Differential sensitivity to ozone in two poplar clones.

The effect of acute O₃ exposure (5 h at 150 ppb) on photosynthetic electron transport and the thylakoid polypeptide pattern has been studied in 2-month-old cuttings of two poplar clones ( Populus deltoides × maximowiczii clone Eridano and P .× euramericana clone I-214), known for their differential response to O₃ in terms of visible symptoms. The more sensitive Eridano developed severe blackish bifacial necrosis concentrated in the interveinal areas of the basal and intermediate leaves, while in the less sensitive I-214 clone, visible symptoms were slight or entirely absent. A generalized, significant decrease in leaf pigment content was shown by both of the stressed clones, although the decline in β -carotene content was much more marked in Eridano than in I-214. Activation of the xanthophyll cycle was not detected in either clone. In both clones, immunoblot analysis of the thylakoid proteins showed a decrease in the levels of all the PSII polypeptides tested following O₃ exposure, whereas the PsaA/B protein in the PSI core was more severely affected in Eridano than in I-214. No changes in the chloroplast structure could be seen on electron microscopic study in either clone. The only visible difference was a great accumulation of starch grains in Eridano. All of these results suggest that O₃ exposure induces alterations in the photosynthetic apparatus in both poplar clones, Eridano being affected to a greater extent than I-214.     

Continuous secretion of organic acids is related to aluminium resistance during relatively long‐term exposure to aluminium stress

Secretion of organic acid has been suggested to be one of the mechanisms for Al resistance in short‐term experiments. In the present study, relatively long‐term response of roots to Al stress was investigated in terms of organic acid secretion. Eight plant cultivars belonging to 5 species that exhibited differential sensitivity to Al were used. Ten days of intermittent exposure to Al (one day in 0.5 m M CaCl₂ containing 50 µ M AlCl₃ at pH 4.5, alternating with one day in nutrient solution without Al) inhibited root growth by 65% in an Al‐sensitive cultivar of wheat ( Triticum aestivum L. Scout 66) and by 25‐50% in two cultivars of oilseed rape ( Brassica napus L. 94008 and H166), two cultivars of oat ( Avena sativa L. Tochiyutaka and Heoats), and an Al‐tolerant cultivar of wheat (Atlas 66). However, root growth was hardly affected by the same treatment in buckwheat ( Fagopyrum esculentum Moench Jianxi) and radish ( Raphanus sativus L. Guangxi). Organic acids were monitored during the first 6 h of each day of Al treatment, and both the kind and amount of organic acids secreted were found to differ among different species. Roots of buckwheat secreted oxalic acid, those of wheat exuded malic acid, while those of rapeseed, oats, and radish secreted both citric and malic acids. Three different patterns in response to relatively long‐term treatment of Al were found in terms of total amount of organic acids secreted: (1) the amount secreted was very low during the treatment (wheat cv. Scout 66, oat), (2) the amount gradually decreased with duration of treatment (wheat cv. Atlas 66, oilseed rape), and (3) the amount maintained at a high level during the whole period of Al treatment (buckwheat and radish). Combined with the results of growth inhibition, it is suggested that the continuous secretion of organic acids at a high level is related to high Al resistance.     

Photosynthesis of two poplar clones contrasting in O3 sensitivity

 Two clones of poplar known for their phenomenological difference in response to ozone were fumigated with 150 nl l^–1 of ozone for 5 h. In both clones the treatment significantly reduced the light-saturated rate of CO₂ uptake of recently mature leaves and this was accompanied by a decrease in stomatal conductance. Intercellular CO₂ concentration of the resistant clone increased following the fumigation. After 20 h of recovery, photosynthesis recovered completely only in the resistant clone. Electrolyte leakage of leaf disks increased in both clones to indicate damage to membranes; after the recovery time this parameter only reached values of the control in the resistant clone. The photochemical efficiency of PSII slightly decreased in the resistant clone. In the other clone, the treatment caused a decline of all chlorophyll fluorescence parameters and only some of them returned to normal values after the recovery time. The physiological response appears to be different in the two clones. In the resistant one, the most probable mechanism involved in the photosynthetic reduction was a regulatory reduction in CO₂ fixation. Also data obtained by the solute leakage indicate that in the resistant clone repair mechanisms play a role. The reduction of photosynthesis observed in the sensitive clone is related both to strong stomatal closure and to an impairment in fluorescence parameters. These alterations can indicate a general disruption at the membrane level as confirmed by the solute leakage data. Received: 30 June 1997 / Accepted: 3 September 1997     

