Leaf photosynthetic properties in a willow (Salix viminalis and Salix dasyclados) plantation in response to fertilization

Specific leaf area (SLA), nitrogen and chlorophyll concentrations and photosynthetic characteristics were studied in upper and lower canopy leaves of Salix viminalis and S. dasyclados grown at two nutrition levels. Fertilization increased SLA and leaf mass-based nitrogen concentration in most cases. Positive effects of fertilization on leaf light-saturated photosynthetic rate (A _max ^A ) and maximum carboxylation rate (V _cmax) were not detected. Significant differences between the leaves from upper and lower canopy layers in area-based nitrogen, A _max ^A , SLA, mass-based chlorophyll, V _cmax and stomatal conductance were found for most plots. We attempted to estimate the fraction of non-photosynthetic nitrogen and found that it tended to be higher due to fertilization. Thus, the insensitivity of leaf photosynthesis to fertilization could be caused by higher proportion of non-photosynthetic nitrogen in the leaves of fertilized plots. Though leaf-level photosynthesis was not increased by fertilization, considerably higher leaf area index of fertilized plots still resulted in increased canopy carbon gain.     

Hormonal physiology of wood growth in willow (Salix viminalis L.): effects of spermine and abscisic acid

Summary Willow cuttings from two-year-old twigs were grown in nutrient solution alone, nutrient solution with 0.1 mM abscisic acid or with the spermine. Roots and leaves emerged within three weeks and the cambium was activated in the shoot. In most cases earlywood was generated, even when the seedlings were made in late summer. In contrast to plantlets grown in regular nutrient solution, those treated with hormones either inhibited (ABA) or advanced (spermine) the formation of roots, leaves and wood. In addition, SEM observations of wood were combined with autoradiographic studies and metabolite analysis.¹⁴C-labeled photoassimilates from the leaves were unloaded from the phloem of the shoots and transported via the rays into the cambial zone and the xylem. In spermine treated plants labeled assimilates were highly concentrated in all cells of the newly built xylem. However, cells from plants treated with abscisic acid appeared only weakly labeled. Quantitative analysis of the assimilates after two-dimensional thin-layer chromatography showed that wood from spermine-treated plants accumulated 19% more assimilates than the control, while xylem from ABA-treated plants imported 81% less labeled compounds from the phloem. Thus, the results strongly support the view that hormones play a key role in wood formation.     

Genetics of field resistance to Melampsora in Salix viminalis

The inheritance of resistance to Melampsora. spp. on Salix viminalis, the variation in resistance over space and time, and rust infection rate in relation to the geographic origin of the host was studied. The analysis showed that there was considerable additive genetic variation for rust resistance, that the results did not have high repeatability over space and time, and that the material from southernmost Sweden was most sensitive to the rusts occurring in south Sweden.     

Uptake and Distribution of Radiocesium in Fast-Growing Salix viminalis L

The accident at the Chernobyl nuclear power plant in 1986 led to a significant increase of radionuclide content in the eastern part of central Sweden. Radioactive cesium (Cs-134 and Cs-137) have accumulated in the soil, waters and living organisms. In agriculture, farmers are looking for alternative crops also in areas with a high radioactive content. Biomass plantations for energy are potential candidates for such soils provided the cycling of radionuclides can be controlled. Nothing IS known so far about the behaviour of cesium in energy forest production systems. The ability to take up cesium and the distribution of Cs-134 and Cs-137 within plants were investigated in a selected fast-mowing willow clone. kesium-contaminatid soil was used as substrate for apot experiment with cutting-derived plants of Salix viminalis. The total plant uptake of Cs-134 + Cs-137 was approximately 0.2% of the cesium present in the soil substrate. Almost 90% of the assimilated cesium was found allocated to the roots. The total amount of cesium in the plants increased over time.     

Relative susceptibility of Salix clones to chrysomelid beetles: evidence from the Stott willow collection at Ness

Willow species and hybrids growing in the Stott willow collection at Ness, UK, differed markedly in their susceptibility to leaf damage by insects, predominantly chrysomelid beetles, with the rank order of susceptibility remaining relatively constant over 2 years. Some species displayed a wide range of variation in susceptibility amongst clones; others very little. The range of susceptibilities of hybrids tended to mirror those of the parent species, with the hybrid usually sustaining leaf damage levels intermediate between those of the parents. Leaf damage in most species was higher on the lower leaf surface up to mid-season, beyond which leaf perforation damage became prevalent. Damage levels did not appear related to leaf toughness. Apparent levels of leaf damage were lower in October versus July/August samples across nearly all species. Heavy leaf damage in one year did not appear to induce the production of leaves that were more resistant to insect attack in the following year.     

