Plants

Question 1

Collenchyma

Answer 1

• ground tissue that provide extra mechanical support to the plant, especially where the plant is actively growing
• thick but flexible cell walls

Question 2

Imbibition

Answer 2

• The absorption of water by the seed
• begins the process of germination in plants

Question 3

Casparian strip

Answer 3

Helps regulate the type and amount of substances that can enter through the roots and travel to the rest of the plant (via vascular tissue)

Question 4

What cells make up the phloem

Answer 4

Sieve cells and companion cells

Question 5

Sieve cells

Answer 5

Long cells with pores that allow substances to flow through them
They lack organelles in order to transport sugars

Question 6

Companion cells

Answer 6

Have the organelles needed in order to carry out metabolic functions (loading sieve cells with sugars to transport)
Companion cells connect to sieve cells via plasmodesmata (gap between cells that connect their cytoplasms)

Question 7

What structures make up the xylem

Answer 7

Tracheids and vessel elements

Question 8

Tracheids

Answer 8

• Long, thin cells that connect to one another via their tapered ends
• Water flows through pits found at the ends of tracheid cells
• Also provides structural support (along with allowing the flow of water throughout the plant)

Question 9

Vessel elements

Answer 9

• Shorter and stouter than tracheid cells
• Maintain contact with other vessel elements
• Water flows through perforations between vessel elements (perforations are better than pits because water flows more efficiently)
• Also provides structural support (along with allowing the flow of water throughout the plant)

Question 10

Pith

Answer 10

Tissue found at the center of the root or stem
Stores and transports materials throughout the plat (functionally similar to vascular tissue)
Made up of parenchyma (ground tissue)

Question 11

Dermal tissue of a plant

Answer 11

Found on the outer layer of the plant
Provides protection to the inside of the plant
Helps regulate how the plant is affected by the external environment

Question 12

What is the function of the casparian strip

Answer 12

Regulates type and amount of substances that enters roots of the plant due to the fact that it is made up fatty, waxy substances that make it impenetrable (substances are forced into the cytoplasm of the root cell and forced to flow through the plasma membrane)
Helps filter substances coming in through the cell wall

Question 13

What causes the opening of the stomata?

Answer 13

Low concentration of CO₂ inside the plant which occurs during the daytime (photosynthesis occurring)
Plants need more CO₂ to carry out photosynthesis
This causes the stomata to open (more carbon dioxide rushes in)

Question 14

How does the stomata open?

Answer 14

K⁺ ions diffuse into guard cells —> this causes a higher concentration of solute within the guard cells which leads to water rushing into the guard cells making them turgid (swollen)

Swollen guard cells = open stomata

Question 15

What causes the closing of the stomata?

Answer 15

High concentration of CO₂ inside the plant (happens at night when photosynthesis is not occurring), the plant does not need [CO₂] for photosynthesis causing plant to close stomata

High temperatures cause plants to close their stomata because they want to prevent transpiration (evaporation of water from the plant) so they close their stomata and water stays in the plant

Question 16

How does the stomata close?

Answer 16

K⁺ ions leave the guard cells —> this causes the outside of the guard cells to have a higher concentration of solute which leads water to rush out of the guard cells, making them *flaccid (shrunken)**

Shrunken guard cells = closed stomata

Question 17

Functions of auxins

Answer 17

• Promote plant growth and elongation of cells by increasing proton concentration in primary cell walls
• enzymes are activated that loosen cellulose fibers, increasing cell wall plasticity and thus tugor pressure expands cells to grow
• function with cytokinins to promote cell differentiation and division
• one of the main hormones responsible for plant tropisms (growth in a certain direction: phototrophism, gravitropism and thigmotrophism)

Question 18

Function of cytokinins

Answer 18

• can regulate cell differentiation and division
• stimulates cytokinesis
• stimulates and influences the direction of organogenesis
• stimulate the growth of lateral buds which weakens the apical dominance created by auxins (growth of apical meristem)
• delay senescence (aging) in plants

Question 19

Functions of gibberllins

Answer 19

• promote cell growth (stem elongation and flower)
• elimination of dormancy of a seed –> promote germination
• promote flowering and fruit production
• inhibition of agining in leaves
• can work with auxins to stimulate growth

Question 20

Function of abscisic acid

Answer 20

• Function in times of plant stress
• Promotes/maintains seed dormancy (prevents premature opening), closes stomata (during drought), inhibits growth, forms scales
• The dormancy caused by this hormone can be broken by an increase in gibberllin or environmental stimuli (such as temperature or light)

Question 21

What type of plants are bryophytes?

