**Endosperm Origin and Evolution:**
– Ancestral flowering plants had seeds with small embryos and abundant endosperm.
– Modern flowering plants like Orchideae and Poaceae show variations in endosperm development.
– About 70% of angiosperm species have polyploid endosperm cells.
– Early angiosperm lineages had triploid endosperms with a 2:1 maternal to paternal genome ratio.
– Double fertilization in angiosperms initially produced two identical embryos.
– Endosperm may be an evolutionary remnant of the gametophyte.
– Evolutionary shifts in gametophyte development led to the triploid transition and antipodal cells.
**Endosperm Formation and Types:**
– Endosperm is formed when two sperm nuclei reach the female gametophyte.
– Double fertilization results in the formation of a zygote and a primary endosperm cell.
– Different types of endosperm formation include nuclear, cellular, and helobial.
– Liquid endosperm, like coconut water, and cellular endosperm development in Acoraceae are examples of endosperm variation.
**Role of Endosperm in Seed Development:**
– Endosperm can persist as storage tissue in some plants.
– Storage function may be distributed between endosperm and embryo in certain species.
– Endosperm tissue plays a crucial role in nutrient transfer and gene imprinting.
– Endosperm in angiosperms contains hormones like cytokinins.
– Orchid seedlings are mycoheterotrophic due to the lack of endosperm.
**Research and Publications:**
– Various research publications have explored endosperm development and evolution.
– Notable publications include Genome Biology, Nature, Evolution, Proceedings of the National Academy of Sciences, and American Journal of Botany.
– Books like ‘Mechanisms of plant growth and improved productivity’ and ‘The diversity and evolution of plants’ provide further insights into endosperm-related topics.
**Regulation and Historical References:**
– Regulation of endosperm development is studied by researchers like Becraft PW and Gutierrez-Marcos.
– Historical references like the ‘Endosperm’ entry in ‘The New Students Reference Work’ by Chandler B. Beach provide insights into early understanding.
– Additional resources by authors like Houk WG and Friedman WE contribute to the comprehensive study of endosperm.
The endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This can make endosperm a source of nutrition in animal diet. For example, wheat endosperm is ground into flour for bread (the rest of the grain is included as well in whole wheat flour), while barley endosperm is the main source of sugars for beer production. Other examples of endosperm that forms the bulk of the edible portion are coconut "meat" and coconut "water", and corn. Some plants, such as orchids, lack endosperm in their seeds.
