Homework

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Plants: Cells, Tissues, Organs and

Organ Systems

Before we get into plants....... The cell membrane of a cell is a barrier through which everything must pass on

its way into or out of the cell

Passage across the cell membrane occurs through a process of Diffusion the movement of molecules from areas of high concentration to areas of low concentration

Osmosis the diffusion of water across the cell membrane from areas of high concentration to areas of low concentration

The cell membrane is selectively permeable; not all materials can cross

Some materials are kept in or out while other more important materials (e.g. Oxygen and H2O) are allowed to move in and out of the cell

Cell Specialization and Differentiation

How do seeds change into seedlings and finally into adult plants? The answer lies in cell specialization – the process by which cells develop and mature to exhibit specific functions within a multi-cellular organism

Cell Differentiation is the stage of development of a living organism during which specialized cells form to perform different functions in the organism

Cells are specialized according to the set of proteins they contain; genes are responsible for the regulation and production of these proteins

All cells in an organism contain the same genes but not all the genes are turned on; the genes that are turned on in a particular cell will produce proteins that make the cell specialized giving it a particular role or function

Specialized Cells and Tissues in Plants

Meristimatic cells (Meristems) are undifferentiated cells that give rise to a specfic type of specialized cell these cells have the lifelong ability to become cells of new tissues and organs in a particular part of a plant

Groups of specialized cells form tissues – a cluster of similar cells that share the same specialized structure and function; the 3 major types of tissue in plants are; Dermal Tissue Ground Tissue Vascular Tissue

Several types of tissues combine to work together and perform a specific function in organs; the 4 major organs found in plants are; Leaves Stems Roots Flowers

You are responsible to know the name and function of;

The 3 types of tissues found in the body of the plant

The 4 major organ systems in the body of the plant

The Leaf Divided into 3 parts; Upper Leaf, Middle Leaf and Lower Leaf

The leaf’s most important job is to provide a large surface area where photosynthesis can take place

Be familiar with the name and function of the components of the leaf

The Lower Leaf and Gas Exchange

To allow gases (O2 and CO2) to move in and out of the plant, the leaf contains guard cells scattered across the lower surface

Guard cells change their shape to control the opening and closing of pores in the leaf which are called stomata or stoma for singular

Stomata are connected to the open spaces in the spongy parenchyma

The guard cells and stomata play a significant role in; Transpiration (the evaporation of water (H2O) from leaves) The exchange of carbon dioxide and oxygen (O2 exits and CO2 enter )

Chloroplasts Chloroplasts are found on the guard cells within the leaves of a plant

Function by trapping the sun’s light energy and combining it with carbon dioxide (CO2) and water to make glucose, a carbohydrate broken down in the mitochondria to provide energy for cell activity

The above process is known as photosynthesis

Chloroplasts can change their shape and location in a cell to increase the amount of light they capture

Chloroplasts contain little sacs called thylakoids arranged in stacks called granum which contain a light-trapping pigment known as chlorophyll; the part of the chloroplast where photosynthesis occurs

The Stem A plant’s stem has 2 major functions; physical support and transportation

of water, nutrients and sugar

The stem is made up of the Xylem and Phloem

Xylem Dead tubular cells with thick cell walls that form long hollow vessels or “pipes” through which water can flow

Xylem vessels are grouped with phloem vessels in vascular bundles

Phloem Living vertically stacked tubes that are pourous allowing water and minerals to be exchanged and transported between the phloem and neighbouring cells in the plant

The Roots Roots anchor a plant to the ground, allow

it take up water and minerals from the soil and act as a plant’s storage area

The root hairs are the main site of water and mineral absorption

The endodermis helps control the transport of minerals between the cortex and the vascular tissue

The pericycle is a layer of tissue surrounding the phloem and xylem

• The two major types of roots are taproots and fibrous roots you

should know the structure and function of each of these root types

The Flower The flower does not take part in the maintenance of the plant; it is responsible

for reproduction

The flower is made up of specialized leaves, one which is known as pollen which manufactures sperm and another type is responsible for manufacturing a set of eggs

