Abstract
Plants respond to environmental adversities, becoming an indicator for assessing the environment quality. In this aspect, chlorophyll contents as well, carotenoids are used as a reliable indicator to associate environmental quality and pollution, mainly regarding the toxicity of heavy metals in higher plants. So, we aimed to evaluate the content of chlorophyll a, b, and total chlorophylls and carotenoids in plants vetiver [Vetiveria zizanioides (L.) Nash], maize (Zea mays L.) cv. AG 1051, sunflower (Helianthus annuus L.) cv. BRS 122/V-2000, and castor beans (Ricinus communis L. ) cv . Northeastern BRS grown in contaminated soil with lead, with and without correction of soil pH, so they were used as indicators of metal stress by the soil. From the biochemical point of view, the correction of soil pH values caused chlorophyll a, b and total statistically higher for vetiver species and castor beans in the analyzed periods, except for the analysis performed 60 days after transplanting where only the species vetiver benefited from the correction of soil pH on the content of chlorophyll b and total. On the other hand plants without correction of soil pH showed a decrease of all chlorophyll levels. In addition, the largest increase in the synthesis of carotenoids, indicated that under stress the plants have developed alternative routes of dissipation of energy in order to avoid problems of photo-inhibition and photo-oxidation.
Highlights
The environment adversity, understood as stress refers to a set of factors such as extreme temperatures, salinity, presence of metals, among others, exercising a disadvantageous influence on plant, which may present as genetic, metabolic, morphological and physiological mechanisms stable changes such as tolerance to these environments (TAIZ & ZEIGER, 2013)
On one side the chlorophyll are the main chloroplasts pigments responsible for collecting solar radiation which during the photosynthetic process is converted into chemical energy in the form of ATP and NADPH (TAIZ & ZEIGER 2013) and on the other hand carotenoids are essential to photosynthesis acting as secondary pigments, pro-vitamin factor and sunscreen which eliminate free radicals such as ROS in damaged tissue (PANDY et al, 2010)
From the biochemical point of view, the correction of pH of the contaminated soil caused values of chlorophyll a, b and total, statistically superior to castor beans and vetiver species in the analyzed periods, except at 60 days after transplantation where only the vetiver species has benefited with the correction for the contents of chlorophyll b and total
Summary
The environment adversity, understood as stress refers to a set of factors such as extreme temperatures, salinity, presence of metals, among others, exercising a disadvantageous influence on plant, which may present as genetic, metabolic, morphological and physiological mechanisms stable changes such as tolerance to these environments (TAIZ & ZEIGER, 2013). These adjustments relate primarily to changes that come forward in plant leaves, as this organ is of rapid growth and constant renewal. With regard to inhibition of chlorophyll synthesis, it has been suggested that in the presence of Pb (GAUTAM et al, 2011) occurs a reduction of the ALAD enzyme activity (5-Aminolevulinic Acid Dehydratase), which is considered the key enzyme in the route of chlorophyll synthesis
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