Effects of dwarf bamboo (Fargesia denudata) density on biomass, carbon and nutrient distribution pattern

Dense dwarf bamboo population is a structurally and functionally important component in many subalpine forest systems. To characterize the effects of stem density on biomass, carbon and majority nutrients (N, P, K, Ca and Mg) distribution pattern, three dwarf bamboo (Fargesia denudata) populations with different stem densities (Dh with 220 ± 11 stems m^?2, Dm with 140 ± 7 stems m^?2, and Dl with 80 ± 4 stems m^?2, respectively) were selected beneath a bamboo-fir (Picea purpurea) forest in Wanglang National Nature Reserve, Sichuan, China. Leaf, branch, rhizome, root and total biomass of dwarf bamboo increased with the increase of stem density, while carbon and nutrient concentrations in bamboo components decreased. Percentages of below-ground biomass and element stocks to total biomass and stocks decreased with the increase of stem density, whereas above-ground biomass and element stocks exhibited the opposite tendency. Moreover, more above-ground biomass and elements were allocated to higher part in the higher density population. In addition, percentages of culm biomass, above-ground biomass and element stocks below 100 cm culm height (H₁₀₀) increased with the increase of stem density, while percentages of branch and leaf biomass below H₁₀₀ decreased. Pearson’s correlation analyses revealed that root biomass, above-ground biomass, below-ground biomass and total biomass significantly correlated to leaf biomass in H_100?200 and total leaf biomass within high density population, while they significantly correlated to leaf biomass in H_50?150 within low density population. The results suggested that dwarf bamboo performed an efficient adaptive strategy to favor limited resources by altering biomass, carbon and nutrients distribution pattern in the dense population.     

Interactive effects of α-NAA and UV-B radiation on the endogenous hormone contents and growth of Trichosanthes kirilowii Maxim seedlings

The impact of UV-B radiation on endogenous hormones in plants has recently drawn attention from researchers. The mechanism for reduced stem elongation by UV-B might be due to changes in the phytohormone levels, especially IAA, which plays a role in stem elongation. In this study, effects of UV-B radiation on Trichosanthes kirilowii Maxim (T. kirilowii) seedlings in greenhouse-grown plants were investigated. The results indicated that: (1) In comparison to controls, exposure to 0.029 Jm^?2 s^?1. UV-B radiation led to accumulation of endogenous abscisic acid (ABA) and zeatinriboside (ZR) in the plant contents, and decreased contents of endogenous indole-3-acetic acid (IAA) and gibberellic acid (GA_1/3). Exposure to UV-B radiation reduced the height and leaf area of plants. As a result, total biomass (plant dry weight) was lower. (2) In comparison to controls, addition of 2 mg l^?1 α-naphthaleneacetic acid (α-NAA) slightly increased the contents of IAA, GA_1/3 and ZR, and decreased the content of ABA in leaves. This addition of α-NAA significantly increased plant height and leaf area, but only slightly increased total biomass. (3) Addition of α-NAA to UV-B-exposed plants: increased the content of endogenous IAA, GA_1/3 and ZR; decreased accumulation of endogenous ABA; and increased plant height and leaf area in comparison to plants that only were exposed to UV-B. Moreover, total biomass increased slightly. This suggests that addition of α-NAA may compensate to a certain extent for the lack of IAA resulting from UV-B radiation; it also increases the content of GA_1/3 and ZR, decreases the accumulation of ABA, and promotes the growth of plants.     

Effects of intraspecific competition on growth and photosynthesis of Atriplex prostrata

We investigated the effect of intraspecific competition on growth parameters and photosynthesis of the salt marsh species Atriplex prostrata Boucher in order to distinguish the effects of density-dependent growth inhibition from salt stress. High plant density caused a reduction of 30% in height, 82% in stem dry mass, 80% in leaf dry mass, and 95% in root dry mass. High density also induced a pronounced 72% reduction in leaf area, 29% decrease in length of mature internodes and 50% decline in net photosynthetic rate. The alteration of net photosynthesis paralleled growth inhibition, decreasing from 7.6 ± 0.9 μmol CO₂ m⁻² s⁻¹ at low density to 3.5 ± 0.4 μmol CO₂ m⁻² s⁻¹ at high density, indicating growth inhibition caused by intraspecific competition is mainly due to a decline in net photosynthesis rate. Plants grown at high density also exhibited a reduction in stomatal conductance from 0.7 ± 0.1 mol H₂O m⁻² s⁻¹ at low density to 0.3 ± 0.1 mol H₂O m⁻² s⁻¹ at high density and a reduction in transpiration rate from 6.0 ± 0.3 mmol H₂O m⁻² s⁻¹ at low density to 4.3 ± 0.3 mmol H₂O m⁻² s⁻¹ at high density. Biomass production was inhibited by an increase in plant density, which reduced the rate of photosynthesis, stomatal conductance and leaf area of plants.     

