Interactive effects of nitrogen form and pH on growth, morphology, N uptake and mineral contents of Coix lacryma-jobi L.

• Main Authors: Arunothai Jampeetong, Dennis Konnerup, Narumol Piwpuan, Hans Brix
• Format: Journal
• Published: 2018
• Online Access: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84887628371&origin=inward; http://cmuir.cmu.ac.th/jspui/handle/6653943832/47540
• Institution: Chiang Mai University

The effects of N-form and pH on growth, morphology, nitrogen uptake and nutrients allocation in Job's Tears (Coix lacryma-jobi L.) were determined. The plants were grown on a growth medium with either ammonium (NH 4 + ) or nitrate (NO 3 - ) at the same concentration (500μM) and at four levels of pH: 3.5, 5.0, 6.5 and 8.5 under greenhouse conditions for forty days. C. lacryma-jobi prefers NO 3 - nutrition, as plants supplied with NO 3 - had higher relative growth rates than plants supplied with NH 4 + , particularly at neutral and alkaline pH. At low pH (3.5, 5.0) both NH 4 + and NO 3 - fed plants had brighter roots and more lateral roots than at higher pH. The NH 4 + uptake rates were highest at pH 6.5 and 8.5 whereas the NO 3 - uptake rates were highest at pH 5.0. The uptake rates of both NH 4 + and NO 3 - were very low at pH 3.5. The pH of the growth medium significantly affected plant mineral uptake. The calcium (Ca) concentrations in leaves were highest at pH 6.5 and 8.5. The tissue concentrations of potassium (K) were only affected for NO 3 - -fed plants where K concentrations were higher at pH 3.5 and 5.0 than at higher pH. It is concluded that C. lacryma-jobi has a preference for NO 3 - which makes it suitable for wastewater treatment in constructed wetland system where a substantial fraction of the N is on NO 3 - form such as in vertical flow constructed wetlands. © 2013 Elsevier B.V.