Tsumugu Totsuka

The individual and combined effects of ozone and simulated acid rain on growth, gas exchange rate and water-use efficiency of Pinus armandi Franch.

The seedlings of Pinus armandi Franch. were exposed to ozone (O(3)) at 300 ppb for 8 h a day, 6 days a week, and simulated acid rain of pH 3.0 or 2.3, 6 times a week, alone or in combination, for 14 weeks from 15 June to 20 September 1993. The control seedlings were exposed to charcoal-filtered air and simulated rain of pH 6.8 during the same period. Significant interactive effects of O(3) and simulated acid rain on whole plant net photosynthetic rate were observed, but not on other determined parameters. The exposure of the seedlings to O(3) caused the reductions in the dry weight growth, root dry weight relative to the whole plant dry weight, net photosynthetic rate, transpiration rate in light, water-use efficiency and root respiration activity, and increases in shoot/root ratio, and leaf dry weight relative to the whole plant dry weight without an appearance of acute visible foliar injury, but did not affect the dark respiration rate and transpiration rate in the darkness. The decreased net photosynthetic rate was considered to be the major cause for the growth reduction of the seedlings exposed to O(3). On the other hand, the exposure of the seedlings to simulated acid rain reduced the net photosynthetic rate per unit chlorophyll a + b content, but did not induce the significant change in other determined parameters.

Carbon dioxide evolution of an upland rice and barley, double cropping field in central Japan

Carbon dioxide evolution rates from a double cropping, upland rice and barley field were determined in central Japan from June 1992 to May 1994, and regression models were developed to predict soil respiration rate. Diurnal patterns of hourly soil respiration rates (SRh) showed a similar trend with those of soil surface temperatures. Daily soil respiration rate (SRd) obtained by integrating SRh varied from 0.3 to 15.6 g CO2 m−2 for the 2 years. In the summer cropping period, SRd was positively correlated with daily mean soil surface temperature and negatively correlated with volumetric water content in soil. Moreover, this relationship was able to be expressed as a multiple-factor model with an Adj-R2 of 0.925. On the other hand, in the winter cropping period, SRd was able to be represented by a single factor model using soil surface temperature with an Adj-R2 of 0.854. Based on these relationships, seasonal changes in soil respiration rate were estimated. Total soil respiration rates in 1992 and 1993 estimated for the summer cropping period were 1260 g CO2 m−2 and 1094 g CO2 m−2, and for the winter cropping period 624 g CO2 m−2 and 676 g CO2 m−2, respectively. It was considered that the lower values during the summer cropping period in 1993 depended on lower soil surface temperature and higher soil water content.

Effects of O3 and soil acidification, alone and in combination, on growth, gas exchange rate and chlorophyll content of red pine seedlings

One-year-old seedlings of red pine (Pinus densiflora Sieb. and Zucc.) were grown in typic red-yellow forest soil (Typic Hapludults) artificially adjusted to pH (H2O) 3.15, 3.60 or 3.90 by adding H2SO4 solution to the soil (pH 4.60), and exposed to ozone (03) at 150±10 ppb (nl·L−1) for 8 h a day, 6 days a week, for 16 weeks from June 5 to October 5, 1994. The control seedlings were exposed to charcoal-filtered air (CF) and grown in the soil without the additional supply of H+ as H2SO4 solution during the same period.No significant interactive effects of O3 and soil acidification were observed for the determined seedling parameters in this study. However, O3 caused a reduction in needle dry weight, net photosynthetic rate and chlorophyll contents in the needle tip or on whole-needle weight basis, and stimulated rates of dark respiration and photorespiration. There were no significant effects of O3 on chlorophyll contents in the needle middle and basal parts, transpiration rate or water use efficiency (WUE). On the other hand, the seedlings grown in the soil adjusted to pH 3.60 or 3.90 showed a reduction in needle dry weight, net photosynthetic rate, chlorophyll contents in all the needle parts and WUE, and an increase in the rates of dark respiration and photorespiration. The transpiration rate of the seedlings was not significantly affected by soil acidification. All the seedlings grown in the soil adjusted to pH 3.15 died during the first 4 weeks. Soil and needle analysis suggested that high concentrations of Al and low Ca/Al ratios in the acidified soil were stressors.

