Dry mass of Fusarium roseum spores before and after germination
The total dry mass of Fusarium roseum spores and contained lipid bodies were determined before and after spores germinated using quantitative interference microscopy. The mean for spore dry mass before germination was about 57 pg. Lipid bodies accounted for about 61% of that. Areas of lipid bodies in spores before and after germination were about 23 % but the contents of the lipid bodies accounted for only 10% of the spore dry mass after germination. The total dry mass of the spore and germ tube(s) greatly exceeded that of the spore before germination. We infer that nutrients for germ tube growth are derived from within the germinating spore and from the medium which must contain nutrients leached from non-germinating spores.
Interference microscopy of onion epidermal nuclei in response to three fungal pathogens
Abstract Onion bulbs were injured on four sides with a sterile cork borer (5 mm diameter) and three such injuries were used as inoculation sites for Botrytis allii, Aspergillus niger and an unidentified neckrot fungus. Nuclei of cells in control tissue increased in size and dry mass as a result of wounding. Each of the fungi caused a decreased size and dry mass of host nuclei, with Botrytis allii being the most effective in this regard.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.