Effects of Organic Solvents on the Coupling Between ATP Hydrolysis and Sliding of Microtubules in Axonemes from Chlamydomonas Flagella

ABSTRACT. The effects of organic solvents on the ATPase activity and the sliding disintegration of axonemes from Chlamydomonas were investigated. The axonemal ATPase was markedly activated by methanol accompanying with marked inhibition of the sliding disintegration of axonemes. On the contrary, glycerol inhibited the ATPase activity without serious inhibition of the sliding disintegration. As far as the axonemes are not irreversibly denatured by extremely high concentration of solvents, the effects of solvents both on the ATPase and the ability of sliding are reversible. Therefore, the inhibition of sliding accompanied by the activation of ATPase is probably due to an inability to couple the hydrolysis of ATP to sliding between dynein and microtubule in the presence of methanol. The axonemal ATPase was less sensitive to vanadate inhibition after exposure to methanol. This indicates that methanol makes the dyneinADP.Pi complex unstable and increases product release. On the other hand, glycerol and ethylene glycol seem to stabilize the force generation responsible for the sliding through stabilizing the dynein.ADP.Pi complex.     

Coexistence of two congeneric tree species of Lauraceae in a secondary warm‐temperate forest on Miyajima Island,south‐western Japan

We analyzed the spatial distributions of two congeneric tree species, Neolistea aciculata and Neolistea sericea (Lauraceae), in a warm‐temperate forest on Miyajima Island, south‐western Japan. Both species were mainly found in valley sites on the island. Hence, these species shared the same topographic habitat niche. However, we found a clear difference between the spatial distributions of the two species in relation to the light environment. Neolistea aciculata was predominantly found in stands with low light, such as beneath the canopy of dense evergreen broadleaved forest. In contrast, N. sericea was predominantly associated with ample light, such as in secondary Pinus densiflora forest. In stands with moderate light conditions, both species were found. This habitat niche segregation in relation to light conditions presumably allows the coexistence of these two species in the predominantly successional forest on Miyajima Island.     

CH4 emission with differences in atmospheric CO2 enrichment and rice cultivars in a Japanese paddy soil

A pot experiment was conducted to investigate CH₄ emissions from a sandy paddy soil as influenced by rice cultivars and atmospheric CO₂ elevation. The experiment with two CO₂ levels, 370 μL L⁻¹ (ambient) and 570 μL L⁻¹ (elevated), was performed in a climatron, located at the National Institute for Agro‐Environmental Sciences, Tsukuba, Japan. Four rice cultivars were tested in this experiment, including IR65598, IR72, Dular and Koshihikari. Tiller number, root length and grain yield were clearly larger under elevated CO₂ than under ambient CO₂. IR72 and Dular showed significantly higher tiller number, root length and grain yield than Koshihikari and IR65598. Average daily CH₄ fluxes under elevated CO₂ were significantly larger by 10.9–23.8% than those under ambient CO₂, and varied with the cultivars in the sequence Dular ≧ IR72>IR65598 ≧ Koshihikari. Dissolved organic C (DOC) content in the soil was obviously higher under elevated CO₂ than under ambient CO₂ and differed among the cultivars, in the sequence IR72>Dular>Koshihikari>IR65598. The differences in average daily CH₄ fluxes between CO₂ levels and among the cultivars were related to different root exudation as DOC content, root length and tiller number. This study indicated that Koshihikari should be a potential cultivar for mitigating CH₄ emission and simultaneously keeping stable grain yield, because this cultivar emitted lowest CH₄ emission and produced medium grain yield.     

Increased night temperature reduces the stimulatory effect of elevated carbon dioxide concentration on methane emission from rice paddy soil

