Plant nutrition facts for kids
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Plant nutrition is the study of what plants need to "eat" to grow, stay healthy, and make seeds. Just like people need food with vitamins and minerals, plants need special chemical elements. Without these nutrients, a plant cannot grow properly or complete its life cycle.
Plants get their nutrients from three main places: the air, water, and soil. There are 17 essential nutrients that most plants need. The most basic ones are carbon, oxygen, and hydrogen, which they get from carbon dioxide in the air and from water. They get the rest, including nitrogen, from the soil. Some plants, like carnivorous plants, have unique ways of getting nutrients.
Plants need some nutrients in large amounts, called macronutrients. They need others in very small amounts, called micronutrients.
- The macronutrients are: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), carbon (C), hydrogen (H), and oxygen (O).
- The micronutrients (or trace minerals) are: iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), and nickel (Ni).
In the soil, these elements exist as salts, and plants absorb them as ions through their roots. Macronutrients like hydrogen, oxygen, nitrogen, and carbon make up over 95% of a plant's weight. Micronutrients are needed in tiny amounts, but they are still very important.
Most soils around the world provide enough nutrients for the native plants that grow there. However, when we use soil for farming, the nutrients can get used up. Farmers often add fertilizer to the soil to replace these nutrients and help crops grow strong and produce more food.
Contents
History of Plant Nutrition
For a long time, people knew that plants got basic nutrients like carbon, hydrogen, and oxygen from air and water. In 1840, a scientist named Justus von Liebig discovered that plants also need nitrogen, potassium, and phosphorus from the soil to grow well.
He came up with an idea called Liebig's law of the minimum. It says that a plant's growth is limited by the nutrient it has the least of. Think of it like a wooden barrel made of planks. If one plank is shorter than the others, the barrel can only hold water up to the level of that short plank. For a plant, the "short plank" is the nutrient it's missing.
How Plants Get Their Food
Plants absorb nutrients in two main ways. Their roots take up water and minerals from the soil, while tiny pores on their leaves, called stomata, "breathe in" carbon dioxide from the air. This carbon dioxide is used for photosynthesis.
The roots, especially the tiny root hairs, are key for absorbing nutrients. To get minerals from the soil, roots release special substances that help unlock the nutrients from soil particles. This makes it possible for the roots to absorb them.
Once inside the root, nutrients travel through special tissues called xylem and phloem. The xylem carries water and minerals up to the leaves, and the phloem transports the sugary food made during photosynthesis to all parts of the plant.
Helpful Friends in the Soil
Many plants have tiny helpers in the soil that help them get more food. This kind of partnership is called symbiosis. Two important types are:
- Bacteria: Plants like peas and beans, called legumes, have special bacteria called rhizobia living on their roots. These bacteria can take nitrogen gas from the air and "fix" it, which means turning it into a form the plant can use. This is called biological nitrogen fixation.
- Fungi: Many plants partner with mycorrhizal fungi. These fungi connect to the plant's roots and act like a huge web of extra-long roots. This web helps the plant reach much more water and nutrients from the soil than it could on its own.
What Nutrients Do for Plants
Each of the 17 essential nutrients has a special job to do inside the plant. They can be grouped into three main categories.
The Basics: From Air and Water
- Carbon (C): Carbon is the main building block of the plant. It forms the structure of almost everything in the plant, including sugars, starch, and cellulose (which makes up cell walls).
- Hydrogen (H): Hydrogen is needed to build sugars, which provide the plant with energy. Plants get almost all of their hydrogen from water.
- Oxygen (O): Oxygen is part of many molecules in the plant. Plants release oxygen during photosynthesis, but they also need to take in oxygen to perform cellular respiration, which is how they break down sugars to get energy.
Macronutrients: The Main Meal
- Nitrogen (N): Nitrogen is very important for making leaves green and helping the plant grow tall and strong. It is a key part of proteins and chlorophyll.
- Phosphorus (P): Phosphorus helps plants grow strong roots and produce flowers, fruits, and seeds. It is also vital for storing and using energy.
- Potassium (K): Potassium acts like a guard for the plant. It helps it use water well, fight off diseases, and stay healthy in hot or cold weather. It also helps control the opening and closing of the stomata on the leaves.
- Calcium (Ca): Calcium builds strong cell walls, which are like the plant's skeleton. It is especially important for growing new roots and leaves.
- Magnesium (Mg): Magnesium is a key part of the chlorophyll molecule. Without magnesium, the plant cannot capture sunlight to make food.
- Sulfur (S): Sulfur helps make important proteins and vitamins in the plant. It is also needed for chloroplasts to grow and work properly.
Micronutrients: Like Plant Vitamins
Micronutrients are needed in very small amounts, but a plant cannot survive without them.
- Iron (Fe): Iron is needed to make chlorophyll. Even though it's not part of the chlorophyll molecule itself, the plant can't make it without iron.
- Manganese (Mn): Manganese helps with photosynthesis and building chloroplasts (the plant's "solar panels").
- Zinc (Zn): Zinc is important for many plant processes and for growth. A lack of zinc can cause small, stunted leaves.
- Copper (Cu): Copper helps with photosynthesis and making strong cell walls.
- Boron (B): Boron is essential for making flowers, pollen, and seeds. It also helps move sugars around the plant.
- Molybdenum (Mo): Molybdenum helps the plant use nitrogen.
- Nickel (Ni): Nickel helps with nitrogen metabolism in the plant.
- Chlorine (Cl): Chlorine helps the plant balance its water and plays a role in photosynthesis.
Nutrient Problems
When Plants Don't Get Enough Nutrients
When a plant doesn't get enough of a certain nutrient, it is called a deficiency. The plant will show signs that it is unhealthy. These signs can help gardeners and farmers figure out what's missing.
- A common sign is chlorosis, which is when leaves turn yellow because they can't make enough chlorophyll. This often happens when a plant is low on nitrogen or iron.
- Another sign is stunted growth, where the plant is much smaller than it should be.
- Sometimes, you can tell which nutrient is missing by looking at which leaves are affected first. If older leaves at the bottom of the plant turn yellow, it's often a lack of a "mobile" nutrient like nitrogen. The plant moves the last bits of this nutrient to the new, young leaves. If the new leaves at the top are the first to look sick, it's usually a lack of an "immobile" nutrient like calcium or boron, which cannot be moved around the plant.
When Plants Get Too Many Nutrients
Just like not enough nutrients is bad, too many can also be harmful. This is called toxicity. For example, too much boron in the soil can be toxic to most plants and stop them from growing. It is important for plants to have the right balance of all the essential nutrients.
Nutrition in Farming and Gardening
Fertilizers
On farms, the same crops are often grown in the same soil year after year. This can use up the natural nutrients in the soil. To solve this, farmers add fertilizers. Fertilizers are like supplements that put the missing nutrients back into the soil, helping crops grow big and healthy.
Hydroponics
Hydroponics is a way of growing plants without any soil at all. Instead, the plants' roots are placed in water that is mixed with all the essential nutrients they need. This allows people to grow food in places with poor soil, or even indoors in controlled environments.
See also
