9.2 How do plants obtain food, water and minerals?

build up own organic nutrients using build up own organic nutrients using simple inorganic substancessimple inorganic substances

Plants make their own foodPlants make their own food

This is called autotrophic nutrition

This is called autotrophic nutrition

9.2 How do plants obtain food, water and minerals?

All other organisms depend on autotrophs for All other organisms depend on autotrophs for foodfood

They are heterotrophsThey are heterotrophs

9.2 How do plants obtain food, water and minerals?

Have you ever grown a plotted plant?

Why is fertiliser added to the soil regularly?

What does fertiliser contain?

The need for mineralsThe need for minerals

9.2 How do plants obtain food, water and minerals?

9.2 How do plants obtain food, water and minerals?

Elements needed by plantsElements needed by plantsElements needed by plantsElements needed by plants

Experiment 9.1Experiment 9.1

Major elementsMajor elements• needed in relatively large needed in relatively large

amountsamounts• e.g. nitrogen, e.g. nitrogen,

phosphorus, magnesium, phosphorus, magnesium, sulphur, potassium, sulphur, potassium, calcium and ironcalcium and iron

Trace elementsTrace elements• needed in relatively needed in relatively

small amountssmall amounts• e.g. copper, e.g. copper,

molybdenum, sodium, molybdenum, sodium, boron, zinc and boron, zinc and manganese manganese

9.2 How do plants obtain food, water and minerals?

NitrogenNitrogen

comes from nitrates and ammonium salts comes from nitrates and ammonium salts in soilin soilis used to synthesise proteinsis used to synthesise proteins

nitrogen-deficientnitrogen-deficienthealthy leafhealthy leaf

lead to chlorosis

9.2 How do plants obtain food, water and minerals?

PhosphorusPhosphorus

component of nucleic acids, cell component of nucleic acids, cell membranes, ATP and several coenzymesmembranes, ATP and several coenzymes

phosphorus-deficientphosphorus-deficienthealthy leafhealthy leaf

lead to poor growth and turn purple

9.2 How do plants obtain food, water and minerals?

MagnesiumMagnesium

is needed to make chlorophyllis needed to make chlorophyll

healthy leafhealthy leaf magnesium-deficientmagnesium-deficient

lead to chlorosis

Biology and society

9.2 How do plants obtain food, water and minerals?

Absorption of water Absorption of water and mineralsand minerals

9.2 How do plants obtain food, water and minerals?

In August 2007, In August 2007, part of a more part of a more than 200 year than 200 year old tree in old tree in Kowloon Park Kowloon Park fell down fell down suddenly...suddenly...

9.2 How do plants obtain food, water and minerals?

It was believed It was believed that the roots that the roots had been had been damaged.damaged.

Why can’t a tree Why can’t a tree grow healthily if grow healthily if its roots are its roots are damaged?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?

2. Growing pointcells can divide actively by mitosis

1. Root capprevents delicate cells at thegrowing point from damage as root grows deeper into soil

Longitudinal section of a Longitudinal section of a dicotyledonous rootdicotyledonous root

9.2 How do plants obtain food, water and minerals?

4. Region of differentiationcell develop into specialised tissues and structures

Longitudinal section of a Longitudinal section of a dicotyledonous rootdicotyledonous root

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 Transverse section of a dicotyledonous rootdicotyledonous 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

4. Vascular bundle• transports water,

minerals and food• made up of xylem

and phloem

9.2 How do plants obtain food, water and minerals?

Longitudinal section of root tipLongitudinal section of root tip

region of elongation

root cap

growing point

9.2 How do plants obtain food, water and minerals?

Transverse section of root tip

epidermis

cortex

xylemphloem

vascularbundle

9.2 How do plants obtain food, water and minerals?

Absorption of water by rootsAbsorption of water by roots

soil particles epidermis cortex xylem vessel

9.2 How do plants obtain food, water and minerals?

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 cortex xylem vessel

9.2 How do plants obtain food, water and minerals?

soil particles epidermis 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.

9.2 How do plants obtain food, water and minerals?

soil particles epidermis cortex

3. Water passes across the cortex from cell to cell by osmosis or moves along the cell walls.

xylem vessel

9.2 How do plants obtain food, water and minerals?

soil particles epidermis cortex

4. Water is drawn into the xylem vessels.

xylem vessel

9.2 How do plants obtain food, water and minerals?

Absorption of minerals by rootsAbsorption of minerals by roots

Mineral ions are taken up into the root against Mineral ions are taken up into the root against concentration gradient by concentration gradient by active active transporttransport

Active transport requires Active transport requires metabolic energymetabolic energy

Quick PracticeQuick 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 hyphae

Figure 36.10

2.5 mm

9.2 How do plants obtain food, water and minerals?

How do plants obtain nutrients?How do plants obtain nutrients?

Plants build up their own organic nutrients by Plants build up their own organic nutrients by using inorganic substances through the using inorganic substances through the process of photosynthesis.process of photosynthesis.

This mode of nutrition is called autotrophic This mode of nutrition is called autotrophic nutrition. Plants are called autotrophs.nutrition. Plants are called autotrophs.

9.2 How do plants obtain food, water and minerals?

What substances do plants need for growth What substances do plants need for growth and how do plants obtain these and how do plants obtain these substances?substances?

Plants need carbon dioxide and water as Plants need carbon dioxide and water as well as minerals for growth.well as minerals for growth.

Water and minerals are absorbed from the Water and minerals are absorbed from the soil by the roots. Carbon dioxide is obtained soil by the roots. Carbon dioxide is obtained from the atmosphere.from the atmosphere.

9.2 How do plants obtain food, water and minerals?

What minerals does a plant need?What minerals does a plant need?

Mineral elements needed by plants can be Mineral elements needed by plants can be divided into two types:divided into two types:

(1)(1) major elements, which are needed in major elements, which are needed in larger amounts (e.g. nitrogen, larger amounts (e.g. nitrogen,

phosphorus, phosphorus, magnesium etc.)magnesium etc.)

(2)(2) trace elements, which are needed in trace elements, which are needed in much smaller amounts (e.g. copper, much smaller amounts (e.g. copper, sodium etc.)sodium etc.)

9.2 How do plants obtain food, water and minerals?

What are the functions of different elements What are the functions of different elements in supporting plant growth?in supporting plant growth?

Minerals For making Deficiency symptoms

Nitrogen

Phosphorus

Magnesium

- proteins- chlorophyll molecules

- nucleic acids, cell membrane, ATP and several coenzymes

- chlorophyll molecules

- poor growth- yellowing of leaves i.e. chlorosis

- poor growth- turn green leaves purple

- poor growth- yellowing of leaves i.e. chlorosis

9.2 How do plants obtain food, water and minerals?

How are roots adapted to the function of How are roots adapted to the function of water and mineral absorption?water and mineral absorption?

Structure Adaptation

Root hairs

Epidermis

- 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

- 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 By which processes do water and minerals enter into a plant?enter into a plant?

Water enters into a plant by osmosis. Water enters into a plant by osmosis. Minerals usually enter by active transport.Minerals usually enter by active transport.