PLANT GROWTH DEVELOPMENT I Germination the process by

PLANT GROWTH & DEVELOPMENT

I. Germination - the process by which a plant embryo resumes its growth *a seed contains a plant embryo that is in a state of suspended animation *a seed cannot sprout until water and oxygen penetrate the seed coat *many seed coats must be damaged before they can sprout ex: exposure to fire passing through a digestive tract falling down rocks

*seeds sprout in response to certain changes in the environment ex: increase temperature increase soil moisture exposure to light

Seed Germination Shoot – grows toward light Root – grows toward gravity

II. Life Spans perennials – a plant that lives for several years; many reproduce many times during their life span, while others reproduce only once before they die annuals – a plant that completes its life cycle and then dies within one growing season biennial - a flowering plant that takes two growing seasons to complete its life cycle

Perennials (Many Seasons) Annuals (One Season) Biennials (Two Seasons)

III. Meristems – regions of active cell division 1. primary growth – growth that increases the length or height of a plant ex: apical meristems – the tips of stems & roots 2. secondary growth – growth that increases the width of stems and roots ex: cork cambium – lies within the bark and produces cork vascular cambium – lies under bark & produces vascular tissue

IV. Regulating Growth & Development Plant needs: CO 2, water 14 minerals Hormones: chemicals that regulate plant growth and development ex: auxin – stimulates growth causing shoot to elongate

How Auxin Affects Growth

Minerals Needed by Plants:

Responses: 1. tropism is a response to a stimulus *phototropism – response to light *gravitropism – response to gravity *thigmotropism – response to touch *hydrotropism – response to water Fig 6 p. 582 2. positive tropisms – move toward a stimulus negative tropisms – move away from a stimulus

3. photoperiodism – response of a plant to the length of days and nights ( seasonal patterns) 4. dormancy – the condition in which a plant or a seed remains inactive

Tropisms: hydrotropism – external stimulus to water Phototropism – Gravitropism – Thigmotropism - external stimulus to light external stimulus to gravity internal stimulus to hormones

Venus Fly Trap : Nastic Movement – a non-directional response to stimulus ex: response to the external stimulus of pressure from an insect