A student wanted to investigate the transpiration rate of a plant species at varying levels of humidity. The results are recorded in the table shown. Each plant group was given the same amount of water and light throughout the investigation which procedures should have been performed to prevent error in this investigation? (N 11)
Comparison of Transpiration Rates Over a 60 Hour Period
Plant Species
Average
Group
Humidity (96)
Type of Soil Transpiration
(10 Plants (200 g)
Rate
Each)
(g/dm/hr)
35
Group 1
Sand
23.5
46
Group 2
Sand
20.4
58
Group 3
Clay
18.8
20
Group
Clay
14.4
Both groups should have been tested in the same soil type at each humidity level.
The percentage of humidity should have been kept constant
Fewer plants should have been included in each group
Another plant species should have been tested