BOTANY LABORATORY PRACTICAL (PLANT ANATOMY AND MORPHOLOGY) - O.A. SHEVCHUK - 2014

MORPHOLOGICAL AND ANATOMICAL STRUCTURE OF THE ROOT

Background information. The ROOT is an underground vegetative axial organ characterized by unlimited apical growth and The primary function of absorbing Water and nutrients. Characteristic Features of the root include: the absence of leaves and their modifications; the presence of a root cap; radial Symmetry; the lack of chlorophyll and Stomata; and positive geotropism.

Based on their origin, roots are classified as primary (main), lateral, and adventitious. The main root, or the root of the first order, develops from the embryonic root of the seed. As a result of branching, lateral roots of the second order depart from the main root, which in turn give rise to roots of the third and subsequent orders. Roots that form on leaves or shoots (and their modifications) are called adventitious roots (as seen in corn and onions). Lateral roots also branch out from adventitious roots.

The entire set of a plant's roots is called The Root System. There are two MAIN TYPES OF root systems: taproot and fibrous. A taproot system features a well-developed main root that stands out among the lateral roots by its robustness and length. A fibrous root system lacks a main root or has a poorly developed one, with the bulk of the root mass consisting primarily of adventitious roots. If a plant possesses main, adventitious, and lateral roots, its root system is referred to as mixed.

The primary Functions of the root are the absorption of water and minerals and the anchorage of the plant in the soil. In many plants, roots also perform A number of auxiliary functions, resulting in various modifications. The most significant root modifications are storage roots—root crops (developing on the main root axis) and root tubers (formed through the transformation of lateral roots). In addition, plants may feature stilt roots, respiratory roots (pneumatophores), aerial roots, clinging roots, etc.

A specialized function of the root is its ability to form symbioses with Fungi (mycorrhiza) and Bacteria (root nodules).

Anatomical Structure of the root. The root has a relatively consistent structure. In a Cytology/practical/54.html">Longitudinal section of the root, four distinct zones can be identified, differing in anatomical Structure and function: 1) Cell Division; 2) elongation (growth); 3) root hairs (absorption); and 4) branching.

The division zone is represented by meristematic tissue (the apical meristem/growing cone) covered by the root cap. A key feature of this zone is continuous cell division and an increase in root mass. The length of the division zone is 3–4 mm. In the elongation zone, Cells stretch along the axis of the root, acquiring a permanent size and shape, which drives root growth. The length of this zone is several millimeters. The root Hair zone is characterized by cellular specialization. Here, root hairs, vessels, sieve tubes, and fundamental and other Tissues are formed; therefore, this zone is also referred to as the zone of cell specialization. In the branching (vascular) zone, lateral roots are formed, and other developmental changes take place.

Particularly important changes occur in dicotyledonous plants. In these plants, a secondary meristem—the cambium—is formed from permanent tissues and the pericycle, driving the Introduction/11.html">Secondary structure of the root. This leads to changes in both the central cylinder and the peripheral region during the transition from primary to secondary root structure. In some plants (e.g., beets), In addition to the main cambium ring, several additional rings are formed, which differ from the primary one in origin and activity. These drive the substantial thickening of beet roots, a structural type known as tertiary.

TOPIC 1. ROOT MORPHOLOGY AND METAMORPHOSIS

General Remarks. A young plant begins to develop from the root as it transitions to an independent mode of life. This results in The formation of various types of roots, modifications, and root systems that anchor the plant in the soil, supply it with water and dissolved minerals, and perform auxiliary functions. Knowledge of root Morphology, modifications, and their properties enables the application of appropriate agricultural practices for cultivating crops for various purposes.

Objective: to study the MORPHOLOGICAL STRUCTURE OF the root, as well as the developmental Features of the main, lateral, and adventitious roots.

Materials and equipment: herbarium specimens of root systems (corn, lamb's quarters, tomato, lupine), seedlings of peas, beans, wheat, corn, and pumpkin at various Selection/3.html">Stages of development; root crops such as beets, radishes, carrots; dahlia root tubers, permanent micro-slides, laboratory equipment.

Tasks

1. Examine the Structural Features of wheat (Triticum aestivum) and common bean (Phaseolus vulgaris) seedlings.

2. Examine the shapes of roots in various plant species.

3. Examine the types of plant root systems.

4. Examine plant root modifications.

5. Complete Table 1: Structure of Root Systems.

Class="right">Table 1

Label the drawings and draw Conclusions.

QUESTIONS FOR SELF-assessment

1. How are root systems classified according to their origin and relationship to the substrate?

2. Which root is referred to as the primary root?

3. Characterize the taproot system.

4. Name the types of branching in root systems.

5. What is the difference between various Types of Root systems?

6. What is the difference between ectomycorrhiza and endomycorrhiza?

7. Why are mycorrhizae and root nodules considered symbiotic structures?

8. Name the main modifications of the root.

9. From which morphological parts does a root crop develop?

10. What is THE ORIGIN OF root tubers and what function do they perform?

11. What are adventitious and lateral roots?