Plants

Question 1

Shoot System

Answer 1

The shoot system is the part of the flower that is above the ground where light is absorbed for photosynthesis. It consists of stems, leaves and the reproductive parts of the plants (flowers and fruits).

Question 2

Root System

Answer 2

The root system is the part of the plant that is under the ground which is responsible to gathering all the minerals and water. It also provides anchorage for the plant.

Functions…

1) Absorb water needed by leaves for photosynthesis and replace water lost during transpiration.
2) Absorb dissolved mineral and regulate the quantity of these mineral entering the rest of the plant
3) Roots store starch made from the food produced by the leaves. Some of this stored food is used by the cells of the root itself while some is transported to other parts of the plant that need it.

Question 3

Shoot System: Stem

Answer 3

The stem is the plant axis ( the area where reproductive organs and ancillary [ accessory ] organs are attached ) that has appendages with leaves and roots at the base.

→ It spreads out leaves so that there is maximum surface area for photosynthesis
→ Conducts water and minerals to leaves
→ Though most stems are vertical, some grow horizontal ( Strawberry plants ). These are called stolons or runners
↪ Rhizomes are underground, horizontal stems. Some have enlarged sections called tubers (Potatoes are tubers)
↪ Some stems are bulbous underground structures called corms. These are swollen underground plant stems that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat.
→ Has xylem and phloem
→ For some plants it acts as a storage organ

Functions

1) Water and dissolved mineral nutrients are transported from the root to the leaves (Xylem)
2) Newly manufactured food molecules are transported form the leaves to the roots for storage (Phloem)
3) Food stored in the root is transported to any plant part that needs it (Phloem)

Question 4

Stem: Nodes and Internodes

Answer 4

Nodes are points on the stem where buds, leaves and branching twigs originate. They usually look like small knobby areas where the stem is connected to an appendage.

The space between the nodes is called the internode.

Question 5

Shoot System: Leaf

Answer 5

Botanically defined as a flattened green outgrowth from the stem of a vascular plant. It is mainly responsible for photosynthesis.

→ The flattened main portion is called the blade
→ The stalk-like connection to the stem is called a petiole
→ Vascular tissue run through the petiole into the blade
→ In angiosperms leaves have a pair of small mini leaf structures at the base of the petiole
→ The middle section of the leaf is called the mesophyll composed of unspecialized cells called parenchyma and is sandwiched between two layers of epidermis. On the outer most layers there are also stoma and guard cells

Question 6

Shoot System: Flower

Answer 6

A leaf that has been modified for reproductive purposes.

Question 7

Shoot System: Fruit

Answer 7

A characteristic feature of some flowering plants is that their seed is encased in fruit. Fruit is a swollen reproductive structure that acts as an ovary in which seeds are nourished until they can survive the environment.

→ Develops after the fertilization of the flower

Question 8

Shoot System: Lateral Bud

Answer 8

This is a bud that is located between the petiole and stem and will eventually grow into a leaf bearing branch.

→ May produce vegetative or reproductive shoots.

Question 9

Shoot System: Shoot Apex

Answer 9

The tip of the stem which contains meristematic cells and the region of growth. Go on to form lateral branches, leaves, flowers, etc.

Question 10

Root System: Primary Root and Lateral Roots

Answer 10

The first portion of the root to emerge after germination. It can be a fibrous root ( root with branches ) or it can be a taproot ( on singular root )

As the primary root continues to grow, smaller lateral roots emerge and a tangled mass or roots results.
→ Help provide anchorage and absorption of nutrients

Question 11

Leaf: Cuticle

Answer 11

A cuticle is a layer of waxes that help prevent moisture loss from the internal part of a leaf. This substance is usually produced in the epidermis

Question 12

Leaf: Epidermis

Answer 12

A leaf has two epidermal layers, upper and lower.
→ Usually one cell layer thick
→ Protect inner tissues of the leaf
→ Secrete wax for cuticle
→ Interact with the environment
→ Permanent tissues and vary in structure among plants
→ Usually is transparent ( including the wax ) to let light pass through

Question 13

Leaf Epidermis: Stomates

Answer 13

Stomates ( or stomata ) are cells that are formed from epidermal cells and allow the diffusion of water vapor, CO2, and oxygen in an out of the leaf ( important for photosynthesis ).
→ Usually open in day and closed at night
↪ This opening and closing of the stomata is controlled by a series of complex chemical reactions.
→ They are only presence of the lower surface of the leaf.

Question 14

Leaf Epidermis: Guard Cells

Answer 14

Two bean-shaped cells that surround the stomata that control gas exchange by opening and closing the pores of the stomata called stoma.
→ They also release water from the leaf
→ Can control rate of exchange by opening or closing the stomata

Question 15

Leaf: Mesophyll

Answer 15

This is the inner layers of the leaf that are responsible for photosynthesis.
→ Made up of chloroplast-containing parenchyma cells which are undifferentiated cells that are modified to perform various functions (Totipotent).

