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Growing Plants 101 - Understanding the Basic Requirements, Processes, and Outcomes of How Plants Grow
Humans, animals, bacteria, insects, birds, viruses, fungi, and plants have one thing in common. They all have life. But, we all know that everything that has life must eat food. You probably already know where humans and animals get their food, right? Where?
So if animals and people, get their food from plants, other animals and from other living creatures like birds and insects, then we have an interesting question:
Where do plants get food from?
- Soil
- Dead plants and Dead Animals
- Sun
- Seeds
All the above choices seem trivial. Most of the time, we are told that plants get their food from the soil. But is that just one part or the whole truth?
According to VanDerZanden, a researcher at Oregon State University, there is one major difference between plants and animals. Plants make their own food. They manufacture food through the process of photosynthesis, which means “to put together with light.”
So, do we then conclude that soil and other nutrients (from manure and fertilizers) are not important for plant growth? How exactly do plants grow?
Let’s find the answers together. Stay with me!
- Growing Plants 101 - Understanding the Basic Requirements, Processes, and Outcomes of How Plants Grow
Understanding How Plants Grow
The Seed
We know that plant growth starts with the seed. You sow the seeds into the, and they germinate to become plants or crops. But, what do seeds need to become plants? So, they only need moisture, air, and the right temperatures. Seeds will die or fail to germinate in too high or too low temperatures.
Here is the science part of seed germination (I promise I will keep it simple). So, each seed contains enough energy that is used in the initial stages of germination. This energy is the food for the seedling and helps to to establish the seedling before it can start making its own energy through photosynthesis. Remember, photosynthesis requires a plant to have leaves.
So, the seed stores enough energy that is converted into food for the seedling (in presence of moisture) to help in the early stages of germination.
We will understand how this energy is stored in the seed. Let’s carry on.
Water, Light, and Carbon-dioxide(Air)
We know that, all plants have roots, stem, and leaves.
After successful germination, a plant will develop roots, and leaves connected by the stem. This means the plant is ready to start manufacturing food through the process of photosynthesis.
The plant will take Carbon-dioxide(CO2) from Air through the leaves leaves. Then, absorb Water(H20) from the ground through the roots. In presence of sunlight, Water and carbon-dioxide combine to make glucose or carbohydrate/starch(CHO). This is the process of photosynthesis. It converts photo energy from sunlight, into chemical energy that can be transported.
In science, we represent the process of photosynthesis as follows:
Carbon dioxide + Water + Sunlight = Sugar(glucose) + Oxygen
or
6CO2 + 6H20 + Energy => C6H1206 + 602
The glucose (or sugar) is transported from the leaves to the other parts of the plants where it is used, stored, or converted into complex energy compounds such as oils and proteins.
Therefore, this glucose, is the primary source of food for the plant and all its parts. The food products that the plant manufactures from this glucose are called photosynthates. The plant uses these foods to develop new parts and grow.
The excess glucose is not needed immediately by the plant. Instead, it is transported to the roots, fruits, or seeds.
This is interesting. Fruits are used by the plants as energy reserves. This means that fruits store food for the plant to use later. It’s the same thing people do. When the harvest is good, we do not eat everything, we save for the bad days.
Here is another interesting fact. Seeds store glucose for reproduction purposes. Remember when we talked about seeds earlier? We said that seeds have enough energy, to support the plant until it can grow roots and the first leaves. After that, the plant can start making its own food. This energy is stored by the plant from the excess glucose made during photosynthesis.
I hope you are making the connection. Photosynthesis happens in the leaves and produces glucose. Some of the glucose is used immediately for the plant to grow and develop. The rest is stored for futre use in the fruits and the seeds. The rest of the sugar is transported to the roots. It is important to know this because, if your crops have healthy leaves, they make more glucose, which increases yields and produces better seeds.
You’re making great progress. Now that you know how leaves, fruits, and seeds help to grow the plant, How about the roots?.
Come along! Let’s find out together…
The Roots of the Plant (and the underworld)
How do plants grow below the ground? The roots, the soil nutrients, and the microorganisms …
The roots play the most important role to support a healthy growth of the plant. I usually compare roots to the heart in humans. Although the heart does not make food or oxygen, we cannot live without it. Roots do not make food, but they absorb water (Does this make them more like lungs? 🤔)
The most obvious function of the roots is to absorb water and nutrients from the soil. They also support the plant firmly into the soil to prevent uprooting by wind or excess water(like floods).
The roots also transport nutrients and water from the soil to the upper parts of the plant such as the stem and leaves.
There is more: Roots store excess glucose/sugar and other nutrients, produce root exudates, and interact with soil microorganisms.
Storage of sugar and nutrients
Similar to fruits and seeds, the roots also act as stores for excess glucose to reserve nutrients and carbohydrates. Plants store excess sugars, starches, and other nutrients in their roots during periods of abundant resources. These reserves can be mobilized during times of stress, disease, or when additional energy is needed for growth and reproduction.
For example, potatoes and carrots among other tubers, use their roots as storage reserves and also as seeds for reproduction purposes.
