What evolutionary development was most important for terrestrial plants to grow tall?
The correct answer and explanation is:
The most important evolutionary development that allowed terrestrial plants to grow tall was the evolution of vascular tissue, specifically xylem and phloem.
Vascular tissue provided plants with the ability to efficiently transport water, minerals, and nutrients throughout their structure. Xylem conducts water and dissolved minerals from the roots to the rest of the plant, while phloem distributes sugars and organic compounds produced by photosynthesis. This internal transport system allowed plants to overcome the limitations of diffusion, which restricts the size and height of organisms that rely solely on it for nutrient movement.
Before vascular tissue evolved, early land plants were small and low-growing because they depended mainly on direct water absorption and diffusion to transport nutrients and water. This limited their ability to grow tall or develop complex structures. The development of vascular tissue supported the creation of rigid, woody stems through the reinforcement of xylem cells with lignin, a complex polymer that strengthens cell walls. Lignin allowed plants to maintain structural integrity and resist gravity, which is essential for vertical growth.
Tall growth gave plants competitive advantages such as better access to sunlight for photosynthesis and the ability to disperse spores or seeds over a wider area. This evolution contributed to the rise of large trees and forests, which transformed terrestrial ecosystems by creating new habitats and influencing global climate.
In summary, vascular tissue was critical for terrestrial plants to grow tall because it enabled efficient internal transport of water and nutrients and provided structural support. Without this innovation, plants would have remained small and restricted to moist environments where water could be absorbed and transported by simpler means. The evolution of vascular tissue marks a key step in plant adaptation to life on land and the development of diverse, tall plant forms.