Janjira Muenrew and Arunothai Jampeetong

DOI: 10.14456/sjst-psu.2018.156

pp. 1271 - 1280

Abstract

Plants that grow on wastewater are affected not only by low O₂ but also by the presence of iron leading to low
efficiency for nutrient removing from the wastewater treatment systems. Currently, hybrid Napier grass (Pennisetum purpureum
Schumach × P. americanum (L.) Leeke cv. Pakchong 1) was introduced for use in wastewater treatment systems. However, the
ecophysiology of this species has rarely been studied. Therefore, this research investigated the effects of O₂ levels and Fe supply
on growth, morphology, nitrogen uptake, and mineral allocation of hybrid Napier grass. The plants were grown on nutrient
solutions with a NH₄⁺:NO₃^-
ratio of 75:25 at 500 µM-N under three different levels of O₂ (anoxic, hypoxic, and normoxic) with
and without Fe supply (40 mg L^-1
). Plant growth rate dramatically decreased in anoxic conditions, especially in Fe supply
treatment. The root number, root length, and leaf number were negatively affected by O₂ deficiency. Both NH₄⁺and NO₃^- uptake
rates were lowest in the anoxic treatment, and were also low in the presence of Fe. Under anoxic conditions, mineral
concentrations of N, P, K, Mg, and Fe also decreased particularly in the roots. However, the plants responded to low O₂ by
producing adventitious roots and increasing aerenchyma porosity that could support plant growth under low O₂. We concluded
that this species could still grow well at low O₂ supply. Therefore, this species can be used in constructing wetlands to treat
wastewater. Moreover, high nitrogen in the plant tissue makes it appropriate for animal feed or green manure.