Metabolismo de carbono de plantas cultivadas e o aumento de CO2 e de O3 atmosférico:Situação e previsões

Abstract

The activity of atmospheric gases, especially greenhouse gases (GHG), as water vapor, carbonic gas, methane, nitrogen oxides and ozone, became object of studies because of its increase in the atmosphere, causing a rise in air temperature, drought and others. In addition to carbonic gas, there was an increase in the emission of Volatile Organic Compounds (VOC) in the troposphere, as well of nitrogen oxides, which generates ozone, toxic to all living beings. The ozone produced at low altitudes reduces photosynthesis and yield of sensitive species, as soybean and cotton, important Brazilian crops. The prevision of a substantial increase in atmospheric concentration of carbonic gas during the next years will probably cause an increase in photosynthesis and biomass of C3 plants, especially in woody and grasses species, in detriment to leguminous and C4 plants. However, this increase can be lower than predicted by studies carried out under controlled conditions, as demonstrated by field results. The large concentration of these GHG in the atmosphere will rise the air temperature and will reduce the soil water content, which can annul the fertilization effect of carbonic gas, potentially extending the harmful effect of the ozone in the biosphere. The few available studies have been conducted in temperate regions and little is known about the effects of carbonic gas and ozone on the metabolism of crops in tropical regions.