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Assimilation Rate

The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Masaaki Chiwa – 1st expert on this subject based on the ideXlab platform

  • roles of hydroxyl radical generating scavenging mechanisms in pseudo polluted dew in reducing the foliar co2 Assimilation Rate and biomass production of japanese red pine pinus densiflora sieb et zucc seedlings
    Environmental and Experimental Botany, 2007
    Co-Authors: Nobutake Nakatani, Tsuyoshi Kobayashi, Masaaki Chiwa, Sachiko Akane, Hiroshi Sakugawa

    Abstract:

    Abstract Hydroxyl radical ( OH) is one of the most highly reactive of all active oxygen species. Aqueous-phase OH is photochemically geneRated in polluted dew droplets on needle surfaces of Japanese red pine ( Pinus densiflora Sieb. et Zucc., an evergreen coniferous tree) in declining pine forests. In former studies, we examined the effects of OH-generating mist solutions, which simulate polluted dew droplets, on needle ecophysiological traits of pine seedlings. Two types of solution with different OH-generating sources, i.e. the photo-Fenton reaction (H 2 O 2 -Fe-oxalate) and photolysis of HONO and NO 2 − [N(III)], had contrasting functional effects on needle gas exchange characteristics even though they had similar OH photoformation Rates. In the present study, we investigated the effects of OH-generating mist solutions containing mixed-sources of OH (photo-Fenton and N(III)) on needle gas exchange and the biomass production of potted Japanese red pine seedlings. The N(III) and H 2 O 2 concentrations of the OH-generating mist solutions were regulated to the same concentration (0, 25, 50, 75 or 100 μM, pH 5.2–5.3). Treated needles with the lowest photoformation Rate and scavenging Rate constant of OH had the smallest CO 2 Assimilation Rate ( A max ) and needle conductance ( g n ) of all treated pine seedlings. This suggests that the photoformation Rate and scavenging Rate constant do not always explain the ecophysiological disorders of pine needles subjected to OH-generating wet deposition. On the other hand, the calculated steady-state concentration of OH in the mist solutions was significantly negatively correlated with A max . In addition, pine seedlings with reduced A max showed suppressed biomass (dry weight) production. These results suggest that the OH concentration in the mist solutions is the decisive factor in explaining the negative effects of pseudo dew droplets not only on needle but also plant productivity. We propose that the deposition of polluted dew with chemical components and systems that result in a high OH concentration is one of the causes of growth decline of Japanese red pine.

  • variation in co2 Assimilation Rate induced by simulated dew waters with different sources of hydroxyl radical oh on the needle surfaces of japanese red pine pinus densiflora sieb et zucc
    Environmental Pollution, 2002
    Co-Authors: Tsuyoshi Kobayashi, N Natanani, Tsuyoshi Hirakawa, Masayo Suzuki, Takayuki Miyake, Masaaki Chiwa, T Yuhara, N Hashimoto, K Inoue, K Yamamura

    Abstract:

    Abstract The hydroxyl radical (·OH) is geneRated in polluted dew on the needle surfaces of Japanese red pine (Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of ·OH-generating N(III) (HNO2 and NO2−) and HOOH+Fe+oxalate solutions (50 and 100 μM, pH 5.1–5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 μM N(III) tended to have a greater maximum CO2 Assimilation Rate (Amax), a greater stomatal conductance (gs) and a greater needle nitrogen content (Nneedle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 μM HOOH+Fe+oxalate solution showed the smallest Amax, gs, and Nneedle, suggesting that the combination of HOOH+Fe+oxalate caused a decrease in needle productivity. The effects of HOOH+Fe+oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.

C Lu – 2nd expert on this subject based on the ideXlab platform

  • photosynthesis photosystem ii efficiency and the xanthophyll cycle in the salt adapted halophyte atriplex centralasiatica
    New Phytologist, 2003
    Co-Authors: Qingtao Lu, C Lu

    Abstract:

    Summary
    • Here, the effects of salinity (0–400 mM NaCl) on photosynthesis, photosystem II (PSII) efficiency and the xanthophyll cycle were investigated in the halophyte Atriplex centralasiatica grown under outdoor conditions.
    • Leaf sodium and chloride in leaves increased considerably whereas CO2 Assimilation Rate decreased. PSII efficiency (ΦPSII) and the efficiency of excitation energy capture by open PSII reaction centres decreased whereas nonphotochemical quenching (NPQ) increased significantly. There was no change in photochemical quenching (qP) in salt-adapted plants. Salinity induced no changes in the maximum efficiency of PSII photochemistry (Fv/Fm) measured either at midday or at predawn. However, Fv/Fm values were c. 20% lower at midday than at predawn.
    • Contents of chlorophyll (a + b), neoxanthin, lutein and β-carotene were unchanged with increasing salt concentration, but zeaxanthan increased significantly, at the expense of violaxanthin. There was a linear relationship between the de-epoxidation state of the xanthophyll cycle and ΦPSII, , and NPQ.
    • Our results suggest that A. centralasiatica shows high tolerance to both high salinity and photoinhibition and that the xanthophyll cycle played an important role in protecting photosynthetic apparatus from photoinhibitory damage. Tolerance of PSII to salinity and photoinhibition can be viewed as an important stRategy for A. centralasiatica to grow in very high saline soil during the summer season with high irradiance.

