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• • Willow Family• 5. Minute (Tiny) seeds• • orchids and heaths•

Dispersal

• hop hornbeam

Buttercup and Sunflower Families

(a) Black Cottonwood, (b) Fremont Cottonwood, (c) Quaking Aspen, (d) Willow

Minute (Tiny) seeds • orchids and heaths

Wolffia

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

stick to fur of animals

Sedges

touch me not and its seeds

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

• Splitting plants

• Tip layering

• Air layering

• Other ways of propagation

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)

Japanese 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

• Zygote –mitosis-> embryo

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 photoblastic seed is one that is inhibited by light