Plant Biology

Question 1

Explain the role of auxin in phototropism

Answer 1

auxin is a plant hormone;
produced by the tip of the stem/shoot tip;

causes transport of hydrogen ions from cytoplasm to cell wall;
decrease in pH / H+ pumping breaks bonds between cell wall fibres;

makes cell walls flexible/extensible/plastic/softens cell walls;
auxin makes cells enlarge/grow;

gene expression also altered by auxin to promote cell growth;

(positive) phototropism is growth towards light;
shoot tip senses direction of (brightest) light;
auxin moved to side of stem with least light/darker side
causes cells on dark side to elongate/cells on dark side grow faster;

Question 2

Describe the process of mineral ion uptake into roots.

Answer 2

absorbed by root hairs / through epidermis
root hairs increase the surface area for absorption
uses active transport / uses ATP / uses energy
use of proteins / pumps to move ions across membrane
against concentration gradient / diffusion gradients into cell / root
can enter cell wall space / be drawn through cell walls / apoplastic pathway
selective / only specific ions absorbed

Question 3

Describe how water is carried by the transpiration stream

Answer 3

transpiration is water loss (from plant) by evaporation;
flow of water through xylem from roots to leaves is the transpiration stream;
evaporation from spongy mesophyll cells;
replaced by osmosis from the xylem;
(diffusion of water vapour) through stomata;
water lost replaced from xylem / clear diagram showing movement of water from xylem through cell(s) (walls) to air space;
water pulled out of xylem creates suction/low pressure/tension; transpiration pull results;
water molecules stick together/are cohesive;
due to hydrogen bonding/polarity of water molecules;
xylem vessels are thin (hollow) tubes;
adhesion between water and xylem due to polarity of water molecules;
creates continuous column/transpiration stream;

Question 4

Explain how abiotic factors affect the rate of transpiration in a terrestrial plant

Answer 4

less transpiration as (atmospheric) humidity rises
smaller concentration gradient ( of water vapour)
more transpiration as temperature rises
faster diffusion / more kinetic energy (of water molecules)
faster evaporation (due to more latent heat available)
more transpiration as wind (speed) increases
humid air / water vapour blown away from the leaf
increasing the concentration gradient (of water vapour)
more transpiration in the light
due to light causing stomata to open
wider opening with brighter light hence more transpiration
CAM plants opposite
narrower stomata with high carbon dioxide concentration hence less transpiration

Question 5

adaptations of xerophytes

Answer 5

xerophytes are plants that live in dry conditions;

reduced leaves/spines to prevent water loss (by transpiration);

rolled leaves to prevent water loss / stomata on the inside / sunken stomata;

thick waxy cuticle/hairs on leaves to prevent water loss (by transpiration);

reduced stomata to prevent water loss (by transpiration) /
stomata on one side of leaf;
d
eep/widespread roots to obtain more water;

special tissue for storing water;

take in carbon dioxide at night / CAM plant to prevent water loss;

Question 6

the role of the phloem in the active translocation

Answer 6

• living tissue
• composed of companion cells / sieve tube members
  companion cells involved in ATP production
• sucrose / amino acids / assimilate / products of photosynthesis transported
• bi-directional transport
• source / leaves to sink / fruits / roots /storage organs / named storage organ
• pressure flow hypothesis / movement of water into phloem causes transport

Question 7

Explain the functions of the different tissues of a leaf

Answer 7

cuticle (produced by epidermis) prevents water loss
epidermis protects cells inside the leaf
stomata (in epidermis) for gas exchange
palisade parenchyma / mesophyll / layer for photosynthesis
spongy parenchyma / mesophyll / layer for photosynthesis
air spaces for diffusion of O2 / CO2 / gases
spongy mesophyll for gas exchange / absorption of CO2
xylem transports water / mineral salts / ions to the leaves
phloem transports products of photosynthesis / sugars (to flowers / new leaves / stem / roots / fruit)
stomata allow transpiration (which helps transport of mineral nutrients)
guard cells open and close stomata
guard cells close stomata to reduce transpiration

Question 8

Outline the adaptations of plant roots for absorption of mineral ions from the soil.

