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seed anatomy

Seed anatomy

  • Hilum and funiculus: Funicular scar on seed coat that marks the point at which the seed was attached via the funiculus to the ovary tissue.
  • Micropyle: The Micropyle is a canal or hole in the coverings (seed coat) of the nucellus through which the pollen tube usually passes during fertilization. Later, when the seed matures and starts to germinate, the micropyle serves as a minute pore through which water enters. The micropylar seed end has been demonstrated to be the major entry point for water during tobacco seed imbibition and germination. During germination the tobacco testa ruptures at the micropylar end and the radicle protrudes through the micropylar endosperm.
  • Chalaza: Non-micropylar end of the seed. The base of an ovule, bearing an embryo sac surrounded by integuments.
  • Raphe: Ridge on seed coat formed from adnate funiculus.
  • Arillate: General term for an outgrowth from the funiculus, seed coat or chalaza; or a fleshy seed coat.
  • Aril: Outgrowth of funiculus, raphe, or integuments; or fleshy integuments or seed coat, a sarcotesta. Arils probably often aid seed dispersal, by drawing attention to the seed after the fruit has dehisced, and by providing food as an attractant reward to the disperser. The aril of the nutmeg produces the spice mace and the seed itself is the nutmeg.
  • Strophiole: Outgrowth of the hilum region which restricts water movement into and out of some seeds. In some hard-coated legume seeds, e.g. Melilotus alba and Trigonella arabica, a plug covering a special opening – the strophiolar cleft – must be loosened or removed before water can enter, and then only through this region.
  • Operculum: A little seed lid. It refers to a dehiscent cap of a seed or a fruit that opens during germination.
  • Carunculate: Seed with an excrescent outgrowth from integuments near the hilum, as in Euphorbia.
  • Fibrous: Seed with stringy or cord-like seed coat, as mace in Myristica.
  • Funicular: Seed with a persistent elongate funiculus attached to seed coat, as in Magnolia.
  • Strophiolate: Seed with elongate aril or strophiole in the hilum region.
  • Fruit: Strictly, the ripened ovary of a plant and its contents. More loosely, the term is extended to the ripened ovary and seeds together with any structure with they are combined, e. g. the apple (a pome) in which the fruit (core) is surrounded by flesh derived from the floral receptacle.
  • Achene: A small, usually single-seeded, dry indehiscent fruit, e.g. lettuce.
  • Caryopsis: A dry, nut-like fruit typical of grasses, e. g. a cereal grain. It is an achene with the ovary wall united with the seed coat.
  • Elaiosomes: A specialty in the dispersal through animals is that through ants (myrmecochory). Such seeds or fruits bear attachments, the elaiosomes that contain lures and nutriments. Myrmecochory is common with plants that live at the forest soil like violets (Viola).
  • Caruncle: A reduced aril, in the form of a fleshy, often waxy or oily, outgrowth near the hilum of some seeds. Usually it is brightly colored. It acts as an aid to dispersal. Viola seeds have an oily caruncle and are sought and dispersed by ants.
  • Mucilage: A layer of polysaccharide slime produced by some seeds upon imbibition. Serves in water uptake during imbibition and germination.

The structure, anatomy and morphology of mature seeds:
model species in seed biology

Family (clade) Examples Description
Endospermic seeds
Cucurbitaceae
– Core Eudicots
– Rosid clade
muskmelon (Cucumis melo ) In the muskmelon seed the embryo is surrounded by a perisperm/endosperm envelope. Callose (ß-1,3-glucan) deposition in this envelope is responsible for the apoplastic semipermeability of muskmelon seeds. The perisperm/endosperm envelope is weakened prior to the completion of germination.
Fabaceae
– Core Eudicots
– Rosid clade
fenugreek (Trigonella foenum-graecum)
crimson clover (Trifolium incarnatum)
lucerne (Medicago sativa)
Only some legume (Fabaceae) seeds are endospermic, most legume seeds are non-endospermic.
Euphorbiaceae
– Core Eudicots
– Rosid clade
castor bean (Ricinus communis) Castor bean seeds (Malpighiales) are a classical seed system to study endosperm reserve breakdown.
Brassicaceae
– Core Eudicots
– Rosid clade
garden cress (Lepidium sativum)
mouse-ear cress (Arabidopsis thaliana)
Only some Brassicaceae seeds are endospermic, most Brassicaceae seeds are non-endospermic. Mature seeds of Lepidium have 1-2 cell layers of endosperm, while Arabidopsis has a single endosperm cell layer. These two species exhibit, as tobacco, a two-step germination (distinct testa rupture and endosperm rupture). We found that Lepidium is a promising model system for endosperm weakening Müller et al. 2006).
Solanaceae
– Core Eudicots
– Asterid clade
Cestroideae subgroup:
tobacco (Nicotiana tabacum)
other Nicotiana-species
petunia (Petunia hybrida)

