Nutrient deficiency is one of the most common causes of chlorosis. Nitrogen is used in the formation of amino acids — the building block for proteins in plants — showing a close relationship between nitrogen and chlorophyll. This proves that the increase in nitrogen taken up by plants results in an increase of leaf chlorophyll content.
So having nitrogen deficiency means that there is the lack of nitrogen taken up by plants, resulting in the lack of chlorophyll that further causes the symptom of chlorosis to occur. Researches have shown that we can verify the chlorosis caused by nitrogen deficiency by seeing the parts on the leaf turning yellow: it usually begins at the bottom of the branch, which are usually the old leaves, and only the leaf tip and midrib will turn yellow (ARIT EFRETUEI, 2016). While iron deficiency is another deficiency that might also cause chlorosis to occur because iron is as well used in producing chlorophyll. Iron is unavailable to be absorbed when the soil pH is around 5 to 6.5 and also when it is over fertilized with elements such as manganese, calcium, copper, or phosphorus. This causes chlorosis to occur because there is not enough iron to produce enough chlorophyll for the plant to do photosynthesis (Schuster, James, 2008). Iron deficiency usually occurs on the newborn leaves.
We can verify that the chlorosis is caused by it when seeing the area between the leaf veins becomes pale yellow and white. The newborn leave will even turn entirely white and stunted in severe cases (Dr. James Walworth, 2015).
Seasonal change is another common cause of chlorosis. The number of chlorophyll concentration in each plant may differ but researches have shown a certain pattern for each plant. Researchers who have investigated leaf reflectance and transmittance have found out that the spectral data showed a great increase in leaf chlorophyll at the beginning of the growing season, remained that content for several months, then decreases again when leaves are senescent. (V. Demarez, 2010) Dying leaves are also taken into account as a common cause of the lack of chlorophyll.
Leaves usually change to a yellowish color when there is a lack of chlorophyll since it is these pigments that make the left green. Those of the dying leaves, which is shown at the most right side in figure 1, changes to almost fully yellow that indicates the leaf is facing its death instead of just chlorosis. By using this method when picking chlorosis leaves, I can make sure the leaves I picked aren’t dying leaves that have turned almost to be yellow. Instead, it is the leaf at the most left side shown in Figure 1 that are facing only a little chlorosis.