Visual Symptoms as a Diagnostic Tool
Symptoms caused by nutrient deficiencies are generally grouped into five categories:
- Stunted growth,
- Interveinal chlorosis,
- Purplish-red coloring and
Stunting is a common symptom for many deficient nutrients due to their varied roles in the plant. For example, when nutrients involved in plant functions such as stem elongation, photosynthesis, and protein production are deficient, plant growth is typically slow and plants are small in stature.
Chlorosis and interveinal chlorosis are found in plants deficient of nutrients necessary for photosynthesis and/or chlorophyll (green leaf pigment involved in photosynthesis) production. Chlorosis can result in either the entire plant or leaf turning light green to yellow, or appear more localized as white or yellow spotting. Interveinal chlorosis (where the leaf veins stay green) and occurs when certain nutrients [B, Fe, magnesium (Mg), Mn, nickel (Ni) and Zn] are deficient.
Purplish-red discolourations in plant stems and leaves are due to above normal levels of anthocyanin (a purple coloured pigment) that can accumulate when plant functions are disrupted or stressed. This symptom can be particularly difficult to diagnose because cool temperatures, disease, drought and even maturation of some plants can also cause anthocyanin to accumulate. Certain plant cultivars may also exhibit this purple coloring.
Necrosis generally happens in later stages of a deficiency and causes the parts of the plant first affected by the deficiency to brown and die.
Since a number of nutrient deficiencies can produce similar symptoms, further evaluation of symptoms related to particular leaf patterns or locations on the plant are needed to diagnose nutrient specific deficiencies.
The most commonly found macronutrient deficiency and toxicity symptoms are presented in the table below:
The most commonly found micronutrient deficiency and toxicity symptoms are presented in the table below:
Always Rememebr: Deficiency symptoms observed under field conditions often appear different from the ideal text book examples. Diagnoses are often difficult for even the most experienced eyes. Some elements produce similar symptoms and several deficiencies can occur at the same time. Symptoms can also easily be confused with those caused by pests, diseases, under-watering and genetic abnormalities.
Early detection is important because deficiency symptoms are often more unique and easier to distinguish in the early stages. Yield loss can also potentially be avoided. Early detection also prompts the grower to check for other possible causes such as excessive humidity, poor EC, pH and other stress situations. (https://growabundant.com/wp-content/uploads/2019/10/Nutrient-deficiency-symptom-flow-chart.png).
Visual Plant Assessment Key
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