Advantage of menadione-catalyzed chemiluminescent assay for the determination of viable mammalian cell number

A chemiluminescent assay composed of TCPO [bis(2,4,6-trichlorophenyl)oxalate] and harmless rhodamine B is proposed to be superior in the determination of menadione-catalyzed hydrogen peroxide (H₂O₂) production by viable mammalian cells to that composed of TCPO and harmful pyrene [Anal. Biochem. 207 (1992) 255–260]. In tests, the proposed assay showed that the measurable concentration of H₂O₂ and the viable cell number ranged from 10^?9 to 10^?3 M and from 2 × 10² to 2 × 10⁶ cells/100 μl/well in the presence of 10% bovine serum, respectively. The measuring time was approximately 10 min. On the other hand, the measurable cell numbers by the colorimetric WST-1 and MTT assays requiring several hours ranged only from 10³ to 10⁴ cells/100 μl/well and from 10⁴ to 10⁵ cells/100 μl/well, respectively. The cytotoxicity of sodium dodecyl sulfate was also observed at intervals of 1 min by the proposed assay, but not by the above colorimetric assays.     

High carbon storage and oxygen (O2) release potential of Mahagony (Swietenia macrophylla) woodlot plantation in Bangladesh

Woodlot plantation takes our attention nowadays because of having high wood value, biomass and carbon stock. It also has considerable potential for regulating climate change by sinking CO₂. This study investigated the market value of Swietenia macrophylla woodlots concerning the current carbon trade mechanism, local timber and oxygen value. The carbon-di-oxide equivalence (CO_2e) and release oxygen (O_{2 Release}) ranged from 125.5 to 1004.5 Mg/ha (mean 436.3 Mg/ha) and 91.25–730.26 Mg/ha (mean 317.2 Mg/ha), respectively. Form carbon trade, the Swietenia macrophylla woodlots owner will earn 4,285–34,470 BDT/ha (mean 14,900 BDT/ha). It also seemed that the present market value of release oxygen (O_{2 Release}) ranged from 3.2 to 25.5 million BDT/ha (average 11.1 million BDT/ha). However, the study area's average DBH, height, density, and basal area were 18.9 cm, 12.6 m, 1233 stem/ha, and 36.6 m²/ha, respectively. The above-ground biomass, below-ground biomass, and total biomass ranged from 45.9 to 389.7 Mg/ha (mean 166.5 Mg/ha), 22.5–157.7 Mg/ha (mean 71.2 Mg/ha), and 68.4–547.4 Mg/ha (mean 237.7 Mg/ha) correspondingly. Besides, the produced wood volume ranged from 64.95-1225.19 m³/ha (average 481.48 m³/ha). While the price of wood ranged from 0.8 to 15.14 million BDT/ha (mean 5.95 million BDT/ha). However, the above-ground, below-ground, and total carbon ranged 22.97–194.85 Mg/ha (mean 87.27 Mg/ha, 11.23–78.85 Mg/ha (35.61 Mg/ha), and 34.2–273.7 Mg/ha (118.89 Mg/ha) independently. Moreover, our three developed basal area-based allometric models are fit for calculating the carbon stock of Swietenia macrophylla woodlots. This study explores the potentiality of woodlots in Bangladesh. Policymakers should encourage the farmers to create more woodlots that actively participate in climate change mitigation.     

