Final answer:
Marram grass has a thick cuticle that greatly reduces water loss, which is essential for survival in its dry, coastal habitat. The cuticle's impermeability to water also affects gas exchange, but specialized structures like stomata help regulate this. Additionally, trichomes can contribute to the plant's defenses against herbivory and further reduce water loss.
Step-by-step explanation:
Marram grass, which thrives in coastal sand dune ecosystems, has developed a thick cuticle on its leaves to minimize water loss through transpiration. This adaptation is crucial for survival in its harsh, windy, and often dry habitat. The cuticle is a waxy layer that significantly reduces the rate of water loss from the plant's surface, ensuring that the grass retains moisture even under intense sunlight and drying conditions.
However, a thick cuticle can also impede the exchange of gases, including that of carbon dioxide, which is vital for photosynthesis. Marram grass and other plants with thick cuticles have specialized openings called stomata that can open and close to regulate gas exchange and further reduce water loss.
In certain plants, trichomes (small hairs) are present on the leaf surface in addition to the cuticle. These structures can deter herbivory and aid in reducing transpiration by hindering air flow across the leaf surface.