Final answer:
The apical meristem is responsible for primary growth in plants, contributing to the lengthening of roots and shoots. It is a key tissue for plants to reach vital resources such as light and water, differing from lateral meristems which are involved in secondary growth, increasing plant girth.
Step-by-step explanation:
The apical meristems are located at the tips of roots and shoots, enabling plants to extend in height and access more space and resources such as light and water. This is in contrast to lateral meristems and intercalary meristems, which are responsible for secondary growth and growth in girth or special cases of growth in length, respectively. The vascular cambium and cork cambium are two types of secondary meristem that contribute to the increase in girth of the plant. Primary growth is essential for plants as it allows them to explore their environment vertically through the elongation of shoots for sunlight and roots for water and minerals. This growth process is characterized by the division of undifferentiated cells in the apical meristem that give rise to specialized tissues of the plant through differentiation.