Practice question

Encapsulation matrix predominantly used for artificial seeds is sodium alginate linear polysaccharide composed of alternating blocks of beta D mannuronate and alpha L guluronate residues extracted from brown seaweeds Laminaria hyperborea Macrocystis pyrifera. Its utility stems from mild ionotropic gelation ability: aqueous sodium alginate solution 2-4 percent w/v containing somatic embryos dropped into calcium ion bath undergoes rapid crosslinking where calcium binds guluronate blocks in egg box model creating insoluble calcium alginate hydrogel bead entrapping embryo without temperature extremes or toxic organic solvents preserving viability. Resulting hydrogel retains 95 percent water preventing desiccation, porous allowing oxygen diffusion nutrient exchange and radicle emergence during conversion, biodegradable broken down by microbial alginate lyase in soil leaving no residue. Optional additives nutrients sucrose fungicides abscisic acid can be co encapsulated to support germination vigor and prevent microbial contamination. Agar produces denser less permeable gels requiring heat that damages embryos, gelatin liquefies at culture temperatures unstable, pectin forms weaker beads, so alginate remains standard economical biocompatible choice for synthetic seed production commercial horticulture forestry applications.