Final answer:
If Wents placed his agar blocks halfway on the cut surfaces of grass shoots, he would observe the shoots growing upwards due to gravitropism.
Step-by-step explanation:
If Wents placed his agar blocks only halfway on the cut surfaces of grass shoots with their tips removed, he should have observed that the shoots would grow in the new vertical direction. This is because of the phenomenon known as gravitropism, which ensures that roots grow into the soil and shoots grow towards sunlight. When a plant is tilted, the specialized plastids called amyloplasts, which contain starch granules, settle downward in response to gravity. This triggers the shoots to grow in the opposite direction, towards the light.