Final answer:
The correct answer is option 2) Bryophytes : stomata. Bryophytes differ from other plants in that they lack true vascular systems and must absorb moisture directly through their leaves, and they do not rely on stomata to regulate water loss to the same extent as other plants.
Step-by-step explanation:
Plants, except for bryophytes, limit water loss by closing pores in their leaves called stomata. The answer to the student's question is option 2) Bryophytes : stomata.
Leaves are covered by a waxy cuticle on the outer surface that prevents the loss of water, but to facilitate gas exchange for photosynthesis, plants have evolved structures known as stomata, which are pores on the leaf surface regulated by guard cells. These stomata open and close in response to various environmental cues and help to maintain a balance between efficient photosynthesis and minimizing water loss through transpiration.
Bryophytes such as mosses still rely on environmental water for many of their life processes, including reproduction, and they don't have the same vascular structures as other plants to transport water. They lack true roots and thus absorb moisture directly through their leaves. In contrast, vascular plants, including pterophytes like ferns, possess stomata which they can close to reduce water loss in drier environments.