Flowering Plants – Brief Structure and Functions of Plants

A flowering plant has a portion above the ground and also a portion above the ground. Above, there is the shoot and bellow has the root. However this does not imply that anything grown below must be a root. The shoot is typically made up of a stem, which has leaves, buds and flowers.

The Stem

General Characteristics

Along the stem, there are leaves at regular intervals and a terminal bug, which is located at the growing point. The leaf springs along the stem at a point called the node. And along the length of the stem, between the nodes, is called the internode.

Typically the stem is erect and vertical but can be horizontal in some cases, such as strawberry runners.

Young stems are usually green which indicates they contain chlorophyll. The cells in young stems are living and obtain a supply of oxygen from the air through openings called stomata in a place called the epidermis. A thick woody fibrous tissue usually supports older stems, which are added layer on top of a layer. This is what causes the thickness to increase in the stem. Young cells are dependent on the rigidity and turgidity of their cells, the cylindrical distribution of their conducting tissues and the opposing stresses of the pith and epidermis. Throughout the stem there are tubes, which absorb water (in xylems by capillarity action) from the soil to the leaves and also food from the leaves to other various parts of the plant.

Functions of the Stem

1.The stem functions as a support of the shoot.

2.The stem also acts as a way to space out the leaves and so that they are able to receive adequate air and sunlight so the plant can process its own food.

3.The stem also allows the transport of water up the stem from the soil to the leaf by capillarity action and food from the leaves to other various parts of the plant.

4.Allows the flowers to be held above the ground thus assisting the chances of pollination by insects and the wind.

5.Lastly if the stem is green then further photosynthesis may occur producing more energy for the plant.

Structure Examples

A sunflower, which has a typical stem, is in the form of a cylinder. There is an outer layer of cells, which act like the skin called the epidermis. While the inner cells make up the cortex and pith. There are vascular bundles between the cortex and pith. These are specialized cells, which carry food and water.

What is the epidermis? The epidermis is a single layer of closely fitting cells. This makes it effective at holding its cylindrical shape that prevents the loss of water and allowing the protection from damage and preventing the entry of pathogens such as fungi, bacteria and dust. This layer is usually impermeable to most liquids and gases, However oxygen can enter while carbon dioxide can exit the plant only through the stomata in young cells or lenticels in much older stems. Lenticels are small gaps that appear in bark, which are usually slightly raised, oval or circular. The epidermis is normally in a strained state causing it to shrink along its length. This shrinking contributes to the rigidity of the stem.

What is the cortex and pith? Both of these are tissues that consist of fairly large, thin walled cells that pose air spaces between them. The air space system happens throughout the tissues that are living throughout the organism. The air spaces allow the air to circulate from the stomata or lenticels to the living regains of the stem. The cortex and pith help with the rigidity of the stem as it presses out against the epidermis causing the increase in length against the shrinking tendency of the epidermis. These type of tissues also help with the spacing of the vascular bundles. The only problem is that many stems tend to be hollow with a narrow band of pith, which is in the cortex.

The leaf

General Structure of the leaf

A leaf is usually green with a flat and thin look or a blade made from soft tissue of thin walled cells, which is supported by a stronger network of veins. The leaves are usually joined to the stem by a stalk, which then continues into the main vein. But there can be no leaf stalk on some occasions.

Functions of the leaf

The fundamental function of a leaf is to produce food in the form of carbohydrates by a process called photosynthesis. The water that is needed for this process is transported through the veins in the leaf, from the stem, and taken to the parts of the leaf where photosynthesis is occurring. Not only does the leaf receive water for photosynthesis, it needs a supply of carbon dioxide from the air. The air diffuses down its concentration gradient through the stomata into and out of the leaf depending on the gas. Sue to the flat shape of the leaf, it gives a satisfactory large surface area to the air. This helps facilitate a rapid absorption of oxygen and carbon dioxide. It also allows for a larger surface area to absorb sunlight which is also a fundamental requirement of photosynthesis. The leaf also contains chloroplasts which inside has chlorophyll.

When the chlorophyll pigment absorbs light and air it produces energy.


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