Biochemical and physiological time-of-day variations in early-development phase of Agave mapisaga and Agave salmiana.

This research assesses the aboveground matter accumulation and Fv/Fm ratios (maximum quantum efficiency of PSII) in young plants (5months old) of Agave mapisaga and Agave salmiana grown under greenhouse conditions. This study also evaluated changes in the relative abundance of several different metabolites (sugars, free amino acids, and soluble phenols) during the major daily phases (I, III, and IV) of Crassulacean acid metabolism (CAM). These two species were also investigated to determine if differences in these parameters were evident with respect to their geographical origins (i.e. Metepec, Tlajomulco, and Tlaxiaca, in the state of Hidalgo, Mexico). Differences in shoot mass (0.51-0.82g plant-1 ), water content (75-93%), fructose (4-27µmolg-1 ), glucose (57-73µmolg-1 ), sucrose (10-30µmolg-1 ), free amino acids (5-25µmolg-1 ), soluble phenolics (0.7-3.5µmolg-1 ), and Fv/Fm ratios (0.75-0.80) were evident between plants with different origins. Specifically, at the end of Phase I compared to Phase IV, the results showed significant reductions in dry matter (up to 3.3%) and also reductions in fructose/sucrose. Relative amino acid concentrations were lowest in Phase III (8.8µmolg-1 ) compared to Phase I (16µmolg-1 ). These are novel observations, since all these changes and the biochemical and physiological performance in the CAM phases have not been previously determined in Agave plants differing in their geographical origins.

Poinsettia's wild ancestor in the Mexican dry tropics: Historical, genetic, and environmental evidence.

PREMISE OF THE STUDY: The poinsettia (Euphorbia pulcherrima) is the world's most economically important potted plant, but despite its preeminence it is not clear which wild populations are ancestral to the varieties cultivated around the world. Tradition holds that the U.S. envoy to Mexico J. R. Poinsett collected the progenitors of the over 300 varieties in global cultivation on an 1828 excursion to northern Guerrero State, Mexico. It is unknown whether the contemporary cultivars are descended from plants from Guerrero or whether germplasm from other parts of poinsettia's 2000 km long distribution entered into cultivation during the nearly 200 yr of subsequent poinsettia horticulture. METHODS: To identify the wild populations that likely gave rise to the cultivars and test this historical account, we sequenced plastid and nuclear DNA regions and modeled poinsettia's potential distribution. KEY RESULTS: The combination of nuclear and plastid haplotypes characterizing cultivars was found only in northern Guerrero. Distribution modeling indicated that suitable habitat conditions for wild poinsettias are present in this area, consistent with their likely wild status. CONCLUSIONS: Our data pinpoint the area of northern Guerrero as the cultivated poinsettia's probable ancestral region, congruent with the traditional account attributing the original collections to Poinsett. Abundant genetic variation likely offers raw material for improving the many shortcomings of cultivars, including vulnerability to cold, stem breakage, and pathogens such as Pythium and Phytophthora. However, genetic differences between populations make conservation of all of poinsettia's diversity difficult.