Transcript I Love Plants!

Plant General Characteristics
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Carry out photosynthesis (autotrophs)
Produce cellulose in their cell walls
Non-motile (don’t move around)
Reproduce sexually and asexually
Have specialized tissues and organs
Botany: the study of plants
Where did Plants come from?
• Plants likely
evolved from
plant-like Protist
green algae from
a watery
environment.
• Likely evolved
around 500-400
million years ago!
What do Plants Need to Survive?
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Sunlight
Water and Minerals
Gas Exchange
Movement of Water and
Nutrients
Kingdom Plantae adaptations:
Specialized Tissues
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Vascular tissue (like arteries and veins!)
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Xylem – transports materials up from the roots to leaves
and supports the plants as “wood” after the cell dies
Phloem – transports materials down from the leaves to
roots and stem
Vascular Cambium – makes more vascular tissue
Parenchyma – used for storage, surrounded by
vascular tissue
Meristematic tissue – only tissue that produces
new cells by mitosis, found on edges
Cork Cambium – outer bark of trees
Bryophytes – Non Vascular Plants
• Includes: mosses, liverworts, hornworts
• First land plants; had to overcome obstacles
– avoid drying out (desiccation) – live in moist areas
– develop a means of support (roots and stems)
– develop new reproductive methods
– obtaining nutrition
– No vascular tissue, so they are close to the ground
to draw up water by osmosis! Their reproduction
also relies on the use of water!
Tracheophytes – Vascular plants
• Gymnosperms – means “naked seed”, not
protected by fruit. Can reproduce through
wind or other methods on land!
– Class Ginkoopsida – Gingkos; one species exists
today, living fossil
– Class Cycadopsida – Cycads; found in tropics
– Class Pinopsida – cone bearers; 9 families contain
over 300 species, evergreens: pines, spruce,
hemlocks, firs
What does Vasuclar Tissue mean? Means they have xylem (water) and
phloem (sugar) to transport water up from the ground into the rest of the
plant!
Tracheophytes – vascular plants
Angiosperms – flowering plants, produce a form of fruit! (A
wall of tissue surrounding a seed.)
Gives animals a tasty treat to place their offspring
elsewhere. Can reproduce on land.
• Two classes of angiosperms are based upon the number of
Cotyledon: tiny seed leaves that store or absorb food for
developing embryo.
• Class Monocotyledonae – Monocots (1)
• Class Dicotyledonae – Dicots (2)
• Have Unique life spans.
– Those who die in one season are called annuals.
– Those who die in two years are called biannuals.
– Those who live many years are called perennials.
Plant Structure: Roots
• Roots anchor plants into the
ground, absorb water & minerals
from the soil, protect the plant
from bad bacteria/fungi, and
transport these materials to the
stem.
• Contain xylem and phloem in the
center of the root.
• Root pressure – dew is an example of
root (pressure forcing excess water out of
the plant)
• The root cap burrows through the
soil and the cells are replenished
by the apical meristem.
• Meristem = areas of rapidly
dividing cells
Plant Structure: Stems
• Stems can be either woody or
herbaceous.
• Transpiration – as water
evaporates, the energy released
pulls water up the stem
• Vascular tissues are arranged
differently in stems than leaves.
– Monocots: scattered in stem
– Dicots: circular pattern in stem
• Xylem – transports water &
minerals
• Phloem – transports sugars &
hormones
– Portion of a plant that stores
sugar is called a sink.
Plant Structure: Leaves
• Leaves are protected by a
waxy cuticle.
• Petiole – vascular tissues
extending from stem to
leaf (appear as veins)
• Mesophyll – contain
chlorophyll
• Guard cells & Stomata –
regulate water loss through
the underside of the leaf
(Transpiration)
• Monocots: parallel veins
• Dicots: net veined
Plant Asexual Reproduction
• Vegetative
Reproduction – when
plants form new plants
from portions of their
own roots, stems, or
leaves
• Spores – non-seed
vascular plants (ferns)
release spores
Plant Sexual Reproduction Overview
• Pollination – when pollen is deposited on stigma.
• Fertilization – when pollen grain reached the ovary and
fuses with the egg.
• After fertilization, the seed develops food storage regions
for the embryo called fruit.
• Seeds are eventually dispersed using many different
methods. (Wind, Animals, Water, Fruit, etc)
• Remember, this is called the Alternation of Generations!
• Can remain dormant until temperature and moisture cause
the seed to start early growth called germination.
• The systematic cultivation of plants by humans is called
How Plants Reproduce:
Flowers & Flowering
• Flowers are made up of four organs:
(called Perfect Flower)
– Petals – colorful leaf like structure
around the stem.
• They attract insects and other
pollinators of the flower.
– Sepals – green leaf like structure
around the flower stem beneath
the petals.
• They enclose the bud before it opens
and protect the flower while it is
developing.
– Stamens – male part of the flower
where at their tip is the anther that
rests on the filament contains
pollen.
– Carpel– Female part of the flower,
which contains sticky stigma where
pollen grains land and travel down
the style to the ovary and ovules.
Fertilization: Seed & Fruit Production
• 2 sperm fertilize the female, one the
egg (1n), the other the central cell
(2n)
• The walls of the ovule become the
protective seed coat, the central cell
becomes the endosperm or food for
the embryo, and the ovary wall the
fruit.
• Because two fertilization events take
place at the same time, it is called
double fertilization.
• Fruits and seeds are modified for
dispersal.
– Shape of seed can determine type of
dispersal (wind, water, animal, etc)
• Seeds can stay dormant for long
periods of time!
Plant Responses: Hormones
• Hormones cause a physiological
change either in growth or
development.
– Auxins (IAA) – stem elongation.
– Gibberellins – increase rate of
seed germination and allows the
stem to grow taller.
– Cytokinins – stimulate proteins for
cell division and extends the life of
the plant.
– Ethylene – ripens fruits and the
emergence of seeds from the soil.
– Abscisic Acid – helps leaves
prevent water loss by hardening
certain leaf cells.
Plant Responses: Tropisms
• Plants respond to their environment as
other organisms do.
• Photoperiodism affects the timing of flower
production.
– Duration of light and dark periods in the day
– Short-day plants, Long-day plants, day-neutral
plants
• Tropism – a plant’s response to an
external stimulus that comes from a
particular direction.
• Involve growth, so they are not reversible.
– Phototropism (Light)
– Gravitropism (Gravity)
– Thigmotropism (Touch)
• Nastic movement –Do not involve
growth, so are reversible.
– Example: folding of a venus flytrap.