The document discusses the chemical composition of seeds. It states that seeds typically have high lipid content concentrated in storage tissues, providing energy. Lipids are broken down into fatty acids and glycerol. Seeds also contain proteins, carbohydrates like starch, and small amounts of water and soluble sugars. The chemical composition supports the growth of the embryo during germination.

1. Submitted to,
Dr. Tauqeer Ahmad Yasir
Submitted by,
Department of Agronomy
College of Agriculture

3. CHEMICAL COMPOSITION...contd.
 Most seeds have high LIPID content.
 Except for certain fruits, the occurrence of high lipids
concentrations differentiates seeds from other plant
organs.
 Lipids are concentrated in the endosperm or cotyledon
storage tissues in Angiosperms.
 Endosperm is generally solid.
 Lipids provide the highest amount of potential energy
per unit weight

4. Structural Formula of Lipid

5. CHEMICAL COMPOSITION...contd.
 The seed lipid reserve is generally hydrolyzed in
situ to glycerol and fatty acid by lipases.
 The fatty acids are utilized for phospholipids and
glycolipids.
 These are required as constituents of organelles.
 However, most are converted to sugars and
transported to the seedling (body) for growth.

6. CHEMICAL COMPOSITION...contd.
 They dissolve in organic solvents e.g. benzene, acetone,
alcohol, ether but do not dissolve in H2O.
 The value of seed-borne lipids for food and industrial uses
is enormous.
 In contrast to animal fats, their highly unsaturated
chemical nature has caused increased interest in
them for health purposes.
 High lipid content is usually associated with decreased
protein content e.g. soybean, rapeseed.

7. Percentage Of Oil Contents
Crop Storage tissue Oil
1. Cereals
Wheat, Barley, Rye Endosperm 2-3
Maize Endosperm 5-6
Oat Endosperm 6-10
2. Pulses/Legumes
Pea, Broad bean Cotyledons 1-6
Soybean Cotyledons 15-20
3. Oilseeds
Rapeseed Endosperm 45-50
Castor Endosperm 60-66
4. Gymnosperms
Pine Non embryonic 48

8. CHEMICAL COMPOSITION...contd.
 All the basic protoplasmic components are present
in seeds.
 This include amino acid, vitamins, nucleic acid,
co-enzymes and minerals.
 Phosphorus content in most seeds is often very
high. WHY?
 This element occurs most commonly as Phytin-
Salts of inositol hexaphosphate.

9. CHEMICAL COMPOSITION...contd.
 All seed contain PROTEIN as the protoplasmic
component.
 Protein are huge N2 containing molecules with huge
structures, greater part of which yield amino acid upon
hydrolysis of peptide bond.
 They are so important to plant and animal life that all
physiological reactions of living cells revolve around their
physical and chemical properties and those of related
compounds.

10. Structural Formula of Protein

11. CHEMICAL COMPOSITION...contd.
 Aside H2O, they are the principal components of
all protoplasm of both plant and animal cells.
 Seeds often contain unusual amino acids which are not
constituents of proteins.
 This may act as N2 store and may be present to the
extent of several percent of the seed’s dry weight.
 Chlorophyll is absent in seeds.

12. CHEMICAL COMPOSITION...contd.
 In some cases, e.g. legumes, large quantities of
special reserved proteins with a distinctive
chemical composition are also stored.
 The storage proteins occur as membrane
enveloped protein bodies (Aleurone bodies)
 They may occasionally occur as crystals.
 The protein reserve in all cases is sufficient for
growth before the plant becomes self-supporting.

