Plants

Structure of a leaf

• leaf blade - thin, flat, large surface area
• spongy mesophyll tissue - allows for circulation of gases
• plant tissues - permeated by air spaces
• stomatal pores - permit gas exchange

Gases diffuse through stoma into the inter cellular spaces between the spongy mesophyll cells and into the cells.

Adaptations for photosynthesis

• large surface area to capture as mush light as possible
• can orientate themselves, to expose the maximum area to the light
• thin to allow light to penetrate lower layers of cells
• cuticle and epidermis are transparent, allows light to penetrate mesophyll
• palisade cells are elongated and densely arranged in layers
• palisades cells are packed with chloroplast, arranged with long axes perpendicular to surface
• chloroplasts can rotate/ move with palisade cells allowing for efficient absorption of light
• inter cellular air spaces in spongy mesophyll allow carbon dioxide to diffuse to cells and oxygen to diffuse away

Guard Cells

• possess chloroplasts
• unevenly thickened walls, inner wall is thicker and outer wall is thinner
• change shape due to change in tugor

Opening of the stoma

• chloroplasts in guard cells photosynthesis producing ATP
• using ATP potassium ions pumps in the cell membranes of the surrounding epidermal cells actively transporting potassium ions into the guard cells
• stored starch converted to malate
• water potential is lowered, water enters by osmosis
• guard cell becomes turgid, outer…