Which of the following pair of diagrams shows an experiment done to find out if these roots are also phototropic?

Here are the solutions to the questions:

9. Some roots react positively to gravity. Which of the following pair of diagrams shows an experiment done to find out if these roots are also phototropic?

To determine if roots are phototropic (respond to light), an experiment needs to compare the growth of roots in the presence of light with their growth in the absence of light, while keeping other factors constant.

• Diagram 1 shows a seed in a light-proof box, with the root growing downwards due to gravity. This serves as a control for growth in the absence of light.
• Diagram 2 shows a seed in a box with light coming from one side. The root is still oriented vertically, allowing observation of any deviation from gravitational growth due to unilateral light.

Comparing Diagram 1 (no light) and Diagram 2 (unilateral light) allows for the investigation of the effect of light on root growth direction, thus testing for phototropism.

The correct option is A.

10. An experiment was done to investigate the effects of various environmental factors on germination. Four boiling tubes were prepared as shown in the diagram. In which tube would the seeds germinate fastest?

Seed germination requires three main conditions:

1. Water: To activate enzymes and swell the seed.
2. Oxygen: For aerobic respiration to provide energy.
3. Suitable temperature: For optimal enzyme activity.

Let's analyze each tube:

• Tube A: Contains cress seeds, moist cotton wool, water, and is at $25^\circ\text{C}$. All three conditions (water, oxygen from air, suitable temperature) are met.
• Tube B: Contains cress seeds and dry cotton wool at $25^\circ\text{C}$. It lacks water, so germination will not occur.
• Tube C: Contains cress seeds, moist cotton wool, and a substance to absorb oxygen at $25^\circ\text{C}$. It lacks oxygen, so germination will not occur or be severely inhibited.
• Tube D: Contains cress seeds, moist cotton wool, water, but is at $5^\circ\text{C}$. While water and oxygen are present, the temperature is too low for optimal enzyme activity, so germination will be very slow or inhibited.

Tube A provides all the necessary conditions for germination at an optimal temperature, leading to the fastest germination.

The seeds would germinate fastest in tube $\boxed{\text{A}}$.