Martín Ariel Hadad

CHEMICAL COMPOSITION AND ANTIMICROBIAL ACTIVITY OF ESSENTIAL OIL FROM BACCHARIS GRISEBACHII HIERON (ASTERACEAE)

The essential oil of the aerial parts of Baccharis grisebachii was examined by GC and GC-MS and evaluated for its antimicrobial properties. Forty three essential oil constituents were identified representing 94.3% of the total. Thymol, thymol methyl ether, thymyl acetate, alpha pinene, alpha humulene, and globulol were found to be the major components. The oil showed MIC values < 250 μg/mL against Cryptococcus neoformans (125 μg/mL), Aspergillus spp. (125 μg/mL), and particulary against Trichophyton mentagrophytes and T. rubrum (62.5 μg/mL)

Sensitivity of pines in Mexico to temperature varies with age

Mexico has an abundance of Pinus species with P. cooperi as a dominant tree species of great ecological importance. In this study, we compared the climate sensitivity of P. cooperi trees of two age classes growing in the Sierra Madre Occidental: younger (< 80 years) and older (≥ 80 years) trees. A regional curve standardization (RCS) of growth ring width was developed for these two age classes. Our statistical analysis showed that annual tree growth was similar between the two age classes in absolute values of tree-ring widths. However, we found that the effects of rising temperatures during the previous winter are age-dependent; that is, maximum and minimum temperatures have opposite effects on the subsequent tree growth. Warming winter maximum temperatures have negative effects on radial growth, which are stronger in younger trees, whilst minimum winter temperatures enhance the growth. However, no difference in radial growth was observed between the two age classes based on precipitation. In climate change scenarios, an increase in temperature would affect younger trees of P. cooperi more than older trees. These effects of increased temperature may lead to a decrease in the growth and subsequent death of the trees. These results could help land managers to develop criteria related to forest management regarding P. cooperi.