Answer 21

Nonvascular plants: they do not have vascular tissue or roots
Examples: mosses, liverworts, hornworts

Question 22

General characteristics of bryophytes

Answer 22

• They must remain small and short due to the fact that they have no vascular tissue
• They are found in moist habitats
• They grow horizontally in order to be near water and nutrients
• They contain rhizoids (hair-like projections) which aid in water absorption and provide minor anchoring

Question 23

Life cycle of bryophytes

Answer 23

Spend most of their life in the gametophyte stage (haploid, produces gametes)
Gametes produced posses flagellated sperm (motile, thy are able to travel through the moist environment and fuse with other gametes to produce a zygote)
Sporophyte stage uses spores as their dispersal unit
Contain reduced sporophyte which depends on and is attached to the gametophyte

Question 24

Nitrifying bacteria

Answer 24

Convert ammonia and ammonium into nitrites (NO₂^-) and nitrites into nitrates (NO₃^-)

Question 25

Nitrogen-fixing bacteria

Answer 25

Found in the root nodules of legumes Fix atmospheric nitrogen (N₂) into organic nitrogen: ammonia (NH₃) and ammonium (NH₄⁺)

Question 26

Detritus

Answer 26

Formed by dead and decaying plants and animals Are decomposed back into the soil to contribute a nitrogen source (provides soil with nitrates)

Question 27

Denitrifying bacteria

Answer 27

Convert nitrates back into atmospheric nitrogen

Question 28

Low concentration of carbon dioxide inside a plant

Answer 28

Happens during the **daytime** - light is available to carry out photosynthesis and constant photosynthesis depletes the concentration of carbon dioxide levels inside the plant

Question 29

What life cycle do seedless tracheophytes spend most of their life in?

Answer 29

Sporophyte stage (they have *independent* gametophyte and sporophyte stages)

Question 30

Examples of seamless tracheophytes:

Answer 30

Fern, club moss, quillworts and horsetail

Question 31

What does the pressure flow hypothesis explain?

Answer 31

The movement of sugar in the phloem **in relation to the movement of water**

Question 32

Pressure flow hypothesis general steps

Answer 32

1) Source cells in the leaves produce sugar and load sugar into the phloem at the leaves 2) sugar concentration inside phloem cells increases, creating a **gradient** that pulls water from xylem into these phloem cells 3) **turgor pressure** is created in the phloem which results in a **bulk flow movement** of the sugar and water from the source (leaves) down to the sink (roots)

Question 33

What is the main driving force for water entry into roots?

Answer 33

**Root pressure** builds up in roots and produces an **osmotic gradient** which drives water from the soil into the roots and the osmotic pressure pushes the column of water in the xylem upwards

Question 34

translocation in plants:

Answer 34

* movement of carbohydrates through the phloem from the source (leaves) to the sink (site of carbohydrate utilization) * movement described by the **pressure-flow hypothesis**

Question 35

cohesion

Answer 35

* the attraction between like substances (ex: attraction b/w many water molecules) * this allows water within the *xylem cells* to behave as a single, polymer-like column from the roots to the leaves

Question 36

what affect does transpiration have on the pressure inside the plant?

Answer 36

transpiration causes evaporation of water from a plant which causes **negative pressure (tension)** to develop within the **leaves** and the **xylem**

Question 37

cohesion-tension theory:

Answer 37

* theory explaining water movement * major contributor of water movement within a plant * consists of: transpiration, cohesion and bulk flow

Question 38

cotyledons:

Answer 38

storage tissue that provides nutrition to the devoloping seedling

Question 39

cotyledons in dicots vs. monocots

Answer 39

dicots: 2 cotyledons monocots: 1 cotyledon

Question 40

leaf venation and structure in dicots vs. monocots:

Answer 40

dicots: broad leaf with network/branching pattern of veins monocots: long, narrow leaf with parallel veins

Question 41

flower parts in dictos vs. monocots

Answer 41

dicots: flower parts in multiples of 4 or 5s monocots: flower parts in multiples of 3s

Question 42

vascular bundles in dicots vs. monocots:

Answer 42

dicots: orgnized in a ring monocots: scattered

Question 43

root system in dicots vs. monocots:

Answer 43

dicots: taproot (large, single root) monocots: fibrous root system with many fine roots

Question 44

ground tissue:

Answer 44

* provide structural support to the plant * make up most of the plants mass * three types: parenchyma, collenchyma and sclerenchyma

Question 45

parenchyma tissue

Answer 45

* most common ground tissue * thin cell walls * function: storage, photosynthesis, and secretion * ex: mesophyll cells

Question 46

sclerenchyma:

Answer 46

* thicker cell walls than collenchyma * provide mechanical support * tissue produces lignin, a strengthening polymer

Question 47

what are the vascular tissues in plants?

Answer 47

xylem and phloem, which together form vascular bundles

Question 48

root cap

Answer 48

* aka root tip * protects the apical meristem behind it * secretes polysaccharides that moisten the soil, permitting root growth

Question 49

zone of cell division

Answer 49

* formed from the dividing cells of the apical meristem * zone right above the apical meristem

Question 50

zone of elongation

Answer 50

* newly formed cells from the zone of division absorb water and elongate * responsible for our perception of plant growth

Question 51

zone of maturation

Answer 51

* the cells differenciate and mature into the xylem, phloem, parenchyma and epidermal cells (root hairs may grow here too)

Question 52

what plants undergo secondary growth?

Answer 52

conifers and woody dicots

Question 53

where are auxins produced?

Answer 53

at the tips of shoots and roots (apical meristem)

Question 54

auxin is a modified ____ amino acid

Answer 54

tryptophan