Question

Cells of tracheary elements (tracheids and vessels) become dead at maturity and lose their protoplasm due to the deposition of lignocellulosic cell wall thickenings. This is an example of (a) growth (b) differentiation (c) dedifferentiation (d) redifferentiation.

Short answer

The process in which cells of tracheary elements become specialized is an example of (b) differentiation.

Step-by-step solution

Understanding the Definitions

First, understand the definitions of the terms provided in the options. Growth refers to an increase in size and number of cells. Differentiation is the process by which cells undergo a change to become specialized for certain functions. Dedifferentiation is the reversal of differentiation, where specialized cells revert to a more unspecialized form. Redifferentiation is the process by which dedifferentiated cells become specialized again.

Analyze the Given Information

The exercise states that cells of tracheary elements become dead at maturity and lose their protoplasm due to the deposition of cell wall thickenings. This process leads to cells becoming specialized, forming parts of the plant’s vascular system that are responsible for the conduction of water and minerals.

Connect the Information to the Definitions

Since cells of tracheary elements are undergoing specialization to perform a specific function within the plant, the process described in the exercise is an example of differentiation.

Key concepts

Tracheary Elements

Tracheary elements are a crucial component of the vascular system in plants, and they play a vital role in the transportation of water and minerals. These elements are specialized cells which include tracheids and vessel elements. As part of their development, these cells undergo a transformative process in which they become hardened and die. This occurs due to the deposition of lignocellulosic materials in their cell walls, which creates thickened, non-living conduits for water transport.

Despite their dead state at maturity, tracheary elements are of paramount importance in providing mechanical support to the plant as well as facilitating efficient water conduction from roots to leaves. The process through which these cells lose their protoplasm and become functionally mature is a hallmark example of cell specialization within the plant kingdom.

Cell Specialization

Cell specialization, or differentiation, is a fundamental biological process where generalized cells develop into specific cells with unique functions. This is essential for the complex organization of multicellular organisms like plants. In plants, differentiation is a coordinated sequence of events triggered by genetic and environmental factors, leading to the formation of a diverse range of cells, tissues, and organs.

Specifically referring to tracheary elements, differentiation involves the loss of protoplasm and the development of a strong cell wall composed of lignin, a complex polymer that provides rigidity. Through differentiation, cells adapt to perform a unique role effectively, contributing to the overall health, growth, and functionality of the plant.

Vascular System in Plants

The vascular system in plants, consisting of the xylem and phloem, serves a purpose analogous to the circulatory system in animals. It is responsible for the distribution of water, nutrients, and minerals throughout the plant. The xylem primarily transports water and dissolved minerals from the roots to the rest of the plant, and tracheary elements are a critical component of this tissue. The xylem’s effectiveness lies in its specialized structures - the tracheids and vessel elements - which allow for capillary action and the passive transport of fluids against gravity.

Understanding the differentiation of cells into tracheary elements provides insight into how the vascular system maintains plant vitality. Such specialized cells ensure that the vast network of branches and leaves receives adequate water supply, which is fundamental for photosynthesis and the plant's survival.