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  • Created by: Becky
  • Created on: 14-04-13 15:19

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…


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