Transcript section_09_02e_mineral and water uptake

Plants make their own food
build up own organic nutrients using
simple inorganic substances
This is called
autotrophic nutrition
9.2 How do plants obtain food, water and minerals?
All other organisms depend on autotrophs for
food
They are heterotrophs
9.2 How do plants obtain food, water and minerals?
The need for minerals
Have you ever grown a
plotted plant?
Why is fertiliser added
to the soil regularly?
What does fertiliser
contain?
9.2 How do plants obtain food, water and minerals?
9.2 How do plants obtain food, water and minerals?
Elements needed by plants
Major elements
Trace elements
• needed in relatively large
amounts
• e.g. nitrogen,
phosphorus, magnesium,
sulphur, potassium,
calcium and iron
• needed in relatively
small amounts
• e.g. copper,
molybdenum, sodium,
boron, zinc and
manganese
Experiment 9.1
9.2 How do plants obtain food, water and minerals?
Nitrogen
comes from nitrates and ammonium
salts in soil
is used to synthesise proteins
healthy leaf
nitrogen-deficient
lead to chlorosis
9.2 How do plants obtain food, water and minerals?
Phosphorus
component of nucleic acids, cell
membranes, ATP and several coenzymes
healthy leaf
phosphorus-deficient
lead to poor growth
and turn purple
9.2 How do plants obtain food, water and minerals?
Magnesium
is needed to make chlorophyll
healthy leaf
magnesium-deficient
lead to chlorosis
Biology and society
9.2 How do plants obtain food, water and minerals?
Absorption of water
and minerals
9.2 How do plants obtain food, water and minerals?
In August 2007,
part of a more
than 200 year
old tree in
Kowloon Park fell
down suddenly...
9.2 How do plants obtain food, water and minerals?
It was believed
that the roots
had been damaged.
Why can’t a tree
grow healthily if
its roots are
damaged?
9.2 How do plants obtain food, water and minerals?
Different kind of roots
9.2 How do plants obtain food, water and minerals?
9.2 How do plants obtain food, water and minerals?
Root hairs in a germinating seed
9.2 How do plants obtain food, water and minerals?
A Root hair
9.2 How do plants obtain food, water and minerals?
Root hair – an extension of a root
epidermal cell
9.2 How do plants obtain food, water and minerals?
Longitudinal section
of a dicotyledonous
root
2. Growing point
cells can divide actively by mitosis
1. Root cap
prevents delicate cells at the
growing point from damage
as root grows deeper into soil
9.2 How do plants obtain food, water and minerals?
Longitudinal section
of a dicotyledonous
root
4. Region of differentiation
cell develop into specialised
tissues and structures
3. Region of elongation
• cells absorb water and elongate
• have large vacuoles
9.2 How do plants obtain food, water and minerals?
Transverse section of
a dicotyledonous root
9.2 How do plants obtain food, water and minerals?
1. Epidermis
• protects inner tissues
• not covered by cuticle, thus
water can be absorbed easily
2. Root hairs
• increase the surface area for
uptake of water and minerals
3. Cortex
• allows the passage of water and
mineral salts across the root
• stores food as starch
9.2 How do plants obtain food, water and minerals?
Xylem
Phloem
9.2 How do plants obtain food, water and minerals?
4. Vascular bundle
• transports water,
minerals and food
• made up of xylem
and phloem
Longitudinal section of root tip
region of elongation
growing point
root cap
9.2 How do plants obtain food, water and minerals?
Transverse section of root tip
epidermis
cortex
xylem
phloem
9.2 How do plants obtain food, water and minerals?
vascular
bundle
Absorption of water by roots
soil particles
epidermis
9.2 How do plants obtain food, water and minerals?
cortex
xylem vessel
1. The water potential of the soil water is higher than that
of the root hair. Water enters the root hair by osmosis.
soil particles
epidermis
9.2 How do plants obtain food, water and minerals?
cortex
xylem vessel
2. The water potential of the cytoplasm and cell sap of the
epidermal cells is higher than that of cortex cells. Water
passes from epidermal cells to cortex by osmosis.
soil particles
epidermis
9.2 How do plants obtain food, water and minerals?
cortex
xylem vessel
3. Water passes across the cortex from cell to cell by
osmosis or moves along the cell walls.
soil particles
epidermis
9.2 How do plants obtain food, water and minerals?
cortex
xylem vessel
4. Water is drawn into the xylem vessels.
soil particles
epidermis
9.2 How do plants obtain food, water and minerals?
cortex
xylem vessel
Absorption of minerals by
roots
Mineral ions are taken up into the root against
concentration gradient by active
transport
Active transport requires metabolic energy
Quick Practice
9.2 How do plants obtain food, water and minerals?
Mycorrhizae (reference)
• Most plants form mutually beneficial relationships
with fungi, which facilitate the absorption of water
and minerals from the soil
• Roots and fungi form mycorrhizae, symbiotic
structures consisting of plant roots united with fungal
2.5 mm
hyphae
Figure 36.10
9.2 How do plants obtain food, water and minerals?
How do plants obtain nutrients?
Plants build up their own organic nutrients by
using inorganic substances through the
process of photosynthesis.
This mode of nutrition is called autotrophic
nutrition. Plants are called autotrophs.
9.2 How do plants obtain food, water and minerals?
What substances do plants need for growth
and how do plants obtain these substances?
Plants need carbon dioxide and water as
well as minerals for growth.
Water and minerals are absorbed from the
soil by the roots. Carbon dioxide is obtained
from the atmosphere.
9.2 How do plants obtain food, water and minerals?
What minerals does a plant need?
Mineral elements needed by plants can be
divided into two types:
(1) major elements, which are needed in
larger amounts (e.g. nitrogen, phosphorus,
magnesium etc.)
(2) trace elements, which are needed in
much smaller amounts (e.g. copper,
sodium etc.)
9.2 How do plants obtain food, water and minerals?
What are the functions of different elements
in supporting plant growth?
Minerals
For making
Deficiency symptoms
Nitrogen
- proteins
- chlorophyll molecules
- poor growth
- yellowing of leaves i.e. chlorosis
Phosphorus
- nucleic acids, cell
membrane, ATP and
several coenzymes
- poor growth
- turn green leaves purple
- chlorophyll molecules
- poor growth
- yellowing of leaves i.e. chlorosis
Magnesium
9.2 How do plants obtain food, water and minerals?
How are roots adapted to the function of
water and mineral absorption?
Structure
Adaptation
Root hairs
- Long and fine structures which can easily grow between soil
particles
- The great numbers of root hairs increase the surface area for
uptake of water and mineral salts in the soil
Epidermis
- Absence of cuticle and thus water can enter easily
9.2 How do plants obtain food, water and minerals?
By which processes do water and minerals
enter into a plant?
Water enters into a plant by osmosis.
Minerals usually enter by active transport.
9.2 How do plants obtain food, water and minerals?