Transport in Plants

• Substances plant cells require for survival: CO_2 (only in photosynthetic tissue), oxygen, organic molecules (only non-photosynthetic tissue), inorganic ions (e.g. NO_3^-, SO_4^2^-, PO_4^3^-, Mg^2^+) and water (remember: gases are not transported around the plant)
• Plants are multicellular (some very large), so they should have a low SA:V but their branching shape increasing it also as their metabolic rate is low (lower energy requirements - low activity level they can survive with a slower transport system and no pump
• Both transport systems move by mass flow (bulk molecule transport from area of high pressure to area of low pressure); oxygen and carbon dioxide are not transported in xylem or phloem
• Dicotyledon is a flowering plant with large broad leaves, branching veins and two cotyledons in their seeds e.g. peas and beans and Monocotyledon is a flowering plant with long thin leaves, parallel veins and one cotyledon in their seeds e.g. rice and corn
• They are made of 3 basic tissue types

  • Parenchyma: Simple living cells with thin cellulose cell walls (most of trees cortex, leaves photosynthetic tissue, fruit pulp and the endosperm of seeds)
  • Collenchyma: Simple, living cells with some irregular lignin thickening, in corners (supporting tissue for stems/leaves, adjacent to vascular bundle or under epidermal layer; not in roots)
  • Sclerenchyma: Dead cells with thick lignified cell walls (bundles of fibres in the caps on top of stem vascular bundles, small star shaped sclereids - gritty textures of pears; not in roots)