Answer 8

mineral ions are absorbed by active transport;
large surface area;
branching (increases surface area);
root hairs;
root hair cells have carrier protein/ion pumps (in their plasma membrane);
(many) mitochondria in root (hair) cells;
to provide ATP for active transport;
connections with fungi in the soil/fungal hyphae;

Question 9

Explain how abiotic factors affect the rate of transpiration in a terrestrial plant.

Answer 9

less transpiration as (atmospheric) humidity rises
smaller concentration gradient ( of water vapour)

more transpiration as temperature rises
faster diffusion / more kinetic energy (of water molecules)
faster evaporation (due to more latent heat available)

more transpiration as wind (speed) increases
humid air / water vapour blown away from the leaf
increasing the qconcentration gradient (of water vapour)

more transpiration in the light
due to light causing stomata to open
wider opening with brighter light hence more transpiration

CAM plants opposite
narrower stomata with high carbon dioxide concentration hence less transpiration

Question 10

List abiotic factors which affect the rate of transpiration in a typical mesophytic plant.

Answer 10

light
temperature
wind
humidity

Question 11

transpiration

Answer 11

is the germ given to the loss of water vapour from leaves and other aerieal parts of the plant which is replaced by water absorption

Question 12

cuticle

Answer 12

• outermost layer of a leaf

- protects the plant from water loss and insect invasion

Question 13

epidermis

Answer 13

secondary outermost leayer that protects the plant

Question 14

vascular tissue

Answer 14

-phloem
-xylem
together in vascular bundles

Question 15

xylem

Answer 15

• brings water to the leaves

- its red and dead

Question 16

phloem

Answer 16

• carries the products of photosynthesis to the rest of the plant

Question 17

palisade mesophyll

Answer 17

• densely packed region of cylindrical cells in upper portion of leaf
• contain many chloroplasts for photosynthesis

Question 18

spongy mesophyll

Answer 18

• loosely packed cells with few chloroplasts

- many air spaces for gas exchange

Question 19

stomata

Answer 19

are pores that are on the bottom of the leaf surface for oxygen and carbon dioxide exchange between leaf and surrounding environement
- on bottom to allow for less light/temperature to minimize water loss

Question 20

guard cells

Answer 20

specialized cells that control the opening and closing of the stomata
- have uneven cell wall thickness

Question 21

tracheids

Answer 21

dead cells in the xylem that taper at the ends and connec to one another to form a continious column

Question 22

xxlem vessel elements

Answer 22

cells involving water transport; also dead and have thick lignified secondary walls

Question 23

xylem transport + function

Answer 23

• transports water from roots to upper parts of the plant and supports the plant (by transpiration)
• any water lost used to cool leaves and stems

Question 24

xylem primary walls

Answer 24

pits and pores for lateral water movement

Question 25

xylem secondary walls

Answer 25

lignin often interupted by areas of the primary walls

Question 26

lignin

Answer 26

complex organic compounds that greatly strengths cell wall of vascular plant - also water profs plant and add protection against pathogens - primary cell wall made up of cellulose; in some plants they form a secondary cell wall of lignin

Question 27

stomata and guard cell action

Answer 27

- stomata can only be closed on short-term basis in reponse to turgor pressure of the surrounding guard cells - when water enters the cell, guard cells bulge and their cell wall thickens which opens the stoma - when the plant loses water; guard cells sag and that closes the stoma

Question 28

hormone involved in stomata action

Answer 28

abscisic acid; plant hormone that causes potassium ions to diffuse rapidly out of guard cels for stomatal closure -produced in roots during times of water deficiency

Question 29

how does water loss/gain occur in the guard cell

Answer 29

-water loss/gain is due to potassium ion transport that triggers ATP pumps (solute concentration causes osmosis)

Question 30

what affects stomatal opening and closing?