The individual and combined effects of ozone and simulated acid rain on chlorophyll contents, carbon allocation and biomass accumulation of Armand pine seedlings

The seedlings of armand pine (Pinus armand Franch.) were applied to exposure, alone or in combination, to charcoal filtered air (CF) or ozone (O3) at 300±15 nl/l(ppb) for 8 h a day, 6 days a week, and simulated rain of pH 6.8, 3.0 or 2.3, six times a week, alone and in combination, for 14 weeks from June 15 to September 20, 1993. No significant interactive effects of O3 and simulated acid rain were observed on chlorophyll contents, carbon allocation and biomass accumulation of the seedlings in the present study. The O3 caused reductions in biomass accumulation of whole-plant and below-ground parts, but not that of above-ground parts without an acute visible foliar injury. At the same time, the O3 reduced R/S ratio, but raised F/C ratio. Therefore, O3 also altered carbon allocation pattern. On the other hand, chlorophyll contents were increased by simulated acid rain, but other determined parameters were not altered.

Effects of NO2 and O3 exposure alone or in combination on kidney bean plants: amino acid content and composition

The effects of NO2 and O3 exposure alone or in combination were investigated with respect to the amino acid content and composition in kidney bean. The short-term exposure (up to 8 h) to NO2 at a concentration of 4.0 ppm alone or in combination with O3 at a concentration of 0.4 ppm induced a rapid increase in the total amino acid content among which glutamine accounted for most of the part. Total amino acid content was also increased by O3 exposure at 0.4 ppm after 2 hours’ lag period. Ammonium level became higher in the case of combined exposure to NO2 and O3, while it remained constant in the case of exposure to NO2 and O3 alone. When the exposure period was extended to 2 to 7 days (long-term exposure), the increase in the content of the total amino acids was observed in most of treatments. Roots of the plants exposed to various concentrations of NO2 and O3 showed the most remarkable increase in the content of total amino acids. Asparagine, in place of glutamine, became a major amino acid. The percentag...

Differences in ability of NO2 absorption in various broad-leaved tree species.

Absorption of nitrogen dioxide (NO(2)) by various broad-leaved tree species was determined by the (15)N dilution method. The tree seedlings were continuously exposed to 0.3 ppm (microl litre(-1)) NO(2) or the mixture of 0.3 ppm NO(2) and 0.1 ppm O(3) for 30 days. The total amount of NO(2)-nitrogen absorbed by a seedling during the 30-day exposure period primarily depended on the size of the seedling. Among the tested tree species, three cultivars of Populus showed the highest rate of NO(2) absorption per unit leaf area, reaching as much as 0.3 mg N per dm(2) per day. The absorption rates for Populus cultivars were more than four times greater than those for Viburnum or Cinnamomum which had the lowest rate. A highly significant correlation was recognised between the rate of NO(2) absorption and the stomatal conductance among the species. Three cultivars of Populus which had the highest rates of NO(2) absorption were most susceptible to the mixture of NO(2) and O(3). On the contrary, Cinnamomum, Viburnum and Quercus, which showed the lowest rate of NO(2) absorption, were very tolerant to the mixed gas. These results indicate that the species difference in susceptibility to the mixture of NO(2) and O(3) was mainly determined by the difference in rate of absorption of these gases. Exposure to NO(2) alone had no detrimental effect on the tested tree species.

Major activities of acid deposition monitoring network in East Asia (EANET) and related studies

In order to act against acid deposition problems in East Asian regions, the Acid Deposition Monitoring Network in East Asia (EANET) was established on the decision at the First Intergovernmental Meeting in 1998 among participating countries including China, Indonesia, Japan, Malaysia, Mongolia, Philippines, Republic of Korea, Russia, Thailand and Viet Nam. Based on the decision, the preparatory phase activities of EANET were started from 1998, and finished successfully in 2000. From January 2001, the regular phase activities were started. Major activities of EANET are, 1) to implement the national monitoring of acid deposition, 2) to develop and implement the QA/QC (quality assurance/quality control) programs, 3) to develop and implement training programs, etc. The acid deposition monitoring covers four environmental media; wet deposition, dry deposition, soil and vegetation, and inland aquatic environment.

