Problem 9 - Biology: The Dynamic Science

Question

A student left a carrot in her refrigerator. Three weeks later she noticed slender white fibers growing from its surface. They were not a fungus. Instead they represented: a. lateral roots on a taproot. b. adventitious roots. c. root hairs on a fibrous root. d. root hairs on a lateral root. e. young prop roots.

Step-by-Step Solution

Answer

The slender white fibers growing from the surface of the carrot represent root hairs on a lateral root (d).

Step 1: Understand the question

The question is about identifying the type of roots that have grown on the surface of a carrot that has been left in a refrigerator for three weeks. Knowing that carrots are taproots, the slender white fibers observed must be related to this kind of root system.

Step 2: Eliminate incorrect options

Understanding that a carrot is a taproot will help us eliminate options that are inconsistent with this type of root. A fibrous root (option c), adventitious roots (option b), and young prop roots (option e) can be eliminated, as they are not typically associated with a storage organ like a carrot.

Step 3: Choose the correct option

Since a carrot is a taproot, the slender white fibers cannot be lateral roots (option a) because they are not the main root but instead grow from a taproot. Therefore, they should be root hairs, which means that the correct option is (d) root hairs on a lateral root since these root hairs are growing from the carrot, a taproot, and are a common means by which roots increase their surface area to absorb water and nutrients.

Key Concepts

Root Hairs

Root hairs are tiny, hair-like structures that extend from the outer layer of a plant's root cells. Found mostly on younger parts of the root system, they have the important role of maximizing the surface area through which the roots can absorb water and dissolved minerals from the soil.

In the case of the carrot left in the refrigerator, the slender white fibers are actually root hairs that developed as the carrot attempted to grow in its confined environment. Unlike the larger structures of the root system, root hairs are delicate and typically only last for a few days before new ones replace them. They are so small they can penetrate the tinier spaces in the soil, which allows them to absorb moisture and nutrients effectively.

Lateral Roots

Lateral roots are part of the intricate network that makes up a plant's root system. Emerging from the main taproot, lateral roots branch out horizontally and are crucial for providing structural support to the plant and increasing the area for absorption.

They are different from root hairs in that they are larger and can become woody, providing anchorage to the plant. The key distinction drawn in the carrot scenario was recognizing that the slender white fibers were not these structural lateral roots, but instead the more delicate and ephemeral root hairs growing directly from the lateral roots.

Adventitious Roots

Adventitious roots are roots that grow from parts of the plant other than the primary root system. They can emerge from stems, leaves, or even old roots and often arise in response to stress conditions, such as waterlogging, injury, or propagation efforts.

Different from both root hairs and lateral roots, adventitious roots can give rise to new plants in some cases, and are a form of asexual reproduction. In the context of the carrot in the fridge, understanding the distinction between the common roots of a taproot system and the specialized adventitious roots helped in deducing that the slender white fibers were not adventitious but were instead root hairs growing out from the surface of the carrot.