Botany

Question 1

What are the two methods of pollination?

Answer 1

Flowering plants have evolved two pollination methods: 1) pollination without the involvement of organisms (abiotic), and 2) pollination mediated by animals (biotic). About 80% of all plant pollination is by animals. The remaining 20% of abiotically pollinated species is 98% by wind and 2% by water.

Question 2

What is apical dominance?

Answer 2

The phenomenon whereby the main, central stem of the plant is dominant over (i.e., grows more strongly than) other side stems; on a branch the main stem of the branch is further dominant over its own side twigs.

Question 3

What occurs to prevent seed germination?

Answer 3

Seeds might have a hard or thick seed coat (physical dormancy). This can be broken by soaking or scarifying (scratching the surface) the seed.

Other seeds have internal chemical or metabolic conditions that prevent germination (chemical dormancy). Factors affecting seed dormancy include the presence of certain plant hormones–notably, abscisic acid, which inhibits germination, and gibberellin, which ends seed dormancy.

Question 4

What is endosperm?

Answer 4

Endosperm, tissue that surrounds and nourishes the embryo in the seeds of angiosperms (flowering plants).

Question 5

What is nitrogen fixing?

Answer 5

Nitrogen-fixing plants form a mutually beneficial symbiotic relationship with soil bacteria. Inside these root nodules, the bacteria draw nitrogen gas from the air, turning it into fixed nitrogen that is able to be absorbed and used by the plant host.

Question 6

What are three methods of nitrogen fixation?

Answer 6

Free-living bacteria fixation
Associated bacteria fixation
Symbiotic bacteria fixation (including legume nodule formation)

Question 7

Name two biennial plants

Answer 7

Foxglove

Parsley

Question 8

Name two annual plants

Answer 8

Calendula

Sunflower

Question 9

Name two perennial plants

Answer 9

Hawthorn

Guelderrose

Question 10

What is High Performance Liquid Chromatography?

Answer 10

High Performance Liquid Chromatography (HPLC) is a form of column chromatography that pumps a sample mixture or analyte in a solvent (known as the mobile phase) at high pressure through a column with chromatographic packing material (stationary phase).

Question 11

What is translocation?

Answer 11

Photosynthesis produces glucose in the green parts of plants, which are often leaves. This is then converted into sucrose. The sucrose is transported around the plant in phloem vessels. It needs to be able to reach all cells in the plant so that the sucrose can be converted back into glucose for respiration. The movement of sucrose and other substances like amino acids around a plant is called translocation. In general, this happens between where these substances are made (the sources) and where they are used or stored (the sinks):

from sources in the root to sinks in the leaves in early spring time

from sources in the leaves to sinks in the root in the summer

Question 12

Compare and contrast xylem and phloem

Answer 12

Xylem: Transpiration, Moves water and minerals from roots to leaves, Columns of hollow, dead reinforced cells

Phloem: Translocation, Moves food substances from leaves to rest of plant and from stores such as in the roots, Columns of living cells

Question 13

Why is hydrogen bonding important for transpiration?

Answer 13

Water molecules inside the xylem cells are strongly attracted to each other. There is strong cohesion between the molecules because of hydrogen bonding. A continuous column of water is therefore pulled up the stem in the transpiration stream by evaporation from the leaves.

Question 14

What is the purpose of transpiration?

Answer 14

As water travels through the xylem in the stem and leaf, it is being replaced by water taken up by the roots.

Transpiration is an unavoidable consequence of photosynthesis – only five per cent of the water taken up by the plant is used for photosynthesis – but does have its purposes:

provides the water for photosynthesis
transports mineral ions
cools the leaf as water evaporates
provides water that keeps the cells turgid, which supports herbaceous (non-woody) plants

Question 15

How does water and minerals enter the plant?

Answer 15

Root hairs are single-celled extensions of epidermal cells in the root. They grow between soil particles and absorb water and minerals from the soil.

Water enters the root hair cells by osmosis. This happens because soil water has a higher water potential than the cytoplasm of the root hair cell. Minerals enter by active transport.

Question 16

What are the forms of biologically available nitrogen?

Answer 16

Ammonium ions –> Nitrites –> Nitrates

Question 17

What is denritification?

Answer 17

Denitrification is the microbial process of reducing nitrate and nitrite to gaseous forms of nitrogen, principally nitrous oxide (N2O) and nitrogen (N2). A large range of microorganims can denitrify. Denitrification is a response to changes in the oxygen (O2) concentration of their immediate environment (ie. waterlogged soil)

Question 18

What is ammonification?

Answer 18

The process of decomposing bacteria which turns nitrogen in organic material into ammonium ions.

Question 19

What is the nitrogen cycle?