Role of sodium in the ABA‐mediated long‐term growth response of bean to salt stress

Long‐term salt effects on plant growth have often been related to direct ion toxicity due to the accumulation of high ion concentrations in plant tissue. This work examines the relative importance of endogenous ABA, as well as Na⁺ and Cl⁻ toxicity, in the inhibition of leaf growth and photosynthesis, in bean plants grown at 1, 25, 50 and 75 m M NaCl until the fruit‐bearing stage. All salt‐treated plants showed very high leaf Cl⁻ concentrations, with little difference between plants exposed to 50 or 75 m M NaCl. The 25 and 50 mM salt‐treated plants were able to successfully exclude Na⁺ from their leaves, and only suffered an initial decline in the rate of leaf growth. Plants exposed to 75 m M NaCl showed an increase in Na⁺ leaf concentrations with an accompanying decrease in growth and photosynthesis as salt exposure progressed. A high correlation was found between leaf Na⁺ and leaf growth. Leaf ABA significantly increased with salt supply, and was highly correlated with both leaf Na⁺ and leaf growth. Our results suggest that in bean plants under long‐term salt stress, leaf ABA may participate in the regulation of leaf growth, and leaf Na⁺ would be at least partly responsible for increased ABA levels.     

Recording long‐term heart rate in Paranotothenia angustata using an electronic datalogger

A unique heart beat datalogging device was either surgically implanted into the peritoneal cavity (internal‐fish) or attached by nylon anchor tags to the dorsal fin rays (external‐fish) of the black cod Paranotothenia angustata . Both groups had a mean ±  s . e . heart rate of c . 46 beats min⁻¹ after 24 h, and by 20 days external‐fish showed a significant reduction (34 ± 3 beats min⁻¹) whereas internal‐fish did not (44 ± 2 beats min⁻¹). In demersal fishes external attachment of an electronic recording device may be preferable to surgical implantation.     

Short‐term freshwater exposure benefits sea lice‐infected Atlantic salmon

Atlantic salmon Salmo salar were infected with sea lice Lepeophtheirus salmonis (0·08 ± 0·007 sea lice g⁻¹) over a period of 4 h. Both infected and non‐infected fish were swim tested in sea water (SW) and fresh water (FW). The ventral aorta of each fish was fitted with a Doppler cuff in order to measure cardiac output, stroke volume and heart rate during swim testing. Blood samples were taken at rest and after exercise. Critical swimming speed of infected fish in SW (2·14 ± 0·08 body lengths, bl s⁻¹) was significantly lower ( P  < 0·05) than infected fish switched to FW (2·81 ± 0·08 bl s⁻¹) and non‐infected fish in SW (2·42 ± 0·04 bl s⁻¹) and FW (2·61 ± 0·08 bl s⁻¹). Cardiac and blood results indicated infected fish exposed to FW did experience stress, but relief from osmotic and ionic distress probably reduces energy expenditure, allowing the increase in performance. As the performance of sea lice‐infected fish improved upon transfer to FW, it is likely that heavily infected salmonids do return to FW to restore compromised osmotic and ionic balance, and remove sea lice in the process.     

