752
Plants are autotrophs that obtain carbon and oxygen by photosynthesis, and mineral nutrients and water from the soil. Nutrients required by plants are classified as either macronutrients or micronutrients depending on the amount needed. Micronutrients are often needed in such minute amounts that only sophisticated chemical experiments can determine their essentiality.
learning outcomes
You should be able to:
Identify nutrient deficiencies based on observations.
Explain difficulties involved in testing nutrient requirements for plant growth.
Methods for determining whether a particular element is essential for plant growth were established a century and a half ago, yet the essentiality of some elements was discovered only recently. Why?
Solutions that were thought to be pure were not, as they contained trace amounts of elements that could not be detected at the time. Recently developed chemical methods made it possible to detect essential elements that were not previously recognized.
If the young leaves of a plant are yellow, what nutrient deficiencies may be suspected? What if the yellow leaves are the oldest ones?
Yellow leaves in a young plant may be the result of an iron or a sulfur deficiency; yellowness in older leaves suggests a nitrogen deficiency.
You have seen that plants require a specific set of nutrients in large and small amounts for optimal growth and development. Let’s look at how a plant finds and takes up these nutrients from its environment.