Browsing by Author "Woller, Dayla"

Lignin is a key macromolecule in many land plants and plays a role in structural support, water conduction, and defence (Vanholme et al., 2010). In most vascular plants, lignin makes up a significant portion of the total plant biomass, about 20-30% (Robinson, 1990). This is important to consider for a variety of reasons, including the large energetic and monetary cost that the forestry industry incurs when removing lignin from tree biomass during processing. Despite its cost to paper and pulp mills, lignin has large potential in the pharmaceutical, construction, and packaging fields, among others (Albuquerque et al., 2021). With proper bioengineering, lignin could even replace fossil fuels as a feedstock in bioplastics production. However, current research and knowledge of lignification, the process wherein lignin deposition occurs in the plant, is lacking when it comes to our ability to produce commercially viable plants with manipulated lignin properties on a large scale. These gaps in knowledge are why it is important to study species with unusual lignin formation, such as the small North American shrub Dirca palustris, commonly known as eastern leatherwood. Such efforts will enable comparative analyses that will improve our understanding of lignification. Previous work on leatherwood has found that the space between adjacent cell walls, known as the middle lamella, is deficient in lignin even after cell wall lignification has concluded, despite the middle lamellae in most other vascular plant species being highly enriched in lignin (Mottiar et al., 2020). This thesis expands upon that finding by determining through histochemical staining, autofluorescence in confocal microscopy, and transmission electron microscopy, that leatherwood is almost completely devoid of lignin in the middle lamella. Histochemical staining and laser excitation were also used to investigate lignin deficiencies in other leatherwood tissues: root, leaf petiole, and peduncle, the small stem that supports flowers and developing fruit. To provide some context for the lignin patterns in leatherwood, both leatherwood and a distant relative, Daphne mezereum, commonly known as daphne, were studied in this work. The results indicate that lignin deficiencies in the middle lamella of fibres may be unique to the Dirca genus as they do not occur in daphne and, therefore, are not necessarily present throughout the entire Thymelaeaceae family. Research was also done with another important macromolecule, pectin, to assess if leatherwood might also have a unique distribution of pectin. Immunostaining revealed that pectin in leatherwood is found in the middle lamella, the same area where lignin is deficient. This new information highlights the need for more research, especially molecular studies, regarding the spatiotemporal relationship between pectin and lignin biosynthesis. Further work is needed to elucidate the underlying genetic factors for leatherwood’s unique lignin patterning, and potentially unveil pectin’s role in the initiation of lignification.