Acclimation of functional traits leads to biomass increases in leafy green species grown in aquaponics

TL;DR

Plants grown in aquaponics systems show increased biomass and photosynthesis due to better water and nutrient access, suggesting aquaponics could be a sustainable farming solution.

Contribution

This study demonstrates that leafy green plants acclimate to aquaponics systems by increasing biomass and photosynthesis through stomatal and nitrogen adjustments.

Findings

Aquaponics-grown plants showed 185% higher biomass in broccoli, 116% in pak choi, and 362% in salanova compared to soil-grown plants.

Aquaponics plants had higher photosynthetic rates