Unifying selection acts on competitive ability and relative growth rate in Scabiosa columbaria

Q_ST vs. F_ST comparisons can reveal diversifying or unifying selection pressures among populations for specific traits. In this study we performed Q_ST–F_ST analyses on eleven populations of Scabiosa columbaria from the Swiss Jura to reveal genetic differentiation in two quantitative traits (above-ground biomass and relative growth rate of leaf lengths) and in neutral molecular markers. Above-ground biomass of plants under competition has been shown to correlate with their competitive ability, which is an important fitness-related trait. We hypothesized that strong unifying selection acts on above-ground biomass, since underperformance would result in decreased fitness and overperformance is unlikely due to trade-offs with other plant functions.Overall G_ST (an F_ST analogue) was 0.12. Analysis of variance revealed that above-ground biomass and relative growth rate did not differ among populations, but both traits differed among seed families and were heritable (h² = 0.31 and h² = 0.35, respectively). Q_ST was close to zero for above-ground biomass and zero for relative growth rate of leaf lengths, and thus Q_ST was much lower than G_ST, indicating unifying selection on these traits.This conclusion is restricted by the limits of the used methodology. Q_ST < F_ST cannot always be considered as a proof for unifying selection, because in complex traits the assumption of purely additive effects of underlying genes may be violated. However, given the large differences between Q_ST and G_ST, together with substantial heritabilities of the traits under study, we conclude that our findings are not in contradiction with the hypothesis of unifying selection.     

Soybean residues sequestration affected by different tillage practices and the impacts on soil microbial characteristics and enzymatic activities

A large quantity of leaf litter was left on soil surface after soybean (Glycine max) harvest in the black soil region, northeast of China, where soybean was planted with the largest area. This paper investigated the effects of different fall tillage practices on soybean leaf litter sequestration into soil, and the subsequently durative effects on soil biological and biochemical properties during the next growing season. Two practices were investigated, fall tillage (T) and no fall tillage (NT) after soybean harvest in autumn. Results showed that the residue biomass on soil surface and in subsoil profile (0–20 cm) after soybean harvest was about 1450 kg ha^?1 and 340 kg ha^?1, respectively in October 2006. The residue biomass on soil surface and in subsoil profile was about 84 kg ha^?1, 1581 kg ha^?1 for T, and 423 kg ha^?1, 340 kg ha^?1 for NT respectively in May 2007. It was obvious that T practice can more effectively sequester leaf litter into soil compared to NT. Results also showed that T practices after soybean harvest eminently improved soil microbial carbon biomass and nitrogen biomass contents, and significantly improved soil urease and acid phosphate activities than NT. No significant difference of dehydrogenase activity was found between N and NT. The positive effects of T treatment on Soil microbial properties and soil enzymes activities among the next growing season due to soybean residues sequestration performed durative profit.     

Appropriate vegetation indices for measuring the impacts of deer on forest ecosystems

Increasing deer density can cause serious degradation of forests in the Americas, Europe, and Asia. To manage deer impacts, evaluating their current impacts on forest ecosystems is necessary, usually via vegetation indices. However, the relationship between vegetation indices and absolute deer density, while taking into account tree size, snow depth, light condition, and the type of understory vegetation, has never been investigated. We examined the relationship between various vegetation indices and absolute deer density in 344 study plots in the deciduous broad-leaved forest of Yamanashi Prefecture, central Japan. In each plot, debarking and browsing, along with the coverage and maximum height of understory vegetation, were surveyed. Estimated deer densities for 82 5 × 5-km mesh units ranged from 0.8 deer/km² to 32.7 deer/km². The percentages of debarked trees within a plot ranged from 0 to 84%. Debarking was promoted by high deer density, small tree size, and thick snow. The effect of tree size on debarking was stronger than that of deer density. Occurrence of browsing on understory vegetation was higher at higher deer densities, and where understory vegetation was dominated by evergreen dwarf bamboo. Coverage and maximum height of understory vegetation were unaffected by deer density but increased with canopy openness and the dominance of dwarf bamboo in the understory. Overall, we predict that debarking of small trees living in heavy snow areas should occur even at low deer densities (<10 deer/km²). Browsing on dwarf bamboo should occur at intermediate deer densities (10–30 deer/km²), while debarking of thick trees living in low snow areas should occur only at high deer densities (≥30 deer/km²). Our study shows that debarking and browsing on understory vegetation are appropriate indices for evaluating deer impacts on forest ecosystems, but that tree size, snow depth, and the type of understory vegetation should also be considered.     