Answer 19

Ammonium ions –> (bacteria) –> Nitrites –> (bacteria) –> Nitrates –> Plants –> Animals OR Decomposers –> Decomposers –> Ammonium ions

Question 20

What is pharmacognosy?

Answer 20

the study of drugs of natural origin.

Question 21

What is thin layer chromatography (TLC)?

Answer 21

Thin-layer chromatography is a chromatography technique used to separate non-volatile mixtures. Thin-layer chromatography is performed on a sheet of an inert substrate such as glass, plastic, or aluminium foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide, or cellulose.

Question 22

What is the life cycle of an angiosperm?

Answer 22

Dormant Seed
Dispersal
Breaking Dormancy
Germination
Growth and development
Flowering
Pollination
Fertilization and Seed Development

Question 23

What is a monocotyledon?

Answer 23

Seeds contain one embryonic leaf. Flowers and leaves organized in 3s. Leaves have parallel veins.

In the monocotyledon, the scutellum absorbs digested nutrients from the endosperm (a starch store), during germination and early growth.

Question 24

What is a dicotyledon?

Answer 24

Has two embryonic leaves. Leaves have branching veins. In the dicotyledon, the cotyledons form the initial food store but go on to emerge from the soil, and develop ‘seed leaves’ which look quite different from the leaves of the mature plant. They then photosynthesise, making food for the growing seedling.

Question 25

Why is seed dispersal important?

Answer 25

To ensure that at least some of the offspring of a plant ends up in conditions suitable for their growth. For perennial plants it is important that seedlings aren’t competing with their parent for water, nutrients and light.

Question 26

How are seeds dispersed?

Answer 26

Most seeds are dispersed by wind or birds and animals, a few e.g. the coconut, by water and some like Sarothamnus (broom) have a mechanism which flings the seeds from a pod which splits explosively when it dries.

Question 27

How is the development of fruit advantageous?

Answer 27

The structure which contains the seeds is a fruit, derived from the ovary of the flower. The fruit may be attractive and sweet tasting so that it is eaten; the seeds are softened by digestive juices but survive to be deposited with faeces rich in nitrate and phosphate. Some, e.g. Rubus species, contain powerful laxatives to aid the process. Other fruits are inedible, such as the winged seed-bearing fruits of Fraxinus (Ash) and Ulmus, (Elm), and the parachute of Taraxacum (Dandelion), all of which are wind-dispersed, and the barbed fruits of Geranium species and Arctium which rely on clinging to animals and being rubbed off later.

Question 28

What is seed dormancy?

Answer 28

Dormancy is a period which prevents the seed from germinating in unsuitable conditions and allows time for dispersal, so maximizing its chance of surviving and ultimately reproducing. During this time metabolism is minimal and hard protective outer layers protect the embryo from infection and climatic extremes.

Question 29

What are some ways of breaking dormancy?

Answer 29

Some seeds need to pass through the digestive tract of an animal or bird, others need light or the absence of light, some must be scarified – physically abraded by soil and rocks- or the trigger may be increasing temperature or degradation of inhibitory chemicals in or on the seed.

Question 30

What are some examples of breaking dormancy?

Answer 30

Apium graveolens (celery) needs cool soil to germinate. Lactuca spp. (lettuce) need a spell of cold, called stratification. Many Gramineae (Poaceae) species (grasses) need a dry spell first. Iris spp. Have chemicals in the endosperm which must break down to allow germination to begin. Pinus sylvestris cones stay closed until there is a forest fire and only then release the seeds ready for germination. (Note that Pinus spp. are in fact Gymnosperms, ‘naked seeded’ plants, not Angiosperms, which produce enclosed seeds).

Question 31

What is germination?

Answer 31

When the seed is in conditions suitable for growth and (where necessary), dormancy has been broken, water will be taken up by imbibition and this will activate enzymes that break down the insoluble food store into soluble sugars which are then available to the developing embryo

Question 32

What is the radicle?

Answer 32

Embryonic root

Question 33

What is the plumule?

Answer 33

Initial shoot growth

Question 34

How is starch broken down into glucose?

Answer 34

Starch (enzyme: Amylase) --> Maltose (enzyme: Maltase) --> Glucose

Question 35

What are the initial stages of seed growth?

Answer 35

The embryonic root (radicle) grows first, so that water can then be taken up from the soil and shoot growth (plumule) follows, producing leaves which can photosynthesise. Sugars can then be made to sustain the plant after the seed nutrients have been used up. These are active processes which require energy from respiration which in turn needs oxygen, so germinating seeds must not be waterlogged.

Question 36

What is meristem?

Answer 36

The meristem is a type of tissue found in plants. It consists of 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 37

What are primary meristems?

Answer 37

All plants have primary meristems just behind the apices of root and shoot and these produce their increase in height.

