Mycosphaerella species occurring on Eucalyptus globulus and Eucalyptus nitens plantations of Tasmania,Australia

The genus Mycosphaerella Johanson contains many pathogens capable of causing a severe impact on the growth of susceptible eucalypt species. The lack of knowledge about which species are present in Tasmania and their potential risk to the plantation industry prompted this study into the Mycosphaerella species occurring on Eucalyptus globulus and Eucalyptus nitens plantations in Tasmania. A total of 36 plantation and five road verge sites of E. globulus and E. nitens were sampled. Five Mycosphaerella species and three species from associated anamorph genera were isolated and identified in Tasmania; Mycosphaerella nubilosa, Mycosphaerella cryptica, Mycosphaerella tasmaniensis, Mycosphaerella grandis, Mycosphaerella vespa, Coniothyrium ovatum, Sonderhenia eucalypticola and Sonderhenia eucalyptorum. The most frequently isolated species with the highest incidence and severity of infection were M. cryptica and M. nubilosa. These two species appear to have the greatest potential to damage juvenile eucalypt plantations in Tasmania. A link between Mycosphaerella vespa and Coniothyrium ovatum is described for the first time.     

Physiology and anatomy of lenticel-like structures on leaves of Eucalyptus nitens and Eucalyptus globulus seedlings

Intumescences or abnormal, non-pathogenic, blister-like protuberant growths, form on Eucalyptus globulus Labill. and, to a much lesser extent, Eucalyptus nitens (Deane and Maiden) Maiden leaves when plants are grown in a high relative humidity environment. We examined the histology of intumescences and their effects on leaf photosynthetic processes. Intumescences were induced by placing E. globulus and E. nitens seedlings in a relative humidity of 80% in a greenhouse for 5 days. Symptomatic and asymptomatic leaves of plants with intumescence development were compared with leaves of control plants. Light-saturated carbon dioxide (CO(2)) assimilation (A(max)) and responses of CO(2) assimilation (A) to varying intercellular CO(2) partial pressure (C(i)) were measured. Symptomatic and asymptomatic leaf samples were fixed and sectioned and cellular structure was examined. Intumescences greatly reduced the photosynthetic capacity of E. globulus leaves and were associated with reduced electron transport rate and ribulose bisphosphate (RuBP) regeneration capacity. Tissue necrotization and cellular collapse of the palisade mesophyll and deposition of phenolic compounds in the affected areas, probably reduced light penetration to photosynthesizing cells as well as reducing the amount of photosynthesizing tissue. Photosynthetic capacity of E. nitens was unaffected. The intumescences resembled simple lenticels, both morphologically and developmentally. To our knowledge, this is the first time that lenticel-like structures developed in response to environmental conditions have been described on leaves.     

Defence responses in plantation‐grown Eucalyptus globulus and Eucalyptus nitens after artificial fungal inoculation

The formation of reaction and barrier zones was studied in the xylem of Eucalyptus globulus and Eucalyptus nitens tree stems after wounding and artificial inoculation with two white rot fungi. The study had two objectives: to describe host responses in Eucalyptus spp. by light microscopy and to determine whether they would differ in a fungal treatment (wounding and inoculation by one of two fungal isolates) when compared to a control treatment (wounding only). Eucalyptus globulus and E. nitens developed similar reaction and barrier zones. The E. globulus barrier zone was characterized by kino vein formation. In both hosts, the reaction zone was primarily influenced by content and distribution of living tracheids and parenchyma cells within the sapwood. By contrast, the anatomy of the barrier zone showed similarities to the basic xylem structure of each host, except for some cell types that were newly formed (sclereids, kino veins) or increased in number (parenchyma cells, tracheids). Other cell types were reduced in number or completely absent. Host response in terms of barrier zone width appeared to be greater in the fungal than control treatment. Both wood decay fungi appeared to induce a wider barrier zone in both species than that associated with non‐specific damage caused exclusively by wounding. However, the small number of replicates available for this study was possibly insufficient to provide statistical evidence for different barrier zone width between fungal and control treatments.     

