Effects of light source and photoperiod on growth of duckweed Landoltia punctata and its water quality

Abstract

This study investigated the effects of light source [LED white (LW), fluorescent white (T5) and LED blue (LB)] and photoperiod (12:12, 16:08, 24:00 light/dark) on growth of duckweed Landoltia punctata and the resulting effects on its water quality for 16 days.The average daily relative growth rate (RGR) reached about 0.519 g d −1 . Both light source and photoperiod had no significant difference on the mean RGR; however, their interaction had significant effects on duckweed's growth (p ≤ 0.05). Moreover, except T5 (24:00) > [T5 (12:12) ≥ T5 (16:08) ≥ LB (24:00)], LW (12:12) > [T5 (16:08) ≥ LB (24:00)], and LB (12:12) > LB (24:00), there were no differences in RGR in all pair-comparisons of treatment (p ≤ 0.05). Nitrate (NO 3 − ) mostly influenced weight increment (WI), 70%. For light source and photoperiod effects on water quality, no total ammonia nitrogen (TAN) was detected in all treatments after 16 days, while NO 3 − increased gradually. In addition, results show that most of the total nitrogen (TN) was contributed from NO 3 − (R 2 = 0.9999). Overall, our findings could contribute on producing duckweed in a controlled and programmed condition for maximum production and quality. Constructed models and practical application contribute in predicting nutrients sensitivity and proven useful in water management or water quality assessments.

Influence of Light Intensity and Spectrum on Duckweed Growth and Proteins in a Small-Scale, Re-Circulating Indoor Vertical Farm

“…Up to now, only a few investigations concerning this parameter have been carried out regarding duckweed RGR. Landoltia punctata cultivated under fluorescent white light, blue LED and white LED at 110 µmol m −2 s −1 showed no significant RGR differences [40]. There was also no significant difference in the RGR of S. polyrhiza when cultivated at 60 µmol m −2 s −1 using red and blue LEDs (660 and 460 nm, respectively) [41], which is in agreement with our results.…”

Lemnaceae as Novel Crop Candidates for CO2 Sequestration and Additional Applications

“…For the relatively low light intensities used here, a longer photoperiod led to more pronounced uptake of nitrogen compounds than a shorter photoperiod (Figure 5). A similar scenario, with nitrate uptake commencing only after ammonium had been consumed, was also seen in the duckweed genus Landoltia [67,68]. Duckweeds thus have a high fertilizer-use efficiency and capacity for phytoremediation [5] such as removal of fertilizer runoff from freshwater bodies and fertilizer retention in, e.g., rice paddies [69].…”

Shining a light on duckweed: exploring the effects of artificial light at night (ALAN) on growth and pigmentation

“…Increased dry mass was also found in Yin et al (2015) using a different duckweed species, Lemna aequinoctialis , under continuous light exposure. However, a study by Gallego, Chien & Angeles Jr (2022) concluded that photoperiod had no effect on the relative growth rate of Landoltia punctata exposed to three different light sources. Yet, a possible factor explaining this result is that their experiment was only run over 16 days, with only three replicates per treatment combination, and the effects could be too small to be reliably detected.…”

“…Results of such studies were often mixed, with some reporting no effects ( e.g. , Gallego, Chien & Angeles Jr, 2022 ) and others reporting increasing growth rates with longer light exposures ( e.g. , Yin et al, 2015 ).…”