Bioenergetics- plant biology

what is the function of the upper epidermis?

• protects the surface of the leaf

• transparent to allow light to pass through to photosynthetic

• covered with an oily layer (waxy cuticle) to reduce evaporation of water from leaf surface to stop it drying it out

what is the function of the lower epidermis?

• has tiny pores called stomata which allow CO2 to enter and O2 to leave the leaf

• also helps to control amount of water vapour that can pass out of the leaf

• guard cells are found either side of the stomata

what is the function of palisade mesophyll?

palisade cells are full of chloroplasts which are full of chlorophyll, which absorbs light energy needed for photosynthesis

what is the function of spongy mesophyll?

full of air spaces, allowing CO2 to diffuse from the stomata through the spongy mesophyll to the palisade cells. oxygen also diffuses, but in the opposite direction.

what is the function of xylem?

• transports water from the roots to the stem and leaves. some of this water is used in photosynthesis

• also transports minerals such as magnesium which is used to make chlorophyll

how are xylem cells adapted to their function?

• very thick walls containing lignin which provides support to the plant. because the cell walls are sealed with lignin, this makes the xylem cells die (they are dead)

• end walls between cells have broken down so water and dissolved minerals can flow easily

• NO nucleus, cytoplasm, vacuole or chloroplasts (no internal structures makes it easier for water etc to flow)

what is the function of phloem?

• transports dissolved sugars produced by photosynthesis from the leaves to the rest of the plant

  → sugars can be used immediately or stored (RSPCA)

• the movement of sugars and other molecules through phloem tissue is called translocation

how are phloem cells adapted to their function?

consists of vessel cells and companion cells:

• vessel cells have no nucleus and limited cytoplasm, end walls have pores called sieve plates

  → these features allow sugars to move through cell interior

• companion cells are connected by pores

  → mitochondria in these cells provide energy to vessel cells

where is meristem tissue found and what is its function?

found at the tips of shoots and roots, it contains stem cells which can differentiate

how are root hair cells adapted to their function?

• has a hair which increase surface area for maximum effective absorption of water and mineral ions

• thin cell wall for maximum absorption

• lots of mitochondria as energy is needed to absorb mineral ions by active transport

• no chloroplasts as it is underground and can’t carry out photosynthesis

factors which affect the rate of transpiration

• changing temperature

• humidity

• air movement

• light intensity

how is glucose used in a plant?

Respiration

Starch for storage of energy

Protein synthesis (for growth and repair)

Cellulose makes up and strengthens cell walls

And lipids for storage of energy

factor affecting the rate of photosynthesis

• temperature

• carbon dioxide levels

• light intensity