Mackerel icefish size and age differences and long‐term change at South Georgia and Shag Rocks

This study analysed the total length ( L _T)‐frequency distribution of mackerel icefish Champsocephalus gunnari at South Georgia and Shag Rocks from nine bottom trawl surveys at South Georgia and eight at Shag Rocks between 1987 and 2002. The estimated mean L _T of age‐classes 1+, 2+, 3+ and 4+ years during January were, respectively, 14·7, 23·5, 29·8 and 35·1 cm at South Georgia. Age‐classes 1+, 2+ and 3+ years were 18·3, 26·2 and 33·8 cm at Shag Rocks. The derived Bertalanffy growth parameters for South Georgia were: L _∞ = 51·7 cm, k  = 0·27 and t ₀ = −0·26. The mean L _T of each age‐class of C. gunnari at Shag Rocks was significantly larger than at South Georgia, equivalent to c . 5 months growth, although the annual growth in L _T was similar. This is further evidence that C. gunnari hatched earlier at Shag Rocks. At South Georgia, the mean L _T of age‐classes 1+ and 3+ years were correlated, and significantly decreased between 1987 and 2002, and were smaller following warmer summers. This decrease in the size of C. gunnari may be the result of reduced food availability linked to climate warming.     

Water relations and osmotic adjustment in Apium graveolens during long‐term NaCl stress and subsequent relief

Pea plants ( Pisum sativum L. cv. Feltham First) exposed to a heat stress of 37°C for 6 h accumulated two low molecular weight (LMW) heat shock proteins (HSPs) of molecular mass 22 kDa. The two LMW HSPs were associated with purified mitochondria. N‐terminal amino acid sequencing analysis indicates that the more basic of these proteins is a novel protein. The response of other cultivars of P. sativum to heat shock revealed that up to three 22‐kDa HSPs were expressed in a cultivar‐specific manner. Evidence presented suggests that the different 22‐kDa HSPs arise as a result of there being multiple 22‐kDa HSP genes. The expression of the most basic novel HSP was studied in the Feltham First cultivar using two dimensional SDS‐PAGE. Treatment of intact plants with chloramphenicol and cycloheximide prior to heat stress treatment indicated that the LMW HSPs were nuclear encoded and de novo synthesised. The response to heat shock was rapid with protein expression detected within 45 min and the protein remained in excess of 6 days following removal of the stress. The protein accumulated to very high levels with maximal expression being 2% of the total mitochondrial protein. The results are discussed in relation to the likely role of LMW HSPs in thermotolerance.     

Differential ozone sensitivity interferes with cadmium stress in poplar clones

Information on plant responses to combined ozone and cadmium stresses are scarce and limited to herbaceous species. In this research, two poplar clones (I-214 and Eridano), differently sensitive to O₃, were grown for 5 weeks in pots supplied with 0, 53.5, and 160.5 mg(Cd) kg^?1 (soil d.m.) and then exposed to 15-d O₃ fumigation (0.06 mm³ dm^?3, 5 h a day). The effects of the two stressors, alone or in combination, on Cd, Ca, Fe, and Zn accumulation in above-nad below-ground organs, photosynthesis, leaf pigments, and accumulation of H₂O₂ and NO were investigated. Cadmium induced a reduction in stomatal conductance and a significant accumulation of H₂O₂ and NO in both clones nad negatively affected the carotenoid content in I-214. Ozone, on the other hand, counteracted Cd accumulation in the above-ground organs and significantly increased the xanthophyll de-epoxidation state indicating photoinhibition in O₃-treated plants. Surprisingly, O₃ alone or in combination with Cd decreased H₂O₂ accumulation in I-214. The NO production was generally stimulated by Cd, whereas it decreased following O₃ exposure in I-214. The overall data indicate that Cd and O₃ induced clone specific responses. Moreover, when they were applied in combination, antagonistic rather than synergistic effects were observed.     

Estimating age and growth in long‐lived temperate freshwater crayfish using lipofuscin

1. In ecological studies on freshwater crayfish, determination of basic population parameters is often complicated by the lack of a suitable age estimation method.
2. Previously, lipofuscin age pigment in the olfactory lobe cell masses (OLCM) of short‐lived tropical crayfish has been used for accurate age determination. Here we present the first test of this method on a longer‐lived, temperate species, the signal crayfish, Pacifastacus leniusculus .
3. Confocal fluorescence microscopy and image analysis of histological sections were used to quantify OLCM lipofuscin in a reference sample of Swedish P. leniusculus from several known year‐classes, reared under naturally variable temperature conditions. Lipofuscin concentration was linearly associated with age ( r² = 92.4%) and produced much more accurate age estimates than conventional body size‐based procedures.
4. A model derived from the crayfish of known‐age was used to estimate the ages of wild P. leniusculus from an English stream. The relationship between lipofuscin‐estimated age and carapace length suggested relatively slow growth in this wild population, consistent with a high population density and severe competition. The analysis also extended the known longevity of P. leniusculus to approximately 16 years.
5. The lipofuscin method for determining age and growth may be widely applicable to freshwater crayfish, with probable further potential both within and outside the Crustacea.     