Effects of Mycosphaerella leaf disease on the spectral reflectance properties of juvenile Eucalyptus globulus foliage

Mycosphaerella leaf disease (MLD) can cause significant discoloration, necrosis and defoliation in commercial plantations of young Eucalyptus globulus. This study investigated the spectral reflectance changes that result in E. globulus foliage from Mycosphaerella infection. Spectral reflectance measurements were made on healthy and infected E. globulus foliage in the visible and near‐infrared wavelengths (400–1000 nm). Reflectance (R) at 760 nm produced the largest difference between the extremes of disease severity classes. The wavelength most sensitive to infection severity was R678 nm. Other sensitive wavelengths were located between 480 and 500 nm. The wavelengths near 708 and 550 nm appeared relatively insensitive to infection severity. The reflectance index best correlated to leaf infection was R678/R550 (r = 0.841, p < 0.0001). This index was used in a linear regression model for successfully predicting leaf infection levels from an independent data set (r = 0.95, p < 0.0001).     

Mycosphaerella species associated with leaf disease of Eucalyptus globulus in Ethiopia

Eucalyptus spp. are among the most widely planted exotic trees in Ethiopia. Several damaging leaf pathogens are known from Eucalyptus spp. worldwide. Of these, Mycosphaerella spp. are among the most important, causing the disease known as Mycosphaerella leaf disease (MLD). Characteristic symptoms of MLD include leaf spot, premature defoliation, shoot and twig dieback. Recent disease surveys conducted in Ethiopian Eucalyptus plantations have revealed disease symptoms similar to those caused by Mycosphaerella spp. These symptoms were restricted to E. globulus trees growing in several localities in south, south western and western Ethiopia. The aim of this study was to identify the fungi associated with this disease. This was achieved by examining ascospore germination patterns, anamorph associations and sequence data from the Internal Transcribed Spacer (ITS) region of the rRNA operon, for representative isolates. Several different ascospore germination patterns were observed, suggesting that more than one species of Mycosphaerella is responsible for MLD on E. globulus in Ethiopia. Analysis of sequence data showed that three Mycosphaerella spp., M. marksii, M. nubilosa and M. parva were present. This is the first report of these three species from Ethiopia and represents a valuable basis on which to build further studies in the region.     

Water and nutrient supply regimes and the water relations of juvenile leaves of Eucalyptus globulus

Pressure-volume analysis was used to study effects of irrigation and fertilization on the water relations of newly expanded juvenile leaves of Eucalyptus globulus Labill. seedlings growing in Portugal's Atlantic region. In May, at the beginning of the dry season, fertilization and irrigation treatments had no significant effects on the water relations parameters investigated. In September, at the end of the dry season, leaves from non-irrigated plants had a significantly higher apoplasmic water content and a higher dry weight/turgid weight ratio than leaves of similar physiological age from irrigated trees. The osmotic potential at full turgor and the water potential at the wilting point were lower in non-irrigated than in irrigated plants. Changes in osmotic potential at full turgor were negatively correlated with changes in dry weight/turgid weight ratio, suggesting that reductions in osmotic potential at full turgor were largely the result of decreases in cell size. Fertilization had no detectable effect on these variables or on leaf tissue bulk modulus of elasticity. Tissue elasticity was also unaffected by irrigation. Independently of water and nutrient supplies, leaf elasticity was higher and relative water content at the wilting point lower in leaves sampled in May than in leaves sampled in September. In non-irrigated plants, leaves sampled in September had a lower tissue elasticity and a lower osmotic potential at full turgor than leaves sampled in May, indicating that leaves produced at the end of the dry season generate lower water potentials as turgor is lost than leaves expanded early in the season.     

