People need essential vitamins, minerals, and proteins to live and reproduce, and plants also have a set of essential elements for similar purposes. This lesson discusses this subject.
A Plant’s Composition
You’ve heard that, by mass, the average person is about 60% water. This number is quite a bit higher for plants, which are roughly 85% water.
If you were to dry a plant out completely, meaning all the water content would be removed, 96% of the dry mass would be composed of carbohydrates and 4% would be composed of inorganic substances that come from the soil. These inorganic substances are called macronutrients and micronutrients, and they are essential elements of the plant life cycle.
Although they make up only 4% of a plant’s dry mass, the number of different inorganic substances found in plants numbers over 50. When something is said to be inorganic, we basically mean substances that do not contain hydrocarbons, carbon molecules bonded to hydrogen.These 50 inorganic substances, chemical elements, are sometimes essential to the plant. An essential element is an element that a plant requires in order to complete its life cycle and for the purposes of reproduction.
Think of essential elements as vitamins and minerals found in daily vitamin pills you may take. We need them, albeit in relatively small amounts, to live a healthy life and in order to one day reproduce.
To figure out which chemical elements are essential for all plants, scientists turned to hydroponic culture, the process of growing plants in mineral solutions as opposed to soil. In this process, the plant roots are bathed in a flask containing an aerated mineral solution.
The water is aerated so the roots have oxygen for cellular respiration.Scientists can then remove a mineral from the solution to see if it’s essential or not. So, if a plant doesn’t grow to full size because an element like nitrogen is left out, then we know nitrogen is an essential element.
Macronutrients ; Micronutrients
And what do you know? Nitrogen is indeed an essential element in plants.
The other essential elements include 9 additional macronutrients and 8 micronutrients.A macronutrient is an essential element required by a plant in relatively large amounts and a micronutrient is an essential element required by a plant in relatively small amounts. For your reference and completeness, let me list all of these guys.The 9 macronutrients in plants are largely carbon and oxygen, as well as hydrogen, nitrogen, potassium, calcium, magnesium, phosphorus, and sulfur. The 8 micronutrients in plants are boron, chlorine, copper, iron, manganese, molybdenum, nickel, and zinc.Macronutrients are important for the synthesis of the plant’s structure and critical organic molecules, like proteins. Micronutrients help speed up enzymatic reactions within the plants.
And although micronutrients are found in very small amounts in plants, they, like macronutrients, are once again essential for the plant’s growth, life, and reproduction. Plants that are deficient in an essential element can die or display symptoms of mineral deficiency. Just like people who are deficient in a nutrient will look sick or won’t grow to their full potential size, plants suffer similar consequences, depending on what they are deficient in.And like a doctor may suspect a deficiency of vitamin D or calcium if you have brittle bones, we can look for different signs of mineral deficiency in plants to diagnose exactly what they may be deficient in.
Time to play plant doctor!Let’s say that a desperate client brings in a beloved plant with chlorosis, or yellowing of the leaves of a plant; in this particular case, the young leaves of the plant. What’s your diagnosis? Yellowing of the leaves could be caused by a deficiency of magnesium! Or, in some cases, it might be a deficiency of iron that’s to blame. But how can you, as a plant doctor, figure out what the plant needs to survive if it can be a deficiency in magnesium or iron that’s causing the yellowing of the leaves?Well, this is where all that knowledge gained in plant medical school comes in! If a deficient nutrient, like magnesium, is able to move freely within a plant, then older parts of the plant suffer first. This is because younger, growing tissues are preferentially given as many of these mobile nutrients as possible. It’s like your parents would sacrifice their food for you in order to ensure you grow nice and strong if there isn’t enough food to go around for everyone.On the flip side, if a nutrient is unable to move around very freely within a plant, a nutrient like iron, then the young parts of the plant are affected first.
This is because older parts of the plant are able to more effectively retain these relatively immobile nutrients they gained in the past. They have a nice store, a nice emergency supply present in times of need that was built up during better times, while young leaves haven’t had the time to build up such stores.What’s your diagnosis, then, doctor? It’s a deficiency of iron in this case because only the plant’s younger leaves are affected by chlorosis.
Plants contain many inorganic substances, which are substances that do not contain hydrocarbons. Only 17 of the more than 50 inorganic substances found in plants are essential elements.
An essential element is an element that a plant requires in order to complete its life cycle and for the purposes of reproduction.An essential element can be either a macronutrient, an essential element required by a plant in relatively large amounts, or a micronutrient, an essential element required by a plant in relatively small amounts.These essential elements were discovered thanks to hydroponic culture, the process of growing plants in mineral solutions as opposed to soil.
After this lesson, you should feel confident in your ability to:
- Identify the important composition components of plants
- Define inorganic substances
- Determine what substances are essential
- Contrast micronutrients and macronutrients
- Explain the studies using hydroponic cultures