Question

Read the following statements and select the correct option. Statement 1: Anatomically, all the tissues present on the inner side of endodermis such as pericyde, vascular bundles and pith constitute the stele. Statement \(2:\) Eustele is the stele in which voscular bundles are arranged in the form of a ring as is present in dicot stems. (a) Both statements 1 and 2 are correct and statement 2 is the correct explanation of statement 1 . (b) Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1 . (c) Statement 1 is correct and statement 2 is incorrect. (d) Both statements 1 and 2 are incorrect.

Short answer

Both statements 1 and 2 are correct but statement 2 is not the correct explanation of statement 1.

Step-by-step solution

Understanding terms related to plant anatomy

Familiarize with the terms 'endodermis', 'stele', 'pericycle', 'vascular bundles', and 'pith'. The endodermis is the innermost layer of the cortex in plant roots. The stele is the central part of the root or stem containing the pericycle, vascular bundles, and pith. Pith is the central tissue inside the stele.

Assessing Statement 1

Evaluate the accuracy of Statement 1. By definition, the stele includes all tissues inside the endodermis which are the pericycle, vascular bundles, and pith. Therefore, Statement 1 is correct.

Understanding eustele

Know that eustele is a type of stele found commonly in the stems of dicots and some monocots, characterized by a ring of separated vascular bundles.

Assessing Statement 2

Verify the accuracy of Statement 2. Since eustele indeed refers to the arrangement of vascular bundles in the form of a ring as found in dicot stems, Statement 2 is correct.

Determining the relationship between the two statements

Analyze whether Statement 2 is a correct explanation of Statement 1. While both statements are correct, they describe different aspects of plant anatomy. Statement 1 describes the components of the stele, and Statement 2 defines a specific type of stele (eustele). Statement 2 does not explain Statement 1 but rather provides additional information about a type of stele configuration.

Key concepts

Endodermis

The endodermis is a critical layer of cells in plants, signifying the boundary between the outer cortex and the internal vascular tissue. Unique to roots and some lower plant stems, the endodermis acts much like a gatekeeper, determining which substances pass from the soil into the plant's vascular system. Its cells are tightly packed, and they contain a waterproof strip known as the Casparian strip that forces water and dissolved nutrients to pass through the cells—rather than between them—to reach the inner vascular tissue. The Casparian strip ensures that harmful substances are filtered out and nutrients are absorbed efficiently.

Stele

The stele is the innermost part of the plant stem or root, encompassing all tissues inside the endodermis. Think of the stele as the 'core' of the plant's plumbing system, housing the vascular bundles responsible for transport, and the pericycle, which is involved in root and shoot branching. In a cross-section of a root or stem, the stele is visually distinct from the surrounding layers and provides structural support in addition to its transport functions. Different plant groups have different types of steles, which evolved in response to growth habits and environmental challenges.

Eustele

Eustele represents an evolutionary advancement in plant vascular system design. It's typically found in the stems of dicots and some monocots, characterized by a distinct ring of vascular bundles containing both xylem and phloem. In eustelic stems, these vascular bundles are separated from each other by layers of other stem tissues, which can lead to the development of the classic 'woody' stem observed in trees and shrubs. The evolution of eustele enabled plants to better support larger structures like leaves and flowers and to more effectively transport water and nutrients.

Pericycle

The pericycle, a tissue layer found within the stele, lining the outer boundary of the vascular bundles, plays a pivotal role in the capacity of a plant to expand its root system. It is from the pericycle that lateral roots originate and emerge; this cell layer retains its ability to divide even when the plant is mature. Being meristematic—capable of cell division—the pericycle contributes not only to adding more lateral roots but also aids in the plant's ability to heal from damage or respond to environmental stresses, which underscores its significance in overall plant growth and regenerative capabilities.

Vascular Bundles

Vascular bundles are the lifelines of plants, akin to our blood vessels. They are composed of xylem, which transports water and minerals upwards from the roots, and phloem, which distributes sugars and other metabolic products downwards from the leaves. These bundles can be scattered in some plants, as seen in monocots, or organized into a ring as in eustelic plants. The layout of vascular bundles significantly affects a plant's growth pattern and strength, enabling it to stand upright, grow taller, and efficiently manage resource distribution throughout its structure.

Pith

The pith, found in the center of stems and roots, comprises soft, spongy parenchyma cells that are often rich in starch. Its primary function is to store nutrients and help in the transport of water and solutes across the plant. In some plants, the pith dries out and provides structural support, while in others it remains active throughout the plant's life, serving as a storage area. It's a fascinating part of the plant's anatomy because it appears relatively simple but has essential functions that support the plant's growth and survival.