The response of sensitive and tolerant clones of Populus tremuloides to dynamic ozone exposure under controlled environmental conditions

Both sensitive and tolerant clones of aspen ( Populus tremuloides ) were exposed to ozone using four different exposure regimes under controlled environmental conditions. Based on data on ambient ozone from 10 cities in the USA, three treatments of 4-wk exposure to the same SUM06 (an accumulation of hourly O₃ concentrations greater than 0.06 ml l⁻¹) were constructed. The regimes allowed us to investigate: (a) the importance of long (3 wk, treatment 1) versus short (1 wk, treatment 2) duration of regimes with high peaks; (b) the effect of treatments with variable peak occurrence (treatments 1 and 2) versus uniform peak occurrence (treatment 3) during the exposure period. Nonfumigated control plants were maintained at ozone concentrations <10 nl l⁻¹. Bifacial black necrosis, a typical symptom of ozone injury on aspen leaves, occurred on both clones after 2 wk exposure. Up to 60% of the leaves on the sensitive clone were injured, with an average of 6% of total leaf area injured. In the tolerant clone only 10% of the leaves were injured, with less than 1% of the total leaf area symptomatic. The severity of injury was consistently greatest in treatment 2, followed by treatments 1 and 3, respectively. The interval between peak exposures was less important than the occurrence of peaks versus a stable maximum concentration. Premature leaf abscission occurred in the sensitive clone. Measures of gas exchange demonstrated reduced photosynthesis under ozone fumigation, but exposure regime was not a significant factor. Concentrations of two antioxidants, ascorbic acid and glutathione, were almost always greater in the resistant than in the sensitive clone, but the differences were not statistically significant. The levels of these antioxidants in aspen leaves did not change with ozone fumigation or leaf age.     

Early responses to cadmium of two poplar clones that differ in stress tolerance

Soil cadmium (Cd) contamination is becoming a matter of great global concern. The identification of plants differentially sensitive to Cd excess is of interest for the selection of genotype adaptive to grow and develop in polluted areas and capable of ameliorating or reducing the negative environmental effects of this toxic metal. The two poplar clones I-214 (Populus × canadensis) and Eridano (Populus deltoides × maximowiczii) are, respectively, tolerant and sensitive to ozone (O₃) exposure. Because stress tolerance is mediated by an array of overlapping defence mechanisms, we tested the hypothesis that these two clones differently sensitive to O₃ stress factor also exhibit different tolerance to Cd. With this purpose, an outdoor pot experiment was designed to study the responses of I-214 and Eridano to the distribution of different Cd solutions enriched with CdCl₂ (0, 50 and 150 μM) for 35 days. Changes in leaf area, biomass allocation and Cd uptake, photosynthesis, chlorophyll fluorescence, leaf concentration of nutrients and pigments, hydrogen peroxide (H₂O₂) and nitric oxide (NO) production and thiol compounds were investigated. The two poplar clones showed similar sensitivity to excess Cd in terms of biomass production, photosynthesis activity and Cd accumulation, though physiological and biochemical traits revealed different defence strategies. In particular, Eridano maintained in any Cd treatment the number of its constitutively wider blade leaves, while the number of I-214 leaves (with lower size) was reduced. H₂O₂ increased 4.5- and 13-fold in I-214 leaves after the lowest (L) and highest (H) Cd treatments, respectively, revealing the induction of oxidative burst. NO, constitutively higher in I-214 than Eridano, progressively increased in both clones with the enhancement of Cd concentration in the substrate. I-214 showed a more elevated antioxidative capacity (GSH/GSSG) and higher photochemical efficiency of PSII (F_v/F_m) and de-epoxidation degree of xantophylls-cycle (DEPS). The glutathione pool was not affected by Cd treatment in both clones, while non-protein thiols and phytochelatins were reduced at L Cd treatment in I-214. Overall, these two clones presented high adaptability to Cd stress and are both suitable to develop and growth in environments contaminated with this metal, thus being promising for their potential use in phytoremediation programmes.     