Cestroideae subgroup of Solanaceae (tobacco, petunia):
Straight or slightly bent embryos and prismatic to subglobose seeds, two-step germination (distinct testa rupture and endosperm rupture), typically capsules as fruits.

Endospermic seed structure (Eudicots): Brassicaceae –
Lepidium sativum as model system in seed biology

In mature seeds of Lepidium sativum (garden cress) the embryo is surrounded by 1-2 cell layers of endosperm. FA2-type seed.
We found that Lepidium seeds exhibit, as tobacco, a two-step germination process with distinct testa rupture and endosperm rupture.
We found that Lepidium seeds provide an excellent model system for the experimental investigation of endosperm weakening.
Lepidium and Arabidopsis are closely related species and exhibit, except for the size, highly similar seed structure Müller et al. (2006). Besides Arabidopsis and Lepidium, most Brassicaceae seeds are non-endospermic.

Seeds of Lepidium sativum and Arabidopsis thaliana have similar seed anatomy and similar germination physiology.
(A) The larger size of Lepidium seeds allows methods for which Arabidopsis seeds are too small, e.g. puncture force experiments.
(B) Drawing of a mature Lepidium seed; the embryo is enclosed by the endosperm and the surrounding testa.
From Müller et al. (2006).

Structure of a mature seed of Lepidium sativum. Bright field microscopy of longitudinal sections of 2-3 h imbibed seeds stained with toluidine blue. (A) Entire seed, showing the mature and fully differentiated embryo, the endosperm, and the testa (seed coat). The boxed letters refer to the positions of the close-up sections. From Müller et al. (2006).

Structure of a mature seed of Lepidium sativum. (B) Structure of the seed covering layers: Endosperm, a single cell layer; and testa (seed coat), composed of inner and outer integument. Note that the mucilage is generated from the outer testa upon imbibition. (C) Structure of the micropylar cap enclosing the radicle tip. The micropylar endosperm has 1-2 cell layers. (D) Structure of the chalazal seed region. From Müller et al. (2006).

Endospermic seed structure (Eudicots): Brassicaceae –
Arabidopsis thaliana as model system in seed biology

In mature seeds of Arabidopsis thaliana the embryo is surrounded by a single cell layer of endosperm. FA2-type seed.
Arabidopsis seeds exhibit, as tobacco and Lepidium, a two-step germination process with distinct testa rupture and endosperm rupture, as first described by the group of Hiroyuki Nonogaki (Liu et al., Plant J 41:936-944, 2005).
We found that, as shown for tobacco and Lepidium, ABA inhibits endosperm rupture of Arabidopsis, but does not affect testa rupture (Müller et al., 2006).
The testa is the most important covering layer of Arabidopsis seeds and confers coat dormancy. This has been demonstrated by the Arabidopsis testa mutants by the group of Maarten Koornneef (Debeaujon et al., Plant Physiol 122:404-413 and 415-424, 2000).
Although Arabidopsis does not have a massive endosperm layer, the single endosperm cell layer could be involved in regulating endosperm rupture. Only some Brassicaceae seeds are endospermic (Arabidopsis, Lepidium), most Brassicaceae seeds are non-endospermic.

(G) Drawing of a mature Arabidopsis seed; the seed anatomy that is very similar to that of Lepidium. (H-J) Arabidopsis seeds also germinate with testa rupture (H) preceding endosperm rupture (I). Also during the two-step germination process of Arabidopsis, ABA specifically inhibits endosperm rupture (J). Seeds were incubated in continuous light without (control) or with 10 µM ABA added to the medium. From Müller et al., (2006).

