Question

Uneven thickened primary walls with elongated cells is called ____.

• A. Collenchyma’s tissues
• B. Phloem tissues
• C. Xylem tissues
• D. Parenchyma tissues

Hint:

Key structural markers to differentiate simple permanent tissues at a glance: - Parenchyma: Uniformly thin walls (living). - Collenchyma: Unevenly thickened primary walls at corners (living). - Sclerenchyma: Uniformly highly thickened lignified secondary walls (dead).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Simple permanent tissues are classified as parenchyma, collenchyma, or sclerenchyma depending on the nature of their cell wall depositions and cell vitality.

Step 2: Detailed Explanation:
Collenchyma tissue consists of living, elongated cells with primary cell walls that show uneven thickening, particularly localized at the corners. This heavy localized deposition is made up of cellulose, hemicellulose, and pectin. Because it consists of living cells with localized flexible thickening, collenchyma provides mechanical support and elasticity to young, growing plant organs (like petioles and young green stems) without restricting their expansion.

Step 3: Final Answer:
Cells with unevenly thickened primary walls are characteristic of Collenchyma tissues.

Answer 2

The description given, elongated living cells with unevenly thickened primary walls, points to a specific simple tissue type. Checking each option against this description rules out the ones that don't match on wall structure or cell type.

1. Collenchyma's tissues: are made of living, elongated cells whose primary walls thicken unevenly, especially at the corners, due to extra deposits of cellulose, pectin, and hemicellulose. This matches the description exactly and gives young stems and petioles flexible support while they are still growing.
2. Phloem tissues: are a complex tissue made of several different cell types (sieve tubes, companion cells, phloem parenchyma, and phloem fibres) working together to transport food; it is not a single simple cell type with a specific wall-thickening pattern, so this description does not fit.
3. Xylem tissues: are also a complex tissue containing tracheids and vessels with walls that are typically thickened uniformly and heavily lignified for water transport and support, unlike the uneven, non-lignified thickening described here.
4. Parenchyma tissues: normally have thin, uniformly built walls without any localized thickening, since their main role is storage rather than mechanical support, so they do not match the described uneven thickening.

Only one of these tissue types is defined specifically by living, elongated cells with unevenly thickened primary walls.

Therefore, the correct answer is Collenchyma's tissues.