Effects of simulated nitrogen deposition on growth and photosynthesis of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings

To study the impact of nitrogen deposition on 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings in pots, the dissolved NH₄NO₃ was sprayed on the seedlings every 3 days for 1 year. The simulated elevated N depositions were equivalent to N0(0), N1(6 gN/(m² a)), N2(12 gN/(m² a)), N3(24 gN/(m² a)) and N4(48 gN/(m² a)). The results indicated that medium N treatments (N2, N3) enhanced growth significantly. The height, stem base diameter and per-seedling biomass of Chinese fir seedlings increased with N loads and decreased in the high N treatments. Compared to N0, the height and per-seedling biomass were highest in N2 treatment and increased by 10.77% and 12.35%, respectively. The stem base diameter was highest in N3 treatment and increased by 8.81% compared to N0. The net photosynthetic rate (Pn) in treatments N1, N2, N3, N4 increased by 1.20%, 9.28%, 24.23% and 4.30%, and the highest photosynthetic rate by 67.09%, 125.32%, 148.10% and 51.90%, respectively. The N1–N3 treatments, especially N2, stimulated light compensation point (LCP) of the seedlings significantly, but N4 exhibited inhibitive effect. Compared with LCP, light saturation point (LSP) showed weaker response to N loads, positive to N2, but negative to all other N treatments. Low-to-medium N treatments (N1, N2) enhanced Chl (a + b) by 2.19% and 37.15%, while medium-to-high N treatments (N3, N4) reduced Chl (a + b) by 7.95% and 15.56%, respectively. Water use efficiency (WUE) and stomatal conductance (C) decreased slightly with N loads.     

Seed rain and seed bank of Chinese yew (Taxus chinensis var. mairei) population in Tianmu Mountain☆

Seed rain and seed bank of a Chinese yew (Taxus chinensis var. mairei) population in Tianmu Mountain were researched in 2008 and 2009. The seed rain lasted from 16th–23th of October to 5th–14th of December, and the heaviest seed falling period was from 2nd to18th of November. The intensity of seed rain showed a great inter-annual variation, with a good harvest in 2008. The fallen seeds were composed of 49.9% proportion of immature seed, 33.8% proportion of chewed seed and 16.3% proportion of mature seed. The analysis on the soil seed bank under mother forest showed that the number of intact seeds was 122.75 ± 108.08 grain/m² in October, 279.25 ± 210.73 grain/m² in December 2008, and 166.5 ± 165.34 grain/m² in October, 322.5 ± 275.73 grain/m² in December 2009. The increased number of seed was 156.5 ± 222.723 grain/m² in 2008 and 156 ± 275grain/m² in 2009, which showed a significant variation. Large number of intact seeds added into soil seed bank after seed rain each year. The number of intact seeds in soil seed bank decreased 112.75 ± 47.74 grain/m² from December 2008 to October 2009. Large number of intact seeds lost from seed rot and seed predation by animals. The number of seeds in soil bank under bamboo forest was much lower than that of mother tree forest, and the increased number of seeds was 0.63 ± 1.60 grain/m² in 2008 and 2.88 ± 1.86 grain/m² in 2009. The number of seedling was 0.73 ± 1.10 trees/m² in mother tree forest and 0.09 ± 0.35 trees/m² in bamboo forest. Seedling survival ratio was 0.37% in mother tree forest and 10.23% in bamboo forest. The micro-habitat in bamboo forest was fit for seed germination. Birds transported seeds to bamboo forest, and had an important effect on the regeneration of Chinese yew.     