Diurnal variation in extension growth of leaves of Salix viminalis

Diurnal variation in leaf extension and biophysical parameters of leaf growth were measured in young leaves from a stand of Salix viminalis L. in southern Sweden over a two-day period of clear skies during late July. Leaf growth rate (irreversible extension) was greatest during the late afternoon and early evening, falling to negligible values during the night and early morning.Leaf water potential and leaf osmotic potential showed declining values in the morning with subsequent recovery in the late afternoon. Diurnal variation in osmotic potential (-1.3 to -1.7 MPa) was small compared with that of leaf water potential (-0.1 to -1.2 MPa). Calculated values of leaf turgor pressure during the night (1.2 MPa) were double the midday values. Growth rate correlated poorly with turgor, which (except on one occasion) was always above a calculated value of yield turgor at 0.53 MPa.Diurnal variation in extension growth rate was large compared with that in plastic extensibility of leaf tissue as measured by an Instron technique. Values of extensibility were low and showed little diurnal variation, which is consistent with a proposed negative feedback of expansive growth rate on extensibility. Extension growth rate correlated well with air temperature, suggesting that the rate of leaf expansion may have been limited by a temperature-dependent rate of cell wall loosening.     

菲胁迫下蒿柳抗氧化系统的响应

[目的]研究菲胁迫下活性氧和抗氧化物质的变化规律,探究蒿柳抗氧化系统的防御机制,为提高其对多环芳烃(PAHs)的抗性及加强植物修复的研究提供理论依据。[方法]以蒿柳扦插苗为试验材料,采用水培方式,研究其在0、1.0 mg·L^-1菲处理下活性氧、抗氧化酶、抗氧化剂以及丙二醛(MDA)的动态变化,处理时间为16 d。[结果]研究表明:(1)菲处理后第4天,H2O2含量和氧自由基(O₂^·-)生成速率迅速增加,MDA含量升高,过氧化氢酶(CAT)活性显著上升;第8天超氧化物歧化酶(SOD)和过氧化物酶(POD)活性显著升高;第16天时,H2O2含量下降到与对照无显著差异,O₂^·-和MDA的增加量下降。(2)还原型谷胱甘肽(GSH)和谷胱甘肽还原酶(GR)在处理后第4天即迅速上升,谷胱甘肽-S-转移酶(GST)呈缓慢上升趋势。(3)还原型抗坏血酸(AsA)含量在处理后第4天低于对照,但随着处理时间的延长呈上升趋势,在第16天时高于对照。[结论]菲胁迫下,O₂     

柳树在环境污染生物修复中的应用

柳树适应性强、根系发达、生物量大、生长速度快、萌芽更新能力强,耐水湿,可以吸取各种污染物,是环境遭受污染后的重要生物修复树种。深入地论述了柳树对重金属污染、有机物污染和水体富营养化的生物修复作用,以及对土壤污染、水体污染、大气污染的生物修复作用。     

Diurnal variation in leaf extension of Salix viminalis at two nitrogen supply rates

To investigate how nitrogen supply might affect the biophysical factors controlling diurnal variation in leaf extension, pot-grown Salix viminalis L. were supplied with nitrogen at a low relative addition rate of 0.05 g N g(-1) N day(-1) (low N) or were given free access to all nutrients (high N). Leaf extension, turgor pressure, turgor after stress relaxation and the plastic extensibility of leaf tissue were determined for growing leaves every 4 h during two days of clear skies in August. Plants in the high-N treatment had a significantly higher relative growth rate, dry weight, shoot/root ratio, leaf nitrogen concentration, total leaf area, final area of single leaves and epidermal cell size than plants in the low-N treatment. The periodicity of leaf extension was similar in both treatments with high values during the afternoon and early evening, and negligible values during the night and in the early morning. The maximum rate of leaf extension was higher in high-N than in low-N plants. Leaf water potential and leaf osmotic potential decreased in the morning and increased in the afternoon with highest values during the night. Calculated values of turgor pressure showed no consistent diurnal trend and did not correlate with the rate of leaf extension. There was no consistent difference in turgor between treatments. Turgor after stress relaxation varied diurnally. The difference between turgors before and after stress relaxation also varied diurnally and was largely in phase with the diurnal pattern of leaf extension. These data are consistent with either a causal role for growth turgor (difference between turgors before and after stress relaxation) in the regulation of cell expansion, or a diurnal variation in turgors after relaxation, attributable to different capacities for cell wall loosening at different times of day. Plastic extensibility of leaf tissue showed no diurnal pattern but consistently higher values were found in high-N than in low-N plants. We conclude that the effects of nitrogen supply on leaf water relations did not limit leaf extension, but that nitrogen supply did affect processes associated with cell wall loosening and enlargement. Nitrogen supply did not affect final values of turgor after relaxation, but it presumably affected the rate at which relaxation proceeded.     

