Question

What is meant by positive and negative tropic movements in plants? Explain them by giving suitable examples.

Answer 1

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀$\checkmark$Positive tropic movement in plants means the direction of movement of the plant towards the stimulus.

Examples:-

(1) The plants are grown in light illuminating them from all directions grow more or less upwards.

(2) Roots growing towards the earth’s gravity.

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀$\checkmark$Negative tropic movement in plants means the direction of movement of the plant away from the stimulus.

Examples:-

(1) Growth of roots away from the light

(2) Roots growing away from the earth’s gravity.

Answer 2

Explanation:

Let the length of the piece be x metres. Then, rate per metre =Rs.

x

200

New length =(x+5) metres

Since the cost remains same

New rate per metre =Rs.

x+5

200

It is given that

x

200

−

x+5

200

=2

⇒

x(x+5)

200(x+5)−200x

=2⇒

x(x+5)

1000

=2

⇒x

2

+5x=500⇒x

2

+5x−500=0$

⇒x

2

+25x−20x−500=0

⇒(x+25)(x−20)=0⇒x+25=0

orx−20=0⇒x=20orx=−25

But x cannot be negative. So, x=20

Rate per metre Rs.

x

200

=Rs

20

200

=Rs.10

Hence the length of the piece of cloth is 20 meters and rate =Rs. 10 per meter