Botany strengthen the secondary cell walls of xylem tracheids and vessels to keep them from collapsing when a plant sucks water through them under water stress. Lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. Sporopollenin is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. It is widely regarded as a marker for the start of land
Resting spore Resting spore A resting spore is a resistant cell, used to survive adverse environmental conditions. Resting spore is a term commonly applied to both diatoms and fungi. A resting spore can be a spore created by fungi which is thickly encysted (has a thick cell wall) in order to survive through stressful times, such as drought. It protects the spore from biotic (microbial, fungal viral), as well as abiotic (wind, heat, xeric conditions) factors. It is found in "Anabaena". Resting spores of a particular fungus are known create the phenomenon known as late potato blight. They can lie dormant within