8-3: Characteristics of Seed Plants
I. What is a Seed Plant?
A. Have vascular tissue
1. supports the plant
2. transports food and water
a. phloem – food
b. xylem – water
3. include roots, stem, leaves
B. Have complex life cycle
1. Stages
a. gametophyte – microscopic
b. sporophyte – observable plant
2. Reproduce using pollen and seeds
a. unlike seedless plants, do not need watery surroundings
b. pollen
i. contain cells which become sperm cells
ii. delivered by wind, insects, or other animals
c. seed
i. structure that contains a young plant inside a
protective coating
ii. develops from fertilized egg cell
II. How Seeds Become New Plants
A. Seed Structure
1. embryo – partially developed plant
2. cotyledon – stored food
3. seed coat – prevents seed from drying out
B. Seed Dispersal
1. Prevents competition between parent and offspring
2. Methods
a. animals
b. wind
c. water
d. ejection
C. Germination
1. Seed absorbs water
2. Embryo uses stored food to grow
3. Seedling – young plant with observable leaves
III. Roots
A. Function
1. anchor the plant
2. absorb water, minerals
3. store food
B. Types of Root Systems
1. fibrous – tangled mass of similar sized roots
2. taproot – single main root
C. Structure of Root
1. root cap – protects root from rocks as it grows downward
2. root hairs – increases surface area to absorb water
3. vascular tissue
a. phloem
b. xylem
IV. Stems
A. Function
1. carries substances between roots and leaves
2. supports the plant
3. hold leaves to expose to sun
B. Structure
1. herbaceous – soft
2. woody – hard
a. bark
i. cork – outer protective layer
ii. inner bark – layer of living phloem
b. cambium layer
i. sapwood – active phloem, transports water
ii. hardwood – old, inactive; provides strength and support
V. Leaves
A. Function
1. captures sun’s energy
2. photosynthesis – food making process
B. Structure
1. cuticle – waxy, waterproof layer
2. upper layer
a. tightly packed cells trap light energy
b. contain most of the leave’s chloroplasts
3. lower layer
a. widely spaced cells
b. allows gases to exchange between leaf and atmosphere
c. O2, CO2
4. stomata
a. holes that open and close
b. controls water loss
c. transpiration – process where plants lose
water through evaporation