Question

One differentiating characteristic between vascular and nonvascular plants is the lack of active transport structures in the nonvascular plants. How does the lack of xylem or phloem contribute to the smaller size of the nonvascular plants?

Nonvascular plants are smaller because xylem and phloem help a plant stand up taller.
Nonvascular plants have other transport structures that are microscopic and therefore take up less room.
Nonvascular plants rely upon concentration gradients to move food and water, which only works over small distances.
Nonvascular plants are smaller because they don’t photosynthesize as much as vascular plants and don’t get enough food.

Answer 1

Nonvascular plants, lacking xylem and phloem, rely on concentration gradients for water and nutrient movement, limiting their size to small distances suitable for passive transport.

Step-by-step explanation:

The lack of xylem or phloem is a significant factor contributing to the smaller size of nonvascular plants. Unlike vascular plants, nonvascular plants, or bryophytes, do not have specialized tissues to actively transport water, nutrients, and food throughout the plant. This limitation means that nonvascular plants are generally restricted in size and often live in moist environments where they can absorb water and nutrients directly over their surface.

Therefore, the correct statement regarding the smaller size of nonvascular plants is that they rely upon concentration gradients to move food and water, which only works over small distances. This passive transport is less efficient than the active transport facilitated by xylem and phloem in vascular plants, which allows them to grow taller and larger.

The absence of a vascular system means that nonvascular plants cannot support tall structures and are typically found close to the ground where they can access the moisture needed for diffusion and osmosis. Furthermore, the lack of vascular tissue means they do not develop true roots or leaves that would allow for greater water uptake and growth.