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Flashcards in GAS EXCHANGE IN PLANTS Deck (16):
1

Gas exchange during the day vs night (2)

- During the day respire and photosynthesise
- During the night respire only

2

How does oxygen enter the stem and roots

- via diffusion

3

how do gases travel in a leaf

- down a concentration gradient
- in substomatal air chambers diffuse through inter cellular spaces between spongy mesophyll into cells
- direction of diffusion depends on concentration of gases

4

large SA leaf significance for gas exchange and photosynthesis (2)

- room for many stomata
- capture as much light as possible

5

thin leaf significance for gas exchange and photosynthesis (2)

- short diffusion pathway for gases
- light penetrates through leaf

6

transparent cuticle and epidermis significance photosynthesis

- light penetrates to mesophyll

7

elongated palisade cells significance for photosynthesis

- accommodate a large number

8

palisade cells packed with chloroplasts significance for photosynthesis

- capture as much light as possible

9

chloroplasts rotate and move within mesophyll significance for photosynthesis

- move into best positions for maximum absorption of light

10

air spaces in spongy mesophyll significance for gas exchange and photosynthesis? (2)

- allow o2 and co2 to diffuse between stomata and cells
- allow co2 diffuse to photosynthesising cells

11

stomatal pores significance for gas exchange

- allow in and out of leaf

12

stomata (2)

- small pores on bottom of leaves
- where gas exchange occurs

13

guard cell (2)

- epidermal cells with chloroplasts
- unevenly thickened walls - inner > outer

14

how do guard cells work during the day? (2)

- water enters the guard cells they become turgid and swell, opening the pore
- water leaves the guard cell, they become flaccid and the pore closes

15

guard cells work during the day because... (5)

- chloroplasts in the guard cells photosynthesise producing ATP
- ATP provides energy for active transport of K+ into the guard cells
- stored starch converted to malate
- K+ and malate ions lower water potential in guard cells so water enters via osmosis
- guard cells are uneven, absorb water in the thin spots, less in the thick areas

16

why do stomata close? (3)

- at night to prevent water loss (bc no LDR)
- in bright light to prevent water loss due to evaporation
- if there is excessive water loss