Biology EXAM Notes ( Chapters 3-7)
Lecture 3 – Plant cells and Plant tissues
What is the growth difference between plants and animals?
A: The major difference differentiating plants from animas (humans) is the
fact the humans have determinate growth, while plant cells continue to
grow and have indeterminate growth
How do plants grow is respect to plants? How about animals?
A: In Plants: undifferentiated cells undifferentiated AND differentiated
cells indeterminate growth. In animals::::undifferentiated
cellsdifferentiated cells determinate growth
What are the undifferentiated cells in plants cells called?
Totipotent cells in plants are called___________ and in humans are
A: Meristems……… Stem cells
- Did you know that elegans have 959 cells, ONLY. What are Factors that limit growth for plants?
A: Herbivores, strong wind, drought, storms, and soil surrounding the tree
have missing nutrient. All these factors will slow down the growth of the
What are meristems?
A: they are a group of meristematic cells
- Division more meristematic cells and differentiated cells
What two groups can meristems be divided into?
A: Primary Meristem: shoot and root apical meristems, as well as
secondary meristems: many different ones, at very different locations.
( Everything first starts of with Primary Meristems, its key to have them.)
In shoot apical Meristem or (SAM), what protects the shoot apical
A: leaf primoda. They are young baby leaves that surround the meristem,
protecting it. Differentiated plant cells do what?
A: They make up simple or complex plant tissue
Tissue made of one cell type is _____, and tissues made of more than one
A: simple, Complex
What are three very simple plant tissues?
A: Parenchyma, Collenchyma, and Sclerenchyma
- Most common cell type
- Thin walled
- Least specialized
- Often block shaped
Functions : Space filler, Photosynthesis, and storage,
Photosynthesis: Parenchyma in photosynthesis is known as
chlorenchyma . Chlorenchyma that is closest to the sun is stiff, and
arranged in a tight way to maximize light absorption.
While the rest of the collenchyma is arranged more
loosely and allows gas exchange to occur
- Storage: Water nutrients, leaves, seeds, and fruits. . Apples,
- Elongated, Thickened in Cell corners
- Functions - Flexible support in young stems, roots, petioles and
around vascular bundles.
- Typical Location Collenchyma is located surrounding the vascular
tubing system through the plants. In Basil/Mint leaves, it protects it in
a rectangular shape. Like a chunk bracelet around the stem of the
- Dead at maturity, cell interior almost completely filled
- Cell walls thickened with cellulose and usually impregnated with lignin
- Function structural strength
- Expensive to produce
- Comes in two types
o Sclereids – Bulky, makes the crunchy part of pears. Gritty
texture, Makes hard seed coats
o Fibers- thin, example : flax plant cells
Comparative Plant Form and Function: Complex plant Tissue More than one type of cell per tissue, they are specialized for protection,
exchange, uptake, transport, support, and storage.
a) Epidermis- (protection, exchange, uptake) Includes of : Epidermis
Cells, Cuticle, Stoma, guard cells, glands, and hairs.
b) Periderm- (protection, exchange)
c) Xylem ( Transport, Support, Storage)
d) Phloem ( transport)
e) Ground Tissue ( support, storage)
The Waxier the cuticle layer (cutin) it results in maximizing what?
A: The thicker the cuticle, the stronger the protection against water loss. Its
more resistant against pests and bacteria.
Why do grapes shine brighter after you rub them?
A: since you are rubbing the waxy layer evenly, it produces more shine.
What are stomas?
A: Two bordering Guard Cells – they are specialized epidermis cells.
What happens to the stoma when its under water distress? What happens
when it has too much?
A: The stoma will close to retain the water inside; its inner lips will grow
puffier to prevent any water from leaking out. The stoma under excess will
open, the inner lips will open, and water will be released. They are always
located on the lower part of the leaf
Epidermis (Roots, Shoots, and leaves)
- Epidermis cells, Glands, hairs and cuticle are all for protection
- Stoma (2 guard cells) they are used for h20 and air exchange
- Hairs are also there for nutrient uptake ( root hair is located just
behind root camp)
- Non woody plants are one cell layer think and are alive Epidermal Glands
- Hemp Cannabis Sativa- their head has toxic oil
and this is a form of protection. It protects the
plant from herbivores. This plant is extremely
toxic to beetles
- The gender distribution in Hemps are either
female/male where the females are valuable and males aren’t
- To determine whether the hemp is male or female, we look at how
much glands it has.
- What characterizes a gland is the liquid inside.
- The hairs found on the epidermis search for water and other nutrients
- Some can be stinging nettles, which are filled by liquid and enforced
- In stinging nettles hairs are not only located on the roots but
throughout the plants.
- Can grow into cones
- Gives sheen to lure insects for pollen exchange
Lotus Flower- H20 repellent
- The surface of the lotus leaves must be kept dry as possible, so it has
knobs on the leaves, which try to remove the drops of water from the
leaves. So if there’s a drop, it won’t touch the actual leaf. See
diagram. Epidermal Platelets: example: silverberry
- Surface is covered by hair in form of platelets
- Stomata is located underneath platelets resulting in less water loss
- Can grow on berries hence name silverberry
Epidermal Sensing Hairs- example: Venus Fly trap (you know how this
Pitcher Plants- Grows modified hair that functions as a ladder that allows its
prey to easily climb up its walls; however when the prey goes onto the top,
the vase is slippery and causes them to climb in only one direction which is
downward- into their death. 2 choices- slip off and fall to death, or climb
down to death.
