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Transport Systems - Plants - Coggle Diagram
Transport Systems - Plants
As the
size
of an organism
increases
, its
surface area to volume ratio decreases
This means that it has
less surface area for substances to diffuse through
, so diffusion may not be fast enough to meet its cells requirements
Xylem
Water and minerals are transported through stem in xylem vessels
Is tissue consisting of dead, hallowed-out cells that form a system of pipes
Walls of xylem are lignified (strengthened with by lignin)
Plants require water:
For photosynthesis
To transport materials, .e.g minerals
Plant organs include roots, stems and leaves
So
large multicellular organisms cannot rely on diffusion alone
to transport and remove substances, they
also require specialised transport systems
The structure of a leaf has adaptation so that it can carry out photosynthesis efficiently
A leaf needs:
A way to transport water to the leaf, and glucose to other parts of the plant
A way to exchange carbon dioxide and oxygen
The ability to absorb light energy efficiently
Leaf structure:
Palisade mesophyll
Xylem and Phloem
Upper and lower epidermis
Spongy mesohpyll
Waxy cuticles
Guard cells and the stoma
Features of leaves:
Large surface area
- maximise light absorption
Thin
- short distance for carbon dioxide to diffuse
Thin waxy cuticle
- protects leaves without blocking out light
Thin transport epidermis
- allows light to enter
Phloem
Sugar produced by photosynthesis in the leaves is transported up and down the plant in living phloem cells
Companion cells supply energy for the sieve cells
The end walls have pores from which sugar is transported from cell to cell
Water taken up by the roots of a plant is transported through a plant to the leaves where some of it passes into the air. The stages of the process are:
1. Soil to Xylem
Water enters root hair cells
Water moves from cell to cell through the root cortex by osmosis
In the centre of the root the water enters the xylem vessels
2. Xylem to leaf to air
Water moves up the xylem vessels and into the mesophyll cells where it can be used for photosyntehsis
Some water evaporates into the air spaces inside the leaf and then diffuses out through the stomata into the air
Opening and closing of the stomata is controlled by guard cells in the epidermis
The loss of water from the leaves of a plant is called
transpiration
The rate of transpiration is affected by
wind speed, temperature, humidity
and
surface area