Final answer:
Vascular tissues, specifically xylem and phloem, allow land plants to grow in height.
Step-by-step explanation:
The trait of land plants that allows them to grow in height is the presence of vascular tissues, specifically xylem and phloem. Xylem is responsible for conducting water and minerals from the roots to the shoot, while phloem transports food produced during photosynthesis throughout the plant. These tissues provide support and enable the transport of essential materials, allowing land plants to grow taller and compete for light.