Water stress impacts on respiratory rate, efficiency and substrates, in growing and mature foliage of Eucalyptus spp

In previous studies, water stress has induced variable and sometimes contradictory changes in respiration. We used isothermal calorimetry to measure the response of foliar respiration to water deficit in nine eucalypt genotypes. Specific growth rates (R _SG) of shoots and leaves of variable age were measured independently, and the data were applied to both the growth-maintenance and enthalpy balance models. We calculated the oxidation state of respiratory substrate and the enthalpy change for the conversion of substrate carbon to biomass (ΔH _B). Moderate water stress reduced the R _SG of shoots by 38% (P<0.01) and carbon conversion efficiency by 15% (P<0.05). The relationship between carbon conversion efficiency and R _SG was not affected by water deficit for shoots, but was significantly altered for leaves. Water deficit increased maintenance respiration by about 23% (P<0.001). The growth coefficient of respiration was not significantly altered. However, changes in oxidation states of substrate and biomass suggest that the energy requirements of biosynthesis were increased under water stress. Our results confirm that carbohydrates are the major respiratory substrates in growing tissues, though mature leaves utilized a substantial component of more reduced substrate. Mature leaves had variable oxidation states for respiration substrate, which indicates a variable relationship between CO₂ evolution and ATP production. Measured ΔH _B in shoots and leaves were too small for reliable estimation of R _SG by the enthalpy balance model. We also found significant effects of water stress on the oxidation state of substrate and ΔH _B.     

Early ovule development following self- and cross-pollinations in Eucalyptus globulus Labill. ssp. globulus

The study was conducted to identify the self-incompatibility mechanism in Eucalyptus globulus ssp. globulus. Controlled self- and cross-pollinations were conducted on individual flowers from three mature trees that had self-incompatibility levels of 76, 99.6 and 100%. Flowers were harvested at 4, 6 and 8 weeks after pollination. Embryology was investigated by bright field microscopy on material harvested at 4 and 6 weeks after pollination. Fertilization had taken place at 4 weeks after pollination with zygotes and free nuclear endosperm visible. There was a greater proportion of healthy, fertilized ovules in the cross- compared with the self-pollination treatment, and approx. half the ovules examined from both pollen treatments were not fertilized or were degenerating. By 6 weeks after pollination a few zygotes were starting to divide. The number of healthy, fertilized ovules was still greater in the cross-pollination treatment, but the number of healthy fertilized ovules was lower in both treatments compared with 4 weeks after pollination, and many ovules were degenerating. Fertilized ovules were significantly larger than non-fertilized or degenerating ovules and this difference was detectable by eye at 6 and 8 weeks after pollination. The mechanism of self-incompatibility appears to have both late pre- and post-zygotic components.     

CO2 enrichment predisposes foliage of a eucalypt to freezing injury and reduces spring growth

Seedlings of Eucalyptus pauciflora, were grown in open-top chambers fumigated with ambient and elevated [CO₂], and were divided into two populations using 10% light transmittance screens. The aim was to separate the effects of timing of light interception, temperature and [CO₂] on plant growth. The orientation of the screens exposed plants to a similar total irradiance, but incident during either cold mornings (east-facing) or warm afternoons (west-facing). Following the first autumn freezing event elevated CO₂-grown plants had 10 times more necrotic leaf area than ambient CO₂ plants. West-facing plants had significantly greater (25% more) leaf damage and lower photochemical efficiency (F_v/F_m) in comparison with east-facing plants. Following a late spring freezing event east-facing elevated CO₂ plants suffered a greater sustained loss in F_v/F_m than west-facing elevated CO₂- and ambient CO₂-grown plants. Stomatal conductance was lower under elevated CO₂ than ambient CO₂ except during late spring, with the highest leaf temperatures occurring in west-facing plants under elevated CO₂. These higher leaf temperatures apparently interfered with cold acclimation thereby enhancing frost damage and reducing the ability to take advantage of optimal growing conditions under elevated CO₂.     

Anticariogenic and phytochemical evaluation of Eucalyptus globules Labill.

In the present study, in vitro anticariogenic potential of ethyl acetate, hexane and methanol and aqueous extracts of plant leaves of Eucalyptus globules Labill. were evaluated by using four cariogenic bacteria, Lactobacillus acidophilus, Lactobacillus casei, Staphylococcus aureus and Streptococcus mutans. Agar well diffusion method and minimum inhibitory concentration (MIC) were used for this purpose. The ethyl acetate extracted fraction of plant leaves showed good inhibitory effects against all selected bacteria. In Eucalyptus globules, hexane and ethyl acetate extracts found highly effective against, Lactobacillus acidophilus with MIC value of 0.031 and 0.062 mg/mL, respectively. Qualitative phytochemical investigation of above extracts showed the presence of alkaloids, phenolic compounds, steroids, cardiac glycosides and terpenes. Based on the MIC value and bioautography, ethyl acetate of plant leaf was selected for further study. Further investigation on the structure elucidation of the bioactive compound using IR, GC-MS and NMR techniques revealed the presence of alpha-farnesene, a sesquiterpene. Eucalyptus globules plant leaf extracts have great potential as anticariogenic agents that may be useful in the treatment of oral disease.     