Answer 30

- Carbon dioxide levels - Circadian rhythms - Hormonal changes - Humidity and droughts - Temperature

Question 31

turgor definition

Answer 31

refers to pressure in a cel that liquid exerts on the membrane and/or cell wall

Question 32

cohesion-tension theory

Answer 32

- explains the movement of water vertically in the plant using intermoleculer attraction like cohesion and adhesion

Question 33

transpiration process

Answer 33

1. water moves down concentration gradient (spaces within leaf have high water vapour concentration so water moves to atmosphere where there is a lower water concentration); water leaves by evaporation 2. water lost by transpiraiton replaced by water from vessels (replacing water from vessels maintains a high water vapour concentration in air spaces of leaf) 3. the vessel water column is manintained by cohesion and adhesion (cohesion involves hydrogen bonds between water molecules and adhesion involves hydrogen bonds between water molecules and xylem vesel sides) 4. tension occurs in the columns of water in the xylem (loss of water in leaves replaced by water xylem so water flow is continous because of cohesion and adhesion) 5. water is pulled from the root cortex into xylem cells (cohesion and adhesion mantain columns under tension by transpiration) 6. water is pulled from the soil into roots, root hair cells and roots have large surface area and water enters by osmosis (as a result of the tension created by transpiration and continiious maintenance of a continious column of water)

Question 34

root and fluid movement in plant

Answer 34

Water moves into root hairs through plasma membranes from soil due to the higher solute concentration within the roots (osmosis) and into the vascular cylinder (phloem and xylem)

Question 35

function of roots

Answer 35

provide mineral ion and water uptake for plant (absorbtion)

Question 36

why are roots efficent?

Answer 36

- extension branching patterns and specialised epidermal structures (such as root hairs cells that increase surface area)

Question 37

what is the role of the root cap?

Answer 37

protects the apical meristem during primary growth of the root in the soil

Question 38

zones of cell development in root zones

Answer 38

area of cell division area of elongation area of maturation

Question 39

area of cell division in root

Answer 39

newly undifferentiated cells are formed in M phase of the cell cycle

Question 40

area of elongation in root

Answer 40

where cells enlarge in size (G1)

Question 41

area of maturation in root

Answer 41

where cells become functional party of plant

Question 42

what proceses allow for mineral ions to enter the root?

Answer 42

1. diffusion of mineral ions and mass flow of water in soil that carries these ions 2. action of fungal hyphae 3. active transport

Question 43

what affects diffusion rate?

Answer 43

1. difference in concentration 2. length of diffusion path 3. surface area

Question 44

what is the action of fungal hyphase?

Answer 44

- symbiotic relationship between root and fungi where fungi increase surface area for absorbiton and in return hav e a place to live

Question 45

active transport action in roots

Answer 45

ions use transport proteins in membrane due to size or polarity - protons pumps are used to pump - represents a form of chemiosmosis

Question 46

effect of light on transpiration

Answer 46

Speeds up transpiration by warming the leaf and opening stomata

Question 47

effect of humidity on transpiration

Answer 47

Decreasing humidity increases transpiration because of the greater difference in water concentration

Question 48

effect of wind on transpiration

Answer 48

Increases the rate of transpiration because humid air near the stomata is carried away

Question 49

effect of temperature on transpiration

Answer 49

Increasing temperature causes greater transpiration because more water evaporates

Question 50

effect of soil water on transpiration

Answer 50

If the intake of water at the roots does not keep up with the transpiration, turgor loss occurs and the stomata close, and the transpiration rate decreases

Question 51

effect of carbon dioxide on transpiration

Answer 51

High CO2 levels in air around plant usually close the guard cells to lose turgor and the stomata to close

Question 52

xerophyte

Answer 52

plants that live in arid climates (desertes and little water)

Question 53

xerophyte LIFE CYCLE ADAPTATION

Answer 53

Perennial plants bloom only in wet season Dormant seed can survive for many years until optimum growth conditions Plants shed leaves/become dormant in dry season

