOD order. These results suggest that highly effective hydrogen peroxide neutralization is the focal point of surviving UV-inducible oxidative stress and argue against a direct signalling role of hydrogen peroxide in maintaining adaptation to UV, at least in laboratory experiments
Antioxidant defence in UV-irradiated tobacco leaves is centred on hydrogen-peroxide neutralization
Greenhouse grown tobacco (Nicotiana tabacum L. cv. Petit Havana) plants were exposed to supplemental UV centred at 318 nm and corresponding to 13.6 kJ m-2 d-1 biologically effective UV-B (280-315 nm) radiation. After 6 days this treatment decreased photosynthesis by 30%. Leaves responded by a large increase in UV-absorbing pigment content and antioxidant capacities. UV-stimulated defence against ROS was strongest in chloroplasts, since activities of plastid enzymes FeSOD and APX had larger relative increases than other, non-plastid specific SODs or peroxidases. In addition, non-enzymatic defence against hydroxyl radicals was doubled in UV treated leaves as compared to controls. In UV treated leaves, the extent of activation of ROS neutralizing capacities followed a peroxidases > hydroxyl-radical neutralization > SOD order. These results suggest that highly effective hydrogen peroxide neutralization is the focal point of surviving UV-inducible oxidative stress and argue against a direct signalling role of hydrogen peroxide in maintaining adaptation to UV, at least in laboratory experiments