Question 38

What are secondary meristems?

Answer 38

Some plants have secondary meristems which cause an increase in girth; these are mainly found in perennial dicotyledons.

Question 39

Summarize the cell cycle

Answer 39

G1, S and G2 = interphase Go is the phase when a cell leaves the cycle, either temporarily or permanently, e.g. because it is damaged, or has become specialized for a particular function. There are 3 very important checkpoints: 1. During growth phase 1 (G1) to check that the cell has all the organelles needed and is at the right size for division 2. At the end of the second growth phase (G2). 3. After DNA replication to check that the chromosomes have been accurately copied, and during division in metaphase to ensure accurate alignment of chromosomes on the equator of the spindle so that the genetic material is evenly distributed in anaphase. Mitosis actually occupies a very small portion of the cell cycle. The rest comprises the essential events of interphase which prepare and equip the cell for division.

Question 40

What is a tonoplast?

Answer 40

Membrane around vacuole

Question 41

What is a vacuole?

Answer 41

A vacuole is a membrane-bound cell organelle. In plant cells, vacuoles help maintain water balance. Sometimes a single vacuole can take up most of the interior space of the plant cell.

Question 42

What is cell sap?

Answer 42

chemical palette of the vacuole solution

Question 43

What is a plasmodema (plasmodesmata pl.)?

Answer 43

Plasmodesmata are minuscule plasma corridors between plant cells which are of paramount importance for transport, communication and signalling between cells. These nano-channels are responsible for the integrated action of cells within tissues and for the subdivision of the plant body into working symplast units.

Question 44

What is the middle lamella?

Answer 44

The middle lamella serves as a cementing layer between the primary walls of adjacent cells.

Question 45

What are chloroplasts?

Answer 45

Chloroplasts absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant. Chloroplasts capture light energy from the sun to produce the free energy stored in ATP and NADPH through a process called photosynthesis. Chloroplasts are one of the many unique organelles in the plant body, and are generally considered to have originated as endosymbiotic cyanobacteria.

Question 46

What is the Golgi apparatus?

Answer 46

The Golgi apparatus is responsible for transporting, modifying, and packaging proteins and lipids into vesicles for delivery to targeted destinations.

Question 47

What are vescicles?

Answer 47

created by Golgi apparatus to package and transport proteins and lipids to target destinations

Question 48

New cells produced by mitosis elongate under the influence of the hormone...

Answer 48

auxin

Question 49

How do hormones travel in the plant?

Answer 49

diffuse from cell to cell

Question 50

What is phototropism?

Answer 50

a growth response. When a plant is exposed to light from one side, auxin gathers in the shaded side of the shoot and causes elongation of the cells on that side, which makes it bend towards the light.

Question 51

What causes apical dominance?

Answer 51

Auxin is continually made in the shoot tip and diffuses downwards, accumulating around the nodes beside lateral buds. Its presence here inhibits lateral shoot growth, so if you want a bushy plant, you need to remove the terminal region and so remove the area which produces auxin.

Question 52

What are the roles of giberellin?

Answer 52

- promotes lateral shoot growth in the absence of auxin - gibberellins produced by the embryo also play a part in the germination of some seeds by stimulating the production of enzymes which mobilise the food reserves.

Question 53

What is ethene?

Answer 53

Ethene is produced by ageing or mature tissues as a gas which diffuses through the air spaces between cells. It promotes the ripening of fruit. Ethene is also involved in leaf drop – young leaves produce auxin but not ethene. As they age the amount of auxin produced reduces and ethene is produced.

Question 54

What is the abscission layer?

Answer 54

The abscission layer, a barrier of thin-walled parenchyma cells, develops across the stem (or petiole) at the base of a leaf, flower, or fruit as it approaches the time of falling from a plant.

Question 55

What is abscisic acid?

Answer 55

abscisic acid is produced when a plant is under stress, for example lack of water or extreme cold. It stimulates the stomata to close, so reducing water loss by evaporation from the leaves.

Question 56

What are some commercial uses of auxins?

Answer 56

synthetic auxins used as herbicides indole acetic acid (IAA), naturally-occurring auxin, used as rooting hormone coordinate fruit production stimulate fruiting in sterile species such as seedless cucumbers

Question 57

What are some commercial uses for gibberellins (gibberellic acid)?

