Final answer:
Mutants of Arabidopsis thaliana containing a defective sulfolipid synthase showed impaired growth due to a deficiency of sulfolipids.
Step-by-step explanation:
Mutants of Arabidopsis thaliana, a plant model, with a defective sulfolipid synthase showed impaired growth. Sulfolipid synthase is an enzyme responsible for producing sulfolipids, which are important in the structure and function of plant membranes. A defective sulfolipid synthase would result in a deficiency of sulfolipids, leading to impaired growth in the mutant plants.