seed

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.