Antimicrobial activity of certain essential oils against hindgut symbionts of the drywood termite Kalotermes flavicollis Fabr. and prevalent fungi on termite-infested wood

Abstract:  When the kalotermitid Kalotermes flavicollis Fabr. pseudergates exposed to Casuarina wood wafers treated separately with different concentrations (5, 15 and 30  μ l/2 g wood wafer) of the essential oils, their spirochaete and flagellate populations abnormally reduced in numbers and vigour. The lophomonadids Joenia sp. and Mesojoenia sp. were the most adversely affected flagellates followed by the polymastigid Foaina sp. and the trichomonadid Tricercomitus sp. The Taxodium distichum essential oil evidently appeared to have the greatest adverse effect on the flagellates (95–100% decline in numbers within 2–4 days) followed by the Eucalyptus citriodora (89–100%) and the Cupressus sempervirens oils (31–100%). While with the hindgut spirochaetes, the adverse effect seemed to be reversed where the E. citriodora essential oil had the greatest effect (54–100%) followed by C. sempervirens (46–100%) and T. distichum (8–100%) oils. Moreover, the essential oils were assayed for their antifungal activity, at 15, 20, 25, 30, and 50  μ l/1 ml acetone/15 ml Czapek-Dox medium, against isolates of four woodrotting fungi associated with Casuarina timber, Aspergillus sp., Penicillium sp., Fusarium sp. and Mucor sp. by a method based on inhibition of the fungus growth on agar plates. E. citriodora exhibited the most potent fungicidal activity against the tested four fungi, followed by T. distichum oil. While the C. sempervirens essential oil appeared to have the least significant antifungal property.     

Arbuscular mycorrhizal symbiosis can counterbalance the negative influence of the exotic tree species Eucalyptus camaldulensis on the structure and functioning of soil microbial communities in a sahelian soil

The hypothesis of the present study was that bacterial communities would differentiate under Eucalyptus camaldulensis and that an enhancement of arbuscular mycorrhizal (AM) density would minimize this exotic plant species effect. Treatments consisted of control plants, preplanting fertilizer application and AM inoculation. After 4 months of culture in autoclaved soil, E. camaldulensis seedlings were either harvested for growth measurement or transferred into containers filled with the same soil but not sterilized. Other containers were kept without E. camaldulensis seedlings. After 12 months, effects of fertilizer amendment and AM inoculation were measured on the growth of Eucalyptus seedlings and on soil microbial communities. The results clearly show that this plant species significantly modified the soil bacterial community. Both community structure (assessed by denaturing gradient gel electrophoresis profiles) and function (assessed by substrate-induced respiration responses including soil catabolic evenness) were significantly affected. Such changes in the bacterial structure and function were accompanied by disturbances in the composition of the herbaceous plant species layer. These results highlight the role of AM symbiosis in the processes involved in soil bio-functioning and plant coexistence and in afforestation programmes with exotic tree species that target preservation of native plant diversity.     

Pinimenthol ointment in patients suffering from upper respiratory tract infections – A post-marketing observational study

In order to gain further experience regarding the tolerability of Pinimenthol^® ointment¹ in adolescents (⩾12 years) and adults suffering from upper respiratory tract infections, a post-marketing observational study was performed. In this study, data of 3060 patients were collected (64.9% prospectively over an individual observation period of 5–14 days, 35.1% retrospectively). The prospective documentation also comprised data concerning treatment effects.Sample size of the post-marketing observational study was calculated in the way that adverse drug reactions with an event probability of at least 1:1000 would occur within the study at least once with a probability of 95%.Most patients suffered from cold, acute or chronic bronchitis, bronchial catarrh or hoarseness. Pinimenthol^® ointment was prescribed to inunction (29.6%), inhalation (17.3%) or inunction and inhalation (53.1%), respectively. The mean duration of study participation was 8.0±3.4 days.The tolerability was rated as excellent or good by 96.7% of physicians and 95.7% of patients. A total of 22 patients (0.7%) reported adverse drug reactions which mostly affected the skin or mucus membrane and therefore correspond to the expected adverse effects profile of Pinimenthol^® ointment. The treatment effect was mostly judged as excellent or good (physicians: 88.3%; patients: 88.1%).In conclusion, the study confirms Pinimenthol^® ointment as a well tolerated therapy option for upper respiratory tract infections in both adolescents and adults.