13. Percentage Of Protein Contents
Crop Storage tissue Protein
1. Cereals
Wheat, Barley, Rye Endosperm 10-14
Maize Endosperm 10-14
Oat Endosperm 12-14
2. Pulses/Legumes
Pea, Broad bean Cotyledons 22-26
Soybean Cotyledons 35-40
3. Oilseeds
Rapeseed Endosperm 20-22
Castor Endosperm 18-20
4. Gymnosperms
Pine Non embryonic 35

14. CHEMICAL COMPOSITION...contd.
 Seed storage proteins are less complex than
protoplasmic protein and less likely to be tied up with
lipids.
 The great majority of seed protein are metabolically
inactive and serve merely as food reserve for use by the
growing embryo during germination.
 Active ones are few but they are extremely important
to the developing and germinating seed.
 As enzyme, they catalyze the metabolic processes in
digestion, translocation and utilization of stored food
reserves; no growth can occur without them.

15. CHEMICAL COMPOSITION...contd.
 CARBOHYDRATES are the major storage
substances in seeds.
 Carbohydrates occur mainly as starch or
hemicellulose.
 Other carbohydrates that occur in non storage
forms are peptin and mucilage.

16. Structural Formula of Carbohydrate

17. CHEMICAL COMPOSITION...contd.
 Starch is the principal and most wide spread storage
carbohydrate.
 They are metabolically inactive reserves stored until
needed during germination.
 Starch is stored in two related forms; amylose and
amylopectin which are two polymers of D-glucose.
 Amylose stains blue when exposed to iodine and its 100%
digestible by alpha amylase.

18. CHEMICAL COMPOSITION...contd.
 Amylopeptin on the other hand is only about 50%
digestible by alpha amylase and stains purplish-red when
exposed to iodine.
 However, they are both hydrolyzed by alpha and beta
amylase during normal metabolism and germination.
 Starch is stored as grains (up to 5µm in diameter) as
formed in the amyloplast.
 Hemicellulose are normal cell wall components in all
tissues.

19. Percentage Of (carbohydrate) Contents
Crop Storage tissue Carbohydrate
1. Cereals
Wheat, Barley, Rye Endosperm 75-77
Maize Endosperm 80-82
Oat Endosperm 60-65
2. Pulses/Legumes
Pea, Broad bean Cotyledons 50-56
Soybean Cotyledons 25-30
3. Oilseeds
Rapeseed Endosperm 18-22
Castor Endosperm Trace
4. Gymnosperms
Pine Non embryonic 6

20. CHEMICAL COMPOSITION...contd.
 Hemicellulose are usually found in the thickened
tertially layers of cell walls of the endosperm or
cotyledon instead of the interior region of the
endosperm.
 They are composed principally of mannans with small
amount of glucose, galactose, arabinose as side chain
on the main linear polymers of mannose residues.
 Where they form a major seed reserve, they are laid
down as heavy cell wall thickening, which almost fill
the lumen, as in seeds of the date palm-Phoenix
dactylifera.

21.  Small amounts of soluble sugars are usually present.
 These sugars are concentrated mainly in the growing parts
of the embryo i.e. shoot and root apices where
meristematic activities is highest.

22. CHEMICAL COMPOSITION...contd.
 Water content is often very low ranging between 5-20% on
a fresh weight basis compared to 80-90% of most plants in
an active state.
 This largely accounts for the very low metabolic rate in
ungerminated seed.
 Most of the water in dry seeds are firmly bound to colloides
and inaccessible for hydrolytic reactions (not unfreezable).
 This is only removable by temperature approaching 1000C
or by storage in high vacuum.
 Due to this dehydration, the cells and the subcellular
organelles in dry seeds are often shrunken.

23. CHEMICAL COMPOSITION...contd.
 Seeds also contain growth promoters, such as
cytokinin, and auxin.
 There is also the presence of growth inhibitors and
most of them are phenolic compounds.
 OTHER COMPOUNDS:
 Tannins: Used for tanning process as found in cocoa.
 Tannins contain phenolic and hydroxyl compounds.
 Alkaloids: Complex cyclic compounds containing N2.

24. CHEMICAL COMPOSITION...contd.
 Most are white solids, however, nicotine is a liquid at
room temperature.
 Glucoside
 Hormones:
 Vitamin