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SEEDS AND FRUIT. Fruit and Seed Dispersal. A. Need for Dispersal B. Dispersal by Wind 1. Curved wings • maple samara 2. Inflated sacs • hop hornbeam 3. Plumes • Buttercup and Sunflower Families 4. Cottony or woolly hairs
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Fruit and Seed Dispersal • A. Need for Dispersal • B. Dispersal by Wind • 1. Curved wings • • maple samara • 2. Inflated sacs • • hop hornbeam • 3. Plumes • • Buttercup and Sunflower Families • 4. Cottony or woolly hairs • • Willow Family • 5. Minute (Tiny) seeds • • orchids and heaths
(a) Black Cottonwood, (b) Fremont Cottonwood, (c) Quaking Aspen, (d) Willow
Fruit and Seed Dispersal cont. • C. Dispersal by Animals • 1. Pass through digestive tracks of birds and mammals • 2. Hooks and barbs, stick to fur of animals • D. Dispersal by Water • 1. Inflated buoyant sacs, Hydrophytes • • sedges • 2. Waxy coverings • E. Other Dispersal Mechanisms and Agents • 1. Mechanical, splitting action • • touch-me-nots, dwarf mistletoes • 2. Humans act as dispersal agents
Seeds • A. Structure • 1. Hilum • 2. Micropyle • 3. Seed Coat • 4. Embryo • a. Cotyledons = seed leaves • b. Embryo axis • 1) Epicotyl (stem axis above cotyledon attachment) • 2) Hypocotyl (stem axis below cotyledon attachment) • 3) Radicle (embryonic root) • 4) Plumule (embryonic shoot with immature leaves) • c. Additional structures (e.g., corn seeds) • • coleoptile and coleorhiza
B. Germination • 1. Dormancy • 2. Breaking of dormancy • a. Scarification • • nicking or breaking seed coat • b. After-ripening • • embryo needs further development • c.Stratification • • cold temperature treatment • d. Environmental regulation • 1) Water and oxygen • 2) Role of light • • phytochrome pigment
C. Longevity • 1. Viability • • certain seeds retain capacity to germinate for many years • 2. Professor Beal's viability experiment page 142
Asexual Plant Propagation • Leaf Cuttings
Seeds and germination • 1. annuals – grow from seed each year • 2. bi-annuals – takes two years to mature to flower and seed out. • 3. seeds are resistant to environmental changes can last a long time • 4. genetic variance (recombination)
Seed coat • 1. seed – a structure formed by the maturation of the ovule of seed plants following fertilization. Protects and nourishes developing plant. • 2. fruit – a mature, ripened ovary or group of ovaries, contains the seeds and sometimes includes other parts • Seed from ovule • Fruit from ovary
Some seed anatomy and physiology • 1. seed coat (testa) – outer layer of seed. Develops from the integuments of the ovules • 2. raphe – ridge on the seed formed by the stalk of the ovule • 3. hilum – scar left on the seed after separation from the stalk of the ovule (fanicullus) • 4. micropyle – opening of the ovule through which the pollen tube grew • 5. aril – an extra seed covering which is formed by an outgrowth at the base of the ovary (yew)
Endosperm formation(double fertilization) • 1. endosperm – nutritive material in the seed for the embryo • 2. formed from – polar nuclei and male nucleus union of the central cell (seen only in angiosperms) • 3. endosperm formation (pea plant) • Anther meiosis • Ovule meiosis
Anther meiosis • Your drawing goes here
Ovule meiosis • Your drawing goes here
Double fertilization • Drawing goes here
Embryo 2n • 1. Young plant inside the seed • 2. Epicotyls - part above the cotyledons, but below the next set of leaves • 3. Cotyledons – seed leaves • Monocots – absorbs food • Dicot – stores food • 4. Hypocotyls – portion of the embryo below the cotyledons. But above the radical • 5. Radical – embryonic root
Steps in germination • 1. favorable environment • Water • Oxygen • Temperature • light • 2. imbibition – seed takes in HOH • 3. anaerobic decreased O2 conditions • Aerobic conditions increased oxygen • 4. temperature constraints • Minimum 0-5o C, maximum 45-48o C, optimal 25-30o C • 5. light – day length (photoperiod) tell time of year by the day length • Negative photoblasticseed is one that is inhibited by light
