Unit 4, Lesson 4.4 - The Seed

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Introduction to Science

The SeedUnit Four, Lesson 4.4By Margielene D. Judan

Lesson OutlineThe Seed Parts of a SeedFactors Affecting Seed Germination

The SeedA fertilized ovule

Parts of a SeedSeed coatEndosperm food storeEmbryo the baby plant

Seed coatProtects the seedConsists of 2 layersTegmen (inner; colorless)Testa (outer; colored)A scar called hilum can be seen. Its the mark left by the funiculus that attaches the ovule to the ovary

EndospermStores foodNourishes the seed

EmbryoThe miniature (baby) plantDominant (not active) until some requirements (ex. Water, sunlight) are metHas two basic parts: hypocotyl and epicotyl

EmbryoEpicotyl will become shoot (leaves and stems) via plumule; grows above plant axisHypocotyl connection between cotyledon (seed leaf) and radicle (baby root); grows below plant axis

Seed GerminationThe 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 plantOxygen for cellular metabolism; when the seed breaks open, gas exchange can occurTemperature each plant species has a temperature range within which the seeds will germinate

Seed GerminationAs 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