Class XI, BIOLOGY, "Nutrition in Plants"

Nutrition in Plants

CLASSIFICATION ON THE BASIS OF MODE OF NUTRITION
Plants can be divided into two groups on the basis of their mode of nutrition.
1. AUTOTROPHIC
2. HETEROTROPHIC
1. AUTOTROPHIC NUTRITION
DEFINITION
“Autotrophic nutrition is the type of nutrition in which organic compounds are manufactured from available inorganic raw material taking from surroundings”.
In autotrophic nutrition, the nutrients do not require to be pretreated or digested before taking them into their cells.
TWO METHODS OF AUTOTROPHIC NUTRITION
On the basis of source of energy, autotrophic nutrition can be sub-divided into following sub-types.
(I) Phototrophic nutrition
(II) Chemotrophic nutrition
I. PHOTOTROPHIC NUTRITION
DEFINITION
“The type of autotrophic nutrition is which organic molecules are manufactured from simple inorganic molecules by using light energy as a source is called Phototrophic Nutrition”.
EXAMPLE
a. Green Plants
b. Photosynthetic Bacteria
(I-A) PHOTOTROPHIC NUTRITION IN GREEN PLANTS
Green plants are very prominent example of phototrophic nutrition. They prepare the food by the process of photosynthesis.
RAW MATERIAL
The raw material needed by these organisms are
(1) CO2 AND H20
They provide carbon, hydrogen and oxygen for the synthesis of organic molecules.
(2) MINERALS
The minerals like Nitrogen, Phosphorus and Sulphur and Magnesium are also required.
(3) GREEN PIGMENTS
The green pigments i.e. Chlorophyll a, b, or others are also required to absorb the energy from universal source of light.
(4) LIGHT
In the presence of sun light nutrients are used to synthesis the energy rich compounded (CHO) This process is called “PHOTOSYNTHESIS”.
This process can be represented by equation as follows.
6CO2 + 12H2O -> C6H12O6 + 6O2 + 6H2O
(I-B) PHOTOTROPHIC NUTRITION IN PHOTOSYNTHETIC BACTERIA
Photosynthetic bacteria are unique because they are the only organisms which are capable of synthesizing the carbohydrate food without chlorophyll “a”.
DIFFERENCES BETWEEN PHOTOSYNTHETIC BACTERIA AND GREEN PLANTS
Photosynthesis in bacteria is different from green plants. Some differences are

• Photosynthetic bacteria usually grow in sulphide spring where H2S is normally present.
• Hydrogen is provided by H2S instead of H2O.
• Free oxygen is not released as a by product in bacterial photosynthesis.
• The process takes place at low expenditure of energy.

TWO TYPES OF PHOTOSYNTHETIC BACTERIA
There are two types of photosynthetic bacteria.
(1) THOSE IN WHICH “S” IS RELEASED AS BY PRODUCT
These bacteria use H2S as donor of hydrogen. Light splits hydrogen sulphide. Hydrogen combines with CO2 to form H2O.
2H2S + CO2 -> (CH2O)n + H2O + 2S
EXAMPLES
Purple Sulphur Bacteria ® which use BACTERIO CHLOROPHIL & CARETENOID as photosynthetic pigments.
(2) THOSE IN WHICH “S” IS NOT RELEASED AS BY PRODUCT
These bacteria use H2S as Hydrogen donor where as sulphur is not the by product in their case.
EXAMPLES
PURPLE NON-SULPHUR BACTERIA
BROWN NON-SULPHUR BACTERIA
Both of these contain “BACTERIO CHLORPHYLL” as photosynthetic pigments.
(II) CHEMOTROPHIC NUTRITION
DEFINITION
“The mode of autotrophic nutrition in which organic molecules are manufactured from simple inorganic molecules by using energy produced by the oxidation of certain inorganic substances such as ammonia, nitrates, nitrites, ferrous ions, H2S and etc. This type of nutrition is called CHEMOTROPHIC NUTRITION and process of manufacturing food is called CHEMOSYNTHESIS.”
Mainly Bacteria are
AMMONIA USING BACTERIA
They derive their energy by oxidation of Ammonia.
NH4+ + O2 -> 2NO2 + 2H2O + 4H+ + energy
BACTERIA CONVERTING NITRITES TO NITRATES
2NO2 + O2 -> 2NO3- + energy
IMPORTANCE OF CHEMOSYNTHETIC BACTERIA
The chemosynthetic bacteria that act on nitrogen compounds do play an important role in the maintenance of nitrogen balance in the life system.
2. HETEROTROPHIC NUTRITION IN PLANTS
DEFINITION
“Plants which are not capable of manufacturing their own organic molecules entirely or partially depend for these organic molecular are called “HETEROTROPHIC PLANTS”
CLASSIFICATION OF HETEROTROPHIC PLANTS
On the basis of type of organisms on which heterotrophic plants depend, they can be classified into following two classes.
1. PARASITC PLANTS OR PARASITES
2. SAPROPHYTIC PLANTS OR SAPROPHYTES
1. PARASITES
DEFINITION
“Those heterotrophic plants which depend on living plants and animals for their nutritional requirements are known as PARASITES.”
TYPES OF PARASITES
Parasitic plants can be divided into following types.
A. Obligate or total parasites.
B. Facultative or partial parasites.
1.A TOTAL PARASITES
DEFINITION
Those parasites which depend for their nutrition entirely on other living organisms
CLASSIFICATION OF TOTAL PARASITIC ANGIOSPERMS
Total or obligate parasitic angiosperms are broadly classified into
1. Total stem parasite
2. Total root parasite
1. TOTAL STEM PARASITES
DEFINITION
“Those parasitic plants which depend entirely on the stems of other plants are called “Total stem Parasites”
EXPLANATION
These plants send HAUSTORIA (specialized structures for absorbing nutrients in parasitic plants) inside the tissue of host. The xylem of parasite comes in contact with xylem of host and phloem of parasite to phloem of host. Through xylem it sucks the water and nutrients, through phloem prepared organic material. The host plant eventually dies off due to exhaustion.
EXAMPLE
CUSCUTA (AMER-BAIL)
2. TOTAL ROOT PARASITES
DEFINITION
“Those parasitic plants which suck their nutritional requirements from the roots of host are called “Total root parasites”.
EXAMPLES
OROBANCHE -> attacks the roots of the plants belonging to families Cruciferae and Solanaceae
CISTANCHE -> Parasitizes on the roots of Calatropis.
STRIGA -> Found as parasite on the roots of sugar cane
(1.B)PARTIAL PARASITES
DEFINITION
“Those parasite plants which depend for their nutritional requirements partially on other living organisms are called Falcultave or partial parasites.”

