GCSE Biology: Plant Biology Flashcards

Question 1

Define Epidermal tissue.

Accepted Answer

The single outer layer of cells covering the top and bottom surfaces of a leaf, protecting the tissues inside; the upper epidermis is transparent so light reaches the cells below.

Question 2

Define Waxy cuticle.

Accepted Answer

A waterproof layer of wax secreted over the leaf epidermis that cuts water loss by evaporation and forms a physical barrier against microorganisms.

Question 3

Define Palisade mesophyll.

Accepted Answer

Tightly packed, column-shaped cells just below the upper epidermis, filled with chloroplasts, making this layer the main site of photosynthesis in a leaf.

Question 4

Define Spongy mesophyll.

Accepted Answer

A loosely arranged layer of leaf cells with large air spaces between them, giving carbon dioxide and oxygen a short, open route to diffuse to and from cells.

Question 5

What is Xylem?

Accepted Answer

Plant tissue made of dead cells joined into hollow tubes, strengthened by lignin, that carries water and dissolved mineral ions upward from the roots through the stem to the leaves.

Question 6

What is Lignin?

Accepted Answer

A tough, waterproof substance deposited in xylem cell walls that strengthens the hollow tubes, stops them collapsing, and helps support the whole plant upright.

Question 7

What is Phloem?

Accepted Answer

Transport tissue made of columns of elongated living cells with pores in their end walls, letting cell sap carrying dissolved sugars flow from cell to cell around the plant.

Question 8

What is Translocation?

Accepted Answer

The movement of dissolved sugars such as sucrose through phloem from the leaves to growing tissues and storage organs, where the sugars are used immediately or stored.

Question 9

Define Root hair cell.

Accepted Answer

A root epidermis cell with a long, thin extension that greatly increases surface area for absorbing water by osmosis and mineral ions by active transport.

Question 10

Define Stoma (plural stomata).

Accepted Answer

A tiny adjustable opening, mostly in the lower epidermis of a leaf, through which carbon dioxide diffuses in and oxygen and water vapour diffuse out.

Question 11

Define Guard cells.

Accepted Answer

A pair of bean-shaped cells surrounding each stoma that swell to open it and become floppy to close it, balancing gas exchange against water loss.

Question 12

What is Transpiration?

Accepted Answer

The evaporation of water from leaf surfaces, mostly through the stomata, which draws more water up the xylem from the roots to replace what is lost.

Question 13

Define Transpiration stream.

Accepted Answer

The continuous column of water moving from the soil into root hairs, up the xylem, and out of the leaves as vapour, carrying mineral ions with it.

Question 14

Define Factors affecting transpiration rate.

Accepted Answer

Temperature, humidity, air movement and light intensity: transpiration speeds up when it is warmer, drier, windier or brighter, and slows when any reverses.

Question 15

What is Potometer?

Accepted Answer

Apparatus that measures how quickly a cut shoot takes up water, by timing an air bubble moving along a capillary tube, used to estimate transpiration rate.

Question 16

What is Photosynthesis?

Accepted Answer

The process in chloroplasts where light energy is used to turn carbon dioxide and water into glucose, releasing oxygen: 6CO2 + 6H2O → C6H12O6 + 6O2.

Question 17

Define Endothermic reaction.

Accepted Answer

A reaction that takes in energy from its surroundings; photosynthesis is endothermic because energy is transferred from the environment to the chloroplasts by light.

Question 18

What is Chlorophyll?

Accepted Answer

The green pigment inside chloroplasts that absorbs light energy so it can be used to drive photosynthesis; a leaf with less of it photosynthesises more slowly.

Question 19

Define Limiting factor.

Accepted Answer

Whichever condition is in shortest supply and therefore holds back the rate of a reaction; for photosynthesis it can be temperature, light intensity, carbon dioxide or chlorophyll.

Question 20

Define Inverse square law (light).

Accepted Answer

The rule that light intensity is proportional to 1 divided by distance squared, so doubling the distance from a lamp cuts the intensity to a quarter.

