This document summarizes the stages of seed development, including pollination and fertilization, seed coat development, endosperm development, embryo development, seed growth and maturation. It discusses the key stages and processes in the development of monocot and dicot seeds, including pro-embryo formation, suspensor and embryo development, endosperm formation types, physiological and biochemical changes during seed maturation, and environmental factors that influence development. Physiological maturity is defined as the stage of maximum dry weight accumulation when there is no further increase in seed dry weight.

1. STAGES OF
SEED DEVELOPMENT

2. POLLINATION & FERTILIZATION

7. SEED DEVELOPMENT
• The Integument of the ovule – seed coat
• Nucellus – absorbed and absent
• Endosperm
Monocot : Max morphological development
Dicot : Used up by the developing embryo.

8. EMBRYO DEVELOPMENT
• The first few cell division from the
zygote forms the Pro-embryo. Although
the mature embryo of monocotyledons
and dicotyledons appears considerably
different, their pattern of embryogeny are
similar.

9. • The Pro-embryo is divided into Suspensor
and Embryo proper.
• The suspensor forms into a chain of cells,
pushing the embryo proper into the center
of the ovule thus making it in contact with
the available food supply

11. ENDOSPERM DEVELOPMENT
• Endosperm formation starts prior to
embryo formation.
• Reaches its maximum morphological
development at physiological maturity.

12. • There are 3 types of endosperm
development
(a) nuclear - where the endosperm nucleus
undergoes several divisions prior to
cell wall formation, e.g., wheat apple,
squash.
(b) cellular - in which there is no free
nuclear phase

13. (c) helobial - where the free nuclear division is
preceded, and is followed by cellularization as in
some monocots

14. SEED GROWTH & MATURATION
• The seed is said to have physiologically
matured only when it attains maximum
dry weight, germinability and vigour.
• Normally the seed is harvested at field
maturity, a stage when the moisture
content is reduced to about 6-10 % in
wheat.

15. PHYSIOLOGICAL CHANGES
• Water uptake
• Respiration
• Mobilization of reserve materials
 BIOCHEMICAL CHANGES
• Nucleic acids
• Proteins
• Carbohydrates
• Inorganic nutrients

16. ENVIRONMENTAL FACTORS
• SOIL FERTILITY
• TEMPERATURE
• WATER
• LIGHT

17. MATURATION & DRYING
• Physiological maturity is identified as
maximum seed dry matter accumulation
• Physiological maturity is reached when
there is no further significant increase in
seed dry weight

18. • The first concept of physiological maturity was
proposed by Shaw and Loomis in 1950 as the
stage in which the seed possesses maximum
dry weight and yield.
• Physiological maturity has also been termed
“relative maturity” by Aldrich in 1943,
morphological maturity” by Anderson in 1955
while others prefer to use terms such as
“harvest maturity”& “agronomic maturity”

19. • Probably the most accurate method of
determining physiological maturity is the
measurement of 14C assimilate uptake by the
developing seed. This was demonstrated by
TeKrony et al. (1979)
• Finally, the definition of physiological
maturity based on seed maximum dry weight
should be considered a reference point to
characterize the end of seed development.