Purification of a recombinant heavy chain fragment C vaccine candidate against botulinum serotype C neurotoxin [rBoNTC(H(c))] expressed in Pichia pastoris

A purification process for the manufacture of a recombinant C-terminus heavy chain fragment from botulinum neurotoxin serotype C [rBoNTC(H_c)], a potential vaccine candidate, has been defined and successfully scaled-up. The rBoNTC(H_c) was produced intracellularly in Pichia pastoris X-33 using a three step fermentation process, i.e., glycerol batch phase, a glycerol fed-batch phase to achieve high cell densities, followed by a methanol induction phase. The rBoNTC(H_c) was captured from the soluble protein fraction of cell lysate using hydrophobic charge induction chromatography (HCIC; MEP HyperCel?), and then further purified using a CM 650M ion exchange chromatography step followed by a polishing step using HCIC once again. Method development at the bench scale was achieved using 5–100 mL columns and the process was performed at the pilot scale using 0.6–1.6 L columns in preparation for technology transfer to cGMP manufacturing. The process yielded approximately 2.5 g of rBoNTC(H_c)/kg wet cell weight (WCW) at the bench scale and 1.6 g rBoNTC(H_c)/kg WCW at the pilot scale. The purified rBoNTC(H_c) was stable for at least 3 months at 5 and ?80 °C as determined by reverse phase-HPLC and SDS–PAGE and was stable for 24 months at ?80 °C based on mouse potency bioassay. N-Terminal amino acid sequencing confirmed that the N-terminus of the purified rBoNTC(H_c) was intact.     

Leaf growth and population dynamics of intertidal Zostera japonica on the western coast of Korea

Leaf production and population dynamics of Zostera japonica were examined at three elevations of an intertidal transect in Seungbongdo Island on the western coast of Korea. Morphometrics, shoot density, biomass, leaf production, reproductive effort and environmental factors were monitored from October 2001 to October 2002. Z. japonica grew well in the lower intertidal zone from 0.2 to 1.0 m above mean chart datum. The upper station (St. 1) exhibited a finer sediment grain size and richer organic content than the middle (St. 2) and lower stations (St. 3). The size of shoots and leaves was significantly greater at St. 1 than at St. 3, whereas the rhizome internodes were longer at St. 3. Despite differences in morphological characteristics among three stations, seagrass biomass and shoot density were not significantly different among study sites. Shoot density, biomass, morphometrics and leaf productivity exhibited clear seasonal variations, which varied along with seasonal changes of water and air temperature. Leaf productivity measured by the clip and reharvest method was highest in September (4.3 g DW m⁻² d⁻¹) and lowest in February (0.2 g DW m⁻² d⁻¹). Reproductive shoots rapidly increased to maximum density along with the high water temperature in July to September. In the intertidal zone, Z. japonica exhibited faster vegetative growth on muddy sand than on sand, probably due to the difference in nutrient supply. The seasonal changes of water and air temperature were considered to play an important role in the seasonal leaf growth of Z. japonica.     

Coupled effects of irradiance and iron on the growth of a harmful algal bloom-causing microalga Scrippsiella trochoidea

Effects of irradiance and iron on the growth of a typical harmful algal blooms (HABs) causative dinoflagellate, Scrippsiella trochoidea, were investigated under various irradiances (high light: 70 μmol m^?2 s^?1 and low light: 4 μmol m^?2 s^?1) and iron concentrations (low iron: 0.063 mg L^?1, medium iron: 0.63 mg L^?1 and high iron: 6.3 mg L^?1), and evaluated by the parameters of algal cell density, specific growth rate, optical density and chlorophyll a content. The results indicated that there was significant difference in the cell density of dinoflagellate S. trochoidea between high light and low light intensity treatments across the entire experiments, 7-fold higher at high irradiance as compared with low irradiance, which was further enhanced by the iron concentration. It was found that the maximum cell density of 25 × 10⁴ cell mL^?1 occurred under the combination of high light intensity and high iron concentration, followed by 23 × 10⁴ cell mL^?1 in the combination of high light and medium iron, and 20 × 10⁴ cell mL^?1 in the combination of high light and low iron. There was no significant effect of iron concentration on the cell density under low light intensity. The cell density maintained about 3 × 10⁴ cell mL^?1 across all combinations of iron concentrations and low light in the end of experiments. Such interactive effects of light intensity and iron level dependent were also observed for the specific growth rate, OD₆₈₀ and chlorophyll a content of S. trochoidea. The maximum values of specific growth rate, OD₆₈₀ and chlorophyll a content peaked at the condition of high irradiance and high iron, which were 0.22 d^?1, 0.282 and 0.673 mg L^?1, respectively. In general, their values increased significantly with the increasing of iron concentration at high irradiance, whereas no significant difference was observed among three iron concentrations at low irradiance, all remaining approximately 0.06 d^?1, 0.03 and 0.050 mg L^?1, respectively. Those results suggest that there may be a strong interactive effect between irradiance and iron on microalgal growth and their physiological characteristics. The combination of high light and high iron concentration may accelerate algal cell growth and pigment biosynthesis, thus leading to massive occurrence of HABs.     

