SULPHUR NUTRITION OF THE CORN PLANT: I. EFFECT ON THE NITRATE - NITROGEN FRACTION

Abstract

Corn plants (Dekalb 805) were grown in nutrient solutions supplied with adequate (156.2 uM S) or inadequate (0.6.0 or 15.62 uM s) sulphur. The shoots and roots were analysed for nitrate-nitrogen (NO -N) content as well as for sulphate-sulphur (SO₄-S), total sulphur and organic sulphur. Also, the effect of varying the nitrogen supply (from 3.57 to 7.14 uM N) was studied. The activity of nitrate reductase in the leaves of sulphur deficient (-S) and sulphur adequate (+S) plants was determined.

In (-S) corn leaves, the NO₃-N content was relatively low (.42% dry wt) and the nitrate reductase activity was also low (0.48, u moles NO₂, (g fr wt.)^-1 hr^-l). In contrast, (+S) corn leaves accumulated more NO₃-N (.64% dry wt.) and had a correspondingly higher reductase activity (5.64 u moles NO₃-(g fr wt.)^-1 hr^-1). The soluble protein (expressed in mg. pa g. fresh weight) in (+S) corn leaves was threefold the amount in sulphur deficient corn leaves.