Leaf color is determined by pigment content and concentration. Pigments commonly present in cotton leaves include chlorophylls, carotenoids, tannins and anthocyanins. Differences in pigment properties give each pigment color characteristics; for example, chlorophylls a and b absorb light in the blue and red regions while reflecting light in the green. Similarly, carotenoids are visually associated with yellows and reds, tannins with browns, and anthocyanins with reds and purples.
The content and concentration of these pigments can additionally provide insight into the plant’s current or past growing conditions. For instance, reddening of a leaf can indicate the plant has experienced abiotic or biotic stress such as excessive radiation (Fig. 1) or a nitrogen (N) deficiency (Fig. 2). Since changes in pigments within the plant also changes the color of the leaf, visual observations of the canopy collected through the growing season can be used to gauge plant health. In the case of a reduction of chlorophyll due to an N deficiency, a reduction in chlorophyll is directly associated with a shift from dark green to light green leaf color. Whether used subconsciously or consciously, pigment content and concentration has been used for hundreds of years to diagnose stresses, including nutrient deficiencies, disease, pest damage, and water deficits/excesses. Read More »
Cotton Farming One Grower Publications