Question 54

xerophyte METABOLIC ADAPTATIONS

Answer 54

CAM plants: CO2 is absorbed at night and stored as a 4 carbon compound During the day, photosynthesis is optional Stomata can close during day

Question 55

xerophyte PHYSICAL ADAPTATIONS

Answer 55

Fewer leaves and stomata Rolled leaves and spikes, smaller leaves (decrease surface area of leaves) Stomata in pits with hairs to increase humidity near stomata Deeper roots to reach water Cacti can store water in fleshy watery stems Waxy cuticle that reduces evaporation

Question 56

halophyte

Answer 56

plants adapted to grow in water with high levels of salinity | -some being used for net generation of biofuel as the don't compete with food crops for resources

Question 57

halphyte adaptations

Answer 57

- Many have become succulent by storing water, thus diluting salt concentrations - Several species (like mangroves) secrete salt through salt glands - Some species are able to compartmentalize Na+ and Cl- in the vacuoles therefore preventing NaCl toxicity - Sunken stomata on thickened leaves reduce water loss by creating a higher humidity near the stomata. The thickened leaves often include a more developed cuticle to minimize water loss - Surface of area of the leaves is reduced

Question 58

phloem function

Answer 58

transports organic molecules throughout the plant from source to sink (products of photosynthesis)

Question 59

sink

Answer 59

plant organ that uses or stores sugar | e.g. roots, buds, stems, seeds, fruits

Question 60

source

Answer 60

plant organ that is the net producer of sugar, either by photosynthesis or starch hydrolysis e.g. leaves

Question 61

phloem structure

Answer 61

made up of living cells (sieve plate with pores) a companion cell with a nucleus and dense cytoplasm connected to the sieve tube by plasmodesmata and a sieve tube that lacks a nucleus or cytoplasm

Question 62

pressure-flow hypothesis

Answer 62

hydrostatic pressure cuases contents of phloem to flow towards sink

Question 63

translocation process

Answer 63

1. Loading of sugar into the sieve tube at the source reduces the relative water concentration in the sieve tube members, causing osmosis from surrounding cells. 2/ This is achieved by active transport, energy provided by the companion cells 3. The uptake of water at the source causes a positive hydrostatic pressure in the sieve tube, resulting the the bulk flow of phloem sap 4. Hydrostatic pressure is reduced by sugar removal at the sieve tube at the sink. The sugars are changed at the sink to starch, which is insoluble and has no osmotic effect 5. Xylem recycles the pure water by carrying it from the sink back to the source.

Question 64

How can aphids be used to calculate phloem transport rates?

Answer 64

Aphids are insects that use their stylet to pierce the phloem and eat the sap. 1. Plant grown in lab and is exposed to radioactive CO2 2. Incorporated in photosynthesis which produces radioactive sucrose 3. Apid put on a plant 4. Their sylhet is cut off so phloem fluid flows out 5. The time taken for the sucrose to come out of the cut through leaf measure the rate of phloem sap movement

Question 65

types of plant tissue

Answer 65

- dermal tissue - ground tissue - vascular tissue - meristamatic tissue

Question 66

dermal tissue

Answer 66

outer covering against physical and pathogenic agents | -prevents water loss

Question 67

ground trissue

Answer 67

thin-walled cells for storage, photosynthesis, support and secretion

Question 68

vascular tissue

Answer 68

phloem and xylem for water, mineral, nutrient support | -provide support

Question 69

meristimatic tissue

Answer 69

derived of aggregates of small cells with the same function as stem cells; undifferentiated and used for growth

Question 70

apical meristems

Answer 70

- differentiated based on position in plant (primary meristem) occurs at roots and stems shoot apex; apical meristem and surronding tissue which uses mitosis and cell division stem growth increase with light and carbon dioxide exposre

Question 71

lateral meristems

Answer 71

growth in plant thickness (secondary meristem growth) occurs at cambium; often in trees and shrubs vascular cambium; procues secondary vascular tissue cork cambium; produces cork cells of outer bark in trees

Question 72

plant hormones

Answer 72

Plant developments depends on communication within the plant hormone types: - auxin - abscisic acid

Question 73

Factors that affect plant growth and development:

Answer 73

Environmental factors (day length and water availability) Receptors (which allow plants to detect environmental factors) Genetic makeup of plant Hormones; chemical messengers (move through phloem or cell to cell)

Question 74

tropism? | phototropism?

