ABSTRACT
Desiccation tolerance in vegetative tissues enables resurrection plants to remain quiescent under severe drought and rapidly recover full metabolism once water becomes available. Barbacenia graminifolia is a resurrection plant that occurs at high altitudes, typically growing on rock slits, exposed to high irradiance and limited water availability. We analyzed the levels of reactive oxygen species (ROS) and antioxidants, carotenoids and its cleavage products, and stress-related phytohormones in fully hydrated, dehydrated, and rehydrated leaves of B. graminifolia. This species exhibited a precise adjustment of its antioxidant metabolism to desiccation. Our results indicate that this adjustment is associated with enhanced carotenoid and apocarotenoids, α-tocopherol and compounds of ascorbate-glutathione cycle. While α-carotene and lutein increased in dried-leaves suggesting effective protection of the light-harvesting complexes, the decrease in ß-carotene was accompanied of 10.2-fold increase in the content of ß-cyclocitral, an apocarotenoid implicated in the regulation of abiotic stresses, compared to hydrated plants. The principal component analysis showed that dehydrated plants at 30 days formed a separate cluster from both hydrated and dehydrated plants for up to 15 days. This regulation might be part of the protective metabolic strategies employed by this resurrection plant to survive water scarcity in its inhospitable habitat.
ABSTRACT
BACKGROUND: Cyanobacteria blooms have become a major environmental problem and concern because of secondary metabolites produced by cyanobacteria released into the water. Cyanobacteria produce volatile organic compounds (VOCs), such as the compounds ß-cyclocitral and ß-ionone, which comprise odors, off-flavors, defense compounds, as well as growth regulators. Therefore, the general objective of this work was to evaluate the VOCs produced by two strains of Microcystis aeruginosa, differing in their ability to produce microcystins (LTPNA 01-non-producing and LTPNA 08-toxin-producing). The analysis of VOC production was carried out in (1) normal culture conditions, (2) under different light intensities (LI), and (3) after the external application of ß-ionone in both cultures. RESULTS: The results showed that ß-cyclocitral and ß-ionone are produced in all growth phases of LTPNA 01 and LTPNA 08. Both strains were producers of ß-cyclocitral and ß-ionone in normal culture conditions. It was observed that the ß-cyclocitral concentration was higher than ß-ionone in all light intensities investigated in this study. Additionally, the strain LTPNA 01 produced more ß-cyclocitral than LTPNA 08 at almost all times and LIs analyzed. However, the strain LTPNA 08 produced more ß-ionone, mainly at the initial times. In addition, the experiment results with the external addition of ß-ionone in the cultures showed that the strain LTPNA 01 produced more ß-cyclocitral in control conditions than in treatment. Nonetheless, ß-ionone production was higher in treatment conditions in LTPNA 08, indicating that the addition of ß-ionone may favor the production of these compounds and inhibit the production of ß-cyclocitral. CONCLUSION: Our results showed that some abiotic factors, such as different light intensities and external application of ß-ionone, can be triggers that lead to the production of VOCs.