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Plant Kingdom

posted Jul 15, 2016, 12:41 PM by Upali Salpadoru   [ updated Sep 3, 2017, 12:20 PM ]

Fig 1  The 5 kingdoms of  living things.

 Out of these, plant  kingdom, is the most mportant.
 Only PLANTS can synthesize food by photosynthesis
 Others have to directly or indirectly get it from them.

   
Fig. The  food synthesizing system in the world. 99.9 % of the food is made this way.

Despite the fact 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.that


 Fig.2  Parts of a flowering dicotyledonous plant.

 Only the standard parts, are shown . 

Flowers, thorns tendrils etc, are not included here as they are modifications of these parts . .

Parts of a normal plant.

1. 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 and buds 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 uproot 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.

2.Stem.

Fig.3  Sugar cane stem filled with sugary sap
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.Some stems may remain underground and grow sideways. as in ginger. In that case only the leaves come above the soil.

Do you know? What of the plant is a potato tuber?  A fruit, root or a stem?

Functions;

Fig. A section of a typical stem showing a vascular bundle.
Vascular bundles contain vessels that conduct water. Xylem takes the water from the roots to the shoot while the sugar processed in the leaves is sent down through the phloem.
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. Conducting water and nutrients from root to shoot. (xylem tubes)
v. Conducting food from leaves to roots.(Ohloem tubes)


3. Leaf

leaves are the food factories of the 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 leguminous 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

 

Vascular Plants.

1. Ferns


    Reproduces by spores found on the under surface of leaves.
    Young leaves emerge rolled up from the bud.

eg. Bracken fern. Maiden hair fern (Adiantum). Tree fern.           

There are two main groups of tree ferns in New Zealand: Cyathea and Dicksonia.  They are easily distinguished since Cyathea is scaly and Dicksonia is hairy.

2. Gymnosperms

The ovules or seeds are not enclosed in an ovary.
The word "gymnosperm" comes from the Greek word gymnospermos, meaning "naked seeds". 
                                       
 CYCADS CONIFERS
 
 
The seeds are inside woody cones.                   eg. Pine family.


3. ANGIOSPERMS -Flowering plants.


 MONOCOTYLEDONS  DICOTYLEDONS
 Flower
Lily flower    6 petals and 6 stamens are visible.

eg. Grass, Palms,  

Seed

. One cotyledon in maize.

Leaf

Leaves are generally long and the veins are parallel. (Parallel venation.)

Flower
Hibiscus flower.
Usually pentamerous. (5 Petals,sepals stamens or a multiple of 5)


See
d.


 cotyledons of a bean seed.

Leaf



Reticulate venation.


        SUMMARY of two categories of flowering plants.





 Q.1.0 
    Classify the following into 3 groups. Flowering plants, and Non flowering and others.

  1.Grass.  2. Yeast 3. Silver fern, 4. Tea  5. X'mas tree,  6. Mush room . 7. Kiwi, 8. Ficus, 9. Bracken, 10. Bacteria, 11. Fur tree, 12. Spruce. 13. Centella asiatica (Gotu kola) 14. Moss. 15. Cactus.
2 x15 = 30 marks. 
 Q. 2.0
   Classify the following into 3 groups as  Dicotyledonous, Monocotyledonous and others.
1. Onion, 2. Sun flower,  3. Bean,  4. Bamboo,  5. Cashew nut, 6. Lily, 7. Orchid.      8. pineapple, 9. Lemon, 10. Cycads. 11. Fern.
2 x11 = 22

 Q.3.0
Mention the part of the plant mainly responsible for the respective functions.
 1. Synthesizing food.         2. Storing prepared food.
 3. Conducting the water to shoot.   4.  Bringing food for the roots.
 5. Reproduction.  6. Absorption of nutrients from soil.
3 x 6 = 18

 Q.4.0
Into which major part of a plant could these be assigned ?

3 x 10 =30











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