Rust scorings in a plantation of Salix viminalis clones during ten consecutive years

Among pests and diseases occurring in coppiced willow plantations established to produce biofuel, Melampsora rust is the most widespread and severe. In the present study, the variation in rust attacks in a set of Salix viminalis clones was investigated. The aim was to look for trends possibly arising from changes in rust genotype composition, to get some idea about the risks of rust overcoming resistance bred into new willow varieties. Rust levels on 92 S. viminalis clones belonging to 18 different families were scored once each year during 1987–96 in a plantation in southern Sweden. Rust scorings in 1993 deviated most from the average scoring pattern of the clones. Furthermore there was a successive change, such that the longer the time interval between scorings the lower was the correlation between rust scores. Willow families were identified that deviated from the others over time. Various explanations for inconsistency in rust scores over time are discussed.     

Effect of nitrogen fertilization on growth in a Salix viminalis stand using a response surface experimental design

In order to find a nitrogen fertilization regime that is economically feasible in commercial short‐rotation forest stands of basket willow (Salix viminalis L.), a field trial was established on a clay soil near Västerås, central Sweden, in early 1990. A response surface design was used in which three levels of treatment were chosen for each single year: year 1—0, 30, 60, kg N ha^?1; year 2—0, 60, 120, kg N ha^?1; year 3—0, 90, 180, kg N ha^?1; year 4—0, 60, 120, kg N ha^?1. Thirty‐two combinations of these levels, out of 81 possible, were chosen and divided into four blocks. Thus, eight unique treatments were randomized to the plots within each block, providing no replicates at the end of the experimental period. This gave us a more flexible and informative experiment than many of those used earlier with rather few treatments, although they were replicated. After 4 years the willow stand was harvested and the accumulated stem production of each treatment was assessed. The effect of nitrogen fertilization on accumulated stem growth over the experimental period was found to be significant only for nitrogen applied in years 2 and 3, with a somewhat (statistically significant) larger effect in year 2. Growth response to nitrogen fertilization was best approximated with a function including terms with applied amount of nitrogen in years 2 and 3 and, furthermore, a term of interaction with negative coefficient between these years. The interaction between these years was interpreted as the system's ability to recycle nitrogen from one year to another.     

乔木型柳树无性系镉积累特性研究

研究了25个乔木型柳树无性系的镉吸收积累特性。在镉质量分数为5.0×10-6的营养液培养条件下培养40 d,乔木柳叶片的镉含量为34.88×10-6~289.25×10-6,平均值为119.02×10-6;叶片镉转运系数为2.91%~25.89%,镉积累成本介于0.15 mg/10-6~4.69 mg/10-6之间。枝条的镉含量为44.79×10-6~154.38×10-6,平均值为95.64×10-6;枝条的镉转运系数为3.36%~16.48%,镉积累成本为0.75 mg/10-6~4.47 mg/10-6;镉处理对插穗的萌条高生长多有抑制作用,对插穗不定根发生和根系干重的影响存在差异,有促进、也有抑制作用。     

Leaf responsiveness of Populus tremula and Salix viminalis to soil contaminated with heavy metals and acidic rainwater

Fast-growing trees such as Salix viminalis L. and Populus tremula L. are well suited to phytoremediate heavy metal contaminated soils. However, information on tree performance, particularly leaf function, under conditions of heavy metal contamination is scarce. We used yearly coppiced saplings of S. viminalis and P. tremula growing in model ecosytems to test four hypotheses: (1) heavy metal contamination impairs photosynthesis by injuring leaf structure; (2) the effects of heavy metal contamination are enhanced by acidified rainwater and low soil pH; (3) heavy metal contamination increases dark respiration and, thus, repair processes; and (4) heavy metal contamination is tolerated and remediated better by S. viminalis than by P. tremula. We investigated heavy metal accumulation, tissue injury and gas exchange in leaves of plants subjected to controlled soil contamination with heavy metal dust. Additional treatments included acidic and calcareous natural forest subsoils in combination with irrigation with rainwater at pH 5.5 or 3.5. In both provenances of P. tremula that were studied, but not in S. viminalis, heavy metal treatment reduced photosynthesis and transpiration by varying amounts, except in the hot and dry summer of 2003, but had no effect on dark respiration. At light saturation, net CO(2) uptake and water-use efficiency were reduced by heavy metal contamination, whereas the CO(2) concentration in the leaf intercellular air space was increased. Rainwater pH and subsoil pH only slightly modified the effects of the heavy metal treatment on P. tremula. Gas exchange responses of P. tremula to heavy metals were attributed to leaf structural and ultrastructural changes resulting from hypersensitive-response-like processes and accelerated mesophyll cell senescence and necroses in the lower epidermis, especially along the transport pathways of heavy metals in the leaf lamina. Overall, the effects of heavy metals on P. tremula corroborated Hypothesis 1, but refuted Hypotheses 2 and 3, and were inconclusive for Hypothesis 4. Both P. tremula and S. viminalis showed appreciable potential for storing heavy metals in aging foliage.     

