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STORED RESERVES

IN SEED

What do seeds store?

Carbohydrates

Proteins

Lipids

Other protective or metabolically important compounds

Phytate or phytic acid

Tannins

Cork, mucilage, alkaloids

Hormones, vitamins

Maternal growth environment and seed reserves

Environmental effects

Soil fertility – seed size and weight.

Water availability –during flowering and seed fill

decrease seed size. Early plant development -

seed number

http://financialpress.com/2012/08/05/congre

ss-leaves-farmers-ranchers-high-and-dry/

Environmental effects

Temperature – high temperatures during seed fill

tend to reduce seed size and seed germination

(Gibson and Mullen, 1996; Egli et al., 2005).

Light – in general, reduced light results in smaller

seeds

Position in the plant – related to sink- source effect

and competition for limiting photosynthesis

Phases of Seed Development and Maturation

Seed depends on plant + environment

Seed moisture &

quality depends on

environment

Pollination & fertilization

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Substrates needed by the seed

A source of carbon for metabolic energy and

synthesis of sugars and starch

A source of nitrogen for synthesis of amino acids

Other elements (potassium, calcium, phosphorus,

etc.)

CARBOHYDRATES

Where does the required C

for seed filling comes from?

• Cereal grain: only 15 – 20 % from

carbohydrates stored in vegetative parts of

the plant (pre-anthesis)

• 85 to 90% of C originates in current

photosynthesis

• Seed major sink for photosynthesis products

during grain development

• Longevity of vegetative and reproductive

biomass are critical

Mobilization of stored carbohydrates in

the plant

• Starch is the main polysaccharide in

the plants

• Starch granules consist primarily of

amylose (~30%), amylopectin (~70%),

and in some cases phytoglycogen

Carbohydrates

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Goggi et al., 1993

Floury endosperm in sorghum at physiological maturity

showing starch granules and proteins

Goggi et al., 1993

Floury endosperm in sorghum after defoliation

• Hemicellulose (major carbohydrate in non-

endospermic seeds) are deposited in the cell

walls

• Mucilage – usually a seed dispersal

mechanism recovers seed coat in buckhorn

plantain and flax, also in endosperm of

legumes

• Pectic compounds cell wall

Carbohydrates - Storage polysaccharides

other than starch

Western et al., 2001

Fig. 2.Ruthenium red staining of wild-type and

mutant seeds. A, Wild-type seed placed

directly into stain without agitation. Two layers

of mucilage are present, an outer, cloudy layer,

and an inner, intensely staining layer. B, Wild-

type seed first shaken in water, then stained; the

outer layer of mucilage is not stained. Note

sharp outline to the columellae. C, mum2-1 seed

stained after shaking in water. No capsule of

mucilage is apparent and the columellae are

less defined than in B. D, mum5-1 seed stained

after shaking in water. Columellae are sharply

outlined and a thin layer of palely staining

mucilage is apparent directly around the seed.

E, mum5-1 seed placed directly in stain without

shaking. Both inner and outer layers of mucilage

are present, as in A. F, Wild-type seed stained

after first shaking in presence of EDTA. Only a

thin layer of palely staining mucilage is visible,

as in D. Scale bars = 200 μm.

• 5 to 15 % of the dry matter in pea and bean

seed are stored oligosaccharides of the

raffinose family

• Free sugars (rarely) – sugar maple up to 11%

of dry wt. of mature seed

Other carbohydrates stored in seeds

PROTEINS

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The biological role of storage

proteins is to provide carbon,

nitrogen and sulphur for seedling

growth

70 % of human demand

for protein is met by direct

or indirect (animal)

consumption of seed

• Cereals: 10 – 15% of DW

• Legumes: up to 40 – 50% of DW

T.B. Osborne (1924)

Classification of proteins

according to solubility

• Albumins, soluble in H2O

• Globulins, soluble in diluted salt solutions

• Glutelins, soluble in diluted alkali and acids

solutions

• Prolamins, soluble in aqueous ethanol

Figure 2.20. (A,B) Changes in the endosperm protein fractions during kernel development of normal Bomi

barley (A) and the high-Iysine barley mutant Risø 1508 (B). , Albumins (plus free amino acids); *,

globulins; , hordeins (prolamins); , glutelins. (C) The accumulation of vicilin (), legumin (), and

albumins () in developing cotyledons of broad bean (Vicia faba). (D) Accumulation of , ', and

subunits of the 7 S storage protein -conglycinin in developing soybean seeds. A and B, after Brandt

(1976); C, after Manteuffel et al. (1976); and D, after Gayler and Sykes (1981).

• Usually have no enzymatic activities

• Hygroscopic nature aggregate into small

particles

• Deposited in the cell within protein bodies

surrounded by a single membrane

Storage Proteins

Transmission electron micrographs of protein

bodies from (A) normal sorghum. Henley et al.,

2010. In: Advances in Food and Nutrition

Research, Volume 60 (Chapter 2).