A study on multidimensional time series model of individual age’s measurement in Castanopsis kawakamii population

Studies on disclosing characteristics and endangered mechanisms of Castanopsis kawakamii population ecology have already become an urgent task of protecting C. kawakamii population. The establishment of the standard life table is one of an important work study on C. kawakamii population ecology, and determining individual ages of the plant is necessary for studying age structures and population dynamics of C. kawakamii. There are three main methods of determining individual age of forest population: (1) by annual ring of tree, (2) by individual growth phase, and (3) by DBH and height of tree. However, the three methods have their shortcomings, such as low precision, worse serviceability, high difficulty for operation and so on. In this paper, a new method for determining plant individual ages more accurately is presented on the basis of the method aboU_t “annual ring–time series”. Based on the stem analysis, the multidimensional time series model of diameter growth at breast height in C. kawakamii population was established by U_tilizing the analY_tical method of multidimensional time series: Y_t = 1.325034Y_t-1 ? 0.4711007Y_t-2 ? 284.5648U_t + 569.4783U_t?1 ? 284.8745U_t?2, where Y_t, Y_t-1, Y_t-2 represent diameter growth in C. kawakamii population at t, t ? 10 and t ? 20 years respectively, and U_t, U_t?1, U_t?2 represent individual age in C. kawakamii population at t, t ? 10 and t ? 20 years respectively, the model coefficient correlation is 0.9994. Based on this model CAR(2), the total increment of individual DBH in C. kawakamii population are simulated and regressively verified at different ages. The mean simulating precision of this model was 98.84%, the maximum relative error was 2.56%, bU_t the next was 2.47% and the minimum relative error was 0.07%, showing that this model was suitable for estimating breast-height diameter of C. kawakamii plant. Using the multidimensional time series model, diameter growth of C. kawakamii population for longer time series was estimated in order to gain data for establishing the relationship model of individual age, diameter growth and to increase its precision in determining individual age is by tree ring analysis. A combination method of determining individual age of C. kawakamii population by integrating annual ring data with its diameter using multidimensional time series model, which can improve precision of individual ages in C. kawakami, was produced: A = 9.966671944 + 1.146011591D + 0.041059628D² ? 0.000211907D³, where A and D represent individual age and diameter at breast height respectively in C. kawakamii population, the model coefficient correlation is 0.9998. The combination model, which shows that the regression relationship is significant and the model can exactly predict the individual age of population, is a valuable tool for determining individual ages in endangered plants.     

Predictive modeling of biomass production by Spirulina platensis as function of nitrate and NaCl concentrations

Effects of nitrate (2.0, 2.5, and 3.0 g L^?1) and salt (0.5, 1.0, 1.5, 2.0 g L^?1) concentrations on biomass production by Spirulina platensis was examined in the Schlösser medium. The highest (p < 0.001) biomass yields and chlorophyll a content was observed at 2.5 g L^?1 nitrate and 1.5 g L^?1 NaCl as 3.495 g L^?1 and 29.92 mg L^?1, respectively. Increment rate of biomass production was especially found between 72 and 216 h. Modified Richards, Schnute, Logistic and Gompertz models was successfully predicted (r² > 0.96 and RSS ? 0.003) biomass production by S. platensis as function of nitrate and salt concentrations. Low residual sum of squares (RSS) and high regression coefficients (r²) indicated that used models were well fitted to the experiment data and it could be regarded as sufficient to describe biomass production of Spirulina sp. Biological variables i.e. production rate (μ) and lag time (λ) for S. platensis ranged 0.012–0.034 h^?1 and 2.43–5.85 h, respectively from biomass production were successfully predicted by modified Logistic model according to low RSS and F-testing value.     

