In a study conducted on sugarcane, Jain et al. (2010) observed
increased Chl a, Chl b and carotenoid levels in the leaf tissues of plants
grown on sand cultures and subjected to high Zn concentrations supplied
through nutrient solutions. This response was most likely caused
by the lower production of leaf fresh mass and larger amounts of
pigment per unit of mass (Hewitt, 1983). Nevertheless, Sagardoy et al.
(2009) observed decreased chlorophyll and carotenoid levels resulting
from the increased Zn doses supplied in nutrient solution when the results
were expressed as a function of leaf area. According to Cambrollé
et al. (2012), the decrease in photosynthetic pigments induced by the
high Zn concentrations in the growth media may be attributed to the
adverse effect of excess Zn on the photosynthetic electron transport,
which decreased chlorophyll synthesis or increased chlorophyll degradation.
Furthermore, Upadhyay and Panda (2010) found decreased
levels of total chlorophyll and carotenoids in Spirodela polyrhiza L. plants
grown in nutrient solution and subjected to separate applications of Cu
or Zn. However, plants increased total chlorophyll and carotenoid levels
in plant leaves when Cu and Zn were simultaneously added to the nutrient
solution. This response may be considered a specific Zn response
that causes increased chlorophyll and photosynthate synthesis (Bazzaz
et al., 1992). In this study, increased total chlorophyll and carotenoid
levels in leaves may have occurred as a result of the effect of pigment
concentrations because the plants showed decreased dry matter
production. This effect may be observed in the levels of Chl a, Chl b
and carotenoids in plants from the first crop, especially when 30 to
180 mg Zn kg−1 was applied to the soil.