Lignin is one of the most studied and analyzed materials due to its importance in cell structure and in lignocellulosic biomass. Because lignin exhibits autofluorescence, methods have been developed that allow it to be analyzed and characterized directly in plant tissue and in samples of lignocellulose fibers. Compared to destructive and costly analytical techniques, fluorescence microscopy presents suitable alternatives for the analysis of lignin autofluorescence. Therefore, this review article analyzes the different methods that exist and that have focused specifically on the study of lignin because with the revised methods, lignin is characterized efficiently and in a short time. The existing qualitative methods are Epifluorescence and Confocal Laser Scanning Microscopy; however, other semi-qualitative methods have been developed that allow fluorescence measurements and to quantify the differences in the structural composition of lignin. The methods are fluorescence lifetime spectroscopy, two-photon microscopy, Föster resonance energy transfer, fluorescence recovery after photobleaching, total internal reflection fluorescence, and stimulated emission depletion. With these methods, it is possible to analyze the transport and polymerization of lignin monomers, distribution of lignin of the syringyl or guaiacyl type in the tissues of various plant species, and changes in the degradation of wood by pulping and biopulping treatments as well as identify the purity of cellulose nanofibers though lignocellulosic biomass.

A biomineral is a crystalline or amorphous mineral product of the biochemical activity of an organism and the local accumulation of elements available in the environment. The cactus family has been characterized by accumulating calcium oxalates, although other biominerals have been detected. Five species of Cacteae were studied to find biominerals. For this, anatomical sections and Fourier transform infrared, field emission scanning electron microscopy and energy dispersive x-ray spectrometry analyses were used. In the studied regions of the five species, they presented prismatic or spherulite dihydrate calcium oxalate crystals, as the predominant biomineral. Anatomical sections of Astrophytum asterias showed prismatic crystals and Echinocactus texensis amorphous silica bodies in the hypodermis. New findings were for Ariocarpus retusus subsp. trigonus peaks assigned to calcium carbonate and for Mammillaria sphaerica peaks belonging to silicates.

La lignina es una de las principales estructuras de la pared celular de las plantas y varía en su composición entre los grupos taxonómicos. El objetivo de este estudio fue revisar la estructura de la lignina, el proceso de lignificación y las propuestas de patrones de evolución de esta. Para esto se revisó la literatura existente, cada punto se analizó y explicó para finalmente proponer una hipótesis evolutiva del proceso de lignificación en angiospermas. La lignina está compuesta por diversos monómeros y polímeros, su biosíntesis ocurre en plastidios y retículo endoplasmático, para posteriormente polimerizarse mediante diferentes grupos enzimáticos en la pared celular, donde ocurre el proceso de lignificación cooperativa. Durante la evolución de las plantas se desarrollaron los sistemas genéticos y enzimáticos para la biosíntesis de la lignina. Los dos principales tipos de lignina que se acumulan en los elementos traqueales de las plantas son lignina de tipo guayacilo y lignina de tipo siringilo/guayacilo. La presencia de siringilo en especies de Isoetes, Selaginella, Lycophyta y algas por convergencia evolutiva confirió resistencia a patógenos y rayos UV. La presencia de enzimas promiscuas catalíticamente funcionales propició la aparición de lignina, suberina y cutina, además de que la diversificación anatómica y química de la pared celular en angiospermas favorecieron su distribución en diferentes condiciones ambientales.

Cellulose is the main polymer that gives strength to the cell wall and is located in the primary and secondary cell walls of plants. In Cactaceae, there are no studies on the composition of cellulose. The objective of this work was to analyze the crystallinity composition and anatomical distribution of cellulose in Cactaceae vascular tissue. Twenty-five species of Cactaceae were collected, dried, and milled. Cellulose was purified and analyzed with Fourier transform infrared spectroscopy, the crystallinity indexes were calculated, and statistical analyzes were performed. Stem sections were fixed, cut, and stained with safranin O/fast green, for observation with epifluorescence microscopy. The crystalline cellulose ratios had statistical differences between Echinocereus pectinatus and Coryphantha pallida. All cacti species presented a higher proportion of crystalline cellulose. The fluorescence emission of the cellulose was red in color and distributed in the primary wall of non-fibrous species; while in the fibrous species, the distribution was in the pits. The high percentages of crystalline cellulose may be related to its distribution in the non-lignified parenchyma and primary walls of tracheary elements with helical or annular thickenings of non-fibrous species, possibly offering structural rigidity and forming part of the defense system against pathogens.

Vanilla planifolia is a species of commercial importance. However, vanilla presents gene erosion problems due to its clonal reproduction. In the Huasteca of Hidalgo, there is no information on vanilla populations. Therefore, the objectives of this study were to identify the current populations and the potential distribution of, and the morphological variation in, the labellum of V. planifolia in the Huasteca of Hidalgo. Twenty-two accessions were located and selected. Based on 21 environmental variables, the niche modeling of the potential distribution was carried out with the MaxEnt program; with the Jackknife test being used to identify the variables that contributed to the model. Flowers from 22 accessions were collected and the labellum of each flower was dissected. Subsequently, 64 morphological variables were obtained and various multivariate analyses were performed. The results showed three regions, defined by the highest to the lowest probability that V. planifolia was distributed. The precipitation of the driest month, altitude, and vegetation cover delimited the distribution. Five different morphotypes were distinguished, and the main differences were associated with the middle part of the labellum as well as the entrance of pollinators to the flower; therefore, the characterization of the labellum showed an infraspecific variation in V. planifolia in populations of the Huasteca of Hidalgo.