Eucalyptus globulus Labill.

Transcription

1 Eucalyptus globulus Labill. / / Photo: V. Buono Origin and diffusion Origin: Australia Distribution: Oceania, Africa, Europe, southern America Invasive potential: low Photo: V. Buono Photo:V.Buono Photo: L. Passatore Photo: L. Passatore Introduction Large evergreen tree, with a straight trunk and bent branches, even low positioned, bearing dense clumps of leaves. Blue gum is characterized by the grey-bluish colour of leaves and the bark; the latter with the age progressively peels in long strips and emerges smooth bluish-white and pink areas. The leaves contain terpenes and flavonoids which give it a pungent and very refreshing smell. The oil extracted from the leaves and the steam has flavouring, antimicrobial and pesticide properties. The flowers produce copious nectar that yields a strongly flavoured honey. The solid and flexible structure of the tree makes it an excellent windbreak. It has a great evapotranspiration potential, enabling it to pump large volumes of water from the soil; for this reason it has been largely employed for draining wetlands. Eucalyptus forests are particularly prone to fire-risks but also able to quickly regenerate. Blue gum, native to Australia, has easily naturalized in other continents due to its rapid growth and adaptability to a wide range of conditions. It is especially well-suited to countries with a mediterranean-type climate, but it grows well also in tropics at high altitudes. Common names: Blue Gum (English), Eucalipto (Italian) Photo: L.Passatore Description Life-form and periodicity: : evergreen tree Height: m

2 Fam. myrtaceae Description Roots habit: root system develops mainly in the topsoil but roots can spread several meters deep in the soil, up to 9 m, in search for water. Culm/Stem/Trunk: it has a straight trunk up to two-thirds of its total height. The diameter is 1,2-2,1m. Bark: it sheds often, peeling in large strips, emerging smooth bluish-white and pink areas. Leaf: glossy, thick and leathery. The leaves of the young shoots are ovate, opposite, and horizontal, 7-16 cm long, covered with a blue-grey, waxy bloom, which is the origin of the common name "blue gum"; instead the mature leaves are alternate, cm long, sickle-shaped and dark shining green. Rate of transpiration: l/day/tree Reproductive structure: The white flowers are solitary in the leaf axils. The sepals and petals are united to form a lid which is present on the bud and drops off at anthesis. They are approximately 4-5,5 cm wide and produce copious nectar. The flower has many stamens. Propagative structure: The fruits are woody capsule and range from 1,5 to 2,5 cm in diameter. Numerous small seeds are shed through valves (numbering between 3 and 6 per fruit) which open on the top of the fruit. Development Sexual propagation: Eucalypt flowers are mainly pollinated by insects. Most seed is distributed by wind and gravity, but some is moved by such agents as flood, erosion and birds. Usually seeds fall out within 300 m from the parent tree. The first seeds to leave the globular capsule are infertile. The fertile seeds are located at the bottom of the capsule. In the field, germination should occur no later than 26 days once the appropriate environmental conditions are met. However, seed may remain dormant for several years under dry conditions.. Asexual propagation: by cuttings Growth rate: medium

3 Habitat characteristics Light and water requirement: It prefers full sun and moist soils. Soil requirements: it requires moist, clayish and fertile soils. ph from 6.3 to 6.8. It is well-suited to hydroponic cultivation Tolerance/sensitivity: it is sensitive to the presence of nitrogen; lack of this element implies a reduction of the development of the plant. It can grow under a wide variety of agro-ecological conditions, however it is very sensitive to poor soil structure and shortage or excess of water during early stages of growth Phytotechnologies applications Eucalyptus is an interesting plant for phytoremediation purposes due to its high transpirative activity. It has been employed mainly in hydraulic containment of landfill leachate and contaminated area drainage. Furthermore the rapid growth and the potential use of the wood for energy and paper production, make this species a good candidate for secondary wastewater treatment through tree irrigation. Eucalyptus hydroponic cultivation is another good alternative for contaminated water treatment; several researches demonstrated that eucalyptus is tolerant to heavy metals (Cd, Zn, Cu and Pb) and to arsenic which accordingly with the low translocation factors measured, tend to accumulate mainly in roots. The latter are easy to remove in case of hydroponic culture.(king et al., 2008; Arrigada et al.,2010; Peng et al., 2012;Gomes et al., 2012; Fine et al., 2013) Furthermore the blue-gum leaves can be used as soil amendment in order to stimulate bacterial PCB degradation (Hernandez et al.,1997). Lives contain terpenes, structural analogs of PCBs; these substances act as cometabolite, enhancing the production of enzymes capable to degrade also PCBs (Passatore et al., 2014).

