Decanoic acid is a naturally occurring medium-chain fatty acid used as a contact herbicide that disrupts cell-surface membranes. However, the susceptibility of cell membranes to this disruption can vary significantly between plant species.
Scientists investigated the effect of decanoic acid on grapevine plants (the crop) and black nightshade plants (a common weed).
They cultivated both species under controlled conditions in a greenhouse and divided the plants of each species into two treatment groups:
Following treatment, the scientists cut 30 identical discs from the leaves of plants in each group and submerged them in flasks containing 20 cm3 of de-ionised water. After 10 minutes of incubation, they measured the concentration of ions released into the water from the leaf discs to assess the extent of membrane disruption.
Their results are shown in the table below:
| Group | Treatment | Mean concentration of ions in water / arbitrary units (Grapevine) | Mean concentration of ions in water / arbitrary units (Black nightshade) |
|---|---|---|---|
| C | Water | 12 | 24 |
| D | Decanoic acid | 15 | 78 |
| LSD | 5 | 9 |
The least significant difference (LSD) is the minimum difference between two means required for the difference to be statistically significant at P≤0.05P \le 0.05P≤0.05.
State three environmental variables that must be controlled while growing the plants in the greenhouse prior to the chemical treatment.
Evaluate the suitability of decanoic acid as a selective herbicide for a grapevine crop infested with black nightshade. Use all the information provided in the table to support your answer.
Suggest one reason why the temperature was kept constant during the 10-minute incubation period, and one reason why the flasks containing the leaf discs were continuously shaken.
