All living things are divided into 5 Kingdoms.
1. Monera (Bacteria & some Algae) 2. Protista 3. Fungi 4. Animalia (Animals) 5. Plantae (Plants)
Fig.1 Parts of a normal plant.
Out of these the last mentioned kingdom, Plants are the most mportant. They only can synthesize food by photosynthesis. Others have to directly or indirectly consume what they make. Although all living things have had a common origin, plants have diversified to such an extent they hardly show any relationship to the specimens of the other kingdoms. Let us examine the unique characteristics of this kingdom.
Fig 2 The 5 kingdoms of living things.
A labeled diagram of a typical flowering plant is given below. Only the standard parts, starting from roots, stem with nodes and inter nodes, axils and axillary buds up to the terminal bud are shown here. Fflowers, thorns tendrils etc, are not included here as they are modifications of the parts shown here. .
Fig.2 Plants provide food for Jumbos.
Roots.
These are the parts that grow towards the earth (geotropic) unlike the shoots They also have a tendency to grow towards water. (hydrotropic) As they do not have nodes and internodes leaves are absent. Normal roots arise from the base of the stem but in certain species roots arise from the shoots which are called adventitious roots.
When you up root a plant root hairs break off. Root hairs have only one cell.
Roots perform the following functions;
i. Absorb water and nutrients from the soil.
ii. Holding the plant firmly to the soil against the forces of wind and water.
iii. Storing of food (starch) . Large reservoirs of food are known as yams.
iv. A few plants produce buds that grow into new plants. These are called adventitious buds.
Stem.
The stem has nodes from which the leaves and buds arise. These may be much branched as in most dicots. or single as in palms. They generally grow towards light (phototropic) and upwards but Some stems may remain underground and grow sideways. as in ginger. In that case only the leaves come above the soil.
Fig.3 Sugar cane stem filled with sugary sap.
Functions;
i. To spread the foliage and the flowers, in a way to get the maximum amount of light.
ii. Climbers, creepers and runners produce adventitious roots, tendrils or thorns to hold on to a support.
iii. Some stems store sugar or starch.
iv. Almost all dicot. plants have an amazing power of regeneration. ( If a cutting is planted ie will grow into a new plant)
Leaf
leaves are the food factories of t plants. They take in carbon dioxide from the air and combine with water to make sugar. This is the process known as photosynthesis. As the energy is obtained from sunlight the leaves are generally flat to capture the light. They are also very thin exposing many stomata to the atmosphere for the exchange of gases.(Stomata are the opening on the leaf surface)
Fig.4 The trifoliate leaves of a legume plant.
Functions of a leaf.
i. Leaves manufacture food by photosynthesis.
ii. They exchange gases through stomata , the opening mostly found on the under surface of the leaf.
iii. They store water. which is used for photosynthesis and for cooling, when exposed to direct sunlight.
iv. In some plants they get modified into tendrils, or thorns.
v. In a few rare cases such as bryophillum and begonia the leaf margin can produce young plants.
KINGDOM OF PLANTAE
Three Phyla
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1. BRYOPHYTA
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2. TRACHYOPHYTA
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3. ANGIOSPERMS
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non vascular- Conducting tubes absent
i. Musci (Mosses):-
height is 2 0r 3 cm - grow only in shade.- no proper root system. Attached with rhizoids. – leaves in whorls,
Attached with rhizoids. – leaves only 1 cell tick .
ii. Hepaticae (Liverworts) :-
spreads flat on the ground.
eg, Marchantia
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Vascular bundles present.
i. Filicopsida (Ferns)
eg. Maiden hair fern.
Spores are produced on the under surface of leaf. Leaves come up coiled.
ii. Gymnosperms:- Non flowering ( cone bearers) eg. cycads, conifers.
Produce seeds without flowers.
No fruits either.
A female cone of Cycas.
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Flowering
i. Monocotyledons
eg. A lily, (6 Petals)
ii. Dicotyledons.
eg. Compositae
Leguminosae
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MONOCOTYLEDONS
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DICOTYLEDONS
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Flower
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eg. Coconut flowers
Usually trimerous- (Petals etc. in threes)sometimes 6 (Having separate male and female flowers is not a characteristic of the group)
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Usually pentamerous. Sometimes double that.
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Fruit
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Palm
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Legume
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Seed
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The embryo with a single cotyledon is behind one of the three openings.
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Leaf
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Leaves are generally long and the veins are parallel. (Parallel venation.)
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Reticulate venation.
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Fibrous root system
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Tap root (Main root
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