4 Phytotechnologies applications Experimental studies -Experiment 1- Reference Contaminants of concern Plant species Mechanism involved in phytoremediation: Phytostabilisation/rhizodegradation/phyt oaccumulation/phytodegradation/phytov olatilization/ hydraulic control/ tolerant Types of microorganisms associated with the plant Requirements for phytoremediation (specific nutrients, addition of oxygen) Substrate characteristics Laboratory/field experiment Age of plant at 1st exposure (seed, post-germination, mature) Length of experiment Initial contaminant concentration of the substrate D. J. King, A. I. Doronila, C. Feenstra, A. J.M. Baker, I. E. Woodrow, Phytostabilisation of arsenical gold mine tailings using four eucalyptus species: growth, arsenic uptake and availability after five years. Science of the total environment 406; As E. cladocalyx, E. melliodora, E. polybractea, E. viridis Phytostabilisation Not reported in the publication The tailings were covered with various amendments prior to planting as a previous work had shown that plants did not grow on raw tailings. The inclusion of the oxide rock in either milled or non-milled form has previously been shown to be important in plant establishment. The trees were grown on As-rich sulphidic gold mine tailings, located in Australia. Sulphur (2 6%) was predominantly present as pyrite with lesser amounts of arsenopyrite, pyrrhotite, sphalerite and chalcocite ; arsenic ( %) was present as pyrite and arsenopyrite). The high levels of sulphides have not caused acid generation due to the high neutralizing capacity of the source material (gypsum salts).. Field experiment Young trees 5 years The total arsenic levels in the experimental plots were measured at between 0,2 and 0,4% (w/w)

5 Phytotechnologies applications Post-experiment contaminant concentration of the substrate Post-experiment plant condition Contaminant storage sites in the plant and contaminant concentrations in tissues (root, shoot, leaves, no storage) Not reported It is known that the mine tailings tested here do retard the growth of eucalypts (Doronila, 2006), the fact that the plants have survived and are growing, in some cases quite well, does indicate that the trees are tolerant to the As concentrations to which they are exposed. There was significant variation in height within the four species. For example, the smallest E. cladocalyx was just 1,03 m tall after 5 years. The variation in tree heights was not correlated with As concentrations in either stems or leaves. Arsenic was found in all plants grown on the tailings. The highest concentrations were found in the leaves, while smaller amounts were found in the stems. All four species accumulated low As concentrations, the highest being recorded in mature leaves, ranging from 0,29 to 5,14 μg/g As. E. polybractea had significantly higher foliar As than the other three species. Comparison of those samples taken from cores drilled under trees (<2 m from the nearest tree) with those taken from cores drilled away from trees (>5 m), showed no significant effect of trees on As concentrations. Experiment 2- Reference Contaminants of concern Plant species Mechanism involved in phytoremediation: Phytostabilisation/rhizodegradation/phyt oaccumulation/phytodegradation/phytov olatilization/ hydraulic control/ tolerant C. Arriagada, G. Pereira, I. Garcıa-Romera, J.A. Ocampo, Improved zinc tolerance in Eucalyptus globulus inoculated with Glomus deserticola and Trametes versicolor or Coriolopsis rigida. Soil Biology & Biochemistry 42; Zn Eucalyptus globulus Phytostabilisation and phytoaccumulation