CLASSIFICATION OF PARTIAL PARASITIC ANGIOSPERMS
Partial parasitic angiosperms can be broadly classified into
1. PARTIAL STEM PARASITE
2. PARTIAL ROOT PARASITE
1. PARTIAL STEM PARASITES
DEFINITION
Those partial parasites whose haustoria penetrate in the stem of the host and suck their nutrition from vascular tissues of stem are called PARTIAL STEM PARASITE

EXPLANATION
LORANTHUS, is a partial stem parasite. It has thick green leaves, a woody stem and elaborated haustorial system. It can manufacture some of its food with the help of nutrients and water absorbed from host plants. The seeds get stuck upto the stem of host plant and germinates sending its haustoria in the tissues of the host.
EXAMPLES
LORANTHUS -> found on shrubs, roseaceous tree, Bauhinia and mango
VISCUM -> produce haustorial branches for an internal suckling system.
CASSYTHA FILLIFORMIS -> found in tropics
2. PARTIAL ROOT PARASITES
EXAMPLE
The examples of this category are rare.
One important example is
SANDLE WOOD TREE
SAPROPHYTES
DEFINITION
“Those plants which depend for their nutrition on dead or rotten organic remains of plants or animals are called as SAPROPHYTES”

or

“Plants which break up complex dead food material into simple compounds and use them for their growth and development are called as SAPROPHYTES.”
TYPES OF SAPROPHYTES
Saprophytes can be divided into two types:
1. Total Saprophytes
2. Partial Saprophytes
1. TOTAL SAPROPHYTES
DEFINITION
“Those plants which depend entirely for their nutrition on dead organic matter are called Total Saprophytes.
2. PARTIAL SAPROPHYTES
DEFINITION
“Those plants which depend partially on dead organic matter are called Partial Saprophytes.”
EXAMPLES OF SAPROPHYTES
There are some examples of Saprophytes among flowering plants.
1. Neothia (bird’s net or orchid)
2. Monotrapa (Indian Pipe)
In both of these cases, the roots of plant form a Mycorhizzal Association with fungal mycelium to help in absorption process.
SPECIAL MODE OF NUTRITION
CARNIVOROUS OR INSECTIVOROUS PLANTS
DEFINITION
“The plants which have as their prey, insects and small birds are called Carnivorous plants. It is a special mode of nutrition in partially autotrophic and partially heterotrophic plants.”
EXPLANATION
Partially autotrophic and partially heterotrophic plants are carnivorous, which possess the green pigments and can manufacture CHO but are not capable of synthesizing nitrogenous compounds and proteins. For their nitrogen requirement, carnivorous plants have to depend on insects, which they catch and digest by specific devices developed in them. J.D. Hooker suggested that the digestion of carnivorous plants is like that of animals.
COMMON AREAS WHERE THESE PLANTS GROW
These plants commonly grow in areas where nitrogen is deficient due to unfavourable atmosphere for nitrifying bacteria but favourable atmosphere for denitrifying bacteria.
SOME COMMON EXAMPLES
1. PITCHER PLANT
In Pitcher plant leaf is modified into pitcher like structure which is insect trapping organ.
EXAMPLES
Common examples are :
Nepenthes
Sarracenia
Cephalotus
Neliamphora
Darling tonia
2. DORSERA INTERMEDIA OR SUNDEW
This plant has half a dozen prostrate radiating leaves, which bear hair like tentacles each with gland at its tip. The insects attracted by plant odour are digested.
3. DIONAEA MUSCIPULA OR VENOUS FLY TRAP
Most well known of all carnivorous plants. It has a resette of prostrate radiating leaves with inflorescence in the centre. The petiole of leaf is winged and lamina has two halves, with mid-rib in the centre. Each half has 12-20 teeth. In the centre of dorsal surface of lamina are numerous secretory glands, three hairs projecting out, which are sensitive to touch.
4.ALDROVANDA (WATER FLY TRAP)
It is a root less aquatic plant with floating stem. It has ressettes of modified leaves, which have two lobed mobile lamina having teeth at the margin and sensitive jointed hairs and glands on the surface.
5. UTRICULARIA OR BLADDER WORT
It is a root less plant having branched slender stem. Leaves are also much divided and some leaflets are modified into bladder like traps of about 1/16 to 1/8 inches in diameter.