Ch 28: Plant Structure and Growth

Question 1

List the 4 major organs that make up the plant body

Answer 1

roots, stem, leaves, reproductive organ (flower)

Question 2

List the 3 major tissues types found in plants and describe their location and function in the plant body

Answer 2

dermal - line of defense

vascular - xylem phloem

ground - parenchyma sclerenchyma collenchyma

Question 3

Contrast the structure of xylem and phloem: what cell types are found in each, are the cells dead or alive at functional maturity, etc.

Answer 3

Xylem - tracheids and vessel elements; dead and lignified at maturity

phloem - sieve tube elements and companion cells; alive at maturity

Question 4

Distinguish between parenchyma, sclerenchyma, and collenchyma

Answer 4

Parenchyma - Alive; photosynthetic cells in mesophyll

Collenchyma - Alive; flexible support structure

Sclerenchyma - Dead; lignified; rigid support structure

Question 5

Describe the functions of the root and shoot systems

Answer 5

Root system - roots; anchor plant, absorb water and minerals, store carbs

Shoot system - everything above ground

Question 6

Contrast taproots and fibrous roots

Answer 6

Taproots - massive root; dicots

Fibrous - a lot of small roots; monocots

Question 7

Explain the function of root hairs

Answer 7

root hairs increase the amount of water and nutrients the plant can absorb from the soil.

Question 8

Explain what mycorrhizae are and why they are beneficial

Answer 8

mycorrhizal fungi are made up of a root-like structure and posses a network of mycelium external to the tree roots that extends into the soil. This mycelium absorbs nutrients and translocates them back to the host plant. As a result, there is an increase in the absorption surface area of the roots.

Question 9

Describe the functions of stems

Answer 9

support structure for leaves and elevate reproductive structures

orients shoot to maximize photosynthesis

long distance transport of water/nutrients

Question 10

Identify the following structures: node, internode, petiole, blade, stomata

Answer 10

node - an area on a stem where buds are located

internode - a part between two nodes

petiole - a stalk that attaches a leaf to the plant stem

blade - most frequently the flat, photosynthetic part

stomata - specialized pores or openings present in the epidermis of plant cells, which play a crucial role in gaseous exchange during the process of photosynthesis

Question 11

Describe the structure and function of leaves

Answer 11

photosynthesis

gas exchange

dissipate heat

transpire water

Question 12

Explain why leaves have stomata and describe in detail how stomata are opened and closed

Answer 12

stomata control gas exchange and the transpiration of water, opened and closed via guard cells

Question 13

Describe conditions that would cause stomata to be opened / increase transpiration

Answer 13

Increased Sunlight
Higher temperature
Low humidity / dry air
Higher wind
Higher soil water
Lower CO2 Levels

Question 14

Describe conditions that cause stomata to be closed / decrease transpiration

Answer 14

Decreased sunlight
Lower temperature
High humidity
Low wind
Low soil water
Higher CO2 Levels

Question 15

Define meristem

Answer 15

undifferentiated cells (meristematic cells) capable of cell division. Cells in the meristem can develop into all the other tissues and organs that occur in plants

Question 16

• Distinguish between apical and lateral meristems

Answer 16

Apical Meristems are responsible for growth in length; lengthens the shoots and roots (apical and axillary buds)

Lateral Meristems allow for growth in thickness; increases diameter of stems and roots (Vascular Cambium and Cork Cambium)

Question 17

Define primary and secondary growth and identify which meristems are involved in each type of growth

Answer 17

Primary growth lengthens the shoots and roots, and occurs at apical meristems

Secondary growth increases the thickness, diameter of stems and roots and occurs at lateral meristems

Question 18

Describe the zone of cell division, elongation, and maturation

Answer 18

The zone of cell division is closest to the root tip; it is made up of the actively dividing cells of the root meristem. The zone of elongation is where the newly formed cells increase in length, thereby lengthening the root. Beginning at the first root hair is the zone of cell maturation where the root cells begin to differentiate into special cell types.

Question 19

Identify the cell types produced by the vascular cambium and cork cambium

Answer 19

Vascular cambium: adds layers of vascular tissue: produces secondary xylem & secondary phloem

Cork cambium: replaces the epidermis by periderm: renews and maintains a protective outer layer of cork

• During secondary growth the epidermis is replaced by cork which is formed from the cork cambium
• Outermost layers of cork split and peel off to accommodate new growth
• Bark = all of the tissue outside of the vascular cambium (=>includes the secondary phloem)

Question 20

Explain how and why tree rings form

Answer 20

Tree rings form in the trunk of a treefrom new cells generated in the cambium, themeristem(growing point) that lies just beneath the tree’s bark. The annual growth rings evident in cross sections of most tree trunks in temperate regions result from the yearly activity of vascular cambium. Tree rings provide a record of yearly growth and give indications on environmental (climate) conditions

• Wide growth rings indicate higher growth rates and suggest favorable conditions
• Narrow growth rings indicate slower growth rates and suggest unfavorable conditions

Question 21

List the layers of cells that one would encounter when moving from the outside to the inside of a tree

Answer 21

They are the outer bark, inner bark (phloem), the cambium cell layer, sapwood, and heartwood.

Question 22

NOTES

Answer 22

• Cells of the xylem are always dead when functionally mature.
• Parenchymacells are responsible for most of the metabolic functions of a plant.
• Collenchyma cells help support young parts of the plant shoot.
• Sclerenchyma cells also function as supporting elements in the plant but are much more rigid than collenchyma cells.
• Xylem cells conduct water and dissolved minerals upward from roots into the shoots.
• Phloem cells transports sugars, the products of photosynthesis.
• Secondary xylem and phloem are produced in a root by the vascular cambium.
• Lignin is the primary substance providing strength to the structural supports in woody plants.
• The term stoma (or stomata) can refer to the stomatal pore or to the entire stomatal complex consisting of a pore flanked by two guard cells, the specialized epidermal cells that regulate the opening and closing of the pore. Guard cells are highly specialized and do not play a role in defense, reproduction, or anchoring a plant.
• Sieve-tube elements are phloem transport cells with sieve plates in the end walls between cells.
• Removal or shading of an apical bud, or shoot tip, will result in growth from an axillary bud.