Plant Structure and Photosynthesis

Flowering Plants
Flowering plant structure is broken up into two parts: the shoot system and the root system


Function of the shoot system
–Photosynthesis and transport of water, minerals and food
Functions of the root system
–Anchor the plant into the ground, absorb water and minerals and storage of food



Plant Tissues

Groups of cells which perform specialised functions are called tissues.
There are many types of tissues in a plant that perform different functions:
–Epidermis – outer layer of cells, protection
–Parenchyma – photosynthesis
–Xylem – water transport
–Phloem –food transport
–Meristem – growth
–Collenchyma & Schlerenchyma - support



Plant tissue

–Dermal tissue: outer layer of a plant. Its function is protection
–Ground tissue: its function depends on location. It can be involved in photosynthesis and storage of food
–Vascular tissue is transport tissue. Xylem transports water and minerals, phloem transports sugars.

Xylem
Xylem is composed of two many types of cells
– xylem vessels
–tracheids.

Xylem
Xylem cells are dead cells
Their cell walls are reinforced with lignin
Xylem vessels are much larger than tracheids
Pits in the walls of these cells allow lateral movement of water
Both cells allow a continuous route for water to travel from roots to the leaves.

Phloem
Phloem tissue consists of a sieve tube and a companion cell.

Phloem tissue is composed of living cells
Sieve tubes do not have a nucleus
Companion cells control the activities of the sieve tubes
Movement of sugars on the phloem tissue can occur up or down
In the stems and leaves of plants, xylem and phloem tissue are found together in vascular bundles.



Monocots and Dicots
Flowering plants can be divided into two groups depending on the number of cotyledons or seed leaves they have
–Monocots have one cotyledon
–Dicots have two cotyledons
Grasses and cereals are monocots
Most other flowering plants are dicots.



Dicot root
A dicot root in longitudinal section is broken up into:
Root Cap
Zone of cell division
Zone of elongation
Zone of differentiation

Structure of the Stem
In a dicot stem the vascular bundles are arranged in a circle.
In monocot stems the vascular bundles are scattered around.

Photosynthesis
All energy comes from the sun.
Plants can capture energy by photosynthesis.
The release of this energy is called respiration.
Green plants make their own food so they are autotrophic.
Animals are heterotrophic.

Photosynthesis
Light energy is absorbed by the chlorophyll in the chloroplasts.
A water molecule is split with the release of hydrogen, oxygen and energy.
The energy produced is used to combine the hydrogens with carbon dioxide to form sugar.

CO2 +  H2O  --------> C6H12O6 + O2

Carbon Dioxide +Water ----->Sugar + Oxygen

The Leaf
Specialised organ whose main function is photosynthesis.



Some of the oxygen produced in this reaction is used by the plant cells for respiration. The excess is excreted.

Respiration
Opposite to photosynthesis.
A sugar molecule is broken down to water and carbon dioxide with the release of energy.
Where oxygen is used we call it aerobic respiration and a lot of energy is released.
Some organisms do not need oxygen, they use anaerobic respiration to produce either alcohol or lactic acid instead of carbon dioxide and water. Less energy is produced in this type of respiration.

Respiration cont.
C6H12O6 + O2 ------------>  CO2 + H2O
sugar + oxygen ------------> carbondioxise +water