Question

Which one of the following statements can best explain the term critical concentration of an essential element?
A. Essential element concentration below which plant growth is retarded.
B. Essential element concentration below which plant growth becomes enhanced.
C. Essential element concentration below which plant remains in the vegetative phase.
D. None of the above

Answer 1

Essential elements are the set of elements required by life forms to maintain normal growth, development, and support. Besides the elements present in organic compounds i.e. carbon, hydrogen, oxygen), plants, animals, and microbes all need a spectrum of inorganic elements in various quantities, based on the type of species.

Complete answer:
The concentration of the essential element below whereby the growth of plants is prolonged is known as a critical concentration. Plants begin to show signs of deficiency if a specific element is present well below critical concentration. The element is said to have been deficient when it is found below the critical concentration. We can find critical concentration and depletion values for the minerals Fe and Zn by absorbing morphological changes. If the levels of these elements are below critical values, they can inevitably result in the death of the plant. Morphological changes are indicative of a variety of element deficits and are pointed to as symptoms of deficiency.
So, the correct answer is option (A).

Additional information:
Even, if the concentration of the essential elements exceeds the critical concentrations. It's contributing to toxicity. When the concentration of the critical element is low enough just to severely restrict the yield, as well as the signs of discrete deficiency, are noticeable. Extreme defects may lead to the death of the plant. With intermediate or mild deficiencies may not be clear, but yields would still be reduced. The range of nutrient concentration wherein the added nutrient will not boost its yield but may raise its nutrient concentration. The concept of luxury consumption has also been used to describe the nutrient absorption by a plant which does not influence yield.

Note: Elements required in large quantities are called macronutrients; others needed only in limited or small quantities are considered micronutrients or trace elements. Macronutrient elements comprise carbon, hydrogen, oxygen, nitrogen, sulfur. Essential micronutrients involve iron, manganese, zinc, copper, etc.