Juglone is a natural organic compound produced by walnut trees that acts as a respiratory inhibitor and contact allelochemical, disrupting cell-surface membranes in competing plant species.
Agricultural scientists investigated the potential of juglone as a bio-herbicide to control blackgrass (Alopecurus myosuroides), a highly invasive weed, in fields of winter wheat (Triticum aestivum).
They raised young plants of both species in controlled greenhouse chambers and assigned them to one of two experimental treatments:
Ten hours after spraying, they harvested leaves from both groups, cut 30 uniform discs from each set, and transferred them to flasks containing 20 cm320\text{ cm}^320 cm3 of de-ionised water. After 10 minutes of incubation, they measured the electrical conductivity of the water to determine the mean concentration of leaked ions, which serves as an index of membrane disruption.
Their findings are summarized in the table below:
| Group | Treatment | Mean concentration of leaked ions / arbitrary units (Wheat) | Mean concentration of leaked ions / arbitrary units (Blackgrass) |
|---|---|---|---|
| C | Water control | 12 | 24 |
| J | Juglone | 15 | 58 |
| LSD | 5 | 7 |
The least significant difference (LSD) represents the minimum difference between two means required to be statistically significant at the P≤0.05P \le 0.05P≤0.05 level.
State three environmental growth variables that the scientists must have controlled while cultivating the plants in the greenhouse before applying the sprays.
Evaluate the potential of juglone as a selective bio-herbicide for wheat crops infested with blackgrass. Use all the quantitative data provided in the table to support your answer.
Suggest one biological reason why the scientists kept the temperature strictly constant during the 10-minute incubation period, and one practical reason why they continuously agitated (shook) the flasks during this time.
