Review of beneficial uses of calcium and ammonium salts for stimulating plant growth and metabolite translocation

Numerous investigations have been conducted to quantify Ca-stimulated ammonium (NH4+) absorption by plants [this technology is covered under U.S. patent 4,500,335, patent licensee is Tetra Technologies, 25025 I-45 North, The Woodlands, TX 77380]. Greenhouse and field studies on vegetable crops, field crops and ornamental foliage crops show significant growth increases from increasing Ca++:NH4+ ratios in the growth media. Increased root growth was normally the first plant response, with especially large root and bulb responses observed in onion (Allium cepa L.), beets (Beta vulgaris), radish (Raphanus sativus L.), and bermudagrass (Cynodon dactylon Pers.). Direct measurements of Ca-stimulated NH4+ absorption were obtained with isotopic nitrogen (N-15) in greenhouse trials. As Ca++ concentrations were increased an increase in (NH4+)-N-15 absorption was obtained in all plant species tested. The Ca++ stimulated NH4+ absorption phenomenon in plants is best explained by the "Viets Effect", which describes the use of Ca++ or magnesium (Mg++) to increase plant absorption of potassium (K+). Although, increased NH4 absorption effectively increases plant growth, increasing K+ absorption does not. Increased NH4+ absorption has been associated with enhanced photosynthetic rates as well as increased proportions of new metabolites (compounds initially produced from newly captured carbon dioxide) translocated to the nutrient sinks (seeds, bulbs, roots, etc.). The integrity of the plasmalemma is maintained by the presence of extra Ca++, leading to greater turgor pressure (higher water content) and nutrient retention in cells which produce greater growth potential in plants.