WJEC A2 Biology Unit 3: Photosynthesis: Adaptations for Photosynthesis

Large Surface Area of Leaf

Capture maximum light

Midrib and Vein Network

Supports large surface area

Leaves arranged to minimise overlap

All leaves can gain maximum light absorbance

Thin Leaf Lamina

Light can transmit through whole leaf

Stomatal Pores

Carbon dioxide can move out of leaf

Air spaces in spongy mesophyll

Carbon dioxide can diffuse to photosynthesising cells e.g.palisade cells

Cuticle and upper epidermis are transparent

Allows light to penetrate these layers to reach mesophyll

Thin cellulose cell walls

Allows light to penetrate these layers to reach mesophyll

Large vacuoles are found in palisade cells

Pushes chloroplasts to the edge of cell = single layer of chloroplasts around periphery = no shade from other chloroplasts

Columnar epithelium palisade cells

Large number of palisade cells packed tightly into small space therefore large number of chloroplasts for light absorbance

Palisade cells at right angle to leaf surface

Light only passes through 3 cell walls before reaching a chloroplast (2 epidermal and 1 palisade) so more light is transmitted and less absorbed by cell walls

Chloroplasts can move within palisade cell

Can adjust to different light intensities e.g. at top of cell at low light intensity; bottom of cell at high light intensity to avoid bleaching

Different pigments arranged in the thylakoid membrane of chloroplasts

Can absorb light at a wide range of wavelengths

Single layer of pigments along the thylakoid membrane

Maximise light absorbance as light is more likely to hit a pigment

Chloroplasts have a large surface area

Maximise light absorbance

Chloroplasts rotate within cell

Maximise light absorbance

5x as many chloroplasts in palisade cells than spongy cells

Maximise light absorbance as palisade cells are found on the surface of the leaf

Thylakoid membrane is folded and stacked within the chloroplast

Increase surface area to accommodate more pigments for photosynthesis