A comprehensive table of Arabidopsis hormone mutants summarizes the altered phenotypes regarding germination and dormancy.

Endospermic seed structure (Eudicots): Cestroidae subgroup of Solanaceae –
tobacco and other Nicotiana-species as model systems in seed biology

Nicotiana seeds are the type members of the Cestroideae subgroup of Solanaceae. LA-type seed.
In mature tobacco ( N. tabacum ) seeds the embryo is surrounded by three to five layers of rather thick-walled endosperm cells in the mature seed. The periphery of the endosperm is pressed against the thin testa (seed coat), which consists of an outer layer of cutinized and lignified dead cells and a living inner parenchyma layer. The maternal origin of theis living cell layer interposed between the endosperm and the dead outer testa is suggested by gene promoter studies and by genetic ablation. The micropylar endosperm surrounds the radicle tip and is the place of radicle protrusion during germination. The embryos are straight or slightly bent and the seeds are prismatic to subglobose (size Nicotiana rustica (Color image based on a drawing by Ioan Grintescu, In: Gicquet P and Hitier H, La Production du Tabac, J.-B. Baillière et fils, Paris 1961, p. 51). Color drawing published in Finch-Savage and Leubner-Metzger (2006).

Micropscopic picture of a sectioned dry mature Nicotiana tabacum seed: nuclei in the DAPI stain. The swap image “upon mouseover” shows the corresponding brightfield picture. Note that the testa has been removed except for the labeled testa remnant. © 2003 G. Leubner

Publication and tobacco seed drawings by Avery (1933):

The two drawings below are a redesign by me of Fig. 3K,L,M from Avery (1933).
(K)
Transverse section through seed at the cotyledonary level (x70).
(L)
Longitudinal-median section through seed just prior to endosperm rupture, showing ruptered testa (x50).
(M)
Longitudinal-median section through seedling at 9 days (x50).

Avery GSJ (1933)
American Journal of Botany 20: 309-327

Structure and germination of tobacco seed and the developmental anatomy of the seedling plant.
Avery (1933) – Download a PDF file – 3.7 MB

Endospermic seed structure (Eudicots): Solanoidae subgroup of Solanaceae –
tomato and pepper as model systems in seed biology

Tomato and pepper seeds are type members of the Solanoideae subgroup of Solanaceae.
In mature tomato (Lycopersicon esculentum) and pepper (Capsicum annuum) seeds the embryo is surrounded by an abundance of endosperm cells and by the testa (seed coat). The embryos are curved and flattened, the seeds are discoid, and a micropylar cap-like structure consisting of endosperm and testa covers the radicle tip. This micropylar cap of Solanoideae-type seeds is the place of radicle protrusion, but there is no visible distinction beween testa rupture and endosperm rupture.

Drawing showing a mature seed of Capsicum annum (Color image by Katrin Hermann based on a EM image by Watkins and Cantliffe, Plant Physiol 72: 146-150, 1983). Color drawing published in Finch-Savage and Leubner-Metzger (2006).

Endospermic seed structure (Eudicots): Euphorbiaceae – castor bean – Ricinus communis

The castor bean (Ricinus communis) plant belongs to the Euphorbiaceae family (Rosid clade) and is a perennial shrub with large, palmately lobed leaves and sharply toothed leaf margins. The leaves are usually deep green, but in some strains they have a reddish cast. The fruit is a quarter-sized, round, spiny capsule, often reddish, containing up to three shiny, smooth, mottled seeds. FA1-type seed.

Castor bean seeds are highly toxic to humans and many animal, ingestion of two beans can be lethal to humans. The action of ricin, the toxic water-soluble protein, is well characterized. Ricin accumulates in the seeds, but is also found at lower concentrations in the leaves. The seed coat must be damaged to allow water to penetrate the seed interior for ricin to be absorbed in the intestines.

