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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