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

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 (>100m)
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