Q17 of 70 Page 73

Complete the following by filling the blanks 1 to 5 with appropriate words/terms/phrases:

To test the leaf for starch, the leaf is boiled in the wafer to ................... (1). It is next boiled in methylated spirit to ................... (2). The leaf is placed in warm water to soften it. It is then placed in a dish and ................... (3) solution is added. The region, which contains starch, turns ................... (4) and the region, which does not contain starch, turns……………. (5).

(1) Kill the cells


(2) Remove the chlorophyll


(3) Iodine


(4) Bluish-black


(5) Brown


Explanation:


(1) The leaf cells are killed to avoid further chemical reactions leading to photosynthesis.


(2) To have the proper judgment of chlorophyll formed after the experiment, the chlorophyll formed previously has to be removed by boiling in methylated spirit.


(3) Iodine is used as the reagent as it changes colour in the presence of starch.


(4) A bluish-black coloration is formed in regions containing starch as iodine and starch react together to form polyiodide chains.


(5) Regions of the plant that does not contain starch, turns brown.


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15

How do non-green plants such as fungi and bacteria obtain their nourishment?

 16

All life owes its existence to chlorophyll. Give reason.

 1

A candidate studied the importance of certain factors in photosynthesis. He took a potted plant and kept it in the dark for over 24 hours. In the early hours of the next morning, he covered one of the leaves with dark paper in the centre only. Then he placed the plant in sunlight for a few hours and tested the leaf which was covered with black paper for starch.

(a) What aspect of photosynthesis was being investigated?


(b) Is there any control in this experiment? If so, state it.


(c) Why was the plant kept in the dark before the experiment?


(d) Describe step by step, how the candidate proceeded to test the leaf for the presence of starch.

 2

Photosynthesis in green plants is, directly and indirectly, dependent on so many plant structures. Explain briefly the role of the following structures in this process.

(a) Guard cells


(b) Cuticle


(c) Mesophyll cells


(d) Xylem tissue in the leaf veins


(e) Phloem tissue in Leaf Veins


(f) Stomata