Interaction of drought and elevated CO2 concentration on photosynthetic down-regulation and susceptibility to photoinhibition in Japanese white birch seedlings grown with limited N availability

The interaction of drought and elevated carbon dioxide concentration ([CO(2)]) on carboxylation capacity of Rubisco (V(cmax)) and susceptibility to photoinhibition may be an important determinant of plant responses to seasonal fluctuations in precipitation in an anticipated elevated [CO(2)] environment. Japanese white birch (Betula platyphylla var. japonica) leaves that developed wholly during a period of drought showed an increase in leaf nitrogen and a decrease in leaf carbohydrates that could ameliorate photosynthetic down-regulation, defined as a decrease in V(cmax) in response to elevated [CO(2)]. Photochemical quenching (q(P)) was decreased by elevated [CO(2)] but increased by drought when compared at a given intercellular [CO(2)] (C(i)), indicating that elevated [CO(2)] could increase the risk of photoinhibition, whereas long-term drought could alleviate the risk of photoinhibition. However, only a small variation in q(P) was measured among seedlings in the various water availability x [CO(2)] treatment combinations, consistent with the small treatment differences in chronic photoinhibition among the seedlings, as indicated by the ratio of variable to maximum chlorophyll fluorescence after overnight dark-adaptation. Our results suggest that the offsetting responses-reduced V(cmax) plus increased C(i) at elevated [CO(2)] and increased V(cmax) plus reduced C(i) under drought conditions-resulted in a narrow range of susceptibility to photoinhibition at the growth [CO(2)] in Japanese white birch seedlings grown in various water availability x [CO(2)] treatment combinations.     

Stem-rot damage and the progress of causal fungi in old-aged Japanese larch trees at the foot of Mt. Fuji

Damage caused by stem-rot and the progress of the causal fungi in old-aged Japanese larch (Larix kaempferi (Lamb.) Carr.) was investigated at the foot of Mt. Fuji. Stem-rot was found in 75% of 108 trees investigated, and volume of rot was 6% of the total wood volume in the forest investigated. Stem-rot damage was much greater than the damage by butt-rot.Stereum sanguinolentum (Alb. and Schw. ex Fr.) Fr. infected larch trees at the greatest incidence (49.4%). However,Porodaedalea chrysoloma (Fr.) Imaz. caused the most volume loss to the trees.S. sanguinolentum infected larch stems mainly through stem wounds, and decay caused by the fungus progressed 9.75×10² cm³/year on average.P. chrysoloma infected larch stems mainly through dead branches and wounds, and the average rate of decay progress for the fungus was 2.74×10³ cm³/year.     

Effects of elevated CO2 concentration on growth, annual ring structure and photosynthesis in Larix kaempferi seedlings

We evaluated the effects of elevated carbon dioxide concentration ([CO2]) and two nutrient regimes on stem growth rate, annual ring structure and temporal variations in photosynthetic characteristics of seedlings of Japanese larch (Larix kaempferi (Lamb.) Carr.). Seedlings were grown in phytotron chambers in an ambient (360 ppm) or an elevated (720 ppm) [CO2] in two nutrient regimes for one growing season. Elevated [CO2] reduced stem height and increased stem basal diameter compared with ambient [CO2]. The effect of elevated [CO2] on growth tended to be greater at high-nutrient supply than at low-nutrient supply. Elevated [CO2] had no significant effect on ring width or the number of tracheids per radial file. There was no obvious difference in cell wall thickness or the relative area of the cell wall between seedlings grown in ambient or elevated [CO2]. Although growth in elevated [CO2] resulted in a slight increase in cell diameter, the increase had a relatively minor effect on the relative area of the cell wall. Net assimilation rate increased in response to elevated [CO2]; however, the increase in whole-crown photosynthetic rate (Total Agrowth) in seedlings in the elevated [CO2] treatment was minimal because of the smaller specific needle area and acclimation of the photosynthetic characteristics of the needles to the growth [CO2]. In conclusion, we observed no obvious enhancement in the capacity for carbon fixation in Japanese larch seedlings grown in the presence of elevated [CO2] that might be attributable to changes in stem growth. However, elevated [CO2] caused changes in the temporal pattern of stem growth and in some anatomical features of the tracheids.     

Unchanged Distribution Density of Anionic Sites on the Glomerular Wall in Rats with Active Heymann Nephritis

In various kinds of glomerulonephritis, alteration of anionic charge on the glomerular basement membrane (GBM) and podocytes has been controversial for more than decade. To elucidate the relation between glomerular protein leakage and anionic sites on the glomerular wall, we examined the distribution of anionic sites on the GBM and podocytes of rats with active Heymann nephritis (AHN). Urinalysis for protein levels was conducted, and the kidneys were examined using electron microscopic cytochemistry for the assessment of anionic charge with two cationic probes. The anionic sites on podocytes were decreased in number in the AHN rats; however, the distributions of anionic sites on the GBM were similar in density to those seen in the control animals. From these results, we consider that the decrease in anionic charge density on podocytes might be attributable to protein leakage and that the charge barrier of the GBM is irrelevant to the protein leakage in AHN rats.     

