Seeds and Fruits

Types & Types & DispersalDispersal

Seeds and FruitSeeds and Fruit• Fruits are formed by

seed plants to aid in dispersing seeds

• A seed contains the developing plant embryo in a protective coat (testa)

• Seeds form from ovules fertilized in the ovary

• Ovaries with seeds ripen into dry or fleshy fruits

Parts of a SeedParts of a Seed• External seed coat or testa• Developing plant embryo• Stored food called endosperm• Seeds may be in one part

(monocot) or two parts (dicots)

MONOCOTMONOCOT

DICOTDICOT

Parts of a SeedParts of a Seed

Gymnosperm Seed

• A single fertilization produces the diploid (2n) embryo

• The food source is the haploid megagametophyte

Flowering plant seed

In angiosperms (flowering plants) there is

DOUBLE _______________Which produces a diploid ________(2n)

and,A triploid (3n) __________Endosperm is the

food source

Dicot vs. monocot seed

Dicot has two cotyledons (like bean)

Endosperm (food) is kept in the _________

Monocot has one __________ which absorbs the endosperm tissue during germination (corn)

FruitIn flowering plants – Fruit is a mature,

ripened o_____ that contains the seedsPericarp – the ovary wall ovary

Fruit typesA. SimpleB. AggregateC. Multiple

A. Simple fruitA. Simple fruit – develops from a ______

ovary of a single flower.Simple fruits can be either fleshy or

dry when matureSimple fleshy fruit1. __________2. _________

Simple fleshy fruit1. Berry – entire fruit wall is soft and fleshy at maturity. Inside is slimy.For example, grapes, tomato, etc.

2. _______________ is a berry with tough, leathery rind (peel) Examples: oranges, lemons, other citrus.

Simple fleshy fruit: drupe

3. _______ type – outer part of fruit wall is soft and fleshy, inner part is hard and stony

For example: ______________________

Simple fleshy fruit: pepo

4. ________ – also a fleshy fruit with a tougher outer rind

All member of the squash family: pumpkin, melons, cucumbers

Simple fleshy fruit: pome

5. Pomes: most of the fleshy part of pomes develops from the enlarged base of the perianth (corolla and calyx) that has fused with the ovary wall

Pomes include ___________________

Simple dry fruit: capsule

Simple dry fruits are dry (not fleshy) at maturity. Simple dry fruits that open at maturity include: capsules and legumes

Capsule – fruit is dry at maturity and splits open along several seams

Example: Cotton

Simple dry fruit: LegumesLegumes are dry at maturity and split

open along _______ seamsExamples: pea pods, bean pods,

peanut

Simple dry fruits

Simple dry fruits that do NOT open at maturity include

Caryopsis: seed coat is fused to the ovary wall (cereal grains like ____________________)

Nuts: single-ovary wall and seed coat remain separate, ovary wall is very hard(acorns)

B. _______________________ fruit develops from one flower

with many separate pistils/carpels, all ripening simultaneously

Examples: strawberry, raspberries, blackberries

C. Multiple fruitMultiple fruit develops from ovaries of

several flowers borne/fused together on the same stalk

For example: ____________

What is the purpose of the fruit?The main function of the fruit is to disperse the

seedsDispersal is important because 1. It spreads the progeny in order to colonize

new environments2. Reduces ______________ for resources with

parents3. Reduces the chances of predators

destroying all of the plant’s yearly seed production

Four types of seed dispersal:A. Self dispersalB. ______ dispersalC. Water dispersalD. _______ dispersal

A. Self dispersal

Plants disperse their seeds by forceful ejection – explosive fruits!

Witch hazel, squirting cucumber (jet propulsion)

Self dispersalThe peanut plant sows

(buries) its own seeds!Geocarpic: carpel grows

inside the earth (soil)

B. Wind dispersalFruit and seeds may have special devices

for wind dispersalPlumes catch wind currents: DandelionTrees take advantage of their great

heights for wind dispersal. Fruits with wings are used to slow the descent to land: maple, ash fruit

C. ___________ DispersalFruits and/or seeds use flotation devices

to travel by water (in rivers, oceans, etc.)

Fruit may have air spaces and corky floats: for example ________________

D. Animal dispersalPlants have _____________ with animals to

accomplish seed dispersalMany plants depend on animals for seed

dispersal; they may offer a nutritional reward

Animals learn to recognize ripened fruit colors

Fleshy fruits eaten and dispersed with feces

Animal dispersalSome dry fruit attach and cling to

animals (they hitchhike on the animals)

Some have Velcro-like hooks that cling to animal fur (burdock, cockleburs)

Others have sticky substances that stick to host (mistletoe)

Further Study on Seed Dispersal

What carries the dandelion seeds for miles?What feature of trees gives them a particular

advantage when dispersing seeds by air?How does the squirting cucumber disperse its

seeds?Although plants use wind and water, what do

most plants use as carriers for their seeds?Blackberries on a tree do not ripen

simultaneously, why?What plant do elephants help to disperse?

How do they do it? What percentage of these seeds germinate in elephant dung? Why?