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Seed (種子)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

[plant anatomy, plant morphology, seed germination]

Seed (種子)

≡ fertilized ovules of a flowering plant
fertilization → ovule → development of embryo and albumen → seed development (generation of fruits) [ovary + appendages] → seed formation

 seed1  seed2
[1] A seed of angiospermae. [2] A seed of gymnospermae, not producing fruit.

Hilum (臍): scar from the seed being attached to the parent plant
Plumle (幼芽): the shoot tip with a pair of miniature leaves


Structure of Ricinus communis seed

Drosera rotundifolia L.
Juncus effusus L. var. decipiens Buchen.
Polygonum weyrichii Fr. Schmidt ex Maxim.

seedbank (埋土種子), seed dispersal (種子散布), seed germination (種子発芽)

Seed coat (種皮)

Roles of seed coats, including nut wall
  • barrier to germination cues
  • barrier to seed predators
  • barrier to light
  • pulp attached on vertebrate-dispersal seeds
  • rich in secondary defensive compounds

Fruit (果実)


Pineapple fruit

→ based on number of ovaries in the fruit
1. simple fruit (単果): berried from a single flower and single pistil
2. aggregate fruit (分離複果): derived from a single flower and more than one pistil. Ex. raspberry (Rubus), strawberry (Fragaria)
3. multiple fruit (集合果, 多花果, 複果): derived from a cluster of flowers (= inflorescence)

sorosis (肉質集合果): derived from just the pistils of many unisexual flowers of an inflorescence. Ex. mulberry (Morus)
syconium (無花果状果): derived from numerous ovaries borne on the inside of the fleshy receptacle of an inflorescence. Ex. fig (Ficus)
cone (球果): seeds enclosed by numerous, thickly-lignified scales that are overlapped around central axis. Ex. pineapple

Key to simple fruit types (単果分類鍵)

1. fruit fleshy, usually indehiscent (not splitting) _____ succulent fruit (多肉果) (adj. fleshy 肉厚の/多肉の)

2. flesh of fruit derived from a hypanthium that surrounds the papery carpels _____ pome (梨状果/梨果) Ex. apple, pear, quince (マルメロ)
2. flesh of fruit derived from the ovary wall

3. pericarp with an outer fleshy layer and an inner bony layer (the stone) _____ drupe or stone fruit (核果/石果): (= putamen 果核 = 種子) Ex. peach, cherry

drupelet (小核果): each of small, individual drupes in an aggregate fruit, represented by Rubus

Strawberry fruit
individual fruits = true fruit (fruitlet)
berry (enlarged receptacle) = false fruit

3. pericarp without an inner bony layer, more ore less fleshy throughout _____ berry, bacca (液果/漿果): Ex. tomato, grape

simple berry (単漿果): berry consisting of mono-carpel Ex. Schisandraceae, Berberidaceae
compound berry (複漿果/漿果): consisting of poly-carpel Ex. Vitaceae, Sonalaceae

4. septa evident in crossection; the outer layer leathery _____ hesperidium (柑果/ミカン状果) represented by citrus (柑橘類)

Hesperidium (berry with a leathery rind)
Ex. lemon (Citrus lemon) fruit

4. from a simple pistil, often with a thin shell but not bony

1. fruit dry at maturity, dehiscent (adj. 裂開性の) or indehiscent (adj. 非裂開性の) - dry fruit (乾果)

2. fruit indehiscent (not splitting open) - indehiscent fruit (不裂開果, 閉果)

3. with one or more wings - samara (翼果, 翅果): wing derived from the elongation of pericarp (maple, ash, elm)

(s.s.) wing-like on a part of pericarp → not including wing derived from calyx

3. without wings

4. from a composed pistil, becoming hard and bony-shelled - nut or nutlet if small (堅果): Ex. oak, walnut, hazelnut

nutlet, nucula, nucule, nuculanium (小堅果): small nut(often categorized into achene) Ex. Polygonum, Betula, Carex
utricule (嚢果): particularly for nutlet of Carex

4. from a simple pistil, often with a thin shell but not bony

5. pericarp fused to the seed _____ grain (caryopsis) (頴果/殻果): Ex. rice, wheat, corn
5. pericarp separable from the seed _____ achene or akene (痩果): Ex. aster, sunflower, sedges

cypsela (pl. -e) (下位痩果, 菊果): false fruit, consisting of plural carpels on ovary inferior and fusion of pericarp and calyx tube, generally categorized into achene

2. fruit dehiscent (splitting open) _____ dehiscent fruit (裂開果) (dehiscing 裂開している)

3. from a simple pistil (one carpel)

4. splitting on two suture (consisting of one carpel dorsabdominally dehisced) - legume (豆果) or pod (莢果) Ex. Fabaceae (pea, bean, alfalfa)

loment (節豆果, 節果): having constrictions between the seeds and that breaks into one-seeded segments at maturity

4. splitting on one suture - follicle (袋果) Ex. milkweed, larkspur, peony

3. from a compound pistil (carpels two or more, united)

4. carpels separating from other but each retaining its seed - schizocarp (分離果) or mericarp (分果) Ex. parsnip (Pastinaca sativa), carrot, spignel (Oenanthe javanica, セリ), honewort

in Apiaceae characterized by two one-seeded carpels which split apart at maturity - cremocarp (双懸果)

4. carpels splitting, releasing one or more seeds

5. fruit two-celled carpels, the two valves splitting away from a persistent, thin partition or septum (replum 隔膜) - silique and silicle (角果)

6. long types - silique (長角果) Ex. rape, radish
6. short types - silicle (短角果) Ex. Shepherd’s-purse

5. fruit one-to-several-celled, the partition not persistent if the fruit is two-celled - capsule (蒴果)

6. opening by a lid - circumscissile capsules (circumscissile, adj. 横に裂ける)

7. with a single seed - utricle (胞果) Ex. pigweed, Chenopodium album, Amaranthus
7. with several seeds - pyxidium or pyxis (蓋果), a seed capsule in the form of a box, the seeds being released when the top splits off. Ex. Portulaca, Plantago

6. opening by holes near the top - poricidal capsule (孔開蒴果) Ex. poppy
6. opening by splitting lengthwise

7. splitting on the septae - septicidal capsule (胞間裂開果) Ex. yucca, Hypericaceae, Linaceae, Elatinaceae, Lythrum, Rotala)
7. splitting between the septa and in the locules or chamber - loculicidal capsule (胞背裂開果) Ex. glacier lily, EpilobiumOenotheraPyrolaLiliumIris)
7. opening, or dehiscing, by the breaking away of the outer walls of the carpels from the partitions - septifragal capsule (胞軸裂開果): Ex. Convolvulaceae