trasport in plants ppt
TRANSCRIPT
Why plants need transport system
• By using the CO2 energy ( food ) is produced in the leaves
• The soil is the nearest & richest source of raw materials like nitrogen, phophorous & other minerals
• The absorption of these substances occurs through the part in contact with the soil, called roots if these distances between soil containing regions & chlorophyll containing regions are small energy & raw materials can easily diffuse to all parts of the plant body
• If these distances are large the diffusion pressure will not be sufficient to provide raw materials in leaves & energy in roots
Why plants have low energy needs
• 1. Plants do not move • 2.Plant bodies have large proportion of
dead cells in many tissues As a result plants have low energy
needs & use low transport system
Plant transport systems
• There are two transport systems • 1. One transport system moves water &
minerals from roots to leaves through the xylem
• 1. Another transport system moves energy stores ( food ) from leaves to body parts
•
TRANSPORT OF WATER• It takes place through the Xylem• Vessels & Tracheids are the water
conducting cells in the xylem• In xylem tissue vessels & trachieds of
the roots , stem, leaves are interconnected to form a continuous system of a water conducting channels reaching all parts of the plant
Mechanism of water conduction
• It is explaind by many theories. Important theories among these are
• 1. Root pressure theory• 2. transpiration pull theory
Root pressure theory• At the roots cells in contact wit the soil
actively take up the mineral ions • This creates a difference in the
concentration of these ions between the roots & the soil
• Therefore water moves from the soil into the cells to eliminate this difference
• So there is a steady movement of water into root xylem, creating a column of water that is steadily pushed upwards this is due to the creation of pressure in the xylem vessels of the root
Demerits of root pressure theory
• This pressure is not sufficient to push the water to the great heights
Transpiration pull theory• Plants lose water in the form of water vapour
through the stomata of the leaf• This water loss is replaced by the by the
xylem vessels in the leaf• Evaporation of water from the cells of the
leaf creates a suction which pulls water from the xylem vessels of the root
• It makes the root to absorb water from the soil
• The root pressure is the major driving force during the night time
• During the day when the stomata are open , the transpiration pull is the major driving force
Transpiration
• The loss of water in the form of water vapour from the aerial parts of the plant is called transpiration
Functions of transpiration• 1. It helps in temperature regulation• 2. It helps in absorption& upward
movement of the water minerals dissolved in it from roots to the leaves
Transport of food & other substances
• The transport of soluble products of photosynthesis from leaves to all parts of the plant is called translocation
• Phloem transports the food • Besides the products of photosynthesis the
phloem also transports amino acids & other substances
• These substances are moved to the storage organs of the roots, fruits, seeds & to growing regions
In phloem the food conducting cells are the sieve tubes
The translocation of food & other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward & downward direction
Mechanism of translocation• Translocation utilizes the energy• Sucrose is transferred into phloem
using energy from ATP• This increases the osmotic pressure of
the phloem causing water to move from xylem to phloem
• This pressure moves the materials in the phloem to tissues which have less pressure
• This allows the phloem to move the materials according to the plant needs
• Ex- in the spring sugar stored in roots or stem transported to the buds which need energy to grow
• Translocation takes place both in upward & down ward directions