From my roots' perspective, a lack of nitrogen is one of the most crippling deficiencies I can experience. Nitrogen is fundamental to my very structure, as it is a core component of chlorophyll, the molecule I use to capture sunlight for photosynthesis. Without sufficient nitrogen, my ability to produce food is severely compromised. You will first notice this as a uniform yellowing (chlorosis) of my oldest, lower leaves. This is because I, as a plant, am a pragmatic organism; I will mobilize the limited nitrogen I have from older tissues to support new, vital growth. Consequently, the older leaves will turn pale green, then yellow, and may eventually drop off, while my new growth may appear stunted and pale.
Iron is crucial for me to synthesize chlorophyll, even though it is not part of the chlorophyll molecule itself. A shortage of available iron in the soil directly inhibits my chlorophyll production chain. My reaction to iron deficiency presents a distinct pattern. Unlike nitrogen deficiency, the yellowing occurs between the veins of my youngest, most tender leaves first, while the veins themselves typically remain green. This creates a striking interveinal chlorosis. In severe cases, the entire leaf may turn pale yellow or even white, and my new growth will be severely stunted. This often occurs not because iron is absent from the soil, but because the soil pH is too high (alkaline), which chemically locks the iron into a form that my roots cannot absorb.
Magnesium is the central atom in every chlorophyll molecule; it is literally the heart of the operation that allows me to convert sunlight into energy. A deficiency directly attacks my photosynthetic engine. The symptom pattern is similar to iron deficiency but appears on my older leaves first. You will see interveinal chlorosis, where the tissue between the leaf veins turns yellow while the veins stay green. In advanced stages, reddish-purple blotches may appear on the yellow areas, and the leaves may curl upward at the margins before dropping prematurely. This robs me of my mature, food-producing leaves, weakening me overall.
Manganese plays a supporting role in photosynthesis and nitrogen metabolism. Its deficiency can be easily confused with iron deficiency because I exhibit interveinal chlorosis on my new growth. However, the key difference is in the details. The contrast between the green veins and the yellow tissue is often less sharp than with iron deficiency. More importantly, as the condition worsens, the areas around the veins may develop a tan or grayish colour, and the leaves may appear more netted. The youngest leaves might be small and misshapen. This deficiency is also frequently tied to a high soil pH, which limits my root system's ability to uptake this micronutrient.
