Double fertilization in angiosperms

Double fertilization in angiosperms

Pollen tube development and vs: vegetative cell gs: generative cell sp: sperm cell pt: pollen tube POLLEN ovary pollen ovary egg + synergids central veg. nucleus antipodal cells PISTIL stigma style pollen tube sperm cell veg. cell embryo sack integument chalaza funicle

Structre of embryo sac egg cell central vegetative nucleus (polar nuclei) integument antipodal cells Papaver rhoeas embryo sac

Pollen tube on pistil surface

Double fertilization (diploid vegetative cell)

Double fertilization 2nd sperm cell 1st sperm cell

Development of embryo 1st sperm cell + egg cell zygote embryo 2nd sperm cell + dipl. veg. cell triploid nucleus nutritive tissue (endosperm)

Ovule maturation into seed fertilized egg cell germ / embryo fertilized veg. nucleus inner nutritive tissue / endosperm nucellus outer nourishing tissue / perisperm integument seed coat / testa ovary fruit wall of ovary fruit wall / pericarp seed germination: embryo seedling

Seeds: seed coat endosperm cotyledon 1: castor plant radicle embryo fruit wall seed coat cotyledon 2: pepper endosperm perisperm germ 4: almond 3 rye

Seeds and appendages A. poppy m: seed coat e: endosperm cs: germ B. greater celandine el: elaiosome C. common yew ar: arille (seed envelope) mh: seed coat

SEEDS Heuchera sp. seed coat (testa) Campanula sp. seed coat (testa)

THE FRUIT

Fruit types Number of carpels: monocarpellary/unicarpellary polycarpellary monocarpous follicle polycarpous capsule Degree of carpel fusion: choricarpous / apocarpous (a) a b c coenocarpous - syncarpous (b) Hypericum Lilium - paracarpous (c) http://www.uky.edu/ag/hla/geneve/teaching/pls%20220 /Flowers/Flower%20parts.pdf paracarpous syncarpous

Classification of Fruits Other aspects: position of ovary true or false fruit dry or fleshy opens or remains closed Fruit types: I. DRY DEHISCENT FRUITS II. DRY INDEHISCENT FRUITS III. SIMPLE FLESHY FRUITS IV. COMPOUND FRUITS false fruits of rosehip (Rosa canina) true fruits of cherry (Cerasus avium)

I. DRY, DEHISCENT FRUITS (4 types) 1. Follicle - monocarpous, superior ovary - 1 opening (suture), multiple seeds e.g. milkweed (Asclepias syriaca), forking larkspur (Consolida regalis) 1 2 2. Legume - monocarpous, superior ovary - 2 sutures (ventral + dorsal), many seeds e.g. bean family (Fabaceae) loment e.g. Sophora spiral e.g. clover one-seeded e.g. sainfoin indehiscent e.g. peanut

I. DRY, DEHISCENT FRUITS oilseed rape (Brassica napus) 3. Silique mustard family (Brassicaceae) 2 carpels superior ovary opens by 2 sutures false carpellary wall/ replum Silicle: as long as broad min. 3x longer than broad e.g. black mustard (Brassica nigra) e.g. shepherd s purse (Capsella bursa-pastoris)

I. DRY, DEHISCENT FRUITS 4. Capsule 2 or more carpels, inferior or superior ovary septicidal opens along the fusion of carpels e.g. thorn apple (Datura), Colchicum loculicidal opens along the main vein of carpel e.g. onion (Allium cepa) septifragil opens along the line of carpel fusion AND along the main carpel vein e.g. castor plant (Ricinus) transverse upper part separating like lid of box e.g. henbane (Hyoscyamus) toothed e.g. primrose (Primula) poricidal releases seeds through pores e.g. poppy (Papaver)

poppy (Papaver) Capsule Types thorn apple Datura stramonium onion (Allium cepa) henbane (Hyoscyamus) primrose (Primula) poricidal toothed loculicidal transverse septicidal

II. DRY, INDEHISCENT FRUITS (8 types) 1. Grain / Caryopsis - unicarpellate, superior ovary - 1-seeded, fruit wall fuses with seed coat e.g. grass family (Poaceae) 2. Achene - 1 carpel, superior, unilocular ovary - 1-seeded - usually in fruit aggregates e.g. buttercup family (Ranunculaceae) 1. achenes of Clematis vitalba 2. 3. Double achene / schizocarp - 2 carpels, inferior ovary - mericarps held together by carpophor e.g. carrot family (Apiaceae) 3. achenes of Carum carvi

