Chapters
In this article, we will discuss what role do mineral ions play in the growth of plants. Additionally, we will also discuss the role of hormones in plant growth. So, let us get started.
Plants and Mineral Ions
Plants require minerals for their growth. These minerals are absorbed through the roots via active transport because mineral ions are dissolved in the water present in the soil. We know that plants produce their own food by using sunlight, water, and carbon dioxide by a process referred to as photosynthesis. Plants produce carbohydrates as a result of photosynthesis. Plants also contain other kinds of biological molecules, for instance, lipids, nucleic acid (DNA), and proteins. Plants cannot eat food like animals. Therefore, they make important biological molecules that are critical for their growth themselves.
Carbohydrates are composed of three important elements such as carbon, hydrogen, and oxygen. On the other hand, proteins also contain the additional element nitrogen. Some amino acids may be composed of other elements too.
Other chemicals in plants such as chlorophyll are made up of different types of elements such as magnesium and nitrogen. Now, what does that mean? It means that in the absence of these elements, plants are not able to photosynthesize or even grow properly. These elements are obtained by the plants in the form of mineral ions which they actively absorb from the soil through their root hair cells. The word “mineral” refers to any inorganic substance that occurs naturally.
In the next section of the article, we will discuss the importance of magnesium and nitrate ions for growth of the plants.
Importance of Magnesium and Nitrate Ions in Plant Growth
Plants need magnesium and nitrate ions to grow properly. If the plants do not get these minerals in sufficient quantity, then they show the symptoms of mineral deficiency. Like humans, mineral deficiency in plants affects their growth.
- Magnesium ions: Magnesium in plants is required to make chlorophyll. The deficiency of this mineral ion in the plant causes yellowing between the veins of the leaf. This condition in plants is known as chlorosis.
- Nitrate ions: Nitrate in plants is a source of nitrogen. It is required to make amino acids. The absence of nitrate ions makes plants deficient in proteins. Plants that do not get sufficient nitrogen experience stunted growth and yellowing of leaves.
Fertilizers to Combat Mineral Deficiencies in Plants
Fertilizers are employed to replace minerals required by the plants. Nitrogen fertilizers, for instance, ammonium phosphate and ammonium nitrate provide water-soluble sources of nitrogen to the plants so that they can absorb this nutrient through their roots. These fertilizers help the farmers to enhance the quality and quantity of their crops.
Although fertilizers are beneficial for the growth of the plant, however, their excess can cause several problems. Eutrophication occurs when surplus phosphate or nitrate enters the rivers or lakes from fields. This can prove fatal for fish and other aquatic animals.
Plant Hormones
Hormones play an important role in plant growth. The distribution of the plant hormones throughout the stems and roots is non-uniform which causes the growth of certain parts of the plants in a specific direction.
To survive, plants need water and light for photosynthesis. Plants develop responses known as tropisms to ensure that they grow towards sufficient sources of light and water. Tropisms are of two kinds:
- Positive tropisms: the growth of the plant is towards the stimulus
- Negative tropisms: the growth of the plant is away from the stimulus
Phototropism refers to the response of the plant towards the stimulus of light.
Responses of Different Parts of the Plant to Stimuli
In this section, we have listed down the response of different parts of the plant to stimuli.
- Stem: In the stems of the plants, the responses of light are referred to as a positive phototropism. It means that the stem grows towards the light.
- Root: In the roots of the plants, the responses to light are referred to as negative phototropism. It means that the root grows away from the light.
How Hormones Control Tropisms?
In this section, we will discuss how plant hormones control tropisms. Plants produce hormones known as auxins to coordinate and control their growth. It is pertinent for the plants to be able to grow in response to light known as phototropism and in response to gravity known as gravitropism or geotropism. It means that the growth of the shoots should be upwards, i.e., away from the gravity and towards the light. Due to this behaviour of the plants, their leaves can absorb sunlight. In other words, we can say that shoots must show a positive phototropic and a negative gravitropic response.
The roots need to grow downwards into the soil, away from the light and towards gravity. This is to ensure that the plant absorbs sufficient water and mineral ions from the soil. Hence, we can say that the roots show a negative phototropic response and a positive gravitropic response.
How do Auxins Control Growth in the Shoots?
Auxins belong to a family of plant hormones. They are generated in the tips of the growing roots and stems, which are referred to as apical meristems, and they can diffuse to the other parts of roots or stems. Auxins control plant growth by encouraging cell division and resulting in elongation in plant cells. Elongation in cells means that the plants get longer.
The concentration of auxins encourages different responses in stems and roots. In other words, we can say that the auxins generated in the tips of the roots and shoots diffuse to the cells behind the tips and can have the following effects:
- In the plants' shoots, auxins encourage elongation of cells (growth). It means that more auxin results in more cell elongation which in turn promotes more growth.
- In the roots, auxins hamper the elongation of the cells. In other words, less auxin means less cell elongation and lesser cell growth.
The auxin distribution in the shoots is influenced by gravity and light. On the other hand, auxin distribution in the roots is mainly affected by gravity only.
- If a root or shoot is placed on its side, then because of the gravity the auxins will accumulate along the lower side. Hence, the uppermost side will have a lower concentration of auxin.
- In the shoots, the lower side grows rapidly than the upper side. Hence, the shoots grow upwards.
- In the roots, the growth in the lower side is slower than that of the upper side. Because auxin hampers cell elongation and growth in the roots, the growth of the roots is downwards.
Remember that non-uniform distribution of auxins can result in unequal growth rates in plants shoots and roots.
Did you like this article? Rate it!
Loading...
i like the article
Hi Sam! Thank you! Great to hear that you found this resource useful.
welcome
Hi Suunu! Thanks for reaching out. Hope you’ve found this resource useful 😊!
i have learnt a lot which i did not know
am senior three student but this is cool
Am impressed
Am impressed
learning is the best
I like this one