Paper 3 · June 2017 · aeroponics and fermenter design
Aeroponically grown plants suffer less root disease than plants grown in a nutrient tank because
Athe plants grow so fast that a pathogen has no time at all to become established on them.
Bthe roots produce more lignin and so become physically harder to invade.
Ca pathogen has no film of standing water in which to spread from root to root.
Dthe mist is applied at a pressure high enough to kill any fungal spores.
Explanation
In a tank system every root shares one body of solution, so a pathogen introduced at one plant is carried to all of them. In aeroponics the roots hang separately in air and are wetted only by a mist from a closed sterile supply, so there is no continuous water path between plants. The spray is not a sterilising treatment and the roots are not anatomically different.
Derived from ZIMSEC Biology Paper 3, Jun 2017, Q11