Plants and animals alike need nutrients to survive. But without mouths, how do plants get the necessary nutrients and energy for life? You might be vaguely aware that plants use their roots to absorb nutrients – and plants need sunlight, right?
But how do roots and sunlight come together to help a plant grow? Unless you’re a botanist or you’re in a biology class right now, there’s a good chance you could use some reminders on how plants get nutrients.
We’ll try to keep this complex topic as simple as possible, so you don’t have to be a botanist to understand it!
What nutrients do plants need?
Let’s start with what plants need. Though their exact needs vary, most plants need three main nutrients to survive: Nitrogen (N), Phosphorous (P), and Potassium (K). These nutrients are commonly abbreviated as NPK, the letters of the elements on the periodic table. Without all three of these nutrients, plants cannot survive.
- Nitrogen gives plant leaves their dark green color and promotes growth.
- Plants use nitrogen to build amino acids, which are the building blocks of proteins.
- Phosphorus encourages cell division, helps root growth, protects plants from disease, and allows plants to produce flowers and seeds.
- Phosphorus is necessary for building up nucleic acid structures that regulate protein synthesis
- Potassium protects plants from diseases and encourages root growth. Potassium is also necessary for plants to make chlorophyll.
- Chlorophyll is the green pigment responsible for providing energy to plants by absorbing energy from sunlight.
- They use potassium to help open and close their stomata, which are similar to pores. Stomata allow plants to intake CO2 and build ATP, one of the basic energy units needed for life.
Plants need more than just three nutrients
You won’t be surprised to hear that plants need far more than just three elements to survive. Plants also need many other nutrients in smaller amounts: Carbon (C), Hydrogen (H), Oxygen (O), Phosphorus (P), Potassium (K), Iodine (I), Nitrogen (N), Sulphur (S), Calcium (Ca), and Iron (Fe) make up the other commonly-heard abbreviation, CHOPKINS CaFe.
This still leaves out Magnesium, Zinc, Copper, and several other common elemental needs of plants.
In short, plants need a lot of specific elements in their soil to survive. They use these elements to grow and build organic matter. Some elements play an important role in powering photosynthesis (quick refresher, plants use a process called photosynthesis to turn the energy from light, plus water and carbon dioxide, into energy).
Most of the soil beneath your feet right now is basically tiny crumbles of rock. The elements above are in the soil particles, but plants can’t get to them. Plants can’t just eat the dirt and extract the nutrients – they need a lot of water to be present. The water helps leach the elements away from the soil in simple, small chunks. The plants can then “drink” the water through their roots, getting nutrients mixed in as they go.
Good, fertile soil will have plenty of these nutrients. However, many of these nutrients are easily washed away by rainfall. Using fertilizer or other soil supplements will help keep your plants happy and healthy.
How do plants get nutrients from the soil into their roots?
When plants evolved to live on land, they needed a way to get to water to continue absorbing nutrients. That’s where roots came in handy.
Without getting way too complicated really quickly, let’s look at how roots work for a second.
Plants have complex root systems, consisting (generally) of either a long taproot that descends below the plant with some branches coming off of it, or a fibrous root system that consists of lots of small branch roots that spread out below the plant. If you’ve ever pulled a dandelion up by the roots, you know what a taproot system looks like. Fibrous root systems are more common in some sorts of grasses.
Plants with taproots do well in dry soil because their long taproot helps them explore for water below the earth. Plants with fibrous root systems are excellent for erosion control thanks to their complex root systems.
Fun fact, the deepest roots ever recorded were from a species of fig in South Africa with roots reaching 122 meters. Plants will do crazy things to find water!
Roots have many layers, somewhat like your skin. We won’t get into the names here – it gets complicated quickly! Just know that the outermost layer of the root is generally semi-permeable, allowing water to pass through into the root system.
Most nutrients are absorbed through root hairs near the very tip of the roots. Root hairs are ultra-fine roots that have a large surface area, allowing them to absorb even more water. The majority of plants also partner with different fungi to absorb even more nutrients from the water in the soil.
How fungi help plants get nutrients
Essentially, plants share some of its sugars in exchange for getting help absorbing other nutrients. These mycorrhizal (myco meaning fungi, rhizae meaning root) relationships are most common and beneficial in poor soil.
Think of a child’s toy with differently shaped holes for specific wooden blocks. Roots have microscopic systems that are not unlike these toys, allowing water and certain elements to pass through while keeping out other chemicals. Multiple other layers of the root help screen nutrients and water, store them and direct them through the vascular system of the plant for further use.
After plants absorb the water and nutrients through their roots, they transfer them through the vascular system up to the rest of the plant. Water is brought up to use for photosynthesis, while each nutrient is used for a different part of building the plant.
Roots are incredible, but with how many nutrients plants need, they can use a helping hand too!