Effect of Nutrient Solution Flow Rate on Hydroponic Plant Growth and Root Morphology

Abstract

Crop production under hydroponic environments has many advantages, yet the effects of solution flow rate on plant growth remain unclear. We conducted a hydroponic cultivation study using different flow rates under light-emitting diode lighting to investigate plant growth, nutrient uptake, and root morphology under different flow rates. Swiss chard plants were grown hydroponically under four nutrient solution flow rates (2 L/min, 4 L/min, 6 L/min, and 8 L/min). After 21 days, harvested plants were analyzed for root and shoot fresh weight, root and shoot dry weight, root morphology, and root cellulose and hemicellulose content. We found that suitable flow rates, acting as a eustress, gave the roots appropriate mechanical stimulation to promote root growth, absorb more nutrients, and increase overall plant growth. Conversely, excess flow rates acted as a distress that caused the roots to become compact and inhibited root surface area and root growth. Excess flow rate thereby resulted in a lower root surface area that translated to reduced nutrient ion absorption and poorer plant growth compared with plans cultured under a suitable flow rate. Our results indicate that regulating flow rate can regulate plant thigmomorphogenesis and nutrient uptake, ultimately affecting hydroponic crop quality.

Effect of Substrate Flow Rate on Nutrient Uptake and Use Efficiency in Hydroponically Grown Swiss Chard (Beta vulgaris L. ssp. cicla ‘Seiyou Shirokuki’)

“…As shown in Figure 1, in this study, we achieved a similar result to our previous research [9,12]. That is, in a certain range, with the increase in flow, the growth of plants is enhanced.…”

“…Environmental data such as the air temperature, air pressure, wind speed, and relative humidity in the cultivation room were recorded during the experiment period (Supplementary Data Table S1). This study used the same cultivation device, LED lamp, and nutrient solution as the literature [12]. The details of the cultivation device, operation, and the setting status of the LED light have been described in detail in the literature [12].…”

“…This study used the same cultivation device, LED lamp, and nutrient solution as the literature [12]. The details of the cultivation device, operation, and the setting status of the LED light have been described in detail in the literature [12].…”

“…Plants cultivated in each container were harvested after 14 days and subsequently separated into shoots and roots. The fresh weight and dry weight of shoots and roots, leaf area, and root length were measured using the method described in the literature [12] (Supplementary Data Table S2). Next, dried plant parts were crushed to measure the nutrient content.…”

“…The flow rate of 6 L/min had the best results for fresh weight, dry weight, leaf area, and nitrogen uptake in that study. In addition, in another study [12], the authors carried out floating hydroponics cultivation experiments (also with Swiss chard) under artificial light conditions and investigated the root morphology of plants growing under different flow rates. It was concluded that excessive flow brought excessive physical stimulation, which would make the roots compact and reduce nutrient absorption, thus affecting plant growth.…”