Induction of thaumatin‐like proteins (TLPs) in Rhizoctonia solani‐infected rice and characterization of two new cDNA clones

Thaumatin‐like proteins (TLPs) were shown to be induced in rice plants (cv. IR58) that were infected with the sheath blight fungus, Rhizoctonia solani . Western blot analysis revealed the presence of two TLPs with sizes of 25 and 24 kDa which are different from a previously reported TLP with a size of 15.6 kDa from rice plants infiltrated with the non‐pathogenic bacterium, Pseudomonas syringae pv. syringae . By probing a cDNA expression library prepared from RNA isolated from R. solani ‐infected rice plants with a TLP antibody, several putative TLP cDNA clones were isolated and sequenced. The cDNA clones appeared to be derived from two different genes which shared only 77% sequence identity with each other and a lower percentage of sequence identity with the previously reported TLP cDNA clone. Southern blot analysis with the two TLP cDNAs revealed different rice genomic DNA fragments. Northern blot analysis also confirmed that a 1.1‐kb RNA detectable by the TLP cDNA inserts was induced by fungal infection. Thus rice TLPs are encoded by a family of at least three genes which are differentially expressed in responses to bacterial or fungal pathogens.     

Ecophysiological and morphological adaption to soil flooding of two poplar clones differing in flood-tolerance

Responses to soil flooding of two poplar clones differing in flood-tolerance were studied to elucidate ecophysiological and morphological adaptation to hypoxia. Results showed that Populus deltoides cv. Lux ex. I-69/55 (Lux) was flood-tolerant, whereas P. simonii was flood-susceptible, based on structural and functional differences. They differed in morphological, ecophysiological, and anatomical characteristics when subjected to flooding. The difference between cv. Lux and P. simonii became particular obvious with increased length of the flooding period (8–22 days), but responses to flooding differed already during the first week of flooding. Ecophysiologically, in the beginning of flooding cv. Lux kept a high level of photosynthesis, showed a high free water content and water use efficiency at reduced leaf conductances and leaf water potentials. Chlorophyll content of cv. Lux was reduced so that sunlight absorption was lower as well and destruction of the photosynthesis system by photooxidation was avoided. Free protein content of Lux under flooding was also low, probably in favor of synthesis of other substances that enforce flood tolerance. On the contrary, in P. simonii transpiration only slowly decreased due to slow stomatal closure of leaves in the first day of flooding, and water potential decreased slowly, accompanied with high transformation rate of free water into bound water and low water use efficiency. Slow decomposition of chlorophyll of P. simonii resulted in overabundant light energy absorption and serious destruction of photosynthesis system II (PSII). Net photosynthesis of P. simonii seriously decreased under flooding. At the morphological level, cv. Lux developed many small and obviously functional hypertrophied lenticels throughout the flooding treatment. Bigger hypertrophied lenticels of P. simonii inclined to become rotten. Under complete submergency, cv. Lux could keep an intact leaf structure, whereas epidermis and structure of leaves of P. simonii were destroyed severely. Anatomically, the ultrastructures of leaves of cv. Lux were still intact at the end of flooding, whereas those of P. simonii were destroyed seriously, and many organelles were decomposed.     

