Interaction of nitrate and sulfate reduction in tobacco

Abstract

A series of experiments was conducted to study the effects of apical meristem removal on sulfate and nitrate reduction in ‘Ky14’ tobacco plants (Nicotiana tabacum L.). Apical meristem removal is expected to modify N metabolism since it causes an increase in the synthesis of nicotine in the roots and its accumulation in shoots. There may not be any such complementary effect on S metabolism. Further, the experiments were designed to study the effects of apical meristem removal on the interaction of nitrate (NO₃) and sulfate (SO₄) reduction. Activities of ATP sulfurylase and NO₃ reductase, the first steps of SO₄ and NO₃ reduction, respectively, have been considered indicators of the state of regulation of the assimilatory pathways of SO₄ and NO₃. The effect of apical meristem removal on the activities of the above enzymes in the leaf tissue and the interrelationship between them was examined. Removal of the apical meristem resulted in a large increase in nicotine concentration, a large increase in the activity of ATP sulfurylase, no measurable decrease in SO₄ or total S concentrations, a significant decrease in the activity of NO₃ reductase, and an increase in the NO₃ concentration.

Key words:

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

Notes

Contribution from Dep. of Agronomy, Kentucky Agric. Exp. Stn. This paper No. 85–3–17 is published with approval of the Director of the Kentucky Agric. Exp. Stn.

Research assistant and professor, Dep. of Agronomy, Univ. of Kentucky, Lexington, KY 40545–0091.