6 Phytotechnologies application Types of microorganisms associated with the plant Requirements for phytoremediation (specific nutrients, addition of oxygen) Substrate characteristics Laboratory/field experiment Age of plant at 1st exposure (seed, post-germination, mature) Length of experiment Initial contaminant concentration of the substrate Post-experiment contaminant concentration of the substrate Post-experiment plant condition Contaminant storage sites inthe plant and contaminant concentrations in tissues (root, shoot, leaves, no storage) Saprophytic fungi: Trametes versicolor and Coriolopsis rigida. Arbuscular mycorrhizal: Glomus deserticola G. deserticola inoculum (root-and-soil inoculum consisting of rhizosphere soil containing spores and colonized root fragments of Medicago sativa). C. rigida or T. versicolor inoculum: sterilized barleys seeds were used as saprophytic fungal inoculums carriers. The seeds were inoculated with a thin slice of potato dextrose agar with mycelia of the saprophytic fungi Mixture of sterilized sand:soil at a proportion of 1:1 (V:V). The soil, classified as an Andisol (Acrudoxic Hapludands), with low P content (7,3 mg/kg, NaHCO3-extractable), is moderately acidic (ph 5,4) with good drainage and water infiltration. Laboratory experiment (in vitro and greenhouse). Seedlings 133 days In vitro experiment: in Petri dishes Zn concentrations were 0, 10, 20, 50, 100, and 200 mg Zn/l. Greenhouse experiment. Plants grown at different Zn concentrations (): 0, 10, 100, 500 and 1000 mgzn/kg soil In vitro experiment: the concentration of Zn in the AG growth medium decreased 51-67% after culture with C. rigida and 54-66% after culture with T. versicolor. Greenhouse experiment: in the presence of 500 and 1000 mg kg/l Zn, there were higher metal concentrations in roots and shoots of arbuscular mycorrhizal than in non-arbuscular mycorrhizal plants; furthermore, both saprophytic fungi increased Zn uptake by trees colonized by G. deserticola. At doses higher than 100 mg Zn per kg or liter, the shoot dry weight of plants decreased in all treatments. Plants colonized with Glomus deserticola were less affected than plants not colonized with arbuscular mycorrhizal. The saprophytic fungi T. versicolor and C. rigida increased the shoot dry weight and the tolerance of E. globulus to Zn when these plants were mycorrhizal-colonized. Both saprophytic fungi increased the percentage of arbuscular mycorrhizal root length colonization and elevated its metabolic activity. The higher root to shoot metal ratio observed in mycorrhizal plants indicates that G. deserticola enhanced Zn uptake and accumulation in the root system, playing a filtering/sequestering role in the presence of Zn.

7 Phytotechnologies applications -Experiment 3- Reference Contaminants of concern Mechanism involved in phytoremediation: Phytostabilisation/rhizodegradation/phyt oaccumulation/phytodegradation/phytov olatilization/ hydraulic control/ tolerant Types of microorganisms associated with the plant Requirements for phytoremediation (specific nutrients, addition of oxygen) Substrate characteristics Laboratory/field experiment Age of plant at 1st exposure (seed, post-germination, mature) Length of experiment Initial contaminant concentration of the substrate Post-experiment contaminant concentration of the substrate C. Arriagada, E. Aranda, I. Sampedro, I. Garcıa- Romera, J.A. Ocampo, Interactions of Trametes versicolor, Coriolopsis rigida and the arbuscular mycorrhizal fungus Glomus deserticola on the copper tolerance of Eucalyptus globulus. Chemosphere 77: Cu Phytostabilisation and phytoaccumulation Saprophytic fungi: Trametes versicolor and Coriolopsis rigida. Arbuscular mycorrhizal: Glomus deserticola G. deserticola inoculum (root-and-soil inoculum consisting of rhizosphere soil containing spores and colonized root fragments of Medicago sativa). C. rigida or T. versicolor inoculum: sterilized barleys seeds were used as saprophytic fungal inoculums carriers. The seeds were inoculated with a thin slice of potato dextrose agar with mycelia of the saprophytic fungi. Mixture of sterilized sand:soil at a proportion of 1:1 (V:V). The soil, classified as an Andisol (Acrudoxic Hapludands), with low P content (7,3 mg/kg, NaHCO3- extractable), is moderately acidic (ph 5,4) with good drainage and water infiltration. Laboratory experiment (in vitro and greenhouse) Seedlings 12 weeks In vitro experiment: in Petri dishes concentrations were 0, 10, 20, 30, 60, and 100 mg Cu/l. Greenhouse experiment plants were grown at different Cu concentrations: 0, 10, 100, 1000 and 2000 mgcu/kg soil. In vitro experiment: the Cu concentration in the AG growth medium decreased between 53% and 66% after culture of C. rigida and between 26% and 47% after culture of T. versicolor.

