Bacteria to Plants
Notes 5.1 The Characteristics of Seed Plants
What is a Seed Plant?
All seed plants have two common characteristics…
1) The have vascular tissue.
2) They all reproduce through pollen and seeds.
Vascular Tissue
Vascular tissue allows plants to grow upright and also helps to move food,
water, and nutrients throughout the plant.
Two types of vascular tissue…
1) Phloem-Moves food produced in the leaves to the rest of the plant.
2) Xylem-Moves water and nutrients absorbed by the roots into the stems
and leaves.
Pollen and Seeds
Seed plants can live in a wide range of habitats, since water is not needed for
fertilization to occur.
Pollen becomes the sperm that will fertilize the egg. After the egg is
fertilized, a seed develops.
Seeds are immature plants surrounded by a protective covering that prevents
the plant from drying out.
How Seeds Become New Plants
If seeds land in a favorable environment, they will sprout and develop into a plant.
Seed Structure
Three main parts of a seed…
1) Embryo-The embryo is composed of immature stems and roots, as well as
one or two cotyledons, or seed leaves.
2) Stored food- Some seeds store food in the cotyledon, while others store food
outside the embryo.
3) Seed Coat-The protective covering of the seed that prevents the seed
from drying out, and allows it to remain inactive is conditions
are not favorable.
Seed Dispersal
The scattering of seeds is called seed dispersal. Seeds may be carried by
water, wind, and animals. Animals also spread seeds by eating, then
eliminating them.
Seed Germination
Germination occurs when an embryo begins to develop and push out of the
seed, after water is absorbed by the seed. The roots grow down into the
soil, then the stem and leaves grow upward.
As soon as the leaves of the plant can be seen, the plant is called a seedling.
Roots
Roots anchor a plant into the soil. They absorb nutrients and water from the soil
and sometimes store food.
Two types of roots…
1) Fibrous-Made up of many tangled strands.
2) Taproot-Made up of one main root, with smaller roots coming off of it.
The Structure of a Root
Refer to diagram.
Stems
Stems have two main functions…
1) They carry substances between the leaves and roots.
2) They support the plant and help expose leaves to sunlight.
Some stems, like asparagus, store food.
The Structure of a Stem
Refer to diagram.
Two types of stems…
1) Herbaceous-Do not contain wood and are soft.
2) Woody-Contain wood and are hard.
Annual Rings
Within the heartwood are annual rings that show the amount of growth in
the xylem layer. During the spring, thick, light colored bands develop with
fast growth. During the summer, thin, dark bands develop with slow
growth. A pair of light and dark bands represents one year’s growth.
In a year with more rainfall, these two bands together will be thicker that in
years where there was less rainfall.
Leaves
Leaves capture the sun’s energy and convert it into food for the plant, through
photosynthesis.
The Structure of a Leaf
Refer to diagram.
The Leaf and Photosynthesis
Chloroplasts contain the chlorophyll that produces food through
photosynthesis.
The stomata, or openings in the leaves, allow carbon dioxide to enter the leaf
and oxygen to leave the leaf.
Controlling Water Loss
Plants lose water through evaporation. This is called transpiration.
By closing the stomata, the leaf can prevent water loss.