Answer 57

Gibberellins (gibberellic acid) - Gibberellins (GAs) are a group of plant hormones that stimulate shoot elongation, seed germination, and fruit and flower maturation. GAs are synthesized in the root and stem apical meristems, young leaves, and seed embryos. In urban areas, GA antagonists are sometimes applied to trees under power lines to control growth and reduce the frequency of pruning. GAs break dormancy (a state of inhibited growth and development) in the seeds of plants that require exposure to cold or light to germinate. Abscisic acid is a strong antagonist of GA action. Other effects of GAs include gender expression, seedless fruit development, and the delay of senescence in leaves and fruit. Seedless grapes are obtained through standard breeding methods; they contain inconspicuous seeds that fail to develop. Because GAs are produced by the seeds and because fruit development and stem elongation are under GA control, these varieties of grapes would normally produce small fruit in compact clusters. Maturing grapes are routinely treated with GA to promote larger fruit size, as well as looser bunches (longer stems), which reduces the incidence of mildew infection.

Question 58

What are xylem vessels?

Answer 58

Xylem vessels, which carry water from the roots to the leaves, consist of columns of cells which lose their end walls and become unbroken tubes. The mature cells are dead because they lack any contents to carry out living processes, and their walls are thickened and strengthened with a waterproof substance, lignin, in various patterns.

Question 59

What is lignin?

Answer 59

Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily.

Question 60

How does transpiration take place?

Answer 60

As water evaporates, it ‘pulls’ a chain of water molecules up. They form a chain due to the cohesive forces between them and to the adhesive forces between the water molecules and the sides of the xylem vessels. Another contributory factor is root pressure, a consequence of continual water uptake by root hair cells. This depends on diffusion which is an important concept in plant and animal physiology.

Question 61

What is the Casparian strip?

Answer 61

The Casparian strip is a specialized layer of cells just outside the vascular tissue of the root. It has suberin in its walls, which forces the water to take the symplast pathway and allows selective uptake of mineral ions.

Question 62

What are the three pathways of water intake?

Answer 62

Symplast is via the cytoplasm Apoplast is seeping between cell walls Vacuolar is between vacuoles

Question 63

What are the layers of a leaf?

Answer 63

``` A Waxy Cuticle B Upper epidermis C Palisade cells D Spongy cells E Stomatal pore ```

Question 64

What is the equation of photosynthesis (simplified)?

Answer 64

water + carbon dioxide --> glucose + oxygen

Question 65

What are the two stages of photosynthesis?

Answer 65

The light dependent stage is where light energy is harvested by pigment molecules e.g. chlorophyll, in the thylakoid membranes of chloroplasts, and the products are ATP and the reduced hydrogen acceptor NADPH . The light independent stage or Calvin cycle uses the ATP and NADPH in combination with CO2 to make glucose.

Question 66

What are thylakoids?

Answer 66

a series of membranes in chloroplasts where the light-dependent reactions take place

Question 67

How is the rate of photosynthesis effected?

Answer 67

The rate at which photosynthesis can proceed will depend on the factor which is least favourable. This could be CO2 availability, light intensity or temperature. The Calvin cycle relies on enzyme activity and since enzymes are very temperature-dependent, plants will often have quite a narrow range at which they function best and this will depend on their area of origin.

Question 68

Describe phloem tissue

Answer 68

Transport of food is in phloem tissue which like xylem consists of tubes made from chains of cells, but unlike xylem it is still living. The end walls of the sieve tube elements do not break down completely and there are some contents in the cells. However, this is not enough to maintain the cells and actively move sugars, so each cell has a companion cell which can carry out the necessary metabolic processes.

Question 69

How is glucose used within the plant?

Answer 69

Glucose can then be used as an energy source or converted into other nutrients that the plant needs. For example: It can be built up into the polysaccharide cellulose for cell walls it may react with nitrates to make amino acids, the building blocks of proteins e.g to make enzymes. It can enter a biochemical pathway that produces lipids (fats and oils) e.g. for seeds.

Question 70

Why does the plant make glucose, transport it as sucrose and store it as starch?

Answer 70

Starch is water insoluble so does not affect the way water moves in and out of the cell. Sucrose is a disaccharide so it is easier to transport higher concentrations of energy in these larger molecules.

Question 71

What are rhizomes?

Answer 71

Rhizomes are an underground horizontal stem which store food and have nodes with buds and scale or foliage leaves. Zingiber, Convallaria and Iris all have rhizomes.

Question 72

What are tubers?

Answer 72

Tubers are a swollen underground stem or root which stores food and has buds e.g the ‘ eyes’ of a potato.

Question 73

What are bulbs?

Answer 73

Bulbs are a compressed shoot with fleshy storage leaves e.g. Allium spp

Question 74

What are corms?

Answer 74

Corms do not have the fleshy leaves like a bulb but are a food store in a stem e.g. Crocus spp.

Question 75

What are suckers?

Answer 75

Suckers are basal shoots which grow from a bud on a root. These are often close to the parent plant but do arise a distance away e.g. Ulmus spp.

Question 76

What are stolons?

Answer 76

Stolons (runners) grow from the base of the plant e.g. Fragaria spp.