LIPIDS

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Lipids

Contained primarily in seed (fruits like

olives and avocados)

Source of C during seed germination

20 % of human caloric uptake

in industrialized countries

comes from plant fats

10% of world production is

used for industrial purposes

• Higher content of unsaturated

fatty acids than animal fats

Lipids

For our purpose two kinds of lipids

Storage lipids – deposited in lipid bodies –

Gycerol + fatty acid

Lipids

For our purpose two kinds of lipids

Membranes – polar with a hydrophilic and

an hydrophobic end

MEMBRANE STRUCTURE-

PHOSPHOLIPID BILAYER

Palmitic Stearic Oleic Linoleic Linolenic

Species (16:0) (18:0) (18:1) (18:2) (18:3)

Sunflower 6 4 26 64 0

Maize 12 2 24 61 1

Soybeans 11 3 22 54 8

Canola 5 2 55 25 12

Cotton 27 3 17 52 0

Peanut 12 2 50 31 0

Oil Palm 49 4 36 10 0

Flax - - - 77 17

Animal fat 29 13 43 10 0.5

Table 1.4. The major fatty acid composition of commercial

oils of various plant sources [after Weber (1980) and Miller

(1931)].

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Phytin

Phytin: source of phosphate

and mineral ions

• 50 – 80 % of all P in the seed is in the form of

phytate

• Associated with protein bodies of the aleurone

layer in cereals

http://www.biologie.uni-hamburg.de/b-

online/library/webb/BOT410/Angiosperm/

Seeds/Seed-6Cereal.htm

Physiological roles of phytin

Reserve compound for inositol, phosphate,

and K, Mg, Ca, Fe, Mn

Control of physiological balance of P in

developing seeds and seedlings

Important for plant adaptation to the

surrounding environment Tannins

Tannin

Deposited in the cell wall of the seed coat

(e.g. cocoa and beans)

Defends the seed from attacks by

predator by making them less digestible

Also protects the seed against light and

delays seed decomposition in the soil

Restrict germination by limiting gas flow

Other storage materials

• Cork cell walls with suberine between the

epidermis and other tissues of the seed

• Alkaloids – morphine (poppy), strychnine (nux

vomica), caffeine (coffee, cocoa, tea), nicotine

(tabacco)

Cork Oak seed Poppy seed

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Hormones in the

developing seed

• ABA

• Auxin

• Gibberellins

• Cytokinins

Possible role of seed hormones

Seed growth and development

Accumulation of storage reserves

Storage for later use during germination

Tissues close to the developing fruit

Vitamins

• All vitamins and precursors are synthesized in

plants, although the role of many is unknown

Location of reserves

Storage

organ

Chemical Common name

Cotyledon Proteins &

Carbs

Pea, broad bean, dwarf

bean

“ Lipids &

Prot.

Cucumber, squash,

lettuce, soybean,

cabbages

Endosperm Prot. &

Carbs

Cereals and grasses

Location of reserves (2)

Storage

organ

Chemical Common name

Perispem mannans coffee

Endosperm “ Fenugreek, caraway

“ Lipids &

Prot.

Yucca

Stylized diagram of a seed cell to

show the major components. CW:

cell wall; ER: endoplasmic reticulum

and associated ribosomes of rough

ER; G: Golgi apparatus; L: lipid

bodies; M; mitochondrion; MB:

microbodies or glyoxysomes; ML:

middle lamella; N: nucleus

containing dense nucleoliand

disperse DNA chromatin ( c ); P:

plastid; PD: plasmodesmata; R:

ribosomes; V: Vacuole (some store

proteins, phytin, organic acids,

phenolics, sugars, amino acids and

hormones). From: Black, M., J.D.

Bewley and P. Halmer. Ed. 2006.

The encyclopedia of seeds. CABI,

Cambridge, MA.

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Figure 2,27, The

synthesis of storage

proteins and their

sequestering within

the vacuole/protein

body, as occurs

typically in the

storage parenchyma

cells of the

cotyledons of legume

seeds. ER,

endoplasmic

reticulum; G, Golgi

apparatus; Gv, Golgi-

derived vesicle; M,

mitochondrion; N,

nucleus; Nu,

nucleolus; PI, plastid;

V, vacuole. After

Bewley and

Greenwood (1990).

From: Bewley, J.D.

and M. Black. 1994.

Seeds: physiology of

development and

germination, 2nd ed.

pp. 79. Plenum Press,

NY.

References

•Bewley, J.D. and M. Black. 1994. Seeds: physiology of development and germination,

2nd ed. Plenum Press, NY.

•Egli, D.B., D. M. TeKrony, J. J. Heitholt, and J. Rupe.2005. Air temperature during seed

filling and soybean seed germination and vigor. Crop Sci. 45:1329–1335.

•Heldt, Hans W. 1997. Plant biochemistry & molecular biology. Oxford University

Press.

•Gibson, L. R. and R. E. Mullen. 1996. Soybean seed quality reductions by high day

and night temperature. Crop Sci. 36:1615-1619.

•Goggi, A.S., J.C. Delouche, and L.M. Gourley. 1993. Sorghum [Sorghum bicolor (L.)

Moench] seed inernal morphology related to seed specific gravity, weathering, and

immaturity. J. of Seed Techn. 17: 1-11.

•Seed development and germination. 1995. Edited by J. Kiegel & G. Galili. Marcel

Dekker, Inc.

• Western, T. L., J. Burn, W. L. Tan, D. J. Skinner, L. Martin-McCaffrey, B.A. Moffatt, and

G.W. Haughn. 2001. Isolation and Characterization of Mutants Defective in Seed Coat

Mucilage Secretory Cell Development in Arabidopsis. Plant Phys.127:998–1011.