Plants accomplish pollination with the assistance of the wind and small animals

Flowers attract these animals and insects to the plant through colours and scent

These organisms pick up the pollen from the male part of the flower and transfer this pollen to the female parts of the same or another plant of the same type setting the stage for fertilization

Plant Systems

A plants internal structure contains many interactions between various organs and tissues which perform specific functions These tissue and organ systems working together are known as a system which maintain a constant flow of fluids, nutrients and hormones throughout the plant

A plant has 2 major organ systems Root System consists of all the roots that lie below

the surface of the ground and is responsible for taking in water and minerals from the soil and transporting these substances to the shoot system

Shoot System consists of the remainder of the plant above the ground and is responsible for support the plant and performing photosynthesis and transportation of water minerals and sugar

Plant Systems Work Together The root and shoot system are connected by the flow of water and

nutrients through vascular bundles containing xylem and phloem

Xylem tissue moves water from the roots to the leaves, where this material is needed for photosynthesis

Phloem tissue moves the sugars produced by photosynthesis in the leaves to other parts of the plants; phloem cells utilize the plant’s energy stores to actively pump substance to where they are needed in the plant (e.g. Phloem tissue moves glucose from the leaves to the buds where it is utilized and to the roots where it is stored)

Note: Xylem tissue dies at maturity so it does not use any of the plant’s energy stores

Moving Water Through Systems Water is essential for any plants survival

Nutrients in the soil need to be dissolved in water in order to be

absorbed and move up the phloem in the form of sap

Water is also a critical component of photosynthesis in the leaf

Without sufficient water supply a plant would eventually die, however

too much water in the soil can have negative effects

Keeping water levels balanced and constantly moving through the plant is

vital This requires interactions from the root and shoot system

Moving Through the Roots

The roots helps plants absorb water and minerals from soil; Root hairs expand the roots total surface area water and nutrients are transported into the root through osmosis and diffusion

The nutrients and water move toward the xylem at the centre of the root and then pushed up and into the xylem vessels

The Push and Pull of Water Movement up the Xylem

1) Push From Root Pressure

Root Pressure occurs when transpiration (evaporation of water from

leaves) is low and when soil is moist as root cells bring minerals into the

xylem and phloem, the mineral concentration in these structures increase

The high concentration of minerals causes water to diffuse into the root

xylem by osmosis as water flows in, the root pressure builds in the

xylem which forces fluid up the xylem

2) Transpiration

Xylem tissue ends when it reaches the leaves; here liquid water turns into

water vapour in the middle of the leaf; this is the process of transpiration

Transpiration makes room for more water to come up from the xylem to

move into the leaves, pulling the water column up

Transpiration Root pressure is not sufficient to move water to the top of tall trees alone; Transpiration is the main factor which moves water up the xylem

Transpiration, along with some of water’s unique properties move water up the Xylem

Cohesion ability of water molecules to cling to each other holds the water in the xylem together

Adhesion tendency of water molecules to stick to the surfaces of the walls of the xylem prevents water from flowing back down the roots

The rate of transpiration is controlled by the amount of water vapour in the leaves when their is a lot of water vapour the guard cells open the stomata and water vapour moves out of the leaves when their is little to no water vapour the guard cells relax and close the stomata

Moving Nutrients Through Plants Photosynthesis produces the sugar glucose

Glucose is either used directly or is combined with other molecules to

produce other sugars like sucrose, the main sugar distributed to other

parts of the plant through the phloem

Sucrose that makes its way to the roots is chemically changed into starch

and stored when stored starch is needed by other plant organs, it

must be removed from storage and transported

Starch is not soluble in water, however sucrose is therefore starch is

converted back to sucrose, dissolved in water and is transported as sap

The Movement of Maple Sap In the spring, trees need to nourish the many buds that must divide and

grow to produce leaves the photosynthesize

Sap flows upward from the roots through the phloem of the maple trees in the spring which contains large amounts of sucrose that has been converted from starch

Sap moves through the phloem to where it is needed in the buds where leaves are growing

Once leaves have grown, they can make their own glucose through photosynthesis In the summer and fall as leaves continue to produce more glucose, the extra glucose that is not utilized is transported to other plant tissues or stored in the roots as starch