Leaf growth and population dynamics of intertidal Zostera japonica on the western coast of Korea

Leaf production and population dynamics of Zostera japonica were examined at three elevations of an intertidal transect in Seungbongdo Island on the western coast of Korea. Morphometrics, shoot density, biomass, leaf production, reproductive effort and environmental factors were monitored from October 2001 to October 2002. Z. japonica grew well in the lower intertidal zone from 0.2 to 1.0 m above mean chart datum. The upper station (St. 1) exhibited a finer sediment grain size and richer organic content than the middle (St. 2) and lower stations (St. 3). The size of shoots and leaves was significantly greater at St. 1 than at St. 3, whereas the rhizome internodes were longer at St. 3. Despite differences in morphological characteristics among three stations, seagrass biomass and shoot density were not significantly different among study sites. Shoot density, biomass, morphometrics and leaf productivity exhibited clear seasonal variations, which varied along with seasonal changes of water and air temperature. Leaf productivity measured by the clip and reharvest method was highest in September (4.3 g DW m⁻² d⁻¹) and lowest in February (0.2 g DW m⁻² d⁻¹). Reproductive shoots rapidly increased to maximum density along with the high water temperature in July to September. In the intertidal zone, Z. japonica exhibited faster vegetative growth on muddy sand than on sand, probably due to the difference in nutrient supply. The seasonal changes of water and air temperature were considered to play an important role in the seasonal leaf growth of Z. japonica.     

N-1 and C-3 substituted indole Schiff bases as selective COX-2 inhibitors: synthesis and biological evaluation

A group of N-1 and C-3 disubstituted-indole Schiff bases bearing an indole N-1 (R′ = H, CH₂Ph, COPh) substituent in conjunction with a C-3 –CHN–C₆H₄–4-X (X = F, Me, CF₃, Cl) substituent were synthesized and evaluated as inhibitors of cyclooxygenase (COX) isozymes (COX-1/COX-2). Within this group of Schiff bases, compounds 15 (R¹ = CH₂Ph, X = F), 17 (R¹ = CH₂Ph, X = CF₃), 18 (R¹ = COPh, X = F) and 20 (R¹ = COPh, X = CF₃) were identified as effective and selective COX-2 inhibitors (COX-2 IC₅₀’s = 0.32–0.84 μM range; COX-2 selectivity index (SI) = 113 to >312 range). 1-Benzoyl-3-[(4-trifluoromethylphenylimino)methyl]indole (20) emerged as the most potent (COX-1 IC₅₀ >100 μM; COX-2 IC₅₀ = 0.32 μM) and selective (SI >312) COX-2 inhibitor. Furthermore, compound 20 is a selective COX-2 inhibitor in contrast to the reference drug indomethacin that is a potent and selective COX-1 inhibitor (COX-1 IC₅₀ = 0.13 μM; COX-2 IC₅₀ = 6.9 μM, COX-2 SI = 0.02). Molecular modeling studies employing compound 20 showed that the phenyl CF₃ substituent attached to the CN spacer is positioned near the secondary pocket of the COX-2 active site, the CN nitrogen atom is hydrogen bonded (N?NH = 2.85 Å) to the H90 residue, and the indole N-1 benzoyl is positioned in a hydrophobic pocket of the COX-2 active site near W387.     

An annual cycle of biomass and productivity of Vallisneria americana in a subtropical spring-fed estuary

An annual cycle of biomass and productivity of wild celery (Vallisneria americana) was studied in Kings Bay, FL, USA. In situ growth rates were measured monthly between March 2001 and June 2002 in high-density stands, using a modified hole-punching technique, and applied to shoot density data to obtain areal estimates of production. Mean shoot density varied greatly over the study period, ranging between 200 and 800 shoots m⁻². Mean total biomass ranged between 162 and 1013 g m⁻², with aboveground material comprising, on average, 70% of total biomass. Total annual estimated production of new attached shoots was 519 g m⁻². Leaf growth rates peaked at >50 mg shoot⁻¹ d⁻¹, and mass-specific leaf growth ranged 0.6–1.8% d⁻¹. Annually, individual shoots produced 7.4 g of leaf material and completely replaced standing leaf biomass 3.5 times. Areal leaf production was highest in late spring/summer of 2001, and ranged between 3.6 and 23.0 g m⁻² d⁻¹. Annual total leaf production was 2704 g m⁻². Seasonality was not apparent in most variables monitored monthly; only 1 of the 64 relationships we examined between environmental variables (nutrients, chlorophyll a, and irradiance) and Vallisneria biological variables were significant, with relative growth rate increasing linearly with irradiance. Peak biomass and productivity of Vallisneria in Kings Bay were high compared to literature values for other Vallisneria populations as well as global averages for well-studied seagrasses, emphasizing the potential importance of Vallisneria to whole ecosystem functioning in springs, lakes, and oligohaline reaches of many estuaries.     