Control of growth of juvenile leaves of Eucalyptus globulus: effects of leaf age

Biophysical variables influencing the expansion of plant cells (yield threshold, cell wall extensibility and turgor) were measured in individual Eucalyptus globulus leaves from the time of emergence until cessation of growth. Leaf water relations variables and growth rates were determined as relative humidity was changed on an hourly basis. Yield threshold and cell wall extensibility were estimated from plots of leaf growth rate versus turgor. Cell wall extensibility was also measured by the Instron technique, and yield threshold was determined experimentally both by stress relaxation in a psychrometer chamber and by incubation in a range of polyethylene glycol solutions. Once emerging leaves reached approximately 5 cm(2) in size, increases in leaf area were rapid throughout the expansive phase and varied little between light and dark periods. Both leaf growth rate and turgor were sensitive to changes in humidity, and in the longer term, both yield threshold and cell wall extensibility changed as the leaf aged. Rapidly expanding leaves had a very low yield threshold and high cell wall extensibility, whereas mature leaves had low cell wall extensibility. Yield threshold increased with leaf age.     

Host responses to natural infection by Cytonaema sp. in the aerial bark of Eucalyptus globulus

The chemical and anatomical host responses to natural fungal infection by Cytonaema sp. in the aerial bark of 3‐year‐old Eucalyptus globulus plantation trees were examined. The lesion margin (LM) of the canker‐infected bark was characterized by the formation of a layer of dark extractives visible to the naked eye. Chemical analysis of the LM by gas chromatography‐mass spectrometry (GC‐MS), high‐performance liquid chromatography (HPLC) with ultraviolet detection and HPLC‐MS using negative ion electrospray ionisation indicated the presence of a range of compounds including hydrolysable tannins, polymeric proanthocyanidins, flavonoid glycosides, formlyated phloroglucinol compounds and volatile terpenes. These compounds were either undetectable in healthy tissue or present at significantly lower concentrations than in the LM. The LM of the canker‐infected bark was morphologically distinct from healthy phloem, its characteristics varying depending on severity of canker infection. In superficial infections in which only the phloem was affected, the following LMs were observed: (i) a continuous wound periderm of multiple layers, or (ii) an incompletely differentiated and discontinuous wound periderm. In cases of severe canker infections in which the vascular cambium had been killed, the new phloem formed subsequently contained traumatic oil glands in addition to the responses observed for superficial canker infections. All LMs were characterized by the formation of new parenchyma cells that stained positive for the presence of polyphenols. The significance of the chemical and structural responses as defence mechanisms against fungi causing stem canker is discussed.     

Leaf water relations of Eucalyptus globulus ssp. globulus and E. nitens: seasonal, drought and species effects

In August 1990, a 2-ha plantation was established in an area where rainfall (about 515 mm year(-1)) was insufficient to meet evaporative demand. On nine occasions between September 1991 and April 1993, pressure-volume curves were constructed for irrigated and rainfed Eucalyptus globulus ssp. globulus Labill. and E. nitens (Deane and Maiden) Maiden trees. During the experiment, rainfed trees experienced six periods when predawn water potential was significantly lower than that of irrigated trees. In early spring of 1991 and 1992, osmotic potentials at full turgor and turgor loss point in the irrigated E. nitens were significantly lower than at other times of the year, probably because of winter hardening. Water stress reduced osmotic potential and increased bulk elastic modulus in E. nitens, whereas the reverse occurred in E. globulus. However, treatment differences with respect to changes in osmotic and elastic properties were commonly overshadowed by interspecific differences. These were most apparent at the end of the sixth period of water stress when osmotic potentials at full and zero turgor were significantly higher and bulk elastic modulus and relative water content at turgor loss point were significantly lower in E. globulus than in E. nitens. We conclude that the drought-tolerance responses of E. globulus make it a more suitable species than E. nitens for establishment on sites where moderate water stress is experienced.     