Proximate causes of sexual size dimorphism in Colorado pikeminnow, a long‐lived cyprinid

Evidence for sexual size dimorphism (SSD) and its possible causes were examined in the endangered Colorado pikeminnow Ptychocheilus lucius, a large, piscivorous, cyprinid endemic to the Colorado River system of North America. Individuals representing 18–24% of the upper Colorado River population were captured, measured, sexed and released in 1999 and 2000. Differing male and female total length‐(L_T) frequency distributions revealed SSD with females having greater mean and maximum sizes than males. Although both sexes exhibit indeterminate post‐maturity growth, growth trajectories differed. The point of trajectory divergence was not established, but slowed male growth might coincide with the onset of maturation. Differing growth rate was the dominant proximate cause of SSD, accounting for an estimated 61% of the observed difference in mean adult L_T. The degree of SSD in adults, however, was also related to two other factors. Evidence suggests males become sexually active at a smaller size and earlier age than females; a 2 year difference, suggested here, accounted for an estimated 12% of the between‐sex difference in mean adult L_T. Temporal shifts in gender‐specific survival accounted for an additional 27% of the observed between‐sex difference in mean adult L_T. Estimated age distributions indicated a higher number of older females than older males and more younger males than younger females in the population during the period of sampling. Dissimilarity of age distributions was an unexpected result because the male : female population sex ratio was 1 : 1 and estimates of long‐term annual survival for adult males and females were equal (88%). Future assessments of SSD in this population are apt to vary depending on the prior history of short‐term gender‐specific survival. Without recognizing SSD, non‐gender‐specific growth curves overestimate mean age of adult females and underestimate mean age of adult males of given L_T. Assuming age 8 years for first reproduction in males and age 10 years for females, the adult male : female ratio was estimated as 1·1 : 1 and mean adult age, or generation time, was estimated as 16·4 years for males and 18·4 years for females.     

Interaction of drought and ozone exposure on isoprene emission from extensively cultivated poplar

The combined effects of ozone (O₃) and drought on isoprene emission were studied for the first time. Young hybrid poplars (clone 546, Populus deltoides cv. 55/56 x P. deltoides cv. Imperial) were exposed to O₃ (charcoal‐filtered air, CF, and non‐filtered air +40 ppb, E‐O₃) and soil water stress (well‐watered, WW, and mild drought, MD, one‐third irrigation) for 96 days. Consistent with light‐saturated photosynthesis (A_sat), intercellular CO₂ concentration (C_i) and chlorophyll content, isoprene emission depended on drought, O₃, leaf position and sampling time. Drought stimulated emission (+38.4%), and O₃ decreased it (?40.4%). Ozone increased the carbon cost per unit of isoprene emission. Ozone and drought effects were stronger in middle leaves (13th–15th from the apex) than in upper leaves (6th–8th). Only A_sat showed a significant interaction between O₃ and drought. When the responses were up‐scaled to the entire‐plant level, however, drought effects on total leaf area translated into around twice higher emission from WW plants in clean air than in E‐O₃. Our results suggest that direct effects on plant emission rates and changes in total leaf area may affect isoprene emission from intensively cultivated hybrid poplar under combined MD and O₃ exposure, with important feedbacks for air quality.     

Short‐term survival and movements of Atlantic sharpnose sharks captured by hook‐and‐line in the north‐east Gulf of Mexico

Ultrasonic telemetry was used to compare post‐release survival and movements of Atlantic sharpnose sharks Rhizoprionodon terraenovae in a coastal area of the north‐east Gulf of Mexico. Ten fish were caught with standardized hook‐and‐line gear during June to October 1999. Atlantic sharpnose sharks were continuously tracked after release for periods of 0·75 to 5·90 h and their positions recorded at a median interval of 9 min. Individual rate of movement was the mean of all distance and time measurements for each fish. Mean ± s.e . individual rate of movement was 0·45 ± 0·06 total lengths per second (L_T s^?1) and ranged from 0·28 to 0·92 L_T s^?1 over all fish. Movement patterns did not differ between jaw and internally hooked Atlantic sharpnose sharks. Individual rate of movement was inversely correlated with bottom water temperature at capture (r² = 0·52, P ≤ 0·05). No consistent direction in movement was detected for Atlantic sharpnose sharks after release, except that they avoided movement towards shallower areas. Capture‐release survival was high (90%), with only one fish not surviving, i.e. this particular fish stopped movement for a period of 10 min. Total rate of movement was total distance over total time (m min^?1) for each Atlantic sharpnose shark. Mean total rate of movement was significantly higher immediately after release at 21·5 m min^?1 over the first 1·5 h of tracking, then decreased to 11·2 m min^?1 over 1·5–6 h, and 7·7 m min^?1 over 3–6 h (P ≤ 0·002), which suggested initial post‐release stress but quick recovery from capture. Thus, high survival (90%) and quick recovery indicate that the practice of catch‐and‐release would be a viable method to reduce capture mortality for R. terraenovae.     

