Flowers, Fruits, and Seeds Chapter 8
Dec 31, 2015
Flowers, Fruits, and Seeds
Chapter 8
Outline
Introduction Differences Between Dicots and Monocots Structure of Flowers Fruits Fruit and Seed Dispersal Seeds
Introduction
Annual Plants - cycle completed in single season
• Cycle = from seed germination to mature plant producing seeds
Biennial Plants - cycle completed in 2 growing seasons
Perennial Plants - cycle takes several to many growing seasons or plant produces flowers on new growth, while other plant parts persist indefinitely
Differences Between Dicots and Monocots
2 major classes of flowering plants:• Magnoliopsida (dicots)
• Liliopsida (monocots)
Dicots Monocots
2 cotyledons 1 cotyledonFlower parts in multiples of 4 or f5
Flower parts in multiples of 3
Leaves with distinct network of veins Leaves with parallel 1° veins
Vascular cambium and cork cambium present
Vascular cambium and cork cambium absent
Vascular bundles of stem in ring
Vascular bundles of stem scattered
Pollen grains with 3 apertures
Pollen grains with 1 aperture
Structure of Flowers Flowers begin as embryonic primordium that
develops into bud Flowers occur as specialized branches at tips of
peduncles• May have branchlets of pedicels
Receptacle - swollen end of peduncle or pedicel• Other parts of flower attached to receptacle in
whorls: sepals, petals, stamens, and pistil
Structure of Flowers
Structure of Flowers Ovaries evolved from carpels with margins rolled
inward• Carpel - leaf with ovules on margins−Carpels may be fused together into
compound ovary
−Pistil can consist of 1 to several carpels
Structure of Flowers Superior Ovary - calyx and corolla attached to
receptacle at base of ovary
Inferior Ovary - receptacle grows up and around the ovary• Calyx and corolla appear attached at top of
ovary
Ovary contains ovules• Ovules develop into seeds after fertilization
Structure of Flowers Flowers can be produced singly or in inflorescences• Inflorescence - group of flowers
Fruits• Fruit - matured ovary and its accessory parts– Contains seeds
– Develop from flower ovaries and found exclusively in flowering plants
Tomato fruit
Fruits Fruit Regions• Exocarp – skin
• Endocarp - inner boundary around seed(s)
• Mesocarp - tissue between exocarp and endocarp
• 3 regions collectively called pericarp
Peach fruit
Fruits Variability of fruits• Can consist of only ovary and seeds
• Can include adjacent flower parts
• May be fleshy or dry at maturity
• May split or not split
• May be derived from 1 or more ovaries
Fruits Fleshy Fruits - mesocarp at least partly fleshy at
maturity.
Simple fleshy fruits develop from flower with single pistil
• Drupe - simple fleshy fruit with single seed enclosed by hard, stony endocarp (pit)
Drupes: peaches, almonds, olives
Fruits Simple fleshy fruits • Berry−From compound ovary, with >
1 seed, and with fleshy pericarp
−True Berry - with thin skin and relatively soft pericarp Tomatoes, grapes, peppers,
blueberries, bananas−Pepo - relatively thick rind
Pumpkins, cucumbersGrape berries
Fruits
• Pome – flesh from enlarged floral tube or receptacle that grows up around ovary– Endocarp papery or
leatheryApple pomes
• Berry cont’d.− Hesperidium - leathery skin containing oils
Citrus
Apples, pears - core and little of adjacent tissue from ovary; remainder from floral tube and receptacle
Fruits Dry Fruits - mesocarp dry at maturity• Dehisicent or indehiscent
Dehiscent fruits - split at maturity • Follicle - splits
along 1 side
– Larkspur, milkweed, peony
• Legume - splits along 2 sides
– Legume family: peas, beans, lentils, peanuts
Milkweed follicle
Legumes
Fruits Dehiscent fruits cont’d.• Siliques and Silicles - split along 2 sides, but seeds on
central partition, which is exposed when 2 halves separate
– Silique - more than 3 times longer than wide
– Silicle - less than 3 times longer than wide
– Mustard family: broccoli, cabbage
Silicle
Silique
Fruits Dehiscent fruits cont’d.• Capsules - consist of at least 2 carpels, and split in
variety of ways−Irises, poppies, violets, snapdragons
Capsules
Fruits Indehiscent Fruits – don’t split at maturity• Single seed united
with pericarp
– Achene - base of seed attached to pericarp Sunflower seed,
buttercup, buckwheat
Inside of sunflower
achene
Fruits Indehiscent Fruits cont’d.
– Nut - similar to achene, but larger, with harder and thicker pericarp, and cluster of bracts at base Acorns,
hazelnuts, hickory nuts Acorn
Fruits Indehiscent Fruits cont’d.– Grain (Caryopsis) - pericarp tightly
united with seed Grasses: corn, wheat, rice, oats
−Samara - pericarp extends as wings for dispersal. Maples, ashes, elms
−Schizocarp - twin fruit that breaks into one-seeded segments called mericarps
Corn section
Samaras Schizocarp of mericarps
Parsley family: carrots, anise, dill
Fruits Aggregate Fruits• Derived from single flower
with several to many pistils−Individual pistils mature as
clustered unit on single receptacle.
Raspberries, blackberries, strawberries
Multiple Fruits• Derived from several to many
individual flowers in single inflorescence
Mulberries, Osage orange, pineapples, figs
Blackberry aggregate fruits
Osage orange multiple fruit
Fruit and Seed Dispersal Dispersal by Wind• Fruits: Samaras,
plumes or hairs on fruit
• Seeds: Small and lightweight, or with wings
Fruit and Seed Dispersal Dispersal by Animals• Seeds pass through
digestive tract• Fruits and seeds adhere to
fur or feathers• Oils attract ants
−Elaiosomes on bleeding hearts used as food by ants
Seeds from bleeding hearts. Elaiosome is white.
Water Dispersal• Some fruits contain trapped air for floatation
Seeds Structure• Ovules develop into
seeds−Cotyledons - food
storage organs that function as “seed leaves”
−Embryo - cotyledons and plantlet
−Plumule - embryo shoot
Bean seed
Seeds Structure cont’d.
– Epicotyl - stem above cotyledon attachment
– Hypocotyl - stem below cotyledon attachment
– Radicle - tip of embryo that develops into root
Bean seed
Seeds
• Hypocotyl lengthens, bends and becomes hook-shaped
• Top of hook emerges from ground, pulling cotyledons above ground
Hypogeous germination• Hypocotyl remains short and cotyledons don’t emerge
above surface
Epigeous germination
Epigeous germination
Germination Germination - beginning or resumption of seed
growth• Some require period of dormancy
−Brought about by mechanical or physiological factors, including growth-inhibiting substances present in seed coat or fruit
−Break dormancy by mechanical abrasion, thawing and freezing, bacterial action, or soaking rains Scarification - artificially breaking dormancy
• After ripening - embryo composed of only a few cells when fruit ripens; seeds won’t germinate until embryo develops
Germination Favorable environmental factors needed for
germination• H2O and O2
• Light or its absence• Proper temperature range
Enzymes in cytoplasm begin to function after H2O imbibed
Longevity Seed viability varies,
depending on species and storage conditions• Viability extended:
−At low temperatures −When kept dry
Vivipary - no period of dormancy; embryo continues to grow while fruit still on parent Vivipary in red mangrove
Review Introduction Differences Between Dicots and Monocots Structure of Flowers Fruits Fruit and Seed Dispersal Seeds