Production of root exudates
Root exudates are organic compounds produced by the roots of the plant and strategically released into the soil. Think of exudates like special chemicals.
To me, this is one of the most important functions of the roots in supporting the growth of crops that all farmers should understand. First, it clearly shows us that plants are intelligent. WHY? Because root exudates are products which the plant releases strategically to the area around the roots to help it to grow.
Here, we see that for a plant to grow, it is not enough to be aware of its environment. It also needs to control that environment. This control is achieved through root exudates.
Here is a question: Why do plants need to produce root exudates (these organic compounds) which are not wastes, and release them to the soil - intentionally? Why does a plant need to control its surrounding?
To answer these questions, we need to know what root exudates are made of.
According to a research study by Koo, Adriano, Bolan, and Barton (in 2005), root exudates are a mixture of soluble organic substances, which may contain sugars, amino acids, organic acids, enzymes, and other organic substances. The specific items change depending on the type of plant and the environmental conditions.
Functions of Roots exudates (Why do plants release root exudates?)
Root exudates (chemicals) are important. Let’s see why…
- First reason, nutrient mobilization. For plants to absorb nutrients from the ground, these nutrients must be soluble in water. Most fertilizers contain minerals or nutrients that are soluble. That is why they are easily absorbed by the plant. But, manure and other organic fertilizers contain complex nutrients that must be broken down before they are absorbed by the roots. The plant releases root exudates or chemicals with specific compounds such as organic acids. The chemicals react with complex minerals and nutrients in the soil, which enhance the solubility. The make them mobile, so they can move around. The soluble nutrients are more accessible and ready for plant uptake.
- When plants release root exudates/chemicals, they attract living micro-organisms to the area around the plant roots. You may wonder, is this a good thing? Yes! As we will discuss in more details in the next part, an increase in micro-organisms or microbial interactions in the area around the plant’s roots(which is called rhizosphere) creates a healthy relationship between the microorganisms and the plant. This symbiotic relationship between the plant and micro-organisms(microbes) contributes to nutrient mobilization, enhances disease resistance, and promotes overall soil health.
- Root exudates also influence neighboring plants. By strategically releasing chemicals into the environment, the exudates affect the growth of surrounding plants and micro-organisms. So, this will create a competitive environment. Just like any competition, the chemicals will inhibit, discourage, and prevent the competing plants from developing. In farming, this is a very good thing to know. There are some crops you cannot plant together, because one will not do well. In some other cases, some plants complement each other and we plant them together most of the time. So, the bottom-line is, the roots release some chemicals that can discourage some competing plants from growing, or encourage other beneficial plants to grow.
- Additionally, the organic acids released can modify the pH of the soil around the plant roots(rhizosphere), impacting nutrient availability and microbial activity in the soil.
Note: Rhizosphere is the soil area around the plant roots, that the plant can influence or change by releasing or absorbing nutrients.
From the above functions of the root exudates, we can conclude that they help the plant communicate and transact with the soil. First, the plant learns about its environment. Second, it sends specific organic compounds or chemicals. These compounds are consumed by (1.) microorganisms like bacteria, fungi, earthworms, etc. (2.) other plants living in the soil around the plant’s roots (the rhizosphere).
Therefore, the plant uses the root exudates to selectively control its environment. But why does the plant need to provide food for microorganisms?
This brings us to our next interesting component of plant growth and a function of roots. The interaction with Soil Micro-organisms.
Interaction with Microorganisms or Microbes
Microbes or micro-organisms are small living things that we find in the soil.
But before that, let’s do a quick summary of what we have found so far.
A Recap
The first food consumed by the crop comes from the seed. After germination, the plant uses its new roots to fetch water from the roots. The water is transported to the newly formed leaves.
At the leaves of the young plant, photosynthesis combines water, carbon-dioxide (from air), and sunlight to create sugar/glucose (also called carbohydrates/starch) and oxygen.
The sugar is the original food or energy for the different parts of our plant. Extra sugar is stored in fruits, seeds, and roots. The plant uses the roots to release some of this sugar into the soil as root exudates to feed microorganisms and control its surrounding soil environment (rhizosphere).
Now, let’s get our hands dirty. Let us talk about soil and microorganisms.
What are Microorganisms?
Microorganisms or microbes are tiny living creatures that live as single cells or form colonies.
We find microbes in all types of environments. You will find micr-organisms in the human skin, human stomach, animal guts/digestive system, rainfall, caves, plants, and soils among others. It is estimated that a single gram of soil can contain up to several billion bacteria. That is a lot of bacteria.
How Soil Microbes work
Microbes need an energy source, carbon, and other nutrients to grow and survive in their environment. Just like we humans, they need food. So, what do microbes eat? Well, many microbes use carbon-based materials as their food and source of energy. They use this energy to build their cells.
In soils, microbes get this carbon(food) from dead parts of a plant such as leaves and fruits. They also get food from the glucose released by the plant roots as root exudates. Also, they eat living or dead soil organisms, including other microbes, worms, and insects.
These carbon-based materials from living or dead living things are known as soil organic matter. Soil organic matter come in two categories: “active” and “stable”.
