The SeedUnit Four, Lesson 4.4

By Margielene D. Judan

Lesson Outline

The Seed Parts of a SeedFactors Affecting Seed Germination

The Seed

A fertilized ovule

Parts of a Seed

Seed coatEndosperm – food

storeEmbryo – the baby

plant

Seed coat

Protects the seed Consists of 2 layers1. Tegmen (inner; colorless)2. Testa (outer; colored) A scar called hilum can be

seen. It’s the mark left by the funiculus that attaches the ovule to the ovary

Endosperm

Stores foodNourishes the seed

Embryo

The miniature (baby) plant

Dominant (not active) until some requirements (ex. Water, sunlight) are met

Has two basic parts: hypocotyl and epicotyl

Embryo

Epicotyl – will become shoot (leaves and stems) via plumule; grows above plant axis

Hypocotyl – connection between cotyledon (seed leaf) and radicle (baby root); grows below plant axis

Seed Germination

The process in which the embryonic plant contained within the seed grows.

The first to emerge is the hypocotyl, then the epicotyl.

A young plant called seedling is now seen.

Factors Affecting Seed GerminationWater - causes seeds to swell and break open; when

H2O enters, it activates enzyme and the food is broken down to useful chemicals for the new plant

Oxygen – for cellular metabolism; when the seed breaks open, gas exchange can occur

Temperature – each plant species has a temperature range within which the seeds will germinate

Seed Germination

As the seedling emerges from the seed coat sending out roots and leaves, the stored food is exhausted (used up).

The leaves by this time provides its own food by photosynthesis.

Seed GerminationWhen these factors (water, oxygen,

temperature) are met, the seed could germinate into a new plant.

Assignment: Coupon Bond Art Connection: Refer to p. 141

Deadline: in two days

Sources:

Science Links 7