Endosperm development occurs prior to embryo development and varies by species, with notable differences in beans, cotton, and cereals. There are three types of endosperm formation: nuclear, cellular, and helobial, each characterized by distinct developmental processes. In dicots, endosperm development is often temporary, suggesting evolutionary perspectives linking it to primitive embryos or megagametophytes.

1. Endosperm development
• Endosperm development generally precedes
embryo development
• The fate of endosperm depends upon the
species
• Beans, cotton or Brassicas
• Castor bean, tomato, carrot
• Cereal grains

2. Morphological variation of endosperms
T
obacco Endosperm
Embryo
Most dicots: large cotyledons, small endosperms.
Carrot seed

3. Types of endosperm formation
• Nuclear/non-cellular type: Free nuclear division
gives rise to many nuclei and walls may or not form
e.g., most of monocots and some dicots
• Cellular type: Cell walls form immediately after the
first nuclear division and continue to do so as the
endosperm grows e.g., most of dicots and some
monocots
• Helobial type: regarded as intermediate restricted
to few monocots

5. Developmental domains
1. Transfer cells
2. Embryo surrounding regions (ESR)
3. Aleurone layer cells
4. Starchy endosperm cells
Maize
Barley

7. Endosperm development
•Begin with the
fertilized polar
nuclei
•Triploid
Micropyle
Antipodal cells
Polar nuclei
Synergids
Double fertilization
Egg
Mature ovule
Pollen
tube

8. The cereal endosperm coenocyte

9. Cellularization of the Endosperm Coenocyte

10. Endosperm development in dicots
• Endosperm development in dicots is
ephemeral in many species
• Two views about evolution of endosperm
• Endosperm is derived from a primitive embryo
• Endosperm is thought to be comparable with
megagametophyte

11. The Arabidopsis endosperm coenocyte