Somatic Embryogenesis and Plant Regeneration in Forest Trees

Trees are essential for global biodiversity, pollution reduction, and mitigating the effects of climate change, as well as an alternative source of bioenergy. They provide timber and with the rise of the population, the demand has been increased for large-scale production. The conventional multiplication of forest trees through seed and cuttings faces challenges like long juvenile phases for seed production, and the destruction of mother plants. Seed propagation has limitations of storage as the majority of tree seeds are recalcitrant in nature and non-uniformity of seedlings. These problems can be overcome by utilizing powerful biotechnological approaches like somatic embryogenesis (SE). It is an in vitro micropropagation technique used for mass multiplication of genetically uniform planting materials in a multistep process by exploiting the totipotency nature of plant cells. Here, a somatic plant cell is converted into a somatic embryo under different plant growth regulators and induced stress conditions. Along with hormones, other factors like the genetic makeup of the donor plant, culture conditions, and the type of explants used decide the success of this method. Once the SE is induced, they develop into a complete plantlet as normal seeds with root shoot systems. This method enables large-scale multiplication of true-to-type plants even in cross-pollinated species within a limited space and time. It is also useful for the development of transgenic trees to express specific traits, such as better tolerance to stress or improved wood quality. The recent developments in the somatic embryogenesis of forest trees are discussed in this chapter.