Reproduction In Plants

Pollination Nation: Plant Sex• Pollination the mixing of male gametes

(pollen grains) with female gametes (ovule) to reproduce sexually• Two Styles of Pollination:• Insect-pollination plant grows flowers and

releases scents to attract pollinators (insects/birds)• Symbiosis both groups gain something• Flower has pollen mixed with ovule of different plants• Insect gets nectar (glucose energy drink)

• Wind-pollination plant is designed for pollen to be carried by the wind • No energy wasted on nectar/scents• Pollination success rate is lower

Structure of a Flower (Insect)• Petals display bright colors, patterns,

and scents to attract pollinators• Stamen male organ made of a filament

holding up an anther (produces pollen grain)• Sepal protective layer around carpel• Carpel female sex organ made of the…

• Stigma entrance where pollen grains must land

• Style narrow tube leading to ovary• Ovary container for ovules (eggs)

• Ovule female gametes kept inside two different ovaries; 6 ovules per ovary• Nectary produced nectar for insect

Stamen Anther

Filament

StigmaCarpel

Style

Ovary

Petal

Sepal

Ovule

Nectary

Structure of a Flower (Wind)• Inflorescence groups of spikelets on a

branch• Spikelet group of flowers • Stamen male organ made of filaments

and anthers; millions are pollen grain are produced, but most are wasted• Feathery Stigma long filament with

net-like fibers designed for catching pollen grains in the air• Style tube leading to plant ovary• Ovary contains the female gametes

(ovules)

Filament

Filament

Anther

Stigma

Style

Ovary

Inflorescence

Spikelet

Insect vs. Wind• Compare the structural differences between the two pollination styles:

Structure Insect-Pollination Wind-Pollination

Petals

Nectaries

Stamens

Pollen

Carpels

Present; colorful and scented Absent; no need for them

Present; rewards for insect Absent; no need for them

Attached to short filaments inside the flower

Attached to long filaments and hang outside the flower

Small quantities and sticky; attach to insects easily

Large quantities, smooth, and very light so to be carried by the wind

Sticky, small stigmas inside the flower

Large and feathery for catching pollen; extend outside flower

Self and Cross Pollination• Depending on environmental factors,

flowering plants can be pollinated by another plant or by themselves• Cross-Pollination mixing of gametes from

two different plants of the same species• Produces more variation in offspring’s DNA• Requires pollen from genetically different

partner, that might not be available• Most plants hope for this style

• Self-Pollination Plan B; plant mixes is own gametes together to become fertilized• Because of Meiosis, some variation is made• If plant is not pollinated by a certain point, the

plant will self-pollinate so the gametes are not wasted