Influence of light intensity on growth and flowering ornamental plants in constructed wetlands

Abstract

Light is an indispensable source for the photosynthesis of plants, but also for their growth and development. On the other hand, the production of ornamental plants requires multiple nutrients for their proper development, a source available in high concentrations in wastewater. Recent research on constructed wetlands (CWs) that use ornamental plants to treat wastewater and at the same time are used as a means of growth, is considered a sustainable alternative. This study evaluated the influence of light intensity on the growth and flowering of ornamental plants (Lavandula sp., Anthurium sp., Zantedeschia aethiopica and Spathiphyllum wallisii) in constructed wetlands, fed with domestic wastewater. 30 mesocosms of constructed wetlands were used as a culture medium for ornamental plants, the effect of light intensity on the development of the plants was measured, as well as the removal of Nitrogen (N-NO3), phosphate (P-PO4) and biochemical demand of oxygen (DBQ5). The plants were able to adapt and grew healthy in the three-support media with the exception of Lavandula sp., which did not survive in any of the systems, showing that in the months when the light intensity was higher, a higher growth rate was reached to 9.5 % on average. In terms of the removal of N-NO3 (45- 60%), P-PO4 (20-23%) and COD5 (60-85%), no significant differences were found between any of the substrates. The above allows us to affirm that CWs, are suitable means for cultivation of ornamental plants and the development of them is favored with intensities of light in ranges from 720 to 856 µmol · m −2 · s −1, On the other hand, the substrates used proved to be efficient to remove contaminants, but at the same time to facilitate the healthy development of the used ornamental vegetation, with the exception of the lavender sp. Research is required to evaluate the effects of light intensity on the production of ornamental plants in controlled environments.