Castor bean seeds contain an elaiosome (caruncle, see figure). Elaiosomes are fleshy structures that are attached to seeds of many plant species. They are rich in lipids and proteins an have different shapes. In many cases elaiosomes attract ants, which disperse the seed (myrmecochory). The particular elaiosomes of Euphorbiaceae seeds are called caruncle. Like many other Euphorbiaceae seeds, Ricinus communis are carunculate; seeds without catuncle are called ecarunculate.

Castor bean seeds are endospermic (see figure), the embryo is spatulate axile, and the seed has physiological dormancy (PD). The cotyledons are thin and broad and the endosperm is the major storage tissue. Castor bean seeds are a classical system for studying endosperm reserve breakdown, especially for lipid and protein mobilization. The cells of the endosperm of castor bean seeds undergo programmed cell death after their oil and protein reserves have been mobilized. Castor bean seed germination is epigeal and the cotyledons of the seedling absorbe the nutrients from the endosperm, which encloses the cotyledons until it is obliterated.

Non-endospermic seed structure (Eudicots): Fabaceae –
pea as model system in seed biology

  • Non-endospermic seeds: The cotyledons serve as sole food storage organs. During embryo development the cotyledons absorb the food reserves from the endosperm. The endosperm is almost degraded in the mature seed and the embryo is enclosed by the testa. Examples: rape ( Brassica napus ), and the legume family including pea ( Pisum sativum ), garden or French bean ( Phaseolus vulgaris ), soybean ( Glycine max ).
  • Pea seeds: The embryo of mature seeds of Pisum sativum consists of the embryonic axis and the cotyledons. FA4-type seed. The fleshy storage cotyledons make up most of the seed’s volume and weight. The pea embryo is enclosed by the testa and the endosperm is obliterated during seed development, when it’s nutrients are taken up by the embryo. References on pea seed development: Marinos, Protoplasma 70: 261-279 (1970) and Hardman, Aust J Bot 24: 711-721 (1976).

Drawing of a mature pea (Pisum sativum) seed, a typical non-endospermic seed with storage cotyledons and the testa as sole covering letters. Color drawing published in Finch-Savage and Leubner-Metzger (2006).

Cover photograph of the May 2003 issue of Plant, Cell & Environment:
Germinated seeds of Pisum sativum showing the effect of ethylene on radicle growth. Seeds were
germinated (48 h) and then treated for 8 h with (left) or without (right) 30 µL / L ethylene
Petruzzelli et al., Plant Cell Environ 26: 661-671 (2003)

See the web page”Plant hormones” for information about ethylene and pea seed germination and seedling radicle growth.

Perispermic seed structure (Eudicots): Amaranthaceae –
sugar beet (Beta vulgaris) – a complex seed/fruit as disperal unit

  • Perispermic seeds and fruits: Perisperm is diploid maternal food storage tissue originates from the nucellus. Perisperm is found only in some species, e.g. in Beta vulgaris, Piper nigrum, Coffea arabica , many Caryophyllales. Sugar beet is emerging as a germination model for complex P-type seeds/fruits.
  • Sugar beet fruits and seeds: In the achenes of monogerm cultivars of Beta vulgaris L. (Amaranthaceae, a family of the Caryophyllid clade of the core Eudicots) the ‘botanically true’ seed is surrounded by a thick pericarp (see below, Fig. 1, Hermann et al. 2007). The sugar beet pericarp is known as a fruit tissue that can restrict water and oxygen uptake by the enclosed seed. Except for the basal pore, the pericarp is composed of a dense, impervious layer of sclerenchyma cells. The operculum, i.e. the ovary cap of the fruit is the upper part of the pericarp; and the basal pore, i.e. a pore-like pericarp structure filled with loose cells at the bottom part of the pericarp have both been proposed as major entry points for water and oxygen. Removal of the operculum and/or the use of ‘isolated true seeds’ removed these restrictions and promoted radicle emergence. Based on the peripheral location of the embryo, the sugar beet seed can be structurally classified as being perispermic and P-type (Finch-Savage and Leubner-Metzger, 2006).
  • Sugar beet seed proteome website: Hyperlink to the Seed Proteome Website (http://www.seed-proteome.com) of the
    ‘Joint Laboratory CNRS / Bayer CropScience’ – seed proteome lab of Dr. Dominique Job in Lyon (France) and the
    ‘Laboratory of Seed Biology INRA / AgroParisTech’ – Seed proteome lab of Dr. Philippe Grappin in Paris (France).
  • Sugar beet germination – a comparative study of fruits and seeds (Hermann et al. 2007): Treatment with ethylene or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) promoted radicle emergence of sugar beet fruits and seeds. Abscisic acid (ABA) acted as an antagonist of ethylene and inhibited radicle emergence of seeds, but not appreciably of fruits. Sugar beet radicle emergence appears to be controlled by the pericarp, by ABA and ACC leaching, and by an ABA-ethylene antagonism that affects ACC biosynthesis and ACO gene expression. An embryo-mediated active ABA extrusion system is involved in keeping the endogenous seed ABA content low by ‘active ABA leaching’, while the pericarp restricts ACC leaching during imbibition.