To determine how elevated night temperature interacts with carbon dioxide concentration ([CO₂]) to affect methane (CH₄) emission from rice paddy soil, we conducted a pot experiment using four controlled‐environment chambers and imposed a combination of two [CO₂] levels (ambient: 380 ppm; elevated: 680 ppm) and two night temperatures (22 and 32 °C). The day temperature was maintained at 32 °C. Rice (cv. IR72) plants were grown outside until the early‐reproductive growth stage and then transferred to the chambers. After onset of the treatment, day and night CH₄ fluxes were measured every week. The CH₄ fluxes changed significantly with the growth stage, with the largest fluxes occurring around the heading stage in all treatments. The total CH₄ emission during the treatment period was significantly increased by both elevated [CO₂] (P=0.03) and elevated night temperature (P<0.01). Elevated [CO₂] increased CH₄ emission by 3.5% and 32.2% under high and low night temperature conditions, respectively. Elevated [CO₂] increased the net dry weight of rice plants by 12.7% and 38.4% under high and low night temperature conditions, respectively. These results imply that increasing night temperature reduces the stimulatory effect of elevated [CO₂] on both CH₄ emission and rice growth. The CH₄ emission during the day was larger than at night even under the high‐night‐temperature treatment (i.e. a constant temperature all day). This difference became larger after the heading stage. We observed significant correlations between the night respiration and daily CH₄ flux (P<0.01). These results suggest that net plant photosynthesis contributes greatly to CH₄ emission and that increasing night temperature reduces the stimulatory effect of elevated [CO₂] on CH₄ emission from rice paddy soil.     

Soil organic carbon stocks in China and changes from 1980s to 2000s

The estimation of the size and changes of soil organic carbon (SOC) stocks is of great importance for decision makers to adopt proper measures to protect soils and to develop strategies for mitigation of greenhouse gases. In this paper, soil data from the Second State Soil Survey of China (SSSSC) conducted in the early 1980s and data published in the last 5 years were used to estimate the size of SOC stocks over the whole profile and their changes in China in last 20 years. Soils were identified as paddy, upland, forest, grassland or waste‐land soils and an improved soil bulk density estimation method was used to estimate missing bulk density data. In the early 1980s, total SOC stocks were estimated at 89.61 Pg (1 Pg=10³ Tg=10¹⁵ g) in China's 870.94 Mha terrestrial areas covered by 2473 soil series. In the paddy, upland, forest and grassland soils the respective total SOC stocks were 2.91 Pg on 29.87 Mha, 10.07 Pg on 125.89 Mha, 34.23 Pg on 249.32 Mha and 37.71 Pg on 278.51 Mha, respectively. The SOC density of the surface layer ranged from 3.5 Mg ha⁻¹ in Gray Desery grassland soils to 252.6 Mg ha⁻¹ in Mountain Meadow forest soils. The average area‐weighted total SOC density in paddy soils (97.6 Mg ha⁻¹) was higher than that in upland soils (80 Mg ha⁻¹). Soils under forest (137.3 Mg ha⁻¹) had a similar average area‐weighted total SOC density as those under grassland (135.4 Mg ha⁻¹). The annual estimated SOC accumulation rates in farmland and forest soils in the last 20 years were 23.61 and 11.72 Tg, respectively, leading to increases of 0.472 and 0.234 Pg SOC in farmland and forest areas, respectively. In contrast, SOC under grassland declined by 3.56 Pg due to the grassland degradation over this period. The resulting estimated net SOC loss in China's soils over the last 20 years was 2.86 Pg. The documented SOC accumulation in farmland and forest soils could thus not compensate for the loss of SOC in grassland soils in the last 20 years. There were, however, large regional differences: Soils in China's South and Eastern parts acted mainly as C sinks, increasing their average topsoil SOC by 132 and 145 Tg, respectively. In contrast, in the Northwest, Northeast, Inner Mongolia and Tibet significant losses of 1.38, 0.21, 0.49 and 1.01 Pg of SOC, respectively, were estimated over the last 20 years. These results highlight the importance to take measures to protect grassland and to improve management practices to increase C sequestration in farmland and forest soils.     

A New Entodiniomorphid Ciliate,Troglocorys cava n. g., n. sp., from the Wild Eastern Chimpanzee (Pan troglodytes schweinfurthii) from Uganda

ABSTRACT. Troglocorys cava n. g., n. sp. is described from the feces of wild eastern chimpanzee, Pan troglodytes schweinfurthii, in Uganda. This new species has a spherical body with a frontal lobe, a long vestibulum, a cytoproct located at the posterior dorsal side of the body, an ovoid macronucleus, a contractile vacuole near the cytoproct, and a large concavity on the left surface of the body. Buccal ciliature is non‐retractable and consists of three ciliary zones: an adoral zone surrounding the vestibular opening, a dorso‐adoral zone extending transversely at the basis of the frontal lobe, and a vestibular zone longitudinally extending in a gently spiral curve to line the surface of the vestibulum. Two non‐retractable somatic ciliary zones comprise arches over the body surface: a short dorsal ciliary arch extending transversely at the basis of the frontal lobe and a wide C‐shaped left ciliary arch in the left concavity. Because of the presence of three ciliary zones in the non‐retractable buccal ciliature, the present genus might be a member of the family Blepharocorythidae, but the large left concavity and the C‐shaped left ciliary arch are unique, such structures have never been described from other blepharocorythids.     