Answer 74

Tropism: the growth or movement to directional external stimuli (can be positive or negative) Phototropism: responses/growth to light

Question 75

auxin?

Answer 75

a plant growth hormone that affects the gene expression in shoots; causes cell elongation and development. Found in the embryo of seeds, meristems of apical buds and young leaves. Only work on plants with auxin receptors.

Question 76

how does auxin work?

Answer 76

Affects the patterns of gene expression Redistribution of available auxin to the side of the stem away from the light source. Plant Auxin is called indoleacetic acid (IAA) Auxin efflux pumps that move auxin out of cells closer to light (using ATP) to create a high auxin concentration in the space between cells As a result, auxin moves down the concentration gradient into adjacent cells until (auxin influx) there is a greater conc. Of auxin in darker cells resulting in the elongation of the stem away from the light Elongation of cells is caused by the expansion of the cell walls

Question 77

Sequence of events in stem causing it to bend towards a light source

Answer 77

1. auxin produced by all cells in stem towards light source 2. auxin moves by efflux pump action into nuclei of cells on the side of the stem opposite to light 3. auxin + receptor in nuclei form a complex that activates a proton pump 4. proton pump moves protons into spaces of cell wall 5. these protons cause a pH drop; results in Hydrogen Bonds between cellulsoe fibres of cell wall breaking 6. results in elongation of cell wall away from light source

Question 78

what are auxins involved in?

Answer 78

- cell division stimulation in most meristamtic tissue - xylem and phloem differentiation - lateral root development in tissue cultures - lateral bud growth suppresion when present in apical bud - growth of flower parts stimulation - fruit production without pollination induction

Question 79

micropropagation

Answer 79

Using knowledge of hormones and meristems to clone plants to produce large numbers of progeny - involves placing shoot apexes into nutrient agar gels with growth hormones to get a certain quantitiy of cloned plants - allows for altering of gene expression in plants to help humanity

Question 80

angiosperm

Answer 80

flowering plants | co-evolve with a pollinator species (bats, insects, birds)

Question 81

sepals

Answer 81

protect developing flower while inside bud

Question 82

petals

Answer 82

often coloful to attract pollinators

Question 83

anther

Answer 83

part of the stamen that produces male sex cells

Question 84

filament

Answer 84

stalk of the stamen that holds up the anther

Question 85

stigma

Answer 85

sticky top of the carpel where pollen lands

Question 86

style

Answer 86

structure of carpel that supports stigma

Question 87

ovary

Answer 87

base of carpel; where female sex cells develop and fertilization occurs

Question 88

male part and female part

Answer 88

male; stamen | female; carpel

Question 89

monocot

Answer 89

- parallel venation (system of veins) in leaves - three flower parts/multiple of three - seeds contain only one cotyledon - vascular bundles arranged throughout stem - root system mainly fibrious - pollen grain with one opening

Question 90

dicot

Answer 90

- netlike venation pattern in leaves - four or five flower parts/multiples of four or five - seeds contain two cotyledons - vascular bundles arranged as a ring in the stem - root system involves a taproot (main root) - pollen grain with three openings

Question 91

polllination

Answer 91

act of transferring pollen grains from the male anther to a flower to the female stigma

Question 92

pollination process

Answer 92

Male pollen carried by pollinators or wind to style Most flowering plants have a mutualistic relationship with pollinators in sexual reproduction (reward pollinators with nectar)

Question 93

How do plants attract pollinators?