8 Phytotechnologies applications Post-experiment plant condition Contaminant storage sites in the plant and contaminant concentrations in tissues (root, shoot, leaves, no storage) The presence of high levels of Cu in soil decreases the shoot and root dry weights of E. globulus. However, higher plant tolerance of Cu has been observed in the presence of the fungus G. deserticola. In contrast with other essential metals, Cu is toxic to most fungi even at very low concentrations (Baldrian, 2003). Only the C. rigida- G. deserticola combination increased the tolerance of plants to Cu. It is known that E. globulus was able to accumulate heavy metals in the stem more than in the leaves. The absence of a higher root to shoot metal ratio in the mycorrhizal plants (1,70 0,11) indicated that G. deserticola did not play a filtering/sequestering role against Cu. Plants colonised by G. deserticola had higher metal concentrations in the roots and shoots than do non-mycorrhizal plants. Best results have been achieved with the inoculation of G. deserticola + C. rigida, it increased the plant Cu uptake to levels reached by hyperaccumulative plants (up to 400 mg/kg in shoots and 800 mg/kg in roots). Plants inoculated only with C. rigida and T. versicolor did not accumulate more Cu than noninoculated controls. -Experiment 4- Reference Contaminants of concern Mechanism involved in phytoremediation: Phytostabilisation/rhizodegradation/phyt oaccumulation/phytodegradation/phytov olatilization/ hydraulic control/ tolerant Types of microorganisms associated with the plant C. Arriagada, M. A. Herrera, F. Borie, J.A. Ocampo, Contribution of Arbuscular Mycorrhizal and Saprobe Fungi to the Aluminium Resistance of Eucalyptus globulus. Water Air Soil Pollut 182: Al Phytostabilisation and phytoaccumulation Saprophytic fungi: Fusarium concolor and Trichoderma koningii Arbuscular mycorrhizal: Glomus mosseae and Glomus deserticola

9 Phytotechnologies applications Requirements for phytoremediation (specific nutrients, addition of oxygen) Substrate characteristics Laboratory/field experiment Age of plant at 1st exposure (seed, post-germination, mature) Length of experiment Initial contaminant concentration of the substrate Post-experiment contaminant concentration of the substrate Post-experiment plant condition The possibility of manipulating an arbuscular mycorrhizal inoculation together with a saprobe fungus conferring high aluminium tolerance and accumulation in the shoot by E. globulus could be a good alternative for stimulating plant growth under adverse conditions, such as in soils where acidic conditions and low levels of P, Ca and Mg may contribute to aluminium toxicity. In vitro experiment: The AG medium consisted of 1 g glucose, 0,4 g asparagine, 0,05 g MgSO4, 0,05 KH2PO4 and 100 ml distilled water. Greenhouse experiment: mixture of sterilized sand:vermiculite:sepiolite at a volume proportion of 1:1:1. Laboratory experiment (in vitro and greenhouse) Seedlings 16 weeks In vitro experiment: concentrations in Petri dishes were 0, 500 and 1000 mg Al/l. Greenhouse experiment plants were grown at different Cu concentrations: 0, 150, 600, 1500 and 3000 mgal/kg substrate. Not reported in the publication The application of 1500 mg/kg decreased the shoot and root dry weight, chlorophyll content and total P, Mg, and Ca concentrations in the shoot of E. globulus. Neither saprobe fungi gave any additional aluminum tolerance to E. globulus. However, both mycorrhizal fungi G. mosseae and G. deserticola inoculated alone increased the shoot dry weight of Eucalyptus, with the latter being significantly higher, even at the application rate of 1,500 mg kg 1 The application of 3,000 mg kg 1 decreased the shoot dry weight of plants in all treatments tested. the shoot:root ratio increased with both strains of mycorrhizal inoculum, with G. deserticola being higher; this suggests a greater beneficial effect on plant growth produced by such a mycorrhizal strain.

10 Phytotechnologies application Contaminant storage sites in the plant and contaminant concentrations in tissues (root, shoot, leaves, no storage) Aluminum concentration in shoots of E. globulus plants did not show any differences either at lowest (150 mg kg 1) or highest (3,000 mg kg 1) concentrations when plants were not affected either by AMF or saprobe fungi inoculation. However, at 600 and 1500 mg kg 1, both Glomus strains produced a significant increase in shoot aluminum concentration, which was not reinforced by the two inoculated saprobe fungi. In addition, at the same aluminum level in the growth media, the effect of T. koningii was synergistic with what was presented by G. deserticola inoculation and the highest aluminum concentration was obtained (approximately 27 mg kg 1). Aluminum shoot content in this last treatment increased approximately sixfold in comparison to those obtained in control plants.