Seed Development and Dormancy

Hiro Nonogaki, Associate Professor

Integrative Seed Biology

Oregon State University

Flower

sepal

petal

stigma

stylefilament

ovule

anther

Esau, 1977; Anatomy of Seed Plants

Flower

sepal

petal

stigma

stylefilament

anther

Esau, 1977; Anatomy of Seed Plants

Wild Carrot Flower

Developmental Stages

1 DAP3 DAP

4 DAP6 DAP

7 DAP8 DAP

9 DAP

10 DAP11 DAP

12 DAP13 DAP

14 DAP

15 DAP

16 DAP

17 DAP

18 DAP

19 DAP

20 DAP

21 DAP

22-12

Composite Flowers

21-12

Raven et al., 1999; Biology of Plants

Composite-Type Seeds

embryo

endosperm

pericarp

testa

“Achene”

Tomato Anther

A B

C

D

E

Tomato Pollen Germination

ovule

stigma

Pollen tube

Fertilization

Fertilization

Double Fertilization

Antipodal cells

Central nuclei

Egg cell

Synergid cell

Sperm nuclei Endosperm

Embryo

Embryo and Endosperm

Endosperm

Embryo

Carrot seed

Intact seed Pericarpremoved embryo

endosperm

Fennel Seed

Embryogenesis

Early - Histodifferentiation

These are overlapping phases !

Seed formation

Mid - Enlargement of the cells

Late - Maturation and drying

Developmental Stages

EarlyMid

globular transition heart torpedo maturepre-globular

Buchanan et al, 2000, Biochemistry and Molecular Biology of Plants

Late19.36

Arabidopsis Embryogenesis

Coppersmith JL, Hewitt JR, Nonogaki H, unpublished results

Globular Stage

The fate of cells are already determined !

Hypophysis

Protoderm

Ground meristem

Procambium vascular tissue

parenchyma

root

Buchanan et al, 2000, Biochemistry and Molecular Biology of Plants

epidermal layer

S1S2

S3S4

S5S6

S7

Morphological Maturation

S1 S2 S3 S4 S5 S6 S7

Kristof JR, Nonogaki H, unpublished results

B1 B2 B3 B4 B5 B6 B7

B1 B2B3B4B5B6B7

TW

T W B1 B2 B3 B4 B5 B6 B7

Ger

min

atio

n Po

tent

ial (

%)

B1 B2 B3 B4 B5 B6 B7

cotaxis

100

50

Physiological Maturation

Kristof JR, Nonogaki H, unpublished results

Seed Abortion

•Seed abortion

•Unsuccessful fertilization

•Bee activity

Drought and High Temperature

Concentrated nectar – unattractive to bees

Flower death

Physiological and genetic problem

Overhead misting could help lowering temperature

http://www.ag.ohio-state.edu/~seedsci/vsp02.html

Two to three bulges in ungerminated pollen

One of the bulges germinates

Carrot Pollen Germination

Pollen tube

Seed Abortion

Chaudhury et al., 1997; Proceedings of National Academy of Sciences USA 94: 4223-4228

Onion Seeds

Raven et al., 1999; Biology of Plants, Esau 1977; Anatomy of Seed Plants

Seed Abortion

Ohad et al., 1996; Proceedings of National Academy of Sciences, USA 93: 5319-5324

50% Abortion

100% Normal

Normal Testa Development

Testa development could be separated from embryogenesis

Chaudhury et al., 1997; Proceedings of National Academy of Sciences USA 94: 4223-4228

Lepiniec et al., 2006; Annu. Rev. Plant Biol. 57: 405-430

Viviparous Seeds

Bewley and Black, 1994; Seeds

Developing wheat seeds9.4

Vivipary

Abscisic acid (ABA)

Water 3 µM ABA

Germination inhibitor

Arabidopsis seed

Western et al., 2000, Plant Physiol 122: 345-355

Testa

Testa Pigmentation Mutants

Lepiniec et al., 2006; Annu. Rev. Plant Biol. 57: 405-430

Endothelium layerendospermembryo

(Phenolic compounds)

Proanthocyanidin Synthesis

Wild type

Mutant

Reduction in proanthocyanidin deposition in vacuole

Debeaujon et al., 2001; Plant Cell 13: 853-872

testa

Reduced Dormancy

Maternally inherited

Debeaujon et al., 2001; Plant Cell 13: 853-872

tt12 x WT

WT x tt12WT

tt12

A B C D

Outer cover

Undevelopedembryo

Embryophysiology Combined

Coat-imposed Dormancy

A B C D

Outer cover

Undevelopedembryo

Embryophysiology Combined

Immature Embryo

A B C D

Outer cover

Undevelopedembryo

Embryophysiology Combined

Embryo Dormancy

Induction of Dormancy

5.13

Bewley and Black, 1994; Seeds

Medicago lupulina

R 98FR 3

Dark 4

R, FR 2

R, FR, R, FR 0R, FR, R, FR, R 95

Irradiation Germination (%)

R, FR, R 97

Bewley and Black, 1994; Seeds

Photoreversibility

“Photoreversibility”