Answer 93

Bright colors, scent | Food

Question 94

pollinator types

Answer 94

Pollinators can be generalist or specialist (generally specialist pollinators are crossed with generalist plants and vice versa)

Question 95

types of pollination

Answer 95

self pollination | cross pollination

Question 96

self pollination

Answer 96

a pollen from the anther of the same plant falls upon its stigma (inbreeding + less variation)

Question 97

cross pollination

Answer 97

pollen carried from anther of one plant to a stigma of different plants of same species (increases variation)

Question 98

gametophyte generation

Answer 98

- haploid | - produces the plant gametes by mitosis

Question 99

sporphyte generation

Answer 99

- diploid | - produces spores by meisosi

Question 100

allergic rhinitis

Answer 100

- hay fever - condition caused by pollen causing immune response in people - usually happens from wind pollinated plants

Question 101

fertilization

Answer 101

when the male and female sex cells unite in the ovule to form a diploid zygote -When pollen grain adheres to stigma (covered in sticky substance) it grows a pollen tube

Question 102

fertilization process

Answer 102

Process: 1. Pollen germinates to produce pollen tube 2. Pollen tube grows down style 3. Within the growing pollen tube is the nucleus that will produce sperm 4. The pollen tube completes its growth and enters an opening at the bottom of the ovary 5. The sperm moves from the tube to combine with egg in ovule and form a zygote 6. Zygote develops into seed

Question 103

seed dispersal

Answer 103

the method by which seeds are scattered from plant to a new place where they can grow and develop into a new plant -porential new plant faces reduction in competition for limited resources by moving away from parent Wind, water or animals can disperse seeds

Question 104

testa

Answer 104

a tough, protective outer coat

Question 105

cotyledons

Answer 105

seed leaves that function as a nutrient storage structure

Question 106

microphyle

Answer 106

a scar at the opening where the pollen tube enters the ovule

Question 107

embryo root and shoot

Answer 107

becomes the new plant when germination occurs

Question 108

maturation process of seeds

Answer 108

- invoolves dehydration untill water content is low - seeds usually in dormancy period; adaptive feature of seeds - once conditions favourable; seeds will germinate

Question 109

germination

Answer 109

development of the seed into a functional plant

Question 110

conditions needed for germination

Answer 110

Water to rehydrate dried seed tissues Oxygen for aerobic respiration to produce ATP Appropriate temperature for enzyme action Large amount of seeds due to plantlets fragility/dangers to germination

Question 111

initial process of germination

Answer 111

1. absorbtion of water 2. release of plant growth hormone 3. amylase is produce; hyydrolzes starch into maltose 4. maltose hydrolyzed to glucose for cellular respiration 5. early glucose may also convert into cellulose for cell wall production

Question 112

photoperiodism

Answer 112

a plant's response to light involving the relative lengths of a day and night which is an important factor in flowering control

Question 113

long day plant conditions

Answer 113

- flowers when days are long and nights short | e. g. radish, spinach, lettuce

Question 114

short day plant conditions

Answer 114

- flower when days are shorter | e. g. poinsettias and asters

Question 115

day neutral plant factors

Answer 115

flower regardless of day length e.g. roses, dandelions, tomatoes

Question 116

phytocromes

Answer 116

pigment containing proteins; play an important role in plant regulation as they change back and forth between two isomeric forms - they activate or inhibit gene transcription of flowering

Question 117

Pr

Answer 117

absrobs red light and converts it to infrared during the daytime

Question 118

PFr

Answer 118

absorbs infrared light and converts it to red light during the night time e.g. sedd inhibited by infrared but promoted by red light

Question 119

when do long day plants bloom?

Answer 119

- when nights are short - less Pfr levels found and high Pr (Pr converted to PFr) - high PFr binds to a protein which acts as a trancription factor switching on the gene for flowering

Question 120

why wouldnt a short day plant bloom?

Answer 120

- high Pfr levels= inhibit flowering

Question 121

example of short day plant

Answer 121

chrystanthemums; botanists will place a cloth over this flower over certain period of time to cause plant to flower