Flowers, Fruits, and Seeds

Chapter 8

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Outline

• Dicots versus Monocots• Structure of Flowers• Fruits

Fleshy Dry

• Fruit and Seed Dispersal• Seeds

Germination Longevity

Dicots versus Monocots

• Dicots (Magnoliopsida)• Two cotyledons• Flower parts in fours or

fives• Leaves with distinct

vein network• Vascular cambium

present• Vascular bundles in

ring• Pollen grain with three

apertures

• Monocots (Liliopsida)• One cotyledon• Flower parts in threes• Leaves with parallel

primary veins.• Vascular cambium

absent• Vascular bundles

scattered• Pollen grain with one

aperture

Structure of Flowers

• Each flower, which begins as an embryonic primordium that develops into a bud, occurs as a specialized branch at the tip of a peduncle which may have branchlets of pedicles. Pedicle swells at its tip into a small pad

(receptacle).- Other parts of the flower are attached to

the receptacle.

Structure of Flowers

• Outermost whorl typically consists of three to five sepals. Sepals (calyx) may

be fused together.• Next whorl consists of

three to many petals (corolla). Calyx and corolla

form the perianth.

Structure of Flowers• Several to many stamens

are attached to the receptacle around the base of the pistil. Each stamen consists of

a filament with an anther at the top.

- Pollen grains developed and disseminated in anthers.

Structure of Flowers

• Pistil consists of Stigma, Style, and Ovary. Superior Ovary - Calyx

and corolla are attached to the receptacle at the base of the ovary.

Inferior Ovary - Receptacle grows up and around the ovary.

- Calyx and corolla appear to be attached at the top.

Gymnosperms flowers

Sago palm, however not a true palm: The generic name comes from Greek Koikas, and means "a kind of palm".

About 95 species are currently accepted in the cycad family Cycadaceae.

Gymnosperms flowers

Polen cones-male strobili

Seed cones-female strobili Pollen grains

Monocot flowers

Dicot flowers

Structure of Flowers• Inflorescences - Group of several to

hundreds of flowers

Fruits

• Fruit is an ovary and its accessory parts that have developed and matured. Usually contains seeds. All fruits develop from flower ovaries and

accordingly are found exclusively in flowering plants.

Fruits

• Fruit Regions Exocarp - Skin Endocarp - Inner

boundary around seed(s).

Mesocarp - Fleshy tissue between exocarp and endocarp.

- Three regions are collectively called the pericarp.

Fruits

• Fleshy Fruits Simple fleshy fruits develop from a flower with a

single pistil.- Drupe - Simple fleshy fruit with a single seed

enclosed by a hard, stony endocarp, or pit. E.g,; coconuts,apricot, peach,plum, almond

Fruits

• Berry - Usually develops from a compound ovary and often contains more than one seed. Three types of berries: True berry is a fruit with a thin skin and a

relatively soft pericarp.E.g.;tomatoes, grapes, peppers, eggplants, blueberries, cranberries, pomegrantes.

Fruits

Pepos - Relatively thick rinds (Pumpkins).

Fruits

Hesperidium – Berry with a leathery skin (citrus family)

Fruits• Pomes - Bulk of flesh comes from enlarged floral tube

or receptacle that grows up around the ovary. (Apples)• –Acessory fruits: Fruits developed from more than an

ovary alone i.e. Pomes, pepos and some berries

Fruits

• Aggregate Fruits Derived from a single flower with several to

many pistils.- Individual pistils mature as a clustered

unit on a single receptacle Raspberries, Strawberries.

Aggregate fruits/Raspberries, blackberries

Aggregate fruits/Raspberries, blackberries

Individual pistils

Fruits

• Multiple Fruits Derived from several to many individual

flowers in a single inflorescence. - Pineapples, Figs, Mulberries

Multiple fruits/Pineapples, figs

Fruits

• Dry Fruits That Split at Maturity (Dehiscent) Follicle - Splits along one side or seam

(Milkweed). Legume - Splits along two sides or seams

(Beans, peas,garbanzo beans, lentils,carob, peanuts!).

Silique - Splits along two sides or seams, but seeds are borne on central partition, exposed when the two halves separate (Cabbage, broccoli).

Capsules - Consist of at least two carpels, and split in a variety of ways (Poppies, Lilies).

Silicles-Lunaria (Dollar plant)

Follicles-Milkweed)

Capsule-Orchid

Fruits• Dry Fruits That Do Not

Split at Maturity (Indehiscent) Achene (Sunflower) Nut (filberts=Hazelnut) Grain (Poaceae fam.) Samara( ashes, elms) Schizocarp (parsley,

carrots)

Fruits

• Dry Fruits That Do Not Split at Maturity (Indehiscent) Schizocarp: Twin

fruit (parsley, carrots, anis, dill). Upon drying twin fruits break into two one-seeded segments called mericarps

Fruit and Seed Dispersal

• Wind Dispersal Small and Lightweight

seeds.• Animal Dispersal

Seeds pass through digestive tract.

Fruits and seeds catch in fur or feathers.

Oils attract ants.• Water Dispersal

Some fruits contain trapped air.

• Mechanical Ejection of Seeds

Seed dispersal

Pine Life Cycle

Seeds

Embryo shoot: Plumule

Embryo root: radicle

SEED GERMINATION (DICOTS)

• Structure Cotyledons - Food

storage organs that function as first seed leaves.

Plumule - Embryo shoot.

Epicotyl - Stem above cotyledon.

Hypocotyl - Stem below attachment point.

Radicle - Stem tip developing into a root.

Ovule-ovary attachment point

SEED GERMINATION (MONOCOTS)

Germination

• Germination is the beginning or resumption of seed growth. Seed must be viable.

- Some require a period of dormancy.To break the dormancy artificial techniques might be used such as:

- Scarification: Reduce thickness of the coat- After Ripening: Remove inhibitors- Stratification: Cold requirement mimic

Favorable Environmental Factors- Imbibe water- Temperature: Above freezing but below 45- Light: Required in some (lettuce) but unwanted in

others (California poppy)

Longevity

• Viability of most seeds is significantly extended when the seeds are stored under conditions of low temperatures and kept dry.

- Aquatic lotus-1000 years- Arctic tundra lupine-10 000 years- Willow,orchids, cottonwood and tea-viable for only a few days- Cantoloupe, squash, cucumber- several years- Onion, leek- 2-3 years- Wheat with proper storage:30 years with 30 % viability

1879-William J. Beal- Experiment with 1000 seeds from 20 species of weeds

- every 5 years, after 1920 every 10 years- In 1884 –most seeds of weeds germinated- In 1960-evening primrose, curly dock, moth mullein seeds germinated- In 1980 29 moth mullein, 1 mullein and 1 mallow seeds germinated- Six of original boxes are remaining and scheduled to be open in 2040

A few species produce seeds with no period of dormancy.- Vivipary

Rhizophora mangle (Vivipary)

Review

• Dicots versus Monocots• Structure of Flowers• Fruits

Fleshy Dry

• Fruit and Seed Dispersal• Seeds

Germination Longevity

Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display

Oriental Sacred Lotus/ Nelumbo nucifera