case studies of plants

Question 1

give 5 ways plants generally conserve water

Answer 1

• waxy cuticle
• stomata on underside of leaf
• closeable stomata
• roots that grow down to water in soil
• less stomata

Question 2

xerophyte definition

Answer 2

plants with adaptations enabling them to survive in dry + arid habitats with short water supplies

Question 3

give 2 examples of xerophytes

Answer 3

cacti
marram grass

Question 4

what is the habitat of marram grass

Answer 4

coastal and sandy regions of europe
water drains from sand quickly + salinity is high + often very windy

Question 5

4 adaptations of marram grass to prevent water loss

Answer 5

• leaves are rolled longitudinally which traps air inside and makes it humid as water evaporates from stomata, reducing water loss, leaves can roll more tightly in drier conditions
• spongey mesophyll layer is very dense with few air spaces, lowering available surface area for evaporation
• waxy cuticle layer is thick and located on outer side, reducing water loss
• stomata are found on inner side of rolled leaf, and are sunken into pits that are folded and covered by hair, this enclosure + hair reduces air movement so less water loss

Question 6

what is the habitat of cacti

Answer 6

deserts

Question 7

5 adaptations of cacti to prevent water loss

Answer 7

• green stems containing chlorophyll, maximising photosynthesis ensuring plant has enough nutrients to survive
• spines instead of leaves so lower SA which reduces water loss
• they are succulents, meaning they can store water in their stems causing them to become fleshy + swollen
• stems are often ribbed so they can expand with excess water
• roots are widespread allowing cacti to take advantage of rainfall and maximise water intake

Question 8

how can some xeropytes “avoid the problems” of their environments

Answer 8

• some can be completely dehydrated and regenerate again with water
• some survive as storage organs e.g. tubers
• plants may die by leave seeds which grow rapidly when it rains again

Question 9

hydrophyte definition

Answer 9

plants adapted to survive in very wet habitats or on the surface of water

Question 10

give 1 example of a hydrophyte

Answer 10

water lilies

Question 11

what is the habitat of a water lily

Answer 11

they grow on still/slow moving freshwater, e.g. ponds or lakes

Question 12

4 adaptations of water lilies to survive in very wet environments

Answer 12

• stomata are concentrated on upper epidermis of leaves allowing for gas exchange to occur with air not water
• floating leaves that are large + flat + with large air spaces provides buoyancy, keeping plant closer to water surface so greater contact with air and sunlight
• thin waxy cuticle layer as little need to prevent excess water loss
• smaller, reduced root systems as there is no scarcity of water so roots do not need to be widespread and nutrients can be extracted directly from water to plant tissues

Question 13

what problems are faced by hydrophytes

Answer 13

water logging - air spaces need to be full of air not water
must float on surface of water so can photosynthesise + to be in contact with air

Question 14

what are aerenchyma

Answer 14

specialised parenchyma tissues which have many large air spaces - common in hydrophytes