Effects of temperature on the growth of a Japanese willow (Salix gilgiana Seemen)

The effects of temperature on the growth characteristics of a Japanese willow (Salix gilgiana Seemen) were studied with respect to dry matter production, wood anatomy and the net photosynthetic rates of leaves. Clonal materials were grown in natural-light rooms (phytotrons) at 30°C/25°C, at 25°C/20°C or at 20°C/15°C (day/night: 12 h/12 h), respectively. The elongation rate of shoots from the beginning of June to the end of July was approximately 22 cm per week under the three different sets of conditions. The shoots reached approximately 3 m in height after 4 months of growth. Total dry matter production and dry weights of stems did not differ very much among the three sets of temperature conditions after 9 months of growth. The dry weight of leaves increased at high temperatures while that of roots decreased. The number of vessels increased significantly at 30°C/25°C and 25°C/20°C, whereas the diameters of vessels and fibers, and the double wall thickness of fibers did not vary markedly under all three temperature regimes. The net photosynthetic rate and the respiration rate in mature leaves were highest at 30°C/25°C, and both activities increased with increases in growth temperature. The increase in the photosynthetic rate was much smaller than that in the respiration rate. Individual plants had been completely adapted to the respective growth temperatures, as judged from the decrease in the photosynthetic rate after the transfer to different temperatures. Part of this work was reported at the 102nd Annual Meeting of the Japanese Forestry Society (Nagoya, Japan, 1991). This work was supported by Grants-in-Aid (Integrated Research Program for Effective Use of Biological Activities to Create New Demand) from the Ministry of Agriculture, forestry and Fisheries of Japan (BRP 97-IV-B-10).     

Seasonal fluctuations of starch in root and stem tissues of coppiced Salix viminalis plants grown under two nitrogen regimes

Seasonal changes in starch were studied at the tissue and cellular levels in roots and stems of Salix viminalis L. cuttings. Cuttings were planted in pots containing sand and grown in a controlled environment chamber in which seasons were artificially induced by changes in temperature and photoperiod. Nitrogen was supplied at optimum and low rates, and during dormancy, one-half of the plants were decapitated. Starch concentrations in root and stem tissues were determined regularly during shoot extension growth, dormancy and resprouting after dormancy. We used light microscopy (LM) combined with image analysis (IA) to determine the cellular localization and amount of starch in different cell types of stem and root tissues. Chemical analysis confirmed that starch concentrations were lower in plants receiving a high-N supply rate than in plants receiving a low-N supply rate. In all plants, the highest concentration of starch was in the roots. Light microscopy and IA showed that starch accumulated mainly in the phloem and cortical cells of both root and stem tissues. Starch grains were also regularly found in ray parenchyma cells. The amount of starch as well as the size of the grains showed strong seasonal fluctuations. In both roots and stems, starch concentrations were highest during predormancy and lowest during periods of shoot extension growth. At the time of resprouting, root cells of decapitated plants were more depleted of starch than root cells of intact plants, supporting the hypothesis that starch reserves in roots are important during the early phase of resprouting in coppice systems.     

Diurnal pattern of leaf extension in Salix viminalis relates to the difference in leaf turgor before and after stress relaxation

Relations between leaf dry weight to leaf area (LWA), leaf nitrogen concentration and irradiance inside a natural canopy were studied in Betula pendula Roth., Corylus avellana L. and Lonicera xylosteum L. In all species, LWA increased with increasing irradiance. Relative variability in LWA was smaller in Betula pendula than in the other two species. In Corylus avellana, LWA also depended on total plant height. Foliar nitrogen concentration (on a dry weight basis) increased with increasing irradiance and LWA in Betula pendula, but decreased in the other two species. The interspecific variation in response to light availability and in nitrogen partitioning may be caused by different light demands or different life forms (trees versus shrubs), or both, of the species examined, and must be considered in contemporary canopy models.     

The ecology of fungal cankers on Cupressus macrocarpa in southern England

Bark isolations from cankers on Cupressus macrocarpa in southern England yielded Seiridium cardinale, Pestalotiopsis funerea and Pestalotiopsis monochaetioides. The recovery pattern of the three fungi indicated that only S. cardinale was a primary pathogen; the two Pestalotiopsis species being secondary. Pathogenicity data obtained following the inoculation of C. macrocarpa branches with mycelium of the three fungi confirmed this view. No evidence of vegetative incompatibility was found in S. cardinale, but five vegetative-compatibility (vc) groups were found in P. funerea and six in P. monochaetioides. Different vc groups of the two Pestalatiopsis species were often found in the same S. cardinale lesion, suggesting that a number of separate colonization events were involved. It is possible that this sometimes leads to complete replacement of the pathogen.