Structure and germination of mature fruits and seeds of Beta vulgaris (sugar beet):
(A-H) Visible events during the incubation of sugar beet fruits in water:
(A)
Dry fruit.
(B,E) Operculum opening; note that the radicle tip is still enclosed by the micropylar endosperm and the inner testa.
(C,D,F-H)
Radicle emergence through the seed covering layers (testa and endosperm) is the completion of germination.
(I,J) Seed germination studied with deoperculated fruits. The sugar beet seed has a lentil-like structure (about 3 mm diameter and 1.5 mm thick) and occupies a horizontal position within the fruit.
(J)
Radicle emergence through the seed covering layers (testa and endosperm) is the completion of germination.
(K)
Microscopic section through a dry fruit showing the radicle tip enclosed by the covering layers.
(L) Distinct stages of sugar beet seed germination: Isolated dry seed (1,2); note that the testa was removed in (1) to make the embryo and perisperm visible. Imbibed seed showing rupture of the outer testa (3) and radicle protrusion through all the seed covering layers (4-6).
(M) Section through a mature sugar beet fruit. The curved embryo completely encloses the perisperm, which is dead starch storage tissue localized in the seed center.
(N) Drawing of a sugar beet seed; modified from Bennett and Esau (1936) and reproduced by the kind permission of the United States Department of Agriculture.
(A-N) Figure 1 from Hermann et al. (2007).

Endospermic seed structure (Monocots): Alliaceae – onion

In monocot seeds like onion (Allium cepa, garden onion, bulb onion, ‘Küchenzwiebel’, Alliaceae, Liliales) the curved embryo has one cotyledon. It is embedded in endosperm tissue, which is the main food storage tissue of monocot seeds. The endosperm is surrounded by the testa (seed coat). Most Allium seeds have morphophysiological dormancy (MPD), they are therefore stored for several months to give their “underdeveloped” embryos time to grow (example: A. rothii). After (epigeous) germination the testa and endosperm of onions remains temporally attached to single cotyledon while the seedling primary root grows into the soil. The developing seedling obtains nutrients from the endosperm by way of the cotyledon. In addition, the green cotyledon of onion functions as a photosynthetic leaf, contributing significantly to the food dupply of the developning seedling. The plumule (young foliage leaves) emerges from the protective, sheathlike base of the cotyledon, elongates, and forms the foliage leaves of the seedling.

Seed anatomy Hilum and funiculus: Funicular scar on seed coat that marks the point at which the seed was attached via the funiculus to the ovary tissue. Micropyle: The Micropyle is

Seed Anatomy

1997. XII, 424 pages, 171 figures, 2 tables, 17x24cm, 1190 g
Language: English

ISBN 978-3-443-14024-3, bound, price: 102.00 €

out of print

Keywords

Contents

  • ↓ English description
  • ↓ Review: Quart. Rev. Biol. 74(2), 1999, p.231
  • ↓ Review: The Canadian Field-Naturalist vol. 113, p. 546
  • ↓ Contents

English description top ↑

Review: Quart. Rev. Biol. 74(2), 1999, p.231 top ↑

For my own interests, one of the greatest values of the book is that it will provide systematists with a resource they can use for better understanding and characterizing the morphological diversity of seeds. A highly significant facet of the book is its treatment of life history aspects of seeds, including topics such as desiccation, dispersal, dormancy and longevity.
Given the recent emphasis on the physiology and molecular biology of processes such as dormancy, it is refreshing to have Werker’s review of structures that play a role in the life history events of seeds.

