Botany Basics 5Botany Basics 5

Crop Science 1Crop Science 1

Fall 2004Fall 2004

October 14, 2004October 14, 2004

Fruit StructureFruit Structure

Consists of:Consists of: SeedsSeeds

Fertilized, mature ovulesFertilized, mature ovules

Ovary wallOvary wall May be fleshy, as in an apple, or dry and May be fleshy, as in an apple, or dry and

hard, as in an acornhard, as in an acorn

Fruit StructureFruit Structure

In some fruits, the seeds are enclosed within In some fruits, the seeds are enclosed within the ovary (e.G., Apples, peaches, oranges, the ovary (e.G., Apples, peaches, oranges, squash, and cucumbers)squash, and cucumbers)

In others, seeds are situated on the outside of In others, seeds are situated on the outside of fruit tissue (e.G., Corn and strawberries)fruit tissue (e.G., Corn and strawberries)

The only part(s) of the fruit that contain genes The only part(s) of the fruit that contain genes from both the male and female flowers are the from both the male and female flowers are the seed(s)seed(s)

The rest of the fruit arises from the maternal The rest of the fruit arises from the maternal plant and is genetically identical to itplant and is genetically identical to it

Types of FruitsTypes of Fruits

Classified as: Classified as: SimpleSimple Aggregate Aggregate Multiple Multiple

Simple FruitSimple Fruit Develop from a single ovaryDevelop from a single ovary Include fleshy fruits such as cherries and peaches (drupe), Include fleshy fruits such as cherries and peaches (drupe),

pears and apples (pome), and tomatoes (berries)pears and apples (pome), and tomatoes (berries) Include dry fruitInclude dry fruit

Their wall is either papery or leathery and hard such as peanuts Their wall is either papery or leathery and hard such as peanuts (legume), poppies (capsule), maples (samara), and walnuts (nut)(legume), poppies (capsule), maples (samara), and walnuts (nut)

Fruit or Vegetable?Fruit or Vegetable?

Tomatoes technically are a fruit because Tomatoes technically are a fruit because they develop from a flowerthey develop from a flower

Squash, cucumbers, and eggplants also Squash, cucumbers, and eggplants also develop from a single ovary and are develop from a single ovary and are classified botanically as fruitclassified botanically as fruit

Aggregate FruitAggregate Fruit

Develop from a single Develop from a single flower with many ovariesflower with many ovaries

Strawberries, Strawberries, raspberries, and raspberries, and blackberriesblackberries

Flower is simple with one Flower is simple with one corolla, one calyx, and corolla, one calyx, and one stem, but has many one stem, but has many pistils or ovaries pistils or ovaries

Each ovary is fertilized Each ovary is fertilized separatelyseparately

Multiple FruitMultiple Fruit

Derived from a Derived from a tight cluster of tight cluster of separate, separate, independent independent flowers born on a flowers born on a single structuresingle structure

Each flower has its Each flower has its own calyx and own calyx and corollacorolla

Pineapples and Pineapples and figs figs

SeedsSeeds Contain all of the genetic information needed Contain all of the genetic information needed

to develop into an entire plantto develop into an entire plant Made up of three parts:Made up of three parts:

Embryo Embryo EndospermEndosperm Seed coatSeed coat

Endosperm

EmbryoEmbryo

A miniature plant in A miniature plant in an arrested state of an arrested state of developmentdevelopment

Will begin to grow Will begin to grow when conditions are when conditions are favorablefavorable

EndospermEndosperm

Built-in food supply Built-in food supply In some species the In some species the

cotyledons cotyledons Can be made up of Can be made up of

proteins, proteins, carbohydrates, or carbohydrates, or fatsfats

Seed CoatSeed Coat

Hard outer covering Hard outer covering Protects the seed Protects the seed

from disease and from disease and insectsinsects

Prevents water from Prevents water from entering the seed entering the seed and initiating and initiating germination before germination before the proper time the proper time

GerminationGermination Complex process where a seed embryo goes Complex process where a seed embryo goes

from a dormant state to an active, growing from a dormant state to an active, growing state state

GerminationGermination

The seed absorbs water through its seed The seed absorbs water through its seed coatcoat

Must have enough oxygen and a Must have enough oxygen and a favorable temperaturefavorable temperature

Most species, such as celery, also Most species, such as celery, also require light require light

Others require darknessOthers require darkness

RadicleRadicle

First part of the First part of the seedling to emerge seedling to emerge from the seedfrom the seed

Develops into the Develops into the primary root and primary root and grows downward in grows downward in response to gravityresponse to gravity From this primary From this primary

root, root hairs and root, root hairs and lateral roots developlateral roots develop

HypocotylHypocotyl

Between the radicle Between the radicle and the first leaflike and the first leaflike structure structure

Grows upward in Grows upward in response to lightresponse to light

CotyledonsCotyledons

Seed leavesSeed leaves Encase the embryo Encase the embryo Usually are shaped Usually are shaped

differently than the differently than the mature leaves mature leaves

Monocots produce Monocots produce one cotyledonone cotyledon

Dicots produce twoDicots produce two

DormancyDormancy

Seeds are reproductive structures and Seeds are reproductive structures and important to a species' survivalimportant to a species' survival

Plants have evolved many mechanisms Plants have evolved many mechanisms to ensure their survivalto ensure their survival

One such mechanism is seed dormancy One such mechanism is seed dormancy Dormancy comes in two forms: Dormancy comes in two forms:

Seed coat dormancySeed coat dormancy Embryo dormancyEmbryo dormancy

Seed Coat DormancySeed Coat Dormancy A hard seed coat does not allow water to A hard seed coat does not allow water to

penetrate the seed penetrate the seed Scarification is used to break or soften the Scarification is used to break or soften the

seed coat seed coat Accomplished in nature by:Accomplished in nature by:

Heat of a forest fireHeat of a forest fire Digestion of the seed by a bird or mammalDigestion of the seed by a bird or mammal Partial breakdown of the seed coat by fungi or Partial breakdown of the seed coat by fungi or

insectsinsects Accomplished mechanically by:Accomplished mechanically by:

Nicking the seed coat with a fileNicking the seed coat with a file Chemically softening the seed coat with sulfuric acid Chemically softening the seed coat with sulfuric acid

Embryo DormancyEmbryo Dormancy

Common type of dormancyCommon type of dormancy Seeds must go through a chilling period Seeds must go through a chilling period

before germinating before germinating Stratification is used to break dormancyStratification is used to break dormancy

Seeds are stored in a moist medium at Seeds are stored in a moist medium at temperatures between 32° and 50°Ftemperatures between 32° and 50°F

The length of time required varies by The length of time required varies by speciesspecies

Other Factors Affecting Other Factors Affecting GerminationGermination

Seed age Seed age Older seed less viable than young seedOlder seed less viable than young seed If it germinates seedlings less vigorous and grows more If it germinates seedlings less vigorous and grows more

slowlyslowly

Seedbed preparationSeedbed preparation Seed depthSeed depth

Too shallow may wash away with rain or wateringToo shallow may wash away with rain or watering Too deep won't be able to push through the soilToo deep won't be able to push through the soil

Seedbed moistureSeedbed moisture If over-watered will rotIf over-watered will rot

WeedsWeeds

Many weed seeds are able to germinate Many weed seeds are able to germinate quickly and under less than optimal quickly and under less than optimal conditionsconditions

One reason why they are so difficult to One reason why they are so difficult to deal withdeal with