Leaf orientation,light interception and stomatal conductance of Eucalyptus globulus ssp. globulus leaves

Juvenile and adult leaves of the heteroblastic species Eucalyptus globulus Labill. ssp. globulus did not show active diurnal orientation toward or away from incident radiation. Juvenile leaves of a late-maturing sapling of a Tasmanian provenance were evenly distributed in all azimuth sectors. In contrast, an early-maturing sapling of the same age from Wilsons Promontory, Victoria had a predominance of adult leaf blades facing east and west. Mid-vein and blade angles of juvenile and adult leaves were non-random with an overall vertical declination of the leaves. Both leaf types intercepted a greater irradiance during the morning than at midday. Sub-horizontal juvenile leaves intercepted 22% more irradiance than vertical adult leaves during the middle of the day. The amphistomatal and isobilateral adult leaves intercepted sunlight equally on both leaf surfaces. Stomatal conductance was variable during the period of measurement but was similar for the Tasmanian juvenile (0.4 to 0.9 cm s(-1)) leaves and Wilsons Promontory adult (0.5 to 1.2 cm s(-1)) leaves. Greater light interception by the sub-horizontal juvenile leaves would confer a growth advantage to saplings and regenerating canopies. Reduced light interception and leaf temperature of vertical adult E. globulus leaves would assist in water conservation, particularly at high solar angles.     

Anatomical characteristics of thermally modified Eucalyptus nitens wood in an open and closed reactor system

ABSTRACT

Eucalyptus nitens specimens were thermally modified under open and closed systems. The anatomical characteristics from selected modifications that presented similar mass losses were investigated by analyzing images taken from scanning electron microscopy, transmission light microscopy, and X-ray micro-computed tomography. Wood cell wall thickness, fiber, and lumen area were measured and compared to unmodified specimens, and the crack formation after modification was also analyzed. There was only a slight decrease in the measured characteristics when compared to unmodified specimens. The wood cell wall thickness was less affected than the fiber and lumen areas, and both modifications presented similar crack formations. Overall, there were no significant differences between open and closed system modifications in the anatomical structure.     

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties. I. Basic density

A non-destructive sampling strategy for basic density, based on removing 12 mm bark-to-bark cores, was developed in E. globulus and E. nitens. Fifty trees of each species, aged 5 to 9 years, were sampled across a range of sites. Core samples were removed on both a north-south and an east-west axis from 6 fixed heights in the base of the tree (0.5 m, 0.7 m, …, 1.5 m). Whole-tree values were calculated from disc samples removed at eight percentage heights (0, 10, 20, …, 70%) and correlations between the cores and whole-tree values were used to determine the optimal sampling height. Core samples were found to be reliable predictors of whole-tree density, explaining between 84% and 89% of the variation between trees. Core sampling of E. globulus and E. nitens to estimate basic density of whole-trees and stands is feasible; cores from trees at all E. globulus sites gave high correlations with whole-tree values. For E. nitens, site differences were apparent, and it is recommended that a small destructive sampling program should be undertaken prior to commencing a major sampling program. Recommended optimal sampling heights are 1.1 m for E. globulus and 0.7 m for E. nitens. Core orientation was not important and density was not related to tree size. Six whole-tree samples or eight core samples are required for estimating the mean density of a stand at a specific site to an accuracy of ±20 kg m⁻³ with a 95% confidence interval. Received 17 September 1998     

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties; II. Fibre length and coarseness

