A Study Of The Effects Of Nitrate, Ammonium, And Nitrate + Ammonium Nutrition On Nitrogen Assimilation In Zeamays L.

Abstract.

A brief review of the literature on the effects of nitrate and ammonium nitrogen sources on plant growth, and the

assimilation of those nitrogen sources, has been presented.

A water culture technique for the growth of maize was

developed. The use of a gravel rooting medium with nutrients

recycling through the rooting medium, and an iron supplement in

the form of ferric citrate, resulted in superior growth of

nitrate-fed plants in comparison to that observed with a

hydroponic growth technique and a standard Long Ashton nutrient

solution.

The effects of nitrogen source on plant growth, organic

nitrogen and inorganic nitrogen contents, and the rates of

incorporation into nitrogenous compounds were studied. The

observed differences were explained with reference to the effects

of the various nitrogen sources on the physiology of the plants.

The experimental techniques included assays of the enzymes

nitrate reductase and glutamine synthetase, whole plant growth

exudate and those extracted from the leaf blade, leaf base, and

root regions of maize plants after feeding with a nutrient

solution containing nitrogen as 15 N.

After 48 days of growth ammonium- and nitrate ammonium-fed maize had larger fresh weights than those fed with

nitrate. Plants grown with ammonium as the sole nitrogen source

had greater organic nitrogen contents than those grolii!l with