Complex plant Tissue
- Epidermis ( Protection, Exchange, Uptake of nutrients)
- Periderm ( protection and gas exchange)
- Xylem ( transport, support, and storage)
- Phloem (support and storage)
Periderm - Perennial plants have torn up epidermis that is due the growth of the
stem, and eventually the sealing of the tears is needed, and this is
where Periderm comes into the picture
- Periderm is literally a fancy word for bark
- There are two types of periderm : Cork Cambium and Cork Cells
- Cork Cambium- is the source of new periderm, and is the secondary
- Cork Cells- are for protection. They are dead at maturity, includes
walls of lignin (anit-microbial) and suberin (wax-like, against
- Cork cells are actually what is used for protection
- Cork cells are inserted between epidermis and interior of plant stems
- Tracheid (transport, support, )- dead at maturity
- Vessel members ( transport and support)- dead at maturity
- Fibers ( support)
- Parenchyma (storage)
- ^ these are all systems that are continuous in system transport of
water and minerals from the roots to the rest of the plants
Tracheids vs. Vessel members
- Tracheids are adjacently stacked but not perfectly. The have holes
called pits connecting each tracheid. These pits allow water to move
through one tracheid to the other.
- In vessel members, water moves from one vessel element to the next
through perforations and pits. This was is much more efficient and
less tapered. Tracheid Vessels
- Thick lignified walls - Variably enforced H20 flows
through openings ( perforations
and pits from cell to cell)
- H20 flows through adjacent - Through evolutionary time
pits from cell to cell vessels became more efficient
- Provide more support - As pressure rises the cell
wall the higher the chance for it to
- - Lots of wall enforcement in
rings, spiral, patch working, and
- If vessels for any reason
become blocked, water can flow
freely through pits
Softwood (Conifers) - xylem in softwood is made of tracheid’s only.
Since they only contain that one tissue, they are known to be simple,
while Hardwood (angiosperms) xylem contains various tissues like
vessels, tracheid, and fiber, and therefore they are considered
- Sieve tube members (transport)
- Companion cells ( control center)
- Continuous system transporting dissolved food material (primary
sugars) from leaves to the rest of the plants, much like xylem
- Living cells (contrast to xylem) - Sugar flows through sieve tube members, divided by sieve plates
- Companions cells: control both themselves
and sieve tube members
- Sieve plates are totally empty of organelles,
but still are alive. The metabolism is controlled
by companions’ cells. These companion cells are adjacent of sieve
- Look at the diagram below for locations
- You count the xylem (rings) of the trees to determine the age. The
phloem is near the rough part of the tree
Ground Tissue (Non Woody Plants)
- Tissues other than dermal and vascular tissue systems are ground
- Ground tissue is made up by parenchyma > collenchyma>
- In Photosynthesis it stores nutrients and fills spaces.
- in some plants there is only parenchyma, but in some other there is
both collenchyma, and sclerenchyma as well as parenchyma.
Because there are three tissues, we classify it as ground tissue Lecture Five: From Seed to Tree
- Without and seed dispersal or distribution/adaptions, seeds will fall
closer to the ground and start growing there. Hence they will start
competing with one another for nutrients, water, and light. This will
lead to inbreeding depression
- Because plants don’t want their little babies to compete for survival
they count on distributive agents to come and pick them up and put
them far away Different Dispersal Agents
- Explosive self-dispersal ( + 1 m)
o Jewelweed spreads seeds by with the slightest touch it unzips,
curls, flips, and twists , allowing the seeds to everywhere.
- Wind dispersal (1-60 m)
o Plants have hair like components to their seeds which let them
easily be picked up by wind and carried on. (Example
o Winged maples fall like a helicopter through the wind to a new
- Water Dispersal ( up to 1000s of Km)
o This is the form of dispersal that provides the most distance.
Coconut, and soybeans travel this way
- External hitchhiking ( several km)
o hooks, and barbs play an important role where they attach
themselves to animal fur (or clothing of humans) and travel with
them. Example: burdock- Arctium Minus
- Internal hitchhiking ( up to 100 kms)
o Basically aniamls (birds) eat the berries and they poop out the
seeds somewhere else a little bit farther than the parent plant
- Ant dispersal (1-5 m)
o Elaisomes- fleshly structure attached to seeds rich in lipids and
o There is a very close symbiotic relation between seeds and
plants. Plant want the ant to pick off its seed, so in return it
grows this oil that appeals to the ants. The ants will take up this oil and carry the seed to where its living, feed it to its offspring,
and finally leave the seed somewhere far away from the parent
o Trillium, blood root, daily leaves, are all examples of plants that
use ants for dispersals
- Small mammal dispersal ( less than 20 m)
o When nuts from trees fall on the ground and get picked up by
small mammals like a squirrel, they then store these seeds
away from trees, and the tree hopes the squirrel won’t eat all of
the nuts, and would forget some. Then voila new tree.