Most of the examples discussed are from economically important families, such as Fabaceae and Poaceae, but data from a wide variety of angiosperms are included. Her review, however, is not taxonomically comprehensive — one cannot pick a favored family and expect to find its seeds discussed.
The book is well written and very concise; the text is supplemented by numerous simple line drawings and high

uality micrographs. Werker has provided an exceptionally valuable volume that will have broad application in future investigations of seeds.

Larry Hufford, Marion Owabey Herbanum and Botany, Washington State University, Pullman, Washington Quarterly Review of Biology, Vol. 74(2),1999 p. 231

Review: The Canadian Field-Naturalist vol. 113, p. 546 top ↑

Contents top ↑

2. Introduction 1
2. Morphological characteristics of seeds 2
2.1 Shape 3
2.11 Types of seed shape 3
2.12 Factors determining seed shape 3
2.13 Function 8
2.2 Size and weight 8

2.21 Interspecific variation in seed size 8
2.22 Intraspecific variation in seed size and weight 9
2.23 Factors affecting seed weight 10
2.3 Colouring 10
2.31 Function of colour 10
2.32 Variations in colour 11
2.33 Pigments and other colour-attributing factors 13
2.331 Types 13
2.332 Location (Colour of the seed coat – Colour of the embryo and endosperm
– Colour of special seed structures and appendages) 13
2.34 Timing of colouring 20
13. Seed surface 22
13.1 Surface topography 23

13.11 Patterns caused by inner seed coat layers 40
13.12 Factors outside the seed influencing surface sculpturing 40
3.13 Complex patterns 41
3.14 Differences in surface sculpturing around a seed 44
3.15 Advantages in sculpturing of the seed surface 44
3.16 Surface sculpturing as an aid in taxonomy 44
3.2 Specialized structures of the surface 45
3.21 Stomata 45
3.211 Structure 47
3.212 Development 52
3.213 Function 52
3.22 Trichomes 54
3.221 Number and location of trichomes 56
3.222 Hair length 59 8
3.223 Hair structure 61
3.224 Hair development (Hair development by splitting of cells –
Hair development hv partial disintegration of cell walls) 63
3.225 Function of hairs 65
4. Seed desiccation 65
4.1 Desiccation-tolerant seeds 65
4.11 Pathways of water loss 66
4.12 Factors involved in seed tolerance to desiccation 67
4.121 Timing of water loss 67
4.122 Amount of reserve materials 67
4.123 Water content 68
4.13 Seed coat desiccation 68
4.131 Seeds with fleshy tissues 68
4.14 Desiccation of endosperm and perisperm 69
4.15 Embryo desiccation 69
4.16 Desiccation of seeds in fleshy fruits 70
4.2 Desiccation-intolerant seeds 71
4.21 Recalcitrant seeds 71
4.22 Vivipary 72
5. Longevity 72
5.1 The role of seed coat in seed longevity 73
5.2 Changes that lead to the loss of viability 74
5.21 Damage to reserve tissues 75
6. Funiculus and seed abscission 75
6.1 Funiculus 75
6.11 Funicular morphology 75
6.12 Funicular anatomy 77
6.121 Vasculature 78
6.13 Functions of the funiculus 79
6.14 Funicular modifications 80
6.2 Seed abscission 83
Seed coat 84
7.1 Functions of the seed coat 85
7.2 Seed coat development 86
7.21 Integumental growth 89
7.22 Differentiation 90
7.23 Seed coat thickening 91
7.24 Rate of development 94
7.25 Endothelium 94
7.3 The mature seed coat 95
7.31 Variations within the seed coat around the seed 97
7.32 Viability of seed coat cells 98
7.33 Types of seed coat tissues 98
7.331 Protective structures (Cell wall and cell lumen materials –
Seed coat cuticles – A layer of compressed cells -Wall
thickenings – Crystals) 98
7.332 Sarcotesta (The fleshy layer – Protective layer of the sarco-
testal seed) 121
7.333 Aerenchyma 126
7.334 Chlorenchyma 127
7.335 The seed coat as a reserve tissue 127
7.336 Undifferentiated or degenerated seed coats 128
7.4 Seeds devoid of a seed coat 128
7.5 Specialized structures of the seed coat 129
7.51 The micropyle 129
7.52 The hilum 133
7.53 The rapine 133
7.54 The chalaza 134
7.55 Strophiole and lens 136
7.56 Pleurogram 136
8. Vasculature and passage of nutrients 138
8.1 Seed coat vascular system 138
8.11 Structure 138
8.12 Location 142
8.13 Phylogeny 142
8.14 Function 145
8.15 Degree of differentiation 145

