Question

Assertion: Apical and intercalary meristems are primary meristem. Reason: Both appear early in life and contribute to the formation of primary plant body.

Short answer

Both statements are true, and the reason is the correct explanation for the assertion.

Step-by-step solution

Understanding Apical Meristems

Apical meristems are located at the tips of roots and shoots and at the axillary buds of shoots. These structures contribute to vertical growth and are involved in primary growth that extends the length of the plant.

Understanding Intercalary Meristems

Intercalary meristems are located in plants at the base of nodes and leaf blades and contribute to the elongation of stems and leaves, this is also part of the primary growth of a plant.

Identify the relationship

Both the assertions and reasons are correct, and they have a direct relationship. Both Apical and Intercalary meristems are primary meristems because they appear early in the plant's life and contribute to the formation of the primary plant body.

Key concepts

Understanding Apical Meristems

Apical meristems play a pivotal role in the growth of a plant. Located at the very tip of roots and shoots, they are akin to the growth factories of the plant, consistently dividing and pushing the plant upwards and downwards. Think of these meristems as the captains of a spaceship, charting the course and leading the way for lengthening the plant.

In apical meristems, cells are in a constant state of division, contributing to what we call 'primary plant growth', which is essentially the plant growing longer or taller. Consider a sunflower seedling that eventually becomes a towering plant; the apical meristems are behind this transformation, laying down cells end to end, in a linear fashion. This extends not just to the main stem, but also to the branches, where apical meristems at the axillary buds come into play.

Moreover, putting this into the context of their role in primary meristems, these structures formulate the initial chapters of a plant’s life story, defining its height and reach into the soil.

Intercalary Meristems and Their Role

Now, if apical meristems are the leaders in vertical growth, intercalary meristems are the proficient assistants working within the plant body. These are situated in specific areas at the base of nodes or leaf blades in grasses and contribute significantly to elongating the stems and leaves.

What's fascinating about intercalary meristems is their ability to regenerate and elongate parts of plants that may have been nibbled on by animals or chopped off by the lawnmower. They ensure that grasses such as wheat and barley continue to grow even after parts have been removed. This is essential for the survival and resilience of these plants.

The role of intercalary meristems in primary growth is much like filling in the gaps - both literally, as they help the plant regain its form and figuratively, as they ensure continued growth even after potentially damaging events. They collaborate closely with apical meristems to construct the primary plant body and sustain its growth longitudinally.

The Significance of Primary Plant Growth

When we talk about primary plant growth, we're focusing on how a plant builds its basic structure; it's the groundwork for the plant's development, contributing to its height and root depth. Think of this as the construction of the plant's skeleton, where apical and intercalary meristems are the builders.

Each time the plant grows taller or roots stretch further down, it's primary growth in action. This type of growth is fundamental and happens early in a plant's life, setting the stage for future development and, eventually, the secondary growth that leads to increased girth.

The primary growth enabled by meristematic tissue is where the plant gets its initial shape and size, which is later embellished upon by secondary growth. Understanding the importance of primary growth helps in appreciating the foundation it creates for the full mature structure – much like laying the cornerstone for a building.