A kinetic analysis of cadmium accumulation in a Cd hyper‐accumulator fern,Athyrium yokoscense and tobacco plants

Cadmium (Cd) accumulations in a Cd hyper‐accumulator fern, Athyrium yokoscense (Ay), and tobacco, Nicotiana tabacum (Nt), were kinetically analysed using the positron‐emitting tracer imaging system under two medium conditions (basal and no‐nutrient). In Ay, maximumly 50% and 15% of the total Cd accumulated in the distal roots and the shoots under the basal condition, respectively. Interestingly, a portion of the Cd in the distal roots returned to the medium. In comparison with Ay, a little fewer Cd accumulations in the distal roots and clearly higher Cd migration to the shoots were observed in Nt under the basal condition (maximumly 40% and 70% of the total Cd, respectively). The no‐nutrient condition down‐regulated the Cd migration in both species, although the regulation was highly stricter in Ay than in Nt (almost no migration in Ay and around 20% migration in Nt). In addition, the present work enabled to estimate physical and physiological Cd accumulation capacities in the distal roots, and demonstrated condition‐dependent changes especially in Ay. These results clearly suggested occurrences of species‐/condition‐specific regulations in each observed parts. It is probable that integration of these properties govern the specific Cd tolerance/accumulation in Ay and Nt.     

Developmental morphology of the ovules of Amborella trichopoda (Amborellaceae) and Chloranthus serratus (Chloranthaceae)

The developmental morphology of the outer integument in the pendent orthotropous ovules of Amborella trichopoda (Amborellaceae) and Chloranthus serratus (Chloranthaceae) was studied. In both species the outer integument is semiannular at an early stage and becomes cup-shaped but dorsiventrally somewhat asymmetric at later stages. The outer integument, which is initiated first on the concave and lateral sides of the ovule, differs from that of the anatropous ovules of other basal families with the outer integument semiannular at an early stage or throughout development. The bilateral symmetry of the outer integument is shared by these orthotropous and anatropous ovules. The developmental pattern of the outer integument and ovule incurving characterize the ovule of the Amborellaceae and Chloranthaceae, which is not equivalent to typical orthotropous ovules of eudicots. A phylogenetic analysis of ovule characters in basal angiosperms suggests that anatropous ovules with cup-shaped outer integuments and orthotropous ovules were derived independently in several clades and that the ovules of Amborella and Chloranthus might also be derivative.     

Distribution of greenhouse gases, nitrite, and δ13C of dissolved inorganic carbon in Lake Biwa: Implications for hypolimnetic metabolism

The vertical distribution of dissolved greenhouse gases (CH₄,CO₂ and N₂O), NO ,and ¹³C of CO₂ in Lake Biwa during a stagnantperiod was precisely determined. CO₂ as well as NO was accumulated in the hypolimnion, whereas NO and CH₄concen\-trations were generally higher in theepilimnion than in the hypolimnion. In August, NO andCH₄ were ephemerally accumulated at the thermocline. Theconcentration of CH₄ always exceeded equilibrium with respectto air/water exchange. N₂O was rather uniformly distributed inboth time and space, and remained near equilibrium with respect toair/water exchange. All of these observations are similar to otherstratified, oligotrophic lakes, in which the hypolimnia were welloxygenated. The ¹³C of CO₂ became morenegative with increasing depth, and showed a strong negativecorrelation with apparent oxygen utilization. From the data, the ¹³Cvalue of organic matter decomposed into CO₂ inthe hypolimnion was calculated by isotope mass-balance, and found tobe in a similar range to ¹³C of phytoplankton and benthic algaeand distinctively higher than ¹³C of both terrestrial andsedimentary organic matters. This suggests that autochthonous organicmatter was the major source of CO₂.