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Chapter 9-1
Seed Plants
• General Characteristics:
- Vascular; have true roots, stems, leaves
- reproduce by seeds
- are used for food directly/indirectly; for clothing (cotton); for
homes, paper, rubber (trees); as source of oxygen; source of
medicines
• Types of vascular tissue:
- phloem carries food down the leaves
- xylem carries water and minerals up from the soil
• Parts of a seed:
- protective coat helps against drying out
- embryo is the young plant developing from the zygote
- stored food for the embryo; in some there are cotyledons which
are one or two seed leaves that store food
The seeds need water, nutrients, and light to grow into the young plant.
• Dispersal of seeds:
- animals pass seeds through their digestive systems
- animals have seeds stuck to their fur/clothing
- water
- wind
- some shoot out
Seeds that are dispersed away from their parent have more chance of
survival because of less competition with the parent.
• Germination: early growth of the embryo
• Leaves
- capture sun’s light for photosynthesis in the chloroplasts which
contain chlorophyll. Carbon dioxide from the air through the
stomata combine with water from the soil through the roots to
produce glucose used for food also oxygen that escapes into the air
through the stomata.
- Structure: see page 279 diagram
- Leaves lose water because they have a large surface area and are
exposed to air; water loss, transpiration, can be controlled by the
cuticle or having the stomata closed on hot days.
• Stems
- carry substances between the roots and leaves; provide support by
holding the leaves; some store food
- types:
a. herbaceous – soft ex. pepper and tomato
b. woody – hard, have bark for protection, have heartwood for
additional support, have cambium to produce new xylem and
phloem and increase in width, have pith in the center to store
food/water ex. maple tree, pine tree, and rose
- annual rings are circles in the tree stump made of xylem that tell us
about
a. age (a pair of light and dark circles is one year of growth)
b. seasons (in the spring they are large, thin, light-colored, fast
growing and in the summer they are small, thick, dark-colored,
slow-growing)
c. rain (wider with more xylem)
• Roots
- anchor the plant; absorb waternutrients from soil; some store food
- structure:
a. root cap made of dead cells protect from injury
b. tiny hairs on the root increase the surface area so they can anchor
the plant more and more water/nutrients enter
c. cambium that produces new xylem and phloem
d. vascular tissue for transport
- types:
a. taproot is long, thick main root with thin, branching roots ex.
turnip, radish, dandelion, and cactus
b. fibrous have several main roots from a tangled mass of roots and
soil ex. lawn grass, corn, and most trees
9-2
Gymnosperms
• General
- naked seeds
- needle-like/scale-like leaves
- deep-growing root systems
- most trees, some shrubs, vines; the largest and most diverse
being the conifers that are evergreen and have cones, ex. pine
tree.
• Reproduction by cones that are covered with scales
- male cones are smaller and produce pollen that contains sperm
- female cones are larger and have the ovules that contain eggs
- steps:
~ pollination by wind
~ male cone falls off, scales of female cone close to keep the
pollen in
~ fertilization to produce the seed
~ female cone increases in size and stays on the tree until the
seed matures. Cones with immature seeds point upward,
mature ones release seeds which will become the tiny plant if
landed on a suitable environment.
9-3
Angiosperms
• General
- seeds in a fruit
- flower is the reproductive organ
• Structure of the flower: figure 14
• Reproduction
- pollination by the wind, mostly by birds/insects
- fertilization to produce the seeds
- as the seed develops in the ovary, the ovary enlarges and
becomes the fruit
• Types
Seed Leaf
Petals
Vascular Tissue
Leaves/Veins
Ex.
Monocot
Dicot
1
3 or multiples of 3
Scattered
Narrow/Parallel
Corn, wheat, rice, lily, tulip
2
4,5 or multiples of 4,5
Circular
Wide/Branching
Rose, violet, beans, maple tree,
oak tree, apple tree
• Importance
- rubber for tires
- medicine
- food
- clothing
- furniture/housing
9-4
Plant Responses and Growth
• Tropism: growth response to or from a stimulus
To: positive tropism From: negative tropism
a. Thigmotropism: touch tropism
Ex. vines coiling around an object they touch – positive tropism
b. Phototropism: light tropism
Ex. leaves growing toward light – positive tropism
c. Gravitropism: gravity tropism
Ex. roots growing towards gravity – positive tropism
Ex. stems growing away from gravity – negative tropism
• Hormones: chemicals that affect the growth and development of
plants; they control
- tropisms
- germination
- formation of plant parts
- shedding of leaves
- developing and ripening of fruits
Ex. Auxin controls the growth of plants toward light (read in the
book)
• Life Span of Angiosperms
- Annuals: life cycle is 1 growing season
Ex. Herbaceous plants like the cucumber, tomato, wheat
- Biennials: growing season is 2 years
Ex. Parsley, celery
- Perennials: growing season is more than 2 years
Ex. herbaceous plants like the asparagus and woody plants like
the pine and oak trees