Which of the following occurs in vascular land plants but not in charophytes (stoneworts)?

• A. Alternation of generations
• B. Cell walls containing cellulose
• C. Photosynthesis using chlorophyll a and b
• D. Presence of lignified vascular tissue (xylem and phloem)

Answer: (D)

Verified step by step guidance

1. Understand the key difference between vascular land plants and charophytes. Charophytes are green algae closely related to land plants but lack certain adaptations necessary for terrestrial life.
2. Review the concept of lignified vascular tissue. Vascular tissue in plants includes xylem and phloem, which are specialized for transporting water, nutrients, and sugars. Lignin is a complex polymer that strengthens the cell walls of xylem, allowing plants to grow taller and transport water efficiently.
3. Compare the features listed in the problem. Alternation of generations, cellulose-containing cell walls, and photosynthesis using chlorophyll a and b are shared traits between vascular land plants and charophytes. These traits are not unique to vascular land plants.
4. Identify the unique feature of vascular land plants: the presence of lignified vascular tissue. This adaptation is critical for supporting the plant structure and enabling efficient transport of water and nutrients, which charophytes lack.
5. Conclude that the correct answer is the presence of lignified vascular tissue (xylem and phloem), as this is a defining characteristic of vascular land plants and is absent in charophytes.