Short‐term lime pretreatment of poplar wood

Short‐term lime pretreatment uses lime and high‐pressure oxygen to significantly increase the digestibility of poplar wood. When the treated poplar wood was enzymatically hydrolyzed, glucan and xylan were converted to glucose and xylose, respectively. To calculate product yields from raw biomass, these sugars were expressed as equivalent glucan and xylan. To recommend pretreatment conditions, the single criterion was the maximum overall glucan and xylan yields using a cellulase loading of 15 FPU/g glucan in raw biomass. On this basis, the recommended conditions for short‐term lime pretreatment of poplar wood follow: (1) 2 h, 140°C, 21.7 bar absolute and (2) 2 h, 160°C, and 14.8 bar absolute. In these two cases, the reactivity was nearly identical, thus the selected condition depends on the economic trade off between pressure and temperature. Considering glucose and xylose and their oligomers produced during 72 h of enzymatic hydrolysis, the overall yields attained under these recommended conditions follow: (1) 95.5 g glucan/100 g of glucan in raw biomass and 73.1 g xylan/100 g xylan in raw biomass and (2) 94.2 g glucan/100 g glucan in raw biomass and 73.2 g xylan/100 g xylan in raw biomass. The yields improved by increasing the enzyme loading. An optimal enzyme cocktail was identified as 67% cellulase, 12% β‐glucosidase, and 24% xylanase (mass of protein basis) with cellulase activity of 15 FPU/g glucan in raw biomass and total enzyme loading of 51 mg protein/g glucan in raw biomass. Ball milling the lime‐treated poplar wood allowed for 100% conversion of glucan in 120 h with a cellulase loading of only 10 FPU/g glucan in raw biomass. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

盐胁迫下白杨无性系苗木体内离子分配及比较

以白杨杂种无性系及其亲本当年生苗木为材料 ,分析了盐胁迫下无性系的离子含量 ,及 Na 、K 、Ca 在植物体内运输和分配特点 ,并对无性系间差异进行了比较。研究表明 ,随盐浓度提高 ,植物体内Na 含量迅速提高 ,K 、Ca 含量降低 ;盐分胁迫下 ,根部 Na 含量较高 ,叶片 Na 中含量最低 ,K 、Ca 含量则相反 ,特别是 Ca ,其分布顺序为叶 >茎 >根。杂种无性系 B430及其亲本新疆杨对 K 和 Ca 运输的选择性比毛白杨高 ,而对 Na 运输的选择性则比毛白杨低 ,从而导致根部存留的 Na 较多 ,叶片分配的 Na 数量较少 ,从而减轻 Na 对叶片的伤害。综合分析表明 B430和新疆杨耐盐能力最强 ,毛新杨其次 ,毛白杨最差。     

Fertilization of poplar clones in the nursery

Summary Results of experiments with four poplar clones and various chemical fertilizers in a nursery in southern Greece are presented. At the end of the first growth period the heights of the four clones, without fertilizers, decreased in the order of I-214>I-262>cv. campeator > black poplar 1/64 with significant differences only between black poplar 1/64 and the rest of the clones.Of the fertilizer nutrients N, P, K and Mg only N improved heights of all clones significantly and especially of the clone I-214. One hundred and 200 kg of P fertilizer per ha had minimal or negative effect on height increase of all clones.Ammonium sulfate, ammonium nitrate and potassium nitrate all at 400 kg N per ha were found equally effective in improving height growth of the clone I-214 but ammonium nitrate is the N fertilizer of choice by its higher N content and relatively lower price.Ammonium nitrate at 200 kg N per ha, in two or three equal dosages, during the first growth period, June–July, gave the maximum height increase for two consecutive years of the clone I-214. Six hundred kgs, of N per ha reduced height increase of the same clone and increased losses of N, as NO₃ ^–, in drainage water.