Nitrogen rhizodeposition assessed by a NH3 shoot pulse-labelling of Lolium perenne L. grown on soil exposed to 9 years of CO2 enrichment

The effects of elevated CO₂ concentration upon rhizodeposition of nitrogen were investigated on field-grown Lolium perenne planted in soil cores set into the resident soil of a intensively managed ryegrass sward treated with elevated CO₂ for nine consecutive years, under two contrasted N fertilisation regimes (Swiss FACE Experiment). The planted cores were excavated from the ambiant (35 Pa pCO₂) and enriched (60 Pa pCO₂) rings at two dates during the growing season (spring and early autumn). The cores were brought back to the laboratory for a pulse-labelling of ryegrass shoots with ¹⁵NH₃, in order to quantify ¹⁵N-rhizodeposition.A recovery of 10–16% of the total ¹⁵N administred to the plant was recovered in the plant–soil system 48 h after the pulse-labelling; significant amounts of ¹⁵N were released into the soil adhering (adhering soil: AS) to the roots (0.44 μg ¹⁵N g AS⁻¹ and 0.60 μg g AS⁻¹ in the spring and the autumn samplings, respectively).In the spring sampling, there was no effect of atmospheric CO₂ concentration on N rhizodeposition. In the autumn sampling, elevated CO₂ stimulated N rhizodeposition that amounted to 7.2 and 5.2 mg ¹⁵N m⁻², under elevated and ambient CO₂, respectively. Nitrogen rhizodeposition was higher at high N (56 gN m⁻²) than at low N fertilisation (14 gN m⁻²), whatever the sampling date investigated.The mechanisms by which elevated atmospheric CO₂ leads to a stimulation of the net root-released N flux remains to be investigated: was it caused by a higher nitrogen immobilisation by the microbial biomass and a reduced re-assimilation of mineralized N and/or by a stimulation of N efflux from roots? Concomitant to the observed reduction of C rhizodeposition, the stimulation of net N efflux suggests that the quality of root released compounds was modified under elevated CO₂ concentration.     

Burial depth and diameter of the rhizome fragments affect the regenerative capacity of a clonal shrub

Clonal plants in highly disturbed habitats are often broken into small fragments of various sizes and buried at various soil depths. As a storage organ, rhizome fragments play an important role in enabling plants to survive in such habitats. But few studies have been concerned about the regenerative capacity of rhizome fragments of clonal shrubs of different rhizome diameter and at different burial depths. Here, we investigated whether deeper burial decreased, and diameter of the rhizome fragment increased, the regenerative capacity of a clonal shrub. Research samples of rhizome fragment (rhizome diameters of 2, 5, 10, 15, and 20 mm) of the clonal shrub Calligonum arborescens were buried at different depths (0, 1, 5, 10, and 20 cm). Increasing the diameter of the rhizome fragments significantly increased the survival rate of fragments, and increased the above-ground, below-ground and total biomass production of fragments. Vegetative reproduction ability also increased with an increase in diameter of the rhizome fragments. With an increase in sand burial depth, above-ground, below-ground, total biomass production and vegetative reproduction ability first decreased and then increased, and no fragments survived at the 0 cm burial depth. These results indicate that sand burial depth and diameter of the rhizome fragments significantly affected the regeneration capacity of C. arborescens. Sand burial is one of the essential prerequisites for C. arborescens rhizome fragments’ survival. Moderate burial depth (5 cm) and larger fragment diameter (20 mm diameter) were more suitable for biomass production and vegetative reproduction. These results indicate that reserves stored in rhizome fragments can contribute greatly to the regeneration capacity of the C. arborescens—responses that are very important for C. arborescens survival and establishment in frequently disturbed habitats.