The first layer of mesophyll is called the palisade layer.
→ The palisade cells have a lot of chloroplasts and as a result most photosynthesis happens in this region
→ The shape and arrangement of the columnar cells ( broad and flat ) is optimized to gather the most sunlight.
↪ Situated just below the upper epidermis

The second layer is called the spongy layer
→ Parenchyma cells that are irregular in shape are suspended in a system of interconnected air spaces
↪ These cells also have chloroplasts
→ The loose arrangement allows for the rapid diffusion of carbon dioxide and oxygen during cellular respiration and photosynthesis
↪ Air passes into and out of the cell via the stomata and enter the air spaces in the spongy layer.

Question 16

Xylem Tissue

Answer 16

The xylem is vascular tissue that brings water and nutrients from the soil to the plant’s photosynthetic cells.
→ Made of dead cells impermeable to water
↪ Stiffened with lignin (This make it rigid)
→ Site of transpiration (evaporation of water from the stems and leaves)
↪ Transpiration create a vaccum that creates an upwards suction pressure called the transpiration pull
→ Xylem have tracheids (angiosperms and gymnosperms have these) and vessel elements (only angiosperms have these)
↪ Water (and anything dissolved in it) passes from one tracheid to the next through “pits,” which are thin regions in the adjacent end walls.

Question 17

Phloem Tissue

Answer 17

Phloem is vascular tissue that transports the sugars that are made from photosynthesis and brings it to the non-photosynthetic parts of the plant.

→ Uses active transport

Phloem uses Translocation (Not much is understood about this)
→ Sugary tree sap rises in spring when there are no leaves from which transpiration can occur. So transpiration-tension is not responsible for the movement of dissolved food through phloem
→ Phloem moves food from regions of low concentration to regions of high concentration so it cannot be explained by simple diffusion.
→ Phloem is made of living cells that use oxygen while they are moving food

Question 18

Vascular Bundles

Answer 18

Groups of Xylem and phloem.

Question 19

Root: Root Cap

Answer 19

First Zone. A type of tissue at the tip of the plant root. It is also called the calyptra.
→ Provides protection as the root pushes it’s way through the soil
→ Makes new cells at the root cap to replace worn out cells
→ Protects the apical meristem

Question 20

Root: Apical Meristem

Answer 20

Second Zone. Apical Meristem is a tissue composed of undifferentiated tissue that give rise to new cells through mitosis. That way the plant actually grows out into the soil.

Question 21

Root: Zone of elongation

Answer 21

Third Zone. Cells from the apical meristem increase in size in this zone.

Question 22

Root: Zone of differentiation

Answer 22

Cells start to specialize and differentiate into cells of the epidermis, cortex or vascular cylinder.

Question 23

Root: Epidermis

Answer 23

Surface tissue of the root that protects against invading micro-organisms and environmental stresses.
→ Epidermal cells that are near the zone of differentiation become root hairs ( outgrowth of epidermal cells that look like hair and improve water and mineral absorption by increasing surface area )
→ Have no chloroplasts to produce food but need cellular respiration to stay alive, so get food from the starch in the cortex.

Question 24

Root: Cortex

Answer 24

The region inside the epidermis.
→ Composed of cortex parenchyma cells which are thin-walled cells that can receive mineral ions after they have passed through the epidermis
↪ These cells can be modified to store water and starch
→ There are air spaces between the parenchyma cells as they facilitate free exchange of ions, fluids and gases.
→ Largest area of a young root

Question 25

Root: Vascular Cylinder

Answer 25

The central core of the root is made of a complex groups of tissues known as the vascular cylinder.
→ Outermost tissue of the vascular cylinder is called the endodermis ( single layer of cell that completely encloses the vascular tissue)
↪ Part of these cell walls made of endodermal cells are soaked with a waxy material that regulates the flow of water and minerals from the cortex to the inner tissues of the vascular cylinder. This material forms a collar called the casparian strip.
→ Inside the endodermis is the pericycle which is made up of a layer of parenchyma cells that undergo cell division to produce lateral roots.
↪ They are also responsible for the secondary growth of roots which causes an increase in root diameter
→ Some of the tissue is xylem and phloem, for transportation purposes
→ When the leaves are manufacturing extra glucose, the phloem will conduct dissolved food into the root. When there is a food shortage, the phloem will conduct dissolved food out of the root and upward into the plant’s stem and other structures.

Question 26

Stem: Apical meristem

Answer 26

It is the tip of the stem where cell division occurs and causes elongation ( the stem grows )

Question 27

Stem: Terminal Bud and Lateral Bud

Answer 27

Terminal Bud: Located at the apical meristem, it is the beginning of a new set of leaves

Lateral Buds: Other leaves that arise from the margin of the stem

→ Both look like bud like structures

Question 28

Stem: Leaf scar

Answer 28

The scar that remains after a leaf as fallen. It marks where the petiole attached to the stem ( typically found below a branch ).

