Final answer:
The third adaptation of marram grass is rolled leaves, which helps in reducing transpiration by trapping humid air and protecting stomata.
Step-by-step explanation:
The third adaptation exhibited by marram grass to survive in its environment is rolled leaves. This adaptation is important for reducing water loss in harsh conditions, such as the sand dunes where marram grass often grows. The rolled leaf shape helps to conserve water by trapping air inside, which becomes humid and reduces the transpiration rate. Additionally, this shape protects the stomata that are often on the inside of the rolled leaves, further reducing water loss. Other adaptations of marram grass include an enhanced root system to absorb water efficiently, a thick cuticle to minimize water loss, and reduced numbers of stomata which also lowers transpiration rates.