Effects of Sulfate on the Physiology, Biochemistry, and Activity of Group 1 Sulfate Transporters in Seedlings of Brassica pekinensis

It is well known that some plants have the capability of taking up sulfur as a nutrient from the atmosphere through foliar absorption and can survive well in polluted environments. In order to observe the effects of the relationship between atmospheric hydrogen sulfide (H2S) deposition and soil sulfur nutrition, the current study used Brassica pekinensis as a model plant. The objective in conducting this study was to understand the regulatory mechanisms engaged in the uptake and assimilation of sulfate (SO42-) in plants by studying the modulation of transcription levels of sulfate transporter genes (STGs) (Sultr1;1 and Sultr1;2), changes in growth physiology, and the potential of roots to uptake the SO42- when allowed to grow in the presence or absence of SO42- in a hydroponic nutrient solution. Changes in growth, physico-chemical parameters, and gene expression levels of Group 1 STGs were observed when sulfur-treated and non-treated plants were exposed to phytotoxic H2S levels in the air. Sulfur deficiency enhanced nitrate and free amino acid (FAA) concentrations in the shoot and root regions of the plant. However, there was a significant decrease in the biomass, shoot/root ratio (SRR), chlorophyll content, and thiol content, with p-values < 0.01. This, in turn, increased the sulfur-uptake capacity of plants from the atmosphere through foliar absorption. When the sulfur-uptake capacity of plants increased, there was an increase in the expression level of Group 1 sulfate transporter genes (Sultr1;1 and Sultr1;2), which regulate sulfur transportation through roots. The growth, physico-chemical characteristics, and level of gene expression of Group 1 STGs were unaffected by the availability of excess sulfur in the atmosphere of up to 0.3 & mu;L l(-1).