Pablo Emilio Vanegas-Espinoza

Plastid analysis of pigmented undifferentiated cells of marigold Tagetes erecta L. by transmission electron microscopy

Marigold (Tagetes erecta) flowers are primarily used in industry for their high pigment content. Flower color development implies that chloroplast–chromoplast transition is associated with carotenoid biosynthesis. We report the recovery of undifferentiated pigmented marigold cells, various callus tissues, and their analysis by transmission electron microscopy in order to observe accumulating pigment and development of subcellular structures. Callus was generated from leaf explants and after several rounds of recurrent selection. Green-, yellow-, and brown-colored callus were obtained that showed distinct carotenoid profiles. For green material, violaxanthin, lutein, zeaxanthin, and β-carotene were produced, while yellow callus generated mainly lutein, as did the brown callus. Chloroplast–chromoplast transition was followed by measuring plastid size and shape in undifferentiated marigold cells by digital image analysis. Cellular alterations were evident in brown callus. Chloroplasts were the main structure in green callus, while yellow callus clearly showed the formation of plastoglobules, structures that are correlated with chloroplast–chromoplast transition. The high number of plastoglobules observed in yellow callus is possibly directly related to pigment synthesis and accumulation.

Marigold regeneration and molecular analysis of carotenogenic genes.

Marigold (Tagetes erecta) is an Asteraceous plant of industrial, ornamental and medicinal importance. Tagetes erecta species, popularly known as marigold, is grown as ornamental plant and is adapted to several agro climates. Inflorescences have been utilized as pigment source for food coloring, mainly of poultry skin and eggs. Lutein is the main pigment in marigold flowers. Some carotenoids are well known as provitamin A compounds. There are many reports on carotenoids and their effect on the prevention of certain ocular diseases, ischemic heart disease, strokes, photoprotection, immune response, aging and cancer. Marigold flowers are certainly a good source of carotenoids; they show very different pigmentation levels. This chapter describes the establishment of techniques for plant regeneration, gene expression, pigment extraction and pigment deposition in specific structures of marigold.

Morphostructural characterization of rice grain (Oryza sativa L.) variety Morelos A-98 during filling stages.

The morphostructure of grain rice Morelos A-98 was characterized in five stages of physiological maturation, in order to generate morphometric information during the filling process. Micrographic images from optical and scanning electron microscopy coupled to a digital capture system were used. Images were digitally processed to measure different descriptors such as shape, fractal dimension, and surface texture. Results showed that, two weeks after anthesis, an accelerated grain filling was observed, particularly on those grains positioned in the distal panicle zone, compared to those located in the base of this one. As deposition of assimilates in the grain increased, the area and perimeter of the transversal cut of the grains also increased (P ≤ 0.05); meanwhile, the rounded shape factor tended to increase as well (P ≤ 0.05), while the elliptic shape factor decreased. As the dehydrated endosperm passed from “milky” to “doughy” stages, values of fractal dimension area and endosperm perimeter as well as surface texture values showed that grain borders tended to become smoother and that there was a greater structured endosperm area (P ≤ 0.05).

Comparative Study of Phenolic Profile, Antioxidant Capacity, and Color-composition Relation of Roselle Cultivars with Contrasting Pigmentation

Roselle is a plant that accumulates anthocyanins significantly, hence its importance as food coloring and as a source of antioxidant compounds for human health. This study was aimed to determine phenolic composition and antioxidant capacity of methanolic extracts, and beverages obtained from native roselle cultivars in Mexico (Negra, Sudan, Rosa and Blanca) with different degrees of pigmentation, and to establish the color-composition relationship. Chromatographic methods were used to determine phenolic compounds: flavanols, flavonols, benzoic, hibiscus and phenolic acids as well as two main anthocyanins (cyanidin 3-sambubioside and delphinidin 3-sambubioside). The antioxidant capacity was evaluated by ABTS and FRAP assays. Tristimulus colorimetry showed to be a useful technique to determine the color-composition relationship, leading to equations that allowed to predict anthocyanin content of roselle (R > 0.84). Also, a stepwise linear discriminant analysis (SLDA) was developed in order to classify roselle cultivars. The obtained mathematical model could be an important tool to be used in colorimetric characterization of functional compounds used in food processing.