Life Processes- Nutrition 3





Lesson 3

Welcome back students!
Let us check our answers of yesterday’s assignment.
A1) c
A2) c
A3) Oxygen gas is released. Splitting of water molecules by light energy releases oxygen.
A4) Desert plants keep their stomata closed during day time. They take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.

HOPE YOU GOT YOUR ANSWERS RIGHT!
By the end of today’s class you will be able to
1.      Name the raw materials necessary for photosynthesis.
2.       Show that chlorophyll is necessary for photosynthesis with the help of an activity.
3.      Show that carbon dioxide is necessary for photosynthesis with the help of an activity.

PLEASE COPY EVERYTHING IN YOUR BIOLOGY NOTEBOOK EXCEPT THAT WHICH IS WRITTEN IN RED. KEEP YOUR NCERT WITH YOU FOR ANY REFERENCE.
THE RAW MATERIAS REQUIRED BY A PLANT FOR PHOTOSYNTHESIS ARE CO2 AND H2O. WE WILL NOW SHOW THAT THESE TWO ARE ESSENTIAL FOR PHOTOSYNTHESIS.

ACTIVITY 1
AIM : To show that chlorophyll is necessary for photosynthesis.
MATERIALS REQUIRED : A plant with variegated leaves, tracing paper, water, burner, alcohol. Starch.
PROCEDURE: 1) A potted plant with variegated leaves is taken. (no diagrams to be drawn)












2) The plant is kept in dark for three days to destarch it. (all starch gets used up)

3) The plant is now placed in sunlight for six hours.

4) A leaf is plucked and its green and non green areas are traced on a sheet.
(no diagrams to be drawn)





5) The leaf is boiled in water for few minutes and then boiled in alcohol (in a water bath) for 15 minutes. (boiling in water destroys/ denatures all enzymes and boiling in leaf removes chlorophyll, after boiling in alcohol, alcohol turns green.)
6) The leaf is washed with water and tested with iodine solution.
7) Observations are made.
OBSERVATIONS: The green areas of leaf turned blue black in colour whereas the rest of it remained pale yellow.
INFERENCE: The green areas of leaf contains chlorophyll, hence starch is prepared which gives blue black colour to leaf when tested with iodine solution. (no diagrams to be drawn)





RESULT : Chlorophyll is necessary for photosynthesis.


ACTIVITY 2

AIM : To show that carbon dioxide is necessary for photosynthesis.
MATERIALS REQUIRED: Two potted plants, bell jar, KOH ( potassium hydroxide), alcohol, vaselin Starch.
PROCEDURE: 1) Two potted plants are taken. ( diagrams to be drawn)
2) The plants are kept in dark for three days to destarch it. (all starch gets used up)
3) The plants are now placed in sunlight for six hours.
4) The plants are now kept on glass plates.
5)  Potassium hydroxide is taken in a watch glass and placed next to the first plant.
6) Both plants are coverd with bell jars.

7) Both plants are kept in sunlight for six hours.

8) Leaf is plucked from each, boiled in water then in alcohol and tested with iodine solution.
9) Observations are made.

OBSERVATIONS: The leaf  belonging to the first plant remains pale yellow while the leaf  belonging to the second plant turns blue black in colour

INFERENCE: The  leaf of the first plant did not get CO2 as it gets absorbed by KOH, hence starch is not prepared whereas the leaf of second plant turns blue black colour  when tested with iodine solution as this plant got sufficient CO2.

RESULT : Carbon dioxide is necessary for photosynthesis

ASSIGNMENT
Read pages 96 and 97 NCERT and answer the questions
Q1) List the nutrients required by a plant for photosynthesis other than Carbon hydrogen and oxygen and how do plants get them?
Q2) Why is nitrogen essential for plants?

Location: New Delhi, Delhi, India

Comments

  1. SCS SCIENCE ASHISHMarch 25, 2020 at 8:25 AM

    Dear Learners,

    Go through this new blog and also revise the previous blogs. Pose your query and doubts.

    Ashish

    ReplyDelete
  2. emmanuel gomesMarch 25, 2020 at 8:37 AM

    Sir what is the meaning of "denatures"

    ReplyDelete
  3. emmanuel gomesMarch 25, 2020 at 8:40 AM

    in the 2nd experiment how can we be sure that there is no carbon dioxide present

    ReplyDelete
  4. UnknownMarch 25, 2020 at 8:51 AM

    Sir temperature also help in transpiration of water , reducing water level in cell which lead to the closing of guard cell

    Sir is this correct

    Regards Divij Gogia

    ReplyDelete
    Replies
    1. SCS SCIENCE ASHISHMarch 25, 2020 at 9:16 AM

      It depends of habitat of plants. To be discuss in detail in higher classes.

      High temperatures will also signal stomata to close. High temperatures will increase the water loss from the leaf. With less water available, guard cells can become flaccid and close.

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