Answer:
Because condensation on the slant effects the bacterial growth in the test tube.
Step-by-step explanation:
- When agar is solidify in the test tube tilted, it takes a shape of slide on one side of the tube which is known as slat.
- Slant is used instead of petri dishes because they provide more surface area for growth.
- Water in the slat can invade the test tube, making agar unstable and the bacterial growth on the slat will be affected by moisture in bottom of slant.
- In petri dishes, it is no big problem of moisture condensation.