- Active soil organic matter is ready to be consumed by the microorganisms or microbes. It’s like a ready meal. Microbes consume these directly from the soil.
- Stable soil organic matter cannot be directly consumed by the microorganisms. So, the bacteria and other microbes cannot use them as food. Instead, they become part of the soil minerals or aggregates. Soil minerals are less prone to rapid decomposition. Stable organic matter contributes to soil structure, water retention, and long-term carbon sequestration; thus maintaining soil fertility and structure over time.
In other words, microbes or microorganisms, feed from decaying active organic matter to release nutrients and energy(glucose). These nutrients and glucose become food for the plants and other life forms in the soil.
How Microbes breakdown organic matter into nutrients(Plant food)
The microbes/microorganisms break down complex organic compounds into simple nutrients for the plant to consume.
Microbes, including bacteria and fungi, consume organic matter as a source of energy and nutrients. By consuming the organic matter, they secrete or produce enzymes. These enzymes break down complex organic compounds into simpler molecules.
The breakdown of organic matter results in the production of simpler organic compounds, such as organic acids, amino acids, and sugars, along with various byproducts.
Microbes utilize a portion of the broken-down organic matter for their own energy and growth. In the process, they produce metabolic byproducts, such as organic acids, enzymes, and other compounds, into the surrounding soil.
All these products from bacteria and other microbes are essential in developing and maintaining a healthy soil. For example, one of the products is organic acids which improve mineral solubility, making nutrients more available for plant uptake. This is what we need for our plants.
The breakdown of organic matter by microbes releases nutrients like nitrogen, phosphorus, and potassium, along with other micronutrients, in a plant-available form.
Nutrients may exist in many forms. Not all nutrients can be consumed by the plant. Some become a part of the soil to contribute to soil structure. Others become food for bacteria and microbes. The rest become food for the plants. For instance, nitrogen may be present as ammonium (NH4+) or nitrate (NO3-) depending on microbial activities.
Takeaway on Microbes: The soil consists of a many diverse microorganisms which contribute to essential soil and plant activities including nutrient recycling, protecting soil structure, and pathogen/disease suppression.
Plant Uptake of Nutrients
Plants absorb the nutrients released by microorganisms through their root systems, and transports them to different parts for growth and development.
Additionally, fertilizers provide extra nutrients which are ready to be consumed by the plant.
Together, these nutrients contribute to the plant’s nutritional needs and support various physiological processes, including protein synthesis, cell division, and overall growth.
The remaining nutrients feed the microorganisms and build soil structure. Their presence in the soil increases root development in the plant. A large and healthy root system increases absorption of NPK nutrients and water, and also leads to larger plant size. A large plant has many leaves. Therefore, it can produce more energy through photosynthesis, have more and large fruits. These features translate to more yields for farmers.
Conclusion
That is it. That is the basic science showing us how crops grow.
In Summary:
- Seeds germinate to develop leaves and roots. The roots absorb water from the ground. The leaves capture sunlight and carbon dioxide.
- Photosynthesis occurs on the leaves. Carbon dioxide, water, and sunlight combine to create glucose/sugar(starch).
- Plant uses some of that sugar to promote growth and development of various parts. Additional sugar/glucose is stored in fruits(for future use) and seeds(for reproduction purpose).
- The roots release some sugar as root exudates into the soil. Root exudates are used to control the plant’s environment(rhizosphere).
- Microorganisms in the soil ingest the released sugars among other organic matter in the soil. The microbes breakdown the organic matter into simple nutrient compounds.
- Some of these nutrients released by the microbes are absorbed by the plants. Other more complex produces of microbes become food for other microbes, or become part of the soil to enhance soil structure and encourage root development.
- Plants utilize nutrients available in the soil (from microbes and fertilizers) to supplement the sugar produced and stored from photosynthesis to achieve its growth requirements.
At the end of the day, a healthy plant has access to enough sunlight (to optimize photosynthesis), and a rich soil ecosystem with diverse microbes (for high nutrient concentration). Access to required nutrients and efficient photosynthesis are the two main requirements for plant growth.
We must strive to find ways to grow our plants and crops in a sustainable way. In our day-to-day farming activities, let us aim to improve the health of our soil. In return, the soil provides our crops with the nutrients they need, when they need.
Healthy soil equals healthy plants. This increases crop yields, beautiful farms, and a healthy environment. The harvests increase, our health improves, and our pockets grow fatter.
Grow healthy crops. Live a healthy life.
References
- Oregon State University, & VanDerZanden, A. M. (2008, January 7). Plant Growth and Development. Retrieved from Ag - Community Horticulture/Landscape website
- Koo, B-. J., Adriano, D. C., Bolan, N. S., & Barton, C. D. (2005). ROOT EXUDATES AND MICROORGANISMS. Encyclopedia of Soils in the Environment, 421–428.
- Liao, Z., Fan, J., Lai, Z., Bai, Z., Wang, H., Cheng, M., … Li, Z. (2023). Response network and regulatory measures of plant-soil-rhizosphere environment to drought stress. Advances in Agronomy, 180, 93–196.