Within-tree variation in fibre length and coarseness was studied in fifty trees of E. globulus and E. nitens to develop a non-destructive sampling strategy. Trees, aged 5 to 9 years, were sampled across a range of sites in southern Australia. Simulated core samples were removed at six fixed heights easily accessible from the ground (0.5, 0.7, ... 1.5 m) and at eight percentage heights (0, 10, 20, ... 70%). Whole-tree values, calculated from percentage height data, were correlated with the core data to determine the optimal sampling height. Core samples were found to be reliable predictors of whole-tree fibre length, but results were variable for fibre coarseness. Simulated cores taken from the recommended sampling heights explained 87% and 71% of variation in whole-tree fibre length for E. globulus and E. nitens respectively and 54% and 45% of the variation in whole-tree fibre coarseness. Fibre length at all fixed heights showed good correlations with whole-tree values at all sites for E. globulus. For E. nitens the correlations were slightly lower and variable across sites. Results for fibre coarseness varied across sampling heights and sites for both species. The recommended sampling height for fibre length is 1.5 m for both species, whilst for fibre coarseness, the recommended sampling heights are 0.9 and 1.1 m for E. globulus, and 0.9 and 1.3 m for E. nitens. Radial orientation of cores was not important and neither fibre length nor coarseness were related to tree size or basic density. To estimate stand mean fibre length to an accuracy of ±5% would require sampling 9 whole trees or taking cores from 13 trees for E. globulus and 4 whole trees or cores from 8 trees for E. nitens. For estimating stand mean fibre coarseness, 10 whole trees of E. globulus and 7 whole trees are needed for E. nitens. Core sampling for stand mean coarseness would require more trees: 13 to 21 for E. globulus and 11 to 16 trees for E. nitens. Received 17 September 1998     

Where to shoot your pilodyn: within tree variation in basic density in plantation Eucalyptus globulus and E. nitens in Tasmania

Longitudinal patterns of within tree variation for basic density were determined for plantation Eucalyptus globulus (ages 5 and 10 years) and E. nitens (ages 5, 10 and 15 years) growing in three geographic areas in Tasmania. Each tree was sampled by taking discs from a combination of percentage heights (0, 10, 20 ___ 70%) and fixed height samples (0.5 m, 0.7 m ___ 1.5 m). At each of the fixed heights, a single pilodyn reading was taken from each of 4 aspects. Weighted whole tree density was calculated from the percentage height samples and used for correlation and regression analysis with the fixed height samples. Both species showed an initial drop in density between the felling cut (zero height) and 0.5 m, followed by a linear increase in density between 10% and 70% of tree height. Slope of fitted regressions were parallel within species but differed significantly between the species (1.14 kg/m³ and 1.62 kg/m³ per 1% increase in height above 10% for E. globulus and E. nitens, respectively). Density at all fixed heights was highly correlated with whole tree values for E. globulus, but results were variable across sites for E. nitens. Both species were found to contain trees which produced aberrant pilodyn readings. For E. globulus, the optimal sampling height was 1.3 m above ground and the mean pilodyn reading was found to predict whole tree density with an accuracy of ±21 kg/m³. For E. nitens, optimal sampling height was 1.5 m above ground. However, pilodyn readings around the stem were not very repeatable and correlations with whole tree density were lower, resulting in the accuracy of prediction of whole tree density being ±26 kg/m³.     

Role of nitrogen remobilization from old leaves for new leaf growth of Eucalyptus globulus seedlings

Six-month-old Eucalyptus globulus Labill. seedlings were grown in sand culture irrigated with a nutrient solution containing 6.0 mol N m(-3) for 3 months (November-January). Before rapid growth began in February, seedlings were repotted and irrigated with either 6.0 mol N m(-3) (High-N treatment) or 1.0 mol N m(-3) (Low-N treatment). Seedlings were analyzed during the subsequent flush of growth to determine the role of old leaves, and in particular the leaf protein Rubsico, as a source of N for new leaf growth. During spring growth, the N content of old leaves of High-N seedlings decreased with decreasing leaf dry weight, although there was no change in leaf number. In High-N seedlings, the net loss of N from old leaves provided less than 10% of the N used for new leaf growth, and the new leaves quickly became the dominant sink for N. In contrast, in Low-N seedlings, the net loss of N from old leaves provided 44% of the N used for new leaf growth. During the period of spring growth, the amount of soluble proteins recovered from old leaves of Low-N seedlings dropped, but there was no change in the content of either Rubisco or chlorophyll. The photosynthetic capacity of old leaves remained constant throughout the study period, and there was no evidence that N was remobilized from Rubisco.     