Effects of demecolcine and sucrose on the incidence of cytoplasmic protrusions containing chromosomes in pig oocytes matured in vitro

The present study was carried out to examine whether demecolcine and sucrose affect the formation of a cytoplasmic protrusion containing chromosomes in pig oocytes independently or in combination. In the presence of 20 mM sucrose, the rates of oocytes with a cytoplasmic protrusion after culture for 60 min with 0.2-1.0 microg/ml demecolcine were significantly higher than those with 0.01-0.05 microg/ml demecolcine. When oocytes were cultured for 15 min in the presence of 0.2 microg/ml demecolcine and 20 mM sucrose, 35.1% of them extruded a cytoplasmic protrusion; this rate was significantly lower than those of oocytes cultured for 30-90 min. In the presence of 0.2 microg/ml demecolcine, significantly fewer oocytes extruded a cytoplasmic protrusion after culture for 30 min with 160 mM sucrose than with 0-80 mM sucrose. Significantly more oocytes extruded a cytoplasmic protrusion after culture for 30 min with 0.2 microg/ml demecolcine than without it, regardless of the presence or absence of 20 mM sucrose. In 88.9-100% of the oocytes, the cytoplasmic protrusions contained chromosomes with no significant differences among the different concentrations of demecolcine and sucrose and among the different treatment times. The results of the present study show that the cytoplasmic protrusion containing chromosomes in the pig oocyte is attributable to demecolcine, but sucrose does not affect its formation.     

Effects of cycloheximide on parthenogenetic development of pig oocytes activated by ultrasound treatment

The present study was carried out to examine the parthenogenetic development of pig oocytes treated with different concentrations of cycloheximide for different durations following activation by ultrasound stimulation. When oocytes were treated with 10 microg/ml cycloheximide for different durations, the blastocyst formation rate of oocytes treated for 5 h was significantly (P<0.05) higher than those of oocytes treated for 0-2 h. The blastocyst formation rate of oocytes treated with 10 microg/ml cycloheximide for 5 h was significantly (P<0.05) higher than those of oocytes treated with 0-5 or 15-20 microg/ml cycloheximide for the same duration. When oocytes were treated with different concentrations of cycloheximide for 2 h, however, the blastocyst formation rate of oocytes treated with 40 microg/ml cycloheximide was significantly (P<0.05) higher than those of oocytes treated with 0-10 or 50 microg/ml cycloheximide. The blastocyst formation rate of oocytes treated with 10 microg/ml cycloheximide for 5 h was not significantly different from that of oocytes treated with 40 microg/ml cycloheximide for 2 h. These treatments did not affect the activation status of oocytes compared with controls that were not treated with cycloheximide. The results of the present study showed that cycloheximide improves the parthenogenetic development of pig oocytes activated by ultrasound stimulation.     

Ethylenediurea (EDU) spray effects on willows (Salix sachalinensis F. Schmid) grown in ambient or ozone?enriched air: implications for renewable biomass production

Ground-level ozone -(O3) is a widespread air pollutant causing extensive injuries in plants. However, its effects on perennial energy crops remain poorly under-...     

Does the root to shoot ratio show a hormetic response to stress? An ecological and environmental perspective

Root/shoot(R/S)ratio is an important index for assessing plant health,and has received increased attention in the last decades as a sensitive indicator of plant stress induced by chemical or physical agents.The R/S ratio has been discussed in the context of ecological theory and its potential importance in ecological succession,where species follow different strategies for above-ground growth for light or below-ground competition for water and nutrients.We present evidence showing the R/S ratio follows a biphasic dose–response relationship under stress,typical of hormesis.The R/S ratio in response to stress has been widely compared among species and ecological succession classes.It is constrained by a variety of factors such as ontogeny.Furthermore,the current literature lacks dose-response studies incorporating the full dose–response continuum,hence limiting scientific understanding and possible valuable application.The data presented provide an important perspective for new-generation studies that can advance current ecological understanding and improve carbon storage estimates by R/S ratio considerations.Hormetic response of the R/S ratio can have an important role in forestry for producing seedlings with desired characteristics to achieve maximum health/productivity and resilience under plantation conditions.     

Tradeoff between shade adaptation and mitigation of photoinhibition in leaves of Quercus mongolica and Acer mono acclimated to deep shade

We investigated susceptibility to photoinhibition in leaves acclimated to different light regimes in intermediately shade-tolerant Japanese oak (Quercus mongolica Fisch. ex Turcz. var. crispula (Blume) Ohashi) and shade-tolerant Japanese maple (Acer mono Maxim. var. glabrum (Lév. et Van't.) Hara), to elucidate adaptability to gap formation in leaves differing in shade acclimation. We hypothesized that there is a tradeoff between shade adaptation and capacity to mitigate photoinhibition associated with leaf morphology. We simultaneously measured chlorophyll fluorescence and gas exchange in seedlings that had been grown in full sunlight (open), 10% of full sun (moderate shade) and 5% of full sun (deep shade). Shade-tolerant A. mono adapted to deep shade through changes in leaf morphology, lowering its leaf mass per area (LMA), but Q. mongolica showed little change in LMA between moderate and deep shade. Photochemical quenching (qP) did not differ between species in full sunlight and moderate shade; however, in deep shade, qP of Q. mongolica was higher than that of A. mono, suggesting that Q. mongolica grown in deep shade is less susceptible to photoinhibition at gap formation. This is consistent with the finding that chronic photoinhibition 3 days after the transfer to full sunlight, indicated by the decrease in maximum photochemical efficiency, Fv/Fm, at predawn, was less in deep-shade-grown Q. mongolica than in deep shade-grown A. mono. In deep shade, the electron transport rate (ETR) of Q. mongolica was higher than that of A. mono, whereas thermal energy dissipation through photosystem II antennae, indicated by non-photochemical quenching, was lower in Q. mongolica than in A. mono. In deep shade, the greater ETR capacity in Q. mongolica in association with higher LMA and higher leaf N content could contribute to maintaining high qP and mitigating photoinhibition. These results indicate that, by maintaining a high electron transport capacity even in deep shade, the gap-dependent and intermediate-shade-tolerant Q. mongolica trades improved shade adaptation for higher growth potential when a gap event occurs.