  • enhanced tolerance of photosynthesis against high temperature damage in salt adapted halophyte atriplex centralasiatica plants
    Plant Cell and Environment, 2003
    Co-Authors: C Lu

    Abstract:

    Thermotolerance of photosynthesis in salt-adapted Atriplex centralasiatica plants (100–400 mm NaCl) was evaluated in this study after detached leaves and whole plants were exposed to high temperature stress (30–48 °C) either in the dark or under high light (1200 mol m−2 s−1). In parallel with the decrease in stomatal conductance, intercellular CO2 concentration and CO2 Assimilation Rate decreased significantly with increasing salt concentration. There was no change in the maximal efficiency of PSII photochemistry (Fv/Fm) with increasing salt concentration, suggesting that there was no damage to PSII in salt-adapted plants. On the other hand, there was a striking difference in the response of PSII and CO2 Assimilation capacity to heat stress in non-salt-adapted and salt-adapted leaves. Leaves from salt-adapted plants maintained significantly higher Fv/Fm values than those from non-salt-adapted leaves at temperatures higher than 42 °C. The Fv/Fm differences between non-salt-adapted and salt-adapted plants persisted for at least 24 h following heat stress. Leaves from salt-adapted plants also maintained a higher net CO2 Assimilation Rate than those in non-salt-adapted plants at temperatures higher than 42 °C. This increased thermotolerance was independent of the degree of salinity since no significant changes in Fv/Fm and net CO2 Assimilation Rate were observed among the plants treated with different concentrations of NaCl. The increased thermotolerance of PSII induced by salinity was still evident when heat treatments were carried out under high light. Given that photosynthesis is considered to be the physiological process most sensitive to high temperature damage, increased thermotolerance of photosynthesis may be of significance since A. centralasiatica, a typical halophyte, grows in the high salinity regions in the north of China, where the temperature in the summer is often as high as 45 °C.

Tsuyoshi Kobayashi – 3rd expert on this subject based on the ideXlab platform

  • roles of hydroxyl radical generating scavenging mechanisms in pseudo polluted dew in reducing the foliar co2 Assimilation Rate and biomass production of japanese red pine pinus densiflora sieb et zucc seedlings
    Environmental and Experimental Botany, 2007
    Co-Authors: Nobutake Nakatani, Tsuyoshi Kobayashi, Masaaki Chiwa, Sachiko Akane, Hiroshi Sakugawa

    Abstract:

    Abstract Hydroxyl radical ( OH) is one of the most highly reactive of all active oxygen species. Aqueous-phase OH is photochemically geneRated in polluted dew droplets on needle surfaces of Japanese red pine ( Pinus densiflora Sieb. et Zucc., an evergreen coniferous tree) in declining pine forests. In former studies, we examined the effects of OH-generating mist solutions, which simulate polluted dew droplets, on needle ecophysiological traits of pine seedlings. Two types of solution with different OH-generating sources, i.e. the photo-Fenton reaction (H 2 O 2 -Fe-oxalate) and photolysis of HONO and NO 2 − [N(III)], had contrasting functional effects on needle gas exchange characteristics even though they had similar OH photoformation Rates. In the present study, we investigated the effects of OH-generating mist solutions containing mixed-sources of OH (photo-Fenton and N(III)) on needle gas exchange and the biomass production of potted Japanese red pine seedlings. The N(III) and H 2 O 2 concentrations of the OH-generating mist solutions were regulated to the same concentration (0, 25, 50, 75 or 100 μM, pH 5.2–5.3). Treated needles with the lowest photoformation Rate and scavenging Rate constant of OH had the smallest CO 2 Assimilation Rate ( A max ) and needle conductance ( g n ) of all treated pine seedlings. This suggests that the photoformation Rate and scavenging Rate constant do not always explain the ecophysiological disorders of pine needles subjected to OH-generating wet deposition. On the other hand, the calculated steady-state concentration of OH in the mist solutions was significantly negatively correlated with A max . In addition, pine seedlings with reduced A max showed suppressed biomass (dry weight) production. These results suggest that the OH concentration in the mist solutions is the decisive factor in explaining the negative effects of pseudo dew droplets not only on needle but also plant productivity. We propose that the deposition of polluted dew with chemical components and systems that result in a high OH concentration is one of the causes of growth decline of Japanese red pine.

  • variation in co2 Assimilation Rate induced by simulated dew waters with different sources of hydroxyl radical oh on the needle surfaces of japanese red pine pinus densiflora sieb et zucc
    Environmental Pollution, 2002
    Co-Authors: Tsuyoshi Kobayashi, N Natanani, Tsuyoshi Hirakawa, Masayo Suzuki, Takayuki Miyake, Masaaki Chiwa, T Yuhara, N Hashimoto, K Inoue, K Yamamura

    Abstract:

    Abstract The hydroxyl radical (·OH) is geneRated in polluted dew on the needle surfaces of Japanese red pine (Pinus densiflora Sieb. et Zucc.). This free radical, which is a potent oxidant, is assumed to be a cause of ecophysiological disorders of declining trees on the urban-facing side of Mt. Gokurakuji, western Japan. Mists of ·OH-generating N(III) (HNO2 and NO2−) and HOOH+Fe+oxalate solutions (50 and 100 μM, pH 5.1–5.4) simulating the dew water were applied to the foliage of pine seedlings grown in open-top chambers in the early morning. Needles treated with 100 μM N(III) tended to have a greater maximum CO2 Assimilation Rate (Amax), a greater stomatal conductance (gs) and a greater needle nitrogen content (Nneedle), suggesting that N(III) mist acts as a fertilizer rather than as a phytotoxin. On the other hand, needles treated with 100 μM HOOH+Fe+oxalate solution showed the smallest Amax, gs, and Nneedle, suggesting that the combination of HOOH+Fe+oxalate caused a decrease in needle productivity. The effects of HOOH+Fe+oxalate mist on pine needles were very similar to the symptoms of declining trees at Mt. Gokurakuji.