Q21 of 30 Page 1

Explain giving reasons the bending of the shoot tip of a plant towards light source coming from one side of the plant.

The reason for the bending of the shoot tip of a plant towards light source coming from one side of the plant is due to a phenomenon called positive phototropism during which plant shoots rearrange their chloroplasts in the leaves to maximize photosynthetic energy obtained in order to promote growth.

Auxin is a plant growth hormone present on the cells of the plant and are situated farther away from the light. This causes the plant to have longer cells on that side which is away from the light leading to the bending towards light.


More from this chapter

All 30 →
19

Explain the processes of aerobic respiration in mitochondria of a cell and anaerobic respiration in yeast and muscle with the help of word equations.

 20

In a pea plant, the trait of flowers bearing purple colour (PP) is dominant over white colour (pp). Explain the inheritance pattern of F1 and F2 generations with the help of a cross following the rules of inheritance of traits. State the visible characters of F1and F2 progenies.

 22

It is desired to obtain an erect image of an object, using concave mirror of focal length of 12 cm.

(i) What should be the range of the object distance in the above case?


(ii) Will the image be smaller or larger than the object? Draw a ray diagram to show the formation of image in this case.


(iii) Where will the image of this object be, if it is placed 24 cm in front of the mirror?


 23

Suppose your parents have constructed a two room house and you want that in the living room there should be a provision of one electric bulb, one electric fan, a refrigerator and a plug point for appliances of power up to 2 kilowatts. Draw a circuit diagram showing electric fuse and earthing as safety devices.