Interaction between atmospheric hydrogen sulfide deposition and pedospheric sulfate nutrition in Brassica oleracea L.

Brassica oleracea L. is able to utilize H2S as sulfur source for growth and it can replace pedospheric sulfate as sulfur source. The foliage forms an active sink for atmospheric H2S, which is directly metabolized into cysteine and subsequently into other organic sulfur compounds. H2S exposure results in an increased size and changed composition of the thiol pool. However, the overall foliar H2S uptake by B. oleracea appears to be under strict metabolic control and the uptake and metabolism of H2S by the shoot and that of sulfate by the roots appear to be in tune and adjusted to the actual sulfur requirement for growth. H2S exposure results in a decrease in sulfate reduction in the shoots at the site of adenosine 5'-phosphosulfate reductase and in a down-regulation of the sulfate uptake by the roots. H2S impact studies show to be a useful tool for studying the signals involved in the regulation of sulfur metabolism and its interaction with nitrogen metabolism. A modulation of sulfur nutrition by changing the levels of atmospheric and pedospheric sulfur also shows promise in the studies on i) the potential and usefulness of the channeling of extra sulfur into specific sulfur pools, ii) the role of sulfur compounds (e.g. glutathione) in the protection of plants against oxidative and environmental stress, iii) sulfur-induced resistance of plants against pests and iv) the function of secondary sulfur compounds in plants and the mutual regulation of sulfur and nitrogen metabolism in plants.