Interaction of nitrate and sulfate reduction in tobacco

Abstract

A series of experiments was conducted to study the interrelationship of sulfate (SO₄) and nitrate (NO₃) reduction in ‘Ky14’ tobacco plants (Nicotiana tabacum L.) as influenced by nutrient solution availability of NO₃ and SO₄. The activities of ATP sulfurylase and NO₃ reductase, the first steps of SO₄ and NO₃ reduction, respectively, have been considered as indicators of the state of regulation of the assimilatory pathways of SO₄ and NO₃. Activity of ATP sulfurylase was derepressed when SO₄ was limited in the nutrient solution, provided that there was a net accumulation of reduced N in the tissue. The availability of SO₄ or the lack of N resulted in repressed activity of ATP sulfurylase. Nitrate reductase activity was induced when NO₃ was available in the nutrient solution, provided that there was a net accumulation of reduced S in the tissue. When NO₃ was limited in the nutrient solution or there was a lack of S, repression of NO₃ reductase activity resulted.

Key words:

• Nitrogen
• sulfur
• Nicotiana tabacum
• ATP sulfurylase
• nitrate reductase

Notes

Contribution from Dep. of Agronomy, Kentucky Agric. Exp. Stn. This paper No. 85–3–16 is published with approval of the Kentucky Agric. Exp. Stn.

Research assistant and professor, Dep. of Agronomy, Univ. of Kentucky, Lexington, KY 40546–0091.