A Trip Back Home: Resistance to Herbivores of Native and Non-Native Plant Populations of Datura stramonium.

When colonizing new ranges, plant populations may benefit from the absence of the checks imposed by the enemies, herbivores, and pathogens that regulated their numbers in their original range. Therefore, rates of plant damage or infestation by natural enemies are expected to be lower in the new range. Exposing both non-native and native plant populations in the native range, where native herbivores are present, can be used to test whether resistance mechanisms have diverged between populations. Datura stramonium is native to the Americas but widely distributed in Spain, where populations show lower herbivore damage than populations in the native range. We established experiments in two localities in the native range (Mexico), exposing two native and two non-native D. stramonium populations to natural herbivores. Plant performance differed between the localities, as did the abundance of the main specialist herbivore, Lema daturaphila. In Teotihuacán, where L. daturaphila is common, native plants had significantly more adult beetles and herbivore damage than non-native plants. The degree of infestation by the specialist seed predator Trichobaris soror differed among populations and between sites, but the native Ticumán population always had the lowest level of infestation. The Ticumán population also had the highest concentration of the alkaloid scopolamine. Scopolamine was negatively related to the number of eggs deposited by L. daturaphila in Teotihuacán. There was among-family variation in herbivore damage (resistance), alkaloid content (scopolamine), and infestation by L. daturaphila and T. soror, indicating genetic variation and potential for further evolution. Although native and non-native D. stramonium populations have not yet diverged in plant resistance/constitutive defense, the differences between ranges (and the two experimental sites) in the type and abundance of herbivores suggest that further research is needed on the role of resource availability and adaptive plasticity, specialized metabolites (induced, constitutive), and the relationship between genealogical origin and plant defense in both ranges.

Effect of jasmonic acid on major terpenes and density of glandular trichomes in Lippia graveolens kunth (Verbenaceae).

The effect of exogenous application of jasmonic acid (JA) on the concentration of main terpenes and density of glandular trichomes was investigated in the Mexican oregano, propagated from seeds from 3 localities. JA 1 mM was applied locally and to the whole plant. JA locally applied increased the number of trichomes, with a mean of 20 trichomes more with respect to the controls in plants from Tecomavaca and Zapotitlán Salinas, and significantly increased the thymol concentration by 185% systemically and 255% locally, compared to the control. JA applied to the whole plant decreased the number of trichomes and increased the concentration of caryophyllene from 0.79 to 1.7 mg g-1, and α-caryophyllene from 0.3 to 0.8 mg g-1 in plants from San Rafael with reference to water control. The results suggest a plasticity of morphologic and phytochemical responses, and a potential use of JA to improve phenolic monoterpenes and sesquiterpenes production.

Comparison of Biological Properties of Two Medicinal Extracts of the Tehuacan-Cuicatlan Valley.

In the Valley of Tehuacan-Cuicatlan, Cyrtocarpa procera and Bursera morelensis are located and are used in traditional medicine. In this research, several biological properties were evaluated. The methanol extracts of C. procera (MeCp) and B. morelensis (MeBm) were obtained by maceration. The antibacterial activities of the extracts were evaluated by the Kirby-Baüer disc-diffusion method. The wound healing activity was evaluated by histopathological analysis. Both extracts had a bacteriostatic effect in the Staphylococcus aureus (MeCp MIC = 0.25 mg/mL and MeBm MIC = 1 mg/mL) and the Vibrio cholerae (MeCp MIC = 1 mg/mL and MeBm MIC = 4 mg/mL). Both extracts demonstrated a wound healing efficacy similar to the reference standard (Recoveron). They also showed a high antioxidant capacity (MeCp SC50 = 5.75 µg/mL and MeBm SC50 = 4.27 µg/mL). These results are related to the concentration of phenols (MeCp = 166 and MeBm = 236.6 mg GAe/g) and flavonoids of MeCp = 16 and MeBm = 22 µg Qe/g. Both extracts, acting in a similar way in microorganisms that cause infection thanks to their antioxidant activity, favor the healing of wounds. This is the first study in which the biological properties of these two species are compared.