Metabolic responses to water deficit in two Eucalyptus globulus clones with contrasting drought sensitivity

We compared the metabolic responses of leaves and roots of two Eucalyptus globulus Labill. clones differing in drought sensitivity to a slowly imposed water deficit. Responses measured included changes in concentrations of soluble and insoluble sugars, proline, total protein and several antioxidant enzymes. In addition to the general decrease in growth caused by water deficit, we observed a decrease in osmotic potential when drought stress became severe. In both clones, the decrease was greater in roots than in leaves, consistent with the observed increases in concentrations of soluble sugars and proline in these organs. In roots of both clones, glutathione reductase activity increased significantly in response to water deficit, suggesting that this enzyme plays a protective role in roots during drought stress by catalyzing the catabolism of reactive oxygen species. Clone CN5 has stress avoidance mechanisms that account for its lower sensitivity to drought compared with Clone ST51.     

蓝桉、直干桉综合丰产技术试验示范

试验林采用正交设计，因素为树种、整地方式、密度、施肥，各因素取３个水平，３次重复。用生长量、生物量与投入产出进行评价。试验结果：３．５年生蓝桉、直干桉幼林最佳处理平均高９．５ｍ，平均胸径８．９ｃｍ，每ｈｍ２蓄积量７０．５１２６ｍ３，最佳处理比最差处理树高大２８．４％，胸径大３４．９％，蓄积量大１８３％。用已取得的技术成果营造的示范林，３．５年生平均高９．８ｍ，平均胸径６．５ｃｍ，累计产桉叶２．４３万ｋｇ／ｈｍ２，３年生左右，通过桉油及薪柴的收入可以回收全部造林及加工成本。     

史密斯桉、亮果桉种源选择

１９８６～１９９２年由澳大利亚提供史密斯桉种源１２个，亮果桉种源１７个，分别在保山、昆明、楚雄进行史密斯桉、亮果桉的种源选择试验。试验结果表明：史密斯桉、亮果桉存在种源差异；从生长量、生长稳定性、抗逆性、桉油含量等方面进行综合评定认为，史密斯桉１５５４４、１５０９２、１２１３１种源，亮果桉１２４０１、１３２８１、１４４４９、１６６３６、１６７５０种源是表现较好的种源，４～６年生史密斯桉优良种源，与直干桉对照相比，蓄积量的平均实际增益为５８％；而３～４年生亮果桉蓄积量的平均实际增益为７３％。史密斯桉含油量增益为５７．４％。试验选择出以上述两树种种源可在适宜地区推广。     

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties. III. Predicted pulp yield using Near Infrared Reflectance Analysis

  Within-tree variation in kraft pulp yield, predicted using near infrared reflectance analysis, was studied in thirty trees of E. globulus and fifty trees of E. nitens to develop a non-destructive sampling strategy. Trees, aged 5 to 9 years, were sampled across a range of sites in southern Australia. Simulated core samples were removed at six fixed heights easily accessible from the ground (0.5, 0.7, ... 1.5 m) and at seven percentage heights (0, 20, 30, ... 70%). Whole-tree values, calculated from percentage height data, were correlated with the core data to determine the optimal sampling height. Core samples were found to be good predictors of whole-tree pulp yield for E. globulus, with simulated cores taken from the recommended sampling height (1.1 m) explaining more than 50% of variation in whole-tree pulp yield. Results for E. nitens were variable with large site differences apparent. On high quality sites, core samples from the recommended sampling height (0.9 m) were good predictors of whole-tree pulp yield, explaining around 60% of the variation. On poor quality sites, cores were poor predictors of whole-tree pulp yield. Radial orientation of cores was not important and predicted pulp yield was not related to tree size, basic density or fibre length. To estimate stand mean pulp yield to an accuracy of ±1% would require sampling 6 trees of E. globulus and 4 trees for E. nitens using either multiple discs or core samples. A single sampling height (1.1 m) is recommended for sampling for basic density, fibre length, fibre coarseness and predicted pulp yield in E. globulus. For E. nitens the recommended sampling height for basic density and fibre length is 0.7 m and 0.9 m is recommended for predicted pulp yield on good quality sites. Received 17 September 1998