Plant Stem

A stem is a structural axis that supports the flowers, fruits and leaves of a plant. They are often specialised for protection, support, photosynthesis and asexual reproduction. Here, let’s discuss the structure and functions of the plant stem.

Plant Stem

The shoot system of a plant includes stems. Depending on the type of plant, they can vary in diameter and length from a few millimetres to hundreds of metres. The plant stems are often found above the ground, although some plants, like the potato, have underground stems. Herbaceous (soft) or woody (hard) stems are both existent in nature. Climbers have long and slender stems, and they hold on to supports and ascend, whereas creepers are comparatively weak-stemmed plants that spread out on the ground rather than being able to stand upright.

The plant stems’ primary job is to support the plant by holding its leaves, flowers and buds; occasionally, they also serve as the plant’s food storage structures. Additionally, they aid in the transportation of minerals and water that have been absorbed by the plant.

Plant Stem – Structure

Dermal tissue, ground tissue and vascular tissue are the three tissues that make up a stem.

• The dermal tissue, which covers the stem’s outer surface, often serves as a barrier, protector and regulator of gas exchange. Aquatic plant stems’ dermal tissues are not as waterproof as aerial stems.
• Around the vascular tissue, the ground tissue fills in and often primarily comprises parenchyma cells. It occasionally participates in photosynthesis. In woody stems, much or all ground tissues are destroyed.
• Long-distance transportation and structural support are provided by vascular tissue. Between different plant species, the vascular tissues are arranged very differently.

Growth in Plant Stem

In plants, growth happens as the stems and roots get longer. Some plants, particularly woody ones, thicken over the course of their lives. The growth in plant stems is of two types:

1. Primary growth – It is the lengthening of the shoot and root as a result of cell division in the shoot apical meristem. Herbaceous plants mostly go through primary growth; they rarely go through secondary growth or thickening.
2. Secondary growth – The plant experiences secondary growth, characterised by an increase in thickness or girth, and is brought on by cell division in the lateral meristem. Woody plants typically exhibit secondary growth, which is very noticeable. While some dicot stems experience secondary growth, monocots hardly ever do.

Functions of Plant Stem

The primary functions of plant stem are:

• Plant stems aid in the elevation and support of leaves, fruits and flowers. The stems give the plant a place to hold its flowers and fruits and also keep the leaves in the light. The stem tendrils of cucumber, grapevine and watermelon are used as support structures.
• It is also a nutrient-storing structure. Tuber (potato), rhizome (ginger), bulb (onion), and corm (colocasia) are stem modifications for food storage.
• It also helps in the transportation of minerals and water between the xylem and phloem in the roots and the branches.
• Stems also play a vital role in protecting the plant. Citrus and bougainvillaea stem axillary buds grow into sharp thorns as a defence. They guard the plants against animals.
• It functions in creating new living tissue. Plant cells typically last one to three years. Meristem cells found in stems produce new live tissue every year. Likewise, the lateral branches of jasmine, mint and the underground grass stems function as vegetative reproductive structures.
• Another notable function of plant stem is food assimilation. The flattened stem of the opuntia performs photosynthesis and contains chlorophyll.