Question 29

Stem: Terminal Bud Scar

Answer 29

A stem only makes one terminal bud a year, each year they leave a scar behind. So the age of a stem could be determined by counting the number of scars with each scar representing one year.

Question 30

Stem: Apical Dominance

Answer 30

It is a phenomenon that describe the terminal bud inhibiting the development of lateral buds via a chemical called auxins ( found in the terminal bud ). If the terminal bud were cut off, the lateral buds would grow, otherwise they would be dormant.

Question 31

Stem: Lenticles

Answer 31

Openings in the stem that let gases enter for cellular respiration ( oxygen ) and photosynthesis ( carbon dioxide ).

Question 32

Stem: Inside of a stem

Answer 32

At the center is the pith
→ Derived from parenchyma tissue, it contains a lot intercellular space
→ The high water pressure inside the pith and cortex cells help keep them fully expanded. This condition is called turgor and helps young stems stay upright.

Then comes the Primary Xylem

Next is Vascular Cambium
→ Both the primary xylem and phloem come from the division of cells from the vascular cambium

After is the Primary Phloem

Secondary growth increases the width of the plant and as a result a secondary xylem and phloem is formed
→ Made from cells from the vascular cambium

Then comes the cortex
→ Contain cells that are irregular in shape and arrangement

Finally the epidermis

Question 33

Stem: Development of Xylem and Phloem

Answer 33

1) A cambium cell is the original cell and undergoes mitosis to yield a xylem cell
2) If another division occurs in the original cambium cell, a phloem cell is formed and pushed to the outside of the plant.
3) The cambium cell divides again to create a xylem and is pushed inside
4) The cambium cell divides again to create phloem and is pushed outside
→ Eventually the phloem tissue will disintegrate with each new layer made
→ The xylem cells will form annual rings. However the newest layer will act as a transport channel.
↪ The annual rings ( for example: wood ) are the remains of the previous year’s xylem tissue.

Question 34

Meristematic tissue

Answer 34

These are tissues in which undifferentiated cells stay forever young and are responsible for reproduction. ( Basically the cell factory )

The plants whose stem grows in width, the meristematic tissue is called the apical meristem

Question 35

Protective/Dermal Tissue

Answer 35

Forms the outer layer of cells, also called the epidermis. (There is also the endodermis which is the inner layer of protective cells)
→ Often has a waxy substance called cutin that performs layer called cuticle
→ Sometimes there are periderms (the bark in woody plants)

Question 36

Fundamental/Ground

Answer 36

Parenchyma: Unspecialized cells with thin cells walls, found in all roots, stems, leaves and fruits
→ Parenchyma in leaves have chloroplasts which produces food in the process of photosynthesis

Collenchyma: Similar to parenchyma but, are elongated and have thick cell walls. They strengthen and support leaves and stems.

Sclerenchyma: Consist of thickened cell walls that are found where support is needed. Fibers, are a type of sclerenchyma cell, (found in both xylem and phloem) which are long, strong and flexible

Question 37

Non-vascular Plants

Answer 37

These plants have no vascular tissue
→ They require a moisture
↪ They need the water to carry gametes between plants
↪ Since they have no vascular system, they need nutrients and water surrounding them

→ Some plants may seem to have root-like, stem-like or leaf-like structures but these are not true structures as they lack vascular tissue
↪ Root-like structures can anchor plants but do not absorb water for other parts of the plants
↪ Stem-like structures may hold leaf-like structures but do not transport water or nutrients
↪ The leaf-like structures may carry out photosynthesis and create food but the food has to be diffused to the other parts of the plant

→ Non-vascular plants are restricted in size as they have no way to transport nutrients

→ These plants play a minor role in providing food or other materials for people.

Question 38

Vascular Plants

Answer 38

These plants do have vascular tissue to transport material within the plant.

→ Many of the early forms of vascular plants are now extinct

Question 39

Leaf: Vascular Tissue

Answer 39

Have three main functions…

1) They can conduct water into the leaf
2) They conduct dissolved minerals into the leaf
3) They conduct dissolved carbohydrates ( nutrients ) out of the leaf

Question 40

Stem: Epidermis

Answer 40

A layer of cells that protects the inner tissues. Like leafs, the epidermis is covered by cuticle and perforated with stomata which allows gases to enter and exit.

→ The epidermis cells of young stems contain chloroplasts and can perform photosynthesis.

Question 41

Root: Endodermis

Answer 41

A layer of tissue that is just inside the cortex.
→ Special cells in the endodermis act to ensure the materials travelling to the center of the root are carefully filtered out
↪ Keep harmful toxins out while letting nutrients and water pass
↪ Basically controls what goes inside the plant

Question 42

Leaf: Net

Answer 42

A type of venation where the veins of the leaves of smaller veins run perpendicular to larger veins, basically branching veins.