Optimal Growth Conditions for Azolla pinnata R. Brown: Impacts of Light Intensity, Nitrogen Addition, pH Control, and Humidity

Abstract

Nitrogen pollution from agriculture is a major challenge facing our society today. Biological nitrogen fixation is key to combat the damage that is caused by synthetic nitrogen. Azolla spp. are ideal candidates for fast nitrogen fixation. This study aimed to investigate the optimal growth conditions for Azolla pinnata R. Brown. The growth conditions that were investigated included the growth medium type and strength, light intensity, the presence/absence of nitrogen in the medium, pH control, and humidity. Higher light intensities increased plant growth by 32%, on average. The highest humidity (90%) yielded higher growth rate values than lower humidity values (60% and 75%). The presence of nitrogen in the medium had no significant effect on the growth rate of the plants. pH control was critical under the fast growth conditions of high light intensity and high humidity, and it reduced algal growth (from visual observation). The optimal growth rate that was achieved was 0.321 day−1, with a doubling time of 2.16 days. This was achieved by using a 15% strength of the Hoagland solution, high light intensity (20,000 lx), nitrogen present in the medium, and pH control at 90% humidity. These optimised conditions could offer an improvement to the existing phytoremediation systems of Azolla pinnata and aid in the fight against synthetic nitrogen pollution.

Quail (Coturnix coturnix japonica) Fermented Manure as a Fertilizer to Support Azolla microphylla Growth Rate

“…The aging phase in Azolla cultivation started at P3 (14 days from planting) due to competition for available nutrients to support Azolla growth and reproduction. The growth rate of Azolla in this study was slightly lower than the result of Hossain et al (2021) andda Silva et al (2022), who applied synthetic fertilizer in their research. However, it was higher than the results of research by Nordiah et al (2012), by growing Azolla only on the water without fertilizer, and those of Kösesakal and Yildiz (2019), with the application of Hoagland solution as fertilizer.…”

The Potential Capabilities of two species of Azolla as a Bioaccumulator in Summer

“…culture (El-Bahbohy et al 2014). A higher light intensity and high humidity resulted in higher growth rates of A. pinnata has been reported by da Silva et al (2022) also.…”

A comprehensive study on the assessment of chemically modified Azolla pinnata as a potential cadmium sequestering agent

“…The relative growth rate and doubling time were determined to be 0.148 g/g/d and 5.6 days, respectively, which are lesser than those reported in our current study. In contrast, the recent research investigation on the growth conditions for A. pinnata reported a growth rate and doubling time of 0.321 g/g/d and 2.16 days, respectively that was achieved using the optimised conditions of 15% strength Hoagland solution, higher light intensity, nitrogen present in the medium (Da Silva, 2022). Azolla strains exhibit diverse responses to environmental conditions such as temperature, light intensity, and soil nutrients, leading to variations in their growth characteristics and chemical composition (Chatterjee et al, 2013).…”