Concentrations and depositions of SO2, SO42− etc. in a Chongqing suburban forested area

During the period from 25 May 1991 to 30 May 1992 the atmospheric concentrations and depositions of oxides of sulfur were continuously measured in a suburban masson pine forest which is currently experiencing severe dieback, in Chongqing, China. The annual mean concentrations of SO2 and particulate SO42− were 220 μ g/m3 (77 ppbv) and 32 μ g/m3 respectively. The atmospheric concentrations of these sulfur compounds were high in late autumn and winter. The annual wet and dry depositions of sulfur to the forest as measured by throughfall and stemflow were 93.1 and 46.6 kgSha−1a−1 respectively. These depositions are among the highest level ever reported in the world. Althogh the cause of the dieback of the masson pine trees has not been unequivocally determined, it is probable that the direct impact of SO2 is more likely the cause than acid deposition.

High SO2 resistance ofClethra barbinervis established in a smoke-polluted area of Ashio, Tochigi Prefecture, Japan

The effect of SO2 on the photosynthesis ofClethra barbinervis collected from a smoke-polluted area near the Ashio copper smelter in Tochigi Prefecture was compared withC. barbinervis collected from a nonpolluted district in Tsukuba, Ibaraki Prefecture andQuercus mongolica var.grosseserrata grown in a nonpolluted field in Nagano Prefecture. The plants were exposed to 0.5–1.5 p.p.m. SO2 for 90 min (short-term) and to 0.3 p.p.m. SO2 for 31–39 days (long-term). TheClethra plants from both sites had a lower intrinsic stomatal conductance and photosynthetic rate thanQuercus plants. Short-and long-term fumigation caused stomatal closure inQuercus plants, but had little effect on the stomatal conductance ofClethra plants. Under short-term fumigation, nonstomatal photosynthetic inhibition per unit of absorbed SO2 was smallest inClethra plants from Ashio. Long-term fumigation caused photosynthetic decline and visible foliar injury toQuercus plants, but had no effect onClethra plants from Ashio. Consequently,Clethra plants from Ashio had a higher photosynthetic rate thanQuercus plants after long-term fumigation. These results suggest thatC. barbinervis populations in the smoke-polluted area of Ashio had evolved high SO2 resistance connected with SO2 detoxification ability in mesophyll cells.

Responses of dry weight growth under SO2 stress in an SO2-tolerant plant,Polygonum cuspidatum

The effects of exposure to 0.5–0.7 ppm SO2 for about one month on the dry weight growth and net photosynthesis ofPolygonum cuspidatum were investigate. Furthermore, the carbon and nitrogen concentrations in each plant organ were measured. The results obtained showed no significant decrease in the total dry weight of SO2-treated plants in comparison with controls. On the other hand, the leaf area (LA) and/or leaf dry weight of SO2-treated plants were increased, and the root dry weight (RW) was decreased, in comparison with controls. The leaf carbon assimilation rate (CAR) in SO2-treated plants was slightly decreased in spite of a clear decrease in net photosynthesis, and the value of (SW+RW)/LA (SW stem dry weight) was decreased in comparison with controls, thus minimizing the reduction in CAR. Furthermore, the ratio of total leaf carbon absorption (leaf area x CAR) to total root nitrogen absorption (root dry weight x nitrogen assimilation rate) in SO2-treated plants was similar to that in controls. From these results, it can be concluded that an increase in leaf area and/or leaf dry weight and a decrease in root dry weight inP. cuspidatum under SO2 stress may be induced in order to compensate for the decrease in CAR and to maintain the ratio of total leaf carbon absorption to total root nitrogen absorption in the early stage of vegetative growth.