Morphology of Flowering Plants Class 11 Science Notes Download in PDF-2(the stem),CBSE
Morphology of Flowering Plants Class 11 Science Notes - THE STEM
THE STEM IS THE ASCENDING PART OF THE AXIS OF THE PLANT.
IT BEARS LEAVES, FLOWERS AND FRUITS.
THE STEM DEVELOPS FROM THE PLUMULE OF THE EMBRYO OF THE GERMINATING SEED.
THE STEM BEARS NODES AND INTERNODES.
LEAVES ARE BORN ON THE NODES AND THE REGION BETWEEN TWO NODES IS KNOWN AS INTERNODES.
STEMS BEAR BUDS WHICH MAY BE IN TERMINAL OR AXILLARY IN POSITION.
STEMS ARE GREEN WHEN YOUNG AND BECOMES WOODY AND DARK BROWN LATER.
THE MAIN FUNCTIONS OF THE STEM ARE-
1) SPREADS OUT BRANCHES BEARING LEAVES, FLOWERS AND FRUITS.
2) STEMS CONDUCTS WATER, MINERALS AND PHOTOSYNTHATES.
3) STEMS ALSO PERFORMS THE FUNCTIONS OF STORAGE OF FOOD,SUPPORT AND PROTECTION.
4) STEMS ALSO HELPS IN VEGETATIVE PROPAGATION.
MODIFICATIONS OF STEMS
STEMS GETS MODIFIED TO PERFORM OTHER FUNCTIONS APART FROM PERFORMING ITS MAIN FUNCTIONS.
UNDERGROUND STEMS- THE UNDERGROUND STEMS OF potato,ginger,turmeric,zaminkand,colocasia are modified to store food in them.
underground stems acts as organs of perennation to tide over the conditions unfavourable for growth.
STEM TENDRILS- They develop from axillary buds. They are slender and spirally coiled.
They help the plant to climb. e.g.,gourds(cucumber,pumkins,watermelon) and grapevines.
THORNS- Thorns are the pointed, woody and straight modifications of axillary buds of the plant. e.g., Citrus,Bougainvillea.They protect the plants from browsing animals.
STEM MODIFICATIONS TO CARRY OUT PHOTOSYSNTHESIS- Some plants of arid regions modify their stems into flattened as in Opuntia or fleshy cylindrical structures as in Euphorbia.
these structures contains chlorophyll and carry outs photosynthesis.
STEMS HELPING IN VEGETATIVE REPRODUCTION-
The underground of plants such as grass and strawberry spreads to new niches when the older parts die in order to form new plants.
In plants like mint and jasmine, a lateral root develops from the base of a plant and aerially for sometimes and then arch downwards touching the ground and forms new plant.
In aquatic plants such as Pistia and Eichhornia, lateral branches with short internodes and at each nodes bearing rosette of leaves and tuff of roots are found.
In plants like Banana,Pineapple and Chrysanthemum, the lateral branches originate from the basal and underground portion of the main stem. They grow horizontally beneath the soil and then come out obliquely upward giving rise to leafy shoots.
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THE STEM IS THE ASCENDING PART OF THE AXIS OF THE PLANT.
IT BEARS LEAVES, FLOWERS AND FRUITS.
THE STEM DEVELOPS FROM THE PLUMULE OF THE EMBRYO OF THE GERMINATING SEED.
THE STEM BEARS NODES AND INTERNODES.
LEAVES ARE BORN ON THE NODES AND THE REGION BETWEEN TWO NODES IS KNOWN AS INTERNODES.
STEMS BEAR BUDS WHICH MAY BE IN TERMINAL OR AXILLARY IN POSITION.
STEMS ARE GREEN WHEN YOUNG AND BECOMES WOODY AND DARK BROWN LATER.
THE MAIN FUNCTIONS OF THE STEM ARE-
1) SPREADS OUT BRANCHES BEARING LEAVES, FLOWERS AND FRUITS.
2) STEMS CONDUCTS WATER, MINERALS AND PHOTOSYNTHATES.
3) STEMS ALSO PERFORMS THE FUNCTIONS OF STORAGE OF FOOD,SUPPORT AND PROTECTION.
4) STEMS ALSO HELPS IN VEGETATIVE PROPAGATION.
MODIFICATIONS OF STEMS
STEMS GETS MODIFIED TO PERFORM OTHER FUNCTIONS APART FROM PERFORMING ITS MAIN FUNCTIONS.
UNDERGROUND STEMS- THE UNDERGROUND STEMS OF potato,ginger,turmeric,zaminkand,colocasia are modified to store food in them.
underground stems acts as organs of perennation to tide over the conditions unfavourable for growth.
 |
STEMS
MODIFIED FOR STORAGE OF FOODS
|
STEM TENDRILS- They develop from axillary buds. They are slender and spirally coiled.
They help the plant to climb. e.g.,gourds(cucumber,pumkins,watermelon) and grapevines.
 |
STEMS
MODIFIED FOR PROVIDING SUPPORT TO PLANTS
THORNS- Thorns are the pointed, woody and straight modifications of axillary buds of the plant. e.g., Citrus,Bougainvillea.They protect the plants from browsing animals.
 |
STEMS
MODIFIED FOR PROVIDING PROTECTION FROM BROWSING ANIMALS
|
STEM MODIFICATIONS TO CARRY OUT PHOTOSYSNTHESIS- Some plants of arid regions modify their stems into flattened as in Opuntia or fleshy cylindrical structures as in Euphorbia.
these structures contains chlorophyll and carry outs photosynthesis.
STEMS HELPING IN VEGETATIVE REPRODUCTION-
 |
STEMS HELP
IN VEGETATIVE REPRODUCTION
The underground of plants such as grass and strawberry spreads to new niches when the older parts die in order to form new plants.
In plants like mint and jasmine, a lateral root develops from the base of a plant and aerially for sometimes and then arch downwards touching the ground and forms new plant.
In aquatic plants such as Pistia and Eichhornia, lateral branches with short internodes and at each nodes bearing rosette of leaves and tuff of roots are found.
In plants like Banana,Pineapple and Chrysanthemum, the lateral branches originate from the basal and underground portion of the main stem. They grow horizontally beneath the soil and then come out obliquely upward giving rise to leafy shoots.
PDF DOWNLOAD
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