embryo development

1. globular
2. heart
3. torpedo
4. mature embryo

parts of mature seed
1. radicle (root)
2. seed coat (testa)
3. food reserve organs (endosperm - cereal/monocot, cotyledons - legumes/dicot, megagametophyte (1n) no endosperm - conifer/gymnosperm)

seed is a model of longevity

key processes that occur during seed maturation that impact on seed longevity and vigor:
a) accumulation and mobilization of food reserves - allows the seed to survive before it commences photosynthesis
b) hardening of the protective layers of the seed (seed coat, testa) - for mechanical support, interactions with wind, insects, prevents loss by leaching or absorptions of substances (water, solutes)
c) mechanisms for dispersal - seed flyers
d) intracellular synthesis of protective compounds - resistance to pathogens, antimicrobial, prevent water loss, antioxidant (prevent radical-mediated damage to membranes)
e) development of dormancy in species - Refers to the ability of dispersed seed to delay germination until the environmental conditions are appropriate for survival of the seedling, expression of genes that prevent germination and growth, broken by signals (cold/moist)