8.16 Composition 146
8.2 Vascular structures supplementary to the main vascular system 147
8.21 Scattered or sheath-like tracheidal cells 147
8.22 Tracheid bar 147
8.3 Nucellar vasculature 149
8.4 Passage of nutrients from the vascular system to the embryo sac 150
8.41 Transport through the seed coat and nucellus 151
8.42 Transport from the maternal tissues into the embryo sac 154
8.43 Transfer cells 155
9. Embryo 157
9.1 Embryo location within the seed 160
9.11 Position of the embryo 160
9.2 Embryo morphology 161
9.21 Embryo size 161
9.22 Embryo shape 163
9.23 The cotyledons 170
9.231 Shape of dicotyledonous cotyledons 170
9.232 Number of cotyledons 172
9.24 Classification of the mature embryo 174
9.25 Embryo vasculature 174
9.26 Degree of differentiation of the embryo 176
9.261 Highly differentiated embryos (The monocotyledonous embryo) 176
9.262 Underdeveloped embryos 182
9.263 Modifications in parasitic plants 183
9.3 Embryo cytology 183
9.4 Chlorophyll in the embryo 184
9.5 The embryo as a reserve organ 185
10. Nutritive tissues 185
10.1 Endosperm 188
10.11 Function 188
10.12 Endosperm development 189
10.121 Polyploidy 191
10.13 The mature endosperm 192
10.131 Amount 192
10.132 Cell structure 193
10.133 Reserve materials 193
10.134 Viability 193
10.135 Crystals 194
10.136 Types of endosperm in the mature seed (Fleshy endosperm
-Thick-walled endosperm – Fluidy endosperm – Mucilagi-
nous endosperm- Ruminated endosperm) 194
10.14 Differential development within the endosperm 197
10.141 Transfer cells 197
10.142 Aleurone layer (Endosperm derived aleurone layer- Non-
endospermic aleurone layer) 199
10.2 Nucellus 201
10.21 Nucellus in the developing seed 201
10.211 The hypostase (Functions) 202
10.212 The epistase 207
10.22 Nucellus in the mature seed – perisperm 208
10.221 Reserve materials of the perisperm 208
10.222 Viability 209
10.223 Structure 209
11. Reserve materials 209
11.1 Timing of reserve materials accumulation 210
11.2 Proteins 210
11.21 Structure 211
11.211 Inclusions in protein bodies (Crystal globoids – Soft glob-
oids – Crystalloids – Crystals) 211
11.212 Intraspecific polymorphism of protein bodies 220
11.213 Amorphous reserve protein 222
11.22 Development of reserve protein 222
11.221 Protein bodies (Mode of formation – Accumulation of pro-
tein in the protein body – Polyploidy) 222
11.222 Development of the amorphous reserve protein 225
11.3 Lipids 225
11.31 Development of oil bodies 226
11.4 Carbohydrates 227
11.41 Starch 227
11.411 Starch as a temporary reserve material 227
11.412 Starch in the mature seed 227
11.413 Chemical composition 228
11.414 Structure 228
11.42 Cell walls as reserve material 229
11.5 Variations in distribution of reserve materials 230
12. Seed heteromorphism 231