Question 21

Define Greenhouse economics.

Accepted Answer

Growers add heat, light or carbon dioxide only while that factor is limiting and the extra crop is worth more than the cost of supplying it.

Question 22

What is Starch?

Accepted Answer

An insoluble carbohydrate that plants make from glucose for storage; because it does not dissolve, it does not change the water balance of cells by osmosis.

Question 23

What is Cellulose?

Accepted Answer

A tough carbohydrate built from glucose that forms plant cell walls, strengthening each cell and acting as a physical barrier against invading microorganisms.

Question 24

Define Uses of glucose in plants.

Accepted Answer

Glucose from photosynthesis is used for respiration, stored as starch, fats or oils, built into cellulose cell walls, or combined with nitrate ions to make amino acids for proteins.

Question 25

Define Nitrate ions.

Accepted Answer

Mineral ions absorbed from soil that plants need to turn glucose into amino acids for protein synthesis; a shortage causes stunted growth.

Question 26

Define Chlorosis (magnesium deficiency).

Accepted Answer

Yellowing of leaves caused by too few magnesium ions, which plants need to make chlorophyll; the yellow leaves then photosynthesise less.

Question 27

Define Tobacco mosaic virus (TMV).

Accepted Answer

A widespread viral plant pathogen that causes a patchy, mosaic pattern of discolouration on leaves, reducing photosynthesis and so stunting the plant's growth.

Question 28

Define Rose black spot.

Accepted Answer

A fungal disease that forms purple or black spots on leaves, which yellow and fall early; it spreads by water or wind and is treated with fungicides.

Question 29

What is Aphids?

Accepted Answer

Small sap-sucking insects that pierce plant stems and feed on phloem sap, weakening the plant; ladybirds can be used as a biological control.

Question 30

Define Signs of plant disease.

Accepted Answer

Visible clues that a plant is diseased: stunted growth, spots on leaves, areas of decay (rot), growths, malformed stems or leaves, discolouration, or pests present.

Question 31

Define Identifying plant pathogens.

Accepted Answer

Pinning down which pathogen is responsible by checking a gardening manual or website, sending samples to a laboratory, or using testing kits containing monoclonal antibodies.

Question 32

Define Physical plant defences.

Accepted Answer

Structures that stop microorganisms getting in: cellulose cell walls, a tough waxy cuticle on leaves, and layers of dead cells such as bark that fall off.

Question 33

Define Chemical plant defences.

Accepted Answer

Substances plants make to protect themselves, including antibacterial chemicals that kill microorganisms and poisons that stop herbivores eating them.

Question 34

Define Mechanical plant adaptations.

Accepted Answer

Features that deter animals physically: thorns and hairs, leaves that droop or curl when touched, and mimicry that tricks animals into avoiding the plant.

Question 35

What is Auxin?

Accepted Answer

A plant hormone that controls growth at the tips of shoots and roots; an uneven spread of it makes one side grow faster, so the shoot or root bends.

Question 36

What is Phototropism?

Accepted Answer

Growth in response to light: in a shoot lit from one side, auxin gathers on the shaded side, those cells elongate faster, and the shoot bends toward the light.

Question 37

Define Gravitropism (geotropism).

Accepted Answer

Growth in response to gravity: in a horizontal root, auxin collects on the lower side and inhibits growth there, so the upper side grows faster and the root curves down.

Question 38

What is Gibberellins?

Accepted Answer

Plant hormones that start seed germination; growers use them to end seed dormancy, promote flowering, and increase fruit size.

Question 39

What is Ethene?

Accepted Answer

A gaseous plant hormone that controls cell division and the ripening of fruit; the food industry controls its levels to manage ripening during storage and transport.

Question 40

Define Selective weed killer.

Accepted Answer

A herbicide based on synthetic auxins that makes broad-leaved weeds grow so fast and abnormally that they die, while narrow-leaved grasses and cereal crops are left unharmed.