II. DRY, INDEHISCENT FRUITS 4. Acorn / Nut - 2 or more carpels, superior or inferior ovary - bony (sclerenchymatous) pericarp - fruit sits in cupule: formed from bracts or receptacle e.g. hazelnut, oak, beech, sweet chestnut 4. 5. 5. Nutlet - smaller form of nut, 2 or more carpels - sclerified exocarp protects the seeds (usually 4) e.g. mint family (Lamiaceae) borage family (Boraginaceae) acorns of sessile oak (Quercus petraea)

II. DRY, INDEHISCENT FRUITS (8 types) 6. Cypsela - 2 carpels, inferior ovary - achene-like fruit - derived from florets of capitulum - calyx often modified (e.g. pappus) seed dispersal e.g. aster family (Asteraceae) 1 pappus 6. dandelion (Taraxacum officinale)

II. DRY, INDEHISCENT FRUITS 7. Samara - 2 carpels, superior ovary - type of achene - pericarp membrane-like wing e.g. elms (Ulmus), ashes (Fraxinus) 8. Double samara - schizocarp with wings - fork-like carpophor e.g. maples (Acer) 7. 8. double samara of Acer campestre

III. SIMPLE FLESHY FRUITS (6 types) 1. Berry - outer pericarp (exocarp): thin, leather-like - middle layer (mesocarp) and inner layer (endocarp) of fruit wall: fleshy, juicy - 1 or more seeds e.g. grapes (Vitis) 2. Pepper fruit - inflated berry, pericarp may dry e.g. paprika (Capsicum annuum) berries of tomato

III. SIMPLE FLESHY FRUITS 3. Hesperidium - many carpels, superior, multilocular ovary exocarp: vivid color (yellow, orange), with essential oil cavities mesocarp: white, sponge-like parenchyma endocarp: fluid-filled vesicles (hairs/trichomes) e.g. orange, lemon (Citrus sp.) grapefruit (Citrus paradisi)

III. SIMPLE FLESHY FRUITS 4. Pepo - usually from 3 carpels, inferior ovary - hard-rind pericarp e.g. cucurbit family (Cucurbitaceae) exocarp: leather-like mesocarp: collenchyma, juicy parenchyma endocarp: fleshy partition walls and seeds pumpkin (Cucurbita pepo)

III. SIMPLE FLESHY FRUITS 5. Stone fruit / Drupe 1 or 2 carpels, superior or half-superior ovary exocarp / skin: leather-like, colored mesocarp / flesh: juicy, fleshy endocarp = shell/stone: stone cells (sclereids), seed within endocarp e.g. plum, sweet cherry, sour cherry, peach (Prunoideae), walnut (Juglans), olive (Olea europaea) plum (Prunus domestica)

III. SIMPLE FLESHY FRUITS 6. Pome - false fruit (receptacle, sepals take part in fruit formation) - many carpels, inferior ovary, apocarpous - cartilage-like endocarp around seedcavities, surrounded by fleshy mesocarp e.g. apple (Malus), pear (Pyrus) apple (Malus domestica) seeds quince (Cydonia oblonga) original fruit wall around seeds (endocarp in false fruit)

IV. COMPOUND FRUITS (6 types) AGGREGATE FRUITS 1 FLOWER: 1. Aggregate of follicles -apocarpous, superior ovary e.g. hellebore (Helleborus) 2. Aggregate of drupelets 1. - apocarpous ovary e.g. raspberry, blackberry (Rubus sp.) Helleborus odorus 2.

IV. COMPOUND FRUITS 3. Aggregate of achenes - apocarpous ovary - fleshy receptacle with achenes on its outer surface e.g. strawberry (Fragaria) -fleshy, cup-like receptacle with achenes inside e.g. rose hip (Rosa canina) achenes receptacle Fragaria vesca receptacle

IV. COMPOUND FRUITS MULTIPLE FRUITS INFLORESCENCE 1. Multiple of nutlets nutlets covered by fleshy tepals e.g. mulberry (Morus) 2. Multiple of achenes single achene fruits surrounded by fleshy inflorescence axis e.g. fig (Ficus carica) 2. 1. 3. Multiple of berries fleshy fruits (berries) surrounded by fleshy bracts e.g. pineapple (Ananas comosus) 3.