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Chapter 25: Nutrition in the flowering plant

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Title: Chapter 25: Transport, Food Storage, and Gas Exchange in Flowering Plants Author: J LOUGHLIN Last modified by: brenda and john Created Date – PowerPoint PPT presentation

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Title: Chapter 25: Nutrition in the flowering plant


1
Chapter 25 Nutrition in the flowering plant
  • Leaving Certificate Biology
  • Higher Level

2
Transport in Flowering Plants
  • Plants make their own food by photosynthesis
    therefore they are called autotrophs
  • The substrates necessary for photosynthesis and
    the products of photosynthesis have to be
    transported around the plant
  • Transport in plants is carried out by vascular
    tissue xylem and phloem

3
Uptake and Transport of Water Through Flowering
Plant
  • Water moves into the root hairs by osmosis and
    diffuses through the root cortex, cell by cell
    into the vascular xylem tissue
  • Xylem vessels form a continuous tube from the
    root tip up to the leaf
  • Two mechanisms combine to cause the transport of
    water up to the leaves from the roots
  • Root pressure
  • Transpiration

4
Root Pressure
  • Water builds up in the xylem vessels of the roots
    after it moves in from the root hairs and cortex
  • This build up of water it produces a water
    pressure within the xylem tissue called root
    pressure
  • Root pressure is not enough to send water up to
    leaves of very tall trees

5
Transpiration
  • Transpiration is the loss of water vapour from
    the foliage of plants
  • Transpiration occurs from the stomata on leaves
    and lenticels on woody stems

6
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7
Control of Transpiration
  • Transpiration can be controlled by opening and
    closing stomata
  • The stomata are mostly located on the underside
    of the leaf and are composed of the opening
    (stoma) and two guard cells that are capable of
    causing the stoma to open or close
  • High CO2 concentrations cause stomata to close
    (i.e. at night)
  • Low CO2 concentrations cause stomata to open
    (i.e. during light)

8
Mineral Transport
  • As all minerals are soluble in water they are
    transported along with water through the root
    hairs, root cortex and into xylem tissue
  • It then follows the same route as water except
    that minerals are used within the plant cells,
    whereas water evaporates (transpiration)
  • Examples of minerals transported through plants
    are Ca2, Mg2, Zn2, Na, K, Fe3, Mn2, Cu2

9
Carbon Dioxide
  • Carbon dioxide is a gas produced from respiration
    (C6H12O6 6O2 ? ENERGY 6CO2 6H2O)
  • Carbon dioxide is present within the airspaces of
    the leaves and comes from two sources
  • Respiration within the leaf cells
  • Atmosphere and enters through stomata
  • Carbon dioxide is then used up in photosynthesis
    (6CO2 6H2O SUNLIGHT ? C6H12O6 6O2)

10
Food Transport
  • Food (glucose) is transported around the plant by
    phloem sieve tube elements (see chapter 24)
  • Glucose formed during photosynthesis is
    transported to areas of the plant where it will
    be converted to starch and stored until needed

11
Food Storage
  • Food is stored in various storage organs
    depending on the plant species
  • Modified root
  • Carrot (tap root swells with starch)
  • Modified stem
  • Potato (base of stem that is underground swells
    with starch)
  • Modified leaf
  • Onion (fleshy leaves surround the apical and
    lateral buds and fill with starch as they grow)
  • Modified petiole
  • Celery (petiole swells with starch)

12
Cohesion-Tension Transport Model
  • Water is sometimes transported up to great
    heights in very tall trees (gt100m)
  • Osmosis and root pressure cannot possibly account
    for this as water will only travel a few metres
    by root pressure
  • Other factors that contribute to the height water
    can travels up xylem tissue are
  • Transpiration from the foliage of the plant
  • Cohesion of the water molecules (hydrogen
    bonding)
  • Adhesion of the water molecules to the sides of
    the xylem vessels and tracheids
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