−B

+B

0

15

30

45

Ratio

Greenhouse

g B(OH)₃ plant⁻¹ in field

1/2^*

1.9

12.3

1.9

3.2

2.9

3.2

1/3

2.0

17.7

2.1

4.0

3.7

4.3

1/4

2.2

21.5

2.2

4.8

4.2

4.8

1/5

2.3

27.3

2.4

5.4

4.9

5.7

1/6

2.5

31.2

2.6

6.1

5.8

6.9

1/7

2.7

34.9

2.8

7.1

7.2

8.0