12.1 Structural differences between heteromorphs 234
12.2 Factors correlated with heteromorphism 23G
12.3 The advantage of polymorphism 240
13. Ruminate seeds 240
13.1 Manner of development of ruminated seeds 243
13.11 Ruminate endosperm 243
13.12 Seed coat rumination 243
13.121 Vasculature-correlated rumination 247
13.13 Classification of ruminated seeds 248
13.14 Rumination of the embryo 248
13.15 Rumination due to the pericarp 249
13.2 Function and origin 249
14. Secretory structures in seeds 249
14.1 Phenolics 250
14.11 Function 251
14.2 Mucilage 251
14.21 Mucilage composition 251
14.22 Structure and consistency of mucilage cells 252
14.23 Origin of the mucilaginous layer 258
14.24 Location of mucilage cells 258
14.241 Mucilaginous epidermal cells (Hair-forming mucilaginous
epidermal cells – Mucilage-containing hairs) 259
14.242 Mucilage structures inside the seed coat 261
14.25 Mucilage formation 262
14.26 Functions of the seed coat mucilage 263
14.3 Myrosin cells 264
4.31 Myrosin composition 265
14.32 Structure and ultrastructure of myrosin cells 265
14.4 Laticifers 265
14.5 Oil cells, cavities and ducts 266
14.6 Crystals and silica bodies 267
14.61 Location 267
14.62 Function 269
14.63 Crystal formation 270
15. Seed dispersal 271
15.1 Anemochoryv 272
15.11 Dust seeds 272
15.12 Balloons 273
15.13 Plumed seeds 274
15.14 Wings 277
15.141 The origin of the wing 280
15.142 Wing structure and development 282
15.2 Hydrochory 284
15.21 Floating seeds 284
15.3 Zoochory 286
15.31 Endozoochory 286
15.311 Arils (Aril development and structure – Function) 287

15.32 Synzoochory 293
15.321 Myrmecochory (Elaiosome structure) 293
15.33 Epizoochory 299
15.331 Emergences and hairs 299

15.332 Myxospermy 299
15.4 Autochory 300
15.41 The turgor mechanism 302
15.42 The imbibition mechanism (swelling or shrinkage mechanism) 303
15.43 Cohesion mechanism 303
16. Seed dormancy 303
16.1 Types of dormancy 304
16.11 Factors influencing dormancy 304
16.2 Impermeability to water 305
16.21 Seed coat characteristics responsible for impermeability 305
16.22 Stage of acquisition of water impermeability 312
16.23 Closure of seed coat openings 312
16.231 Micropyle 312
16.232 The chalazal region 313
16.3 Impermeability to oxygen 314
16.31 Physical barrier 315
16.32 Biochemical barrier 316
16.4 Mechanical barrier to radicle protrusion 318
16.41 Endosperm 318
16.42 Seed coat 319
16.43 Accessory envelopes 321
16.5 Dormancy of underdeveloped embryos 321
16.6 Natural release from germination inhibition caused by seed structure 323
17. Germination 324
17.1 Stages in germination 324
17.11 Imbibition 324
17.111 Site of initial water entry (Predetermined sites for water
penetration) 324
17.112 Reversibility of imbibition 325
17.113 Positioning of the seed on the substrate 326

17.114 Swelling on imbibition 326
17.115 Leakage upon imbibition 328
17.12 Sequence of cell reactivation in the embryo 328
17.121 Activation along the embryo 328
17.122 Activation across the embryo 329
17.13 Ultrastructural changes during germination 330
17.14 Embryo penetration through its envelopes 333
17.141 Rupture of the seed coat 335
17.142 Operculum 336
17.143 Micropylar collar 337
17.15 Mobilization of reserve materials 339
17.151 The embryonic absorbing organ (Haustorial cotyledon of
monocotyledons) 339
17.152 Mobilization of cell wall reserve materials (Cotyledon cell
walls – Endosperm cell walls) 342
17.153 Mobilization of reserve materials within the cell (Protein
mobilisation – Myrosin bodies – Degradation of oil bodies
– Starch mobilisation) 345
17.154 Changes in the provascular system 354
17.16 Germination of underdeveloped embryos 355
References 357
Subject index and index of plant names 404

Seed Anatomy 1997. XII, 424 pages, 171 figures, 2 tables, 17x24cm, 1190 g Language: English ISBN 978-3-443-14024-3, bound, price: 102.00 € out of print Keywords Contents