Give three environmental variables that should be controlled when growing the plants before treatment with the different sprays.

1

2

3

Evaluate the use of 2,4-D as a herbicide on a wheat crop that contains wild oats as a weed. Use all the information provided.

The scientists incubated the flasks containing the leaf discs at 26 °C and gently shook the flasks.

Suggest one reason why the scientists ensured the temperature remained constant and one reason why the leaf discs were shaken.

Temperature

Shaken