Coordination & Response in Plants (Cambridge O Level Biology)

2,4-D is a synthetic plant auxin that is used as a weedkiller.

Researchers investigated the effectiveness of different treatments of 2,4-D on the control of the weed Conyza canadensis in fields of maize, Zea mays.

The results are shown in Table 1.

Table 1

treatment	time of treatment			mean dry mass of weeds / g per m2	weed density / number of weeds per m2
	Day 7	Day 23	Day 33
A	✓			7.40	6.20
B		✓		3.90	4.90
C			✓	0.50	1.20
D	✓	✓		0.66	1.90
E	✓		✓	0.18	0.98
F		✓	✓	0.07	0.29
G	✓	✓	✓	0.08	0.51

Maize farmers that had been using treatment C were advised by the researchers to change to treatment F.

Discuss the advantages and disadvantages of changing to treatment F.

Auxin causes the shoots of a plant to grow away from gravity.

State the name of this response.