Transcript Topic 13 - Southwest High School

Topic 13
Plant Science
13.1
Plant Structure
Plant Diversity
The plant kingdom
contains widespread
diversity, as shown by
fundamental structural
differences between four
plant classifications:
bryophytes, filicinophyst,
coniferophytes, and
angiospermophytes.
Bryophytes-Land plants
that lack many standard
terrestrial adaptations.
Filicinophytes-Huh????
Coniferophytes- Plants
whose reproductive
structure is the cone.
AngiospermophytesFlowering plants.
External Plant Parts
Tissue Distribution in the Stem
Tissue Distribution in the Root
Tissue Distribution in the Leaf
Distribution/Function Relationship
Palisade Parenchyma is a layer of tissue that houses
cells for photosynthesis. It is at the top of the leaf,
closest to the light.
Spongy Mesophyll is the airy space in the middle that
allows for the circulation of gases.
The Xylem and Phloem are well protected for the the
transport of water and sugars.
The epidermis is the outside skin that protects the plant’s
vital organs and maintains support.
Xerophyte Adaptations
Xerophytes are plants that
have adapted to dry climates,
like deserts.
They have small thick leaves
for reduced surface area.
The stomata are located in
pores that offer shelter from
dry wind.
Some have adapted to store
water in their fleshy stems.
Some take in CO2 at night
and close their stomata
during the dry day.
Hydrophyte Adaptations
Hydrophytes are plants
that live in water.
They have little or no
structural support,
because the buoyancy of
the water holds them up.
Many have highly divided
leaves to lessen
resistance to flowing
water.
13.2
Transport in Angiospermophytes
Root System Surface Area
Root systems make use
of extensive branching
and root hairs to
increase the surface
area that is able to
absorb water and
mineral ions through the
ground.
Mineral Ion Uptake
Root hairs are permeable to
water.
Soil particles are usually
coated with water and thus
adhere tightly to the root
hairs.
Vital minerals are pulled from
the soil solution through
active transport by cells with
selective membranes.
A ring of waxy material
blocks the parts of the
solution that weren’t
absorbed from entering the
Xylem vessels.
Root Water Absorbtion
There are two routes
from the root hairs to the
Xylem: the symplastic
route is through the
interior of cells, passing
across permeable
membranes; the
apoplastic route is
between the cell walls.
Water initially absorbed by
the hydrophilic root hairs
travels the apoplastic route.
Water and vital minerals are
absorbed through
membranes to the symplastic
route.
Anything still in the
apoplastic route is blocked
by the Casparian strip from
entering the Xylem.
Terrestrial Plant Support
Thickened cellulose, cell
turgor, and xylem all help
to support land plants.
Transpiration
Transpiration is the loss
of water vapor from the
leaves and stems of
plants.
Transpiration Stream
In the center of the leaf,
mesophyll cells are coated
with a thin film of water.
As water vapor diffuses
through the stomata to the
dry air outside, there is a
force on the water film that
attracts it to the hydrophillic
cell walls.
Cohesive forces resist a
change in the surface area of
the water.
A meniscus forms, which
becomes tighter as
transpiration increases.
This meniscus causes
negative pressure, which
exerts a transpirational pull.
This pulls the sap at the top
of the xylem column, and the
rest of it, down to the roots, is
pulled along because of the
sap cohesion.
Stomata
The tiny pores on the
surface of leaves, called
stomata, are each
surrounded by a pair of
guard cells.
The guard cells can open
and close the stomata to
regulate transpiration.
Rate of Transpiration
Transpiration is the
evaporation of water, so
its rate is directly
proportional to the
intensity of sunlight and
temperature.
Dry air also causes a
large increase in
transpiration, as does
wind.
Phloem
Phloem sap is a
multidirectional flow of
sugars and other vital
nutrients
Plant Food Storage
13.3
Reproduction in Flowering Plants
Flower Structure
Pollination
The placement of pollen
into the stigma of a
carpel by wind or animal
carries.
Prerequisite to
fertilization.
Reproduction
Pollination is the process of
carrying pollen from one
plant to another, which can
bring about fertilization.
Fertilization is the union of
two haploid gametes.
Seed dispersal is the
spreading around of fertilized
embryos together with some
food and vital nutrients.
Internal and External Seed Structure
Germination
After a seed has landed in a
moist patch of soil and the
absorption of water has
occurred, a hormone called
gibberellins in released by
the embryo.
This hormone triggers the
starchy protective covering of
the seed to begin producing
amylase.
The amylase catalyses the
breakdown of the protective
covering from starch to
maltose.
The maltose produced in this
reaction is taken in by the
growing embryo, which is
able to break out of the seed
covering as it breaks down
and the embryo grows.
Necessary Germination Conditions
The most important condition
for germination is the
presence of water.
Some desert seeds will
remain in dormancy until
after a strong rain, so that
they are able to develop.
Many seeds also require
sunlight to trigger
germination.