Final answer:
Plants first appeared on land during the Silurian Period, when vascular plants evolved and developed specialized tissues for water and nutrient circulation.
Step-by-step explanation:
The first appearance of plants on land occurred during the Silurian Period, which took place from 440-410 million years ago.
During this period, vascular plants appeared, which had specialized tissues to circulate water and nutrients throughout their bodies, allowing them to grow larger than earlier nonvascular plants.
This development marked an important milestone in the colonization of land by plants.