Underground and Aerial Stem Modifications

Introduction

The experiment titled “Underground and Aerial Stem Modifications” aims to investigate the modifications shown by underground stems in plants like garlic, onion, ginger, potato, and yam and aerial stems in plants like Opuntia, Lemon, and Vitis. Underground stems are plant parts that are modified from stem tissue that exists under the soil surface. 

The stem is the ascending part of the axis, bearing branches, leaves, flowers, and fruits. It develops from the plumule of the embryo of a germinating seed. The stem conducts water, minerals, and photosynthates. In some plants, the stem undergoes modifications to perform additional roles, such as food storage, support, vegetative propagation, and protection.

Procedure

• Closely observe the shape and external morphology of each of the plant specimens.
• Draw diagrams and also observe the morphological differences between the specimens.

Observation

Underground modified stems in garlic and onions are known as bulbs. The bulb in garlic is formed by the overlapping of many nodes in the condensed stem. The onion bulb is a modified stem since it has a large number of fleshy scale leaves. Underground modified stems in ginger are known as rhizomes. It has nodes and internodes.

On the nodes, scale leaves are formed, which bear buds in their axils. Underground modified stems in potatoes are called tubers. The presence of an eye that is a node in a potato indicates that it is an underground plant part, which is a modified stem. An underground modified stem in yam is called a corm. It is a condensed type of rhizome that grows vertically. There are distinct circular nodes and internodes on the corm. Scale leaves and axillary buds grow from the nodes. Underground stem modification helps plants store food material.

Aerial stem modifications are shown in plants like Opuntia, Lemon, and Vitis. The stems of the Opuntia plant are modified aerially into phylloclades to perform photosynthesis. The stems of the lemon plant are modified aerially into thorns for protection. The stems of the Vitis plant are modified aerially into tendrils to provide support for climbing.

FAQs on Underground and Aerial Stem Modifications