Plant Tissues, Organs, and Systems

Question 1

What does the palisade mesophyll do?

Answer 1

• shape allows them to be tightly packed
• cells have lots of chloroplasts (maximsies light energy captured in photosynthesis)

Question 2

What does spongy mesophyll do?

Answer 2

• loosely packed
• large SA + lots of air gaps
• maximises rate of gas exchange for photosynthesis
• gases diffuse easily through leaf to and from stomata

Question 3

What does the epidermal tissue do?

Answer 3

• single outer layer of flattened cells
• protects leaf
• waterproof waxy layer on upper epidermis = prevents water loss
• lower epidermis = many stomata, guard cells

Question 4

What do guard cells do?

Answer 4

• open and close stomata

Question 5

What do stomata do?

Answer 5

• pores in leaf gas can diffuse through

Question 6

What are the parts of a leaf?

Answer 6

• upper epidermis
• lower epidermis
• xylem
• phloem
• spongy mesophyll
• stomata
• guard cells
• palisade mesophyll

Question 7

Describe the process of transpiration

Answer 7

• root hair cells take up water by osmosis, mineral ions by active transport
• xylem carries solution through roots to stems to leaves
• flow of water up through plant = transpiration stream
• water** lost** from leaves by evaporation/ diffusion
• transpiration pulls up more water from roots through xylem

Question 8

How is dissolved food transported in plants?

Answer 8

• food molecules produced in leaves (photosynthesis)
• transported in phloem to rest of plant as dissolved sugars
• used immediately or converted into starch (storage)

Question 9

What is the role of guard cells in transpiration?

Answer 9

• sufficient water = moves into guard cell by osmosis = turgid, opens stomata
• not enough water = moves **out **of cells = **flaccid **= stomata closes

reduces water loss

Question 10

What factors influence transpiration?

Answer 10

• humidity - decrease (conc. grad. reduced)
• temperature - increase (water vaopur molecules have more energy = ⇧ evaporation + diffusion)
• wind intensity - increase (increases conc. grad.)
• light intensity - increase (photosynthesis, stomata open, dark = close to conserve water)

Question 11

How do you investigate the rate of transpiration?

Answer 11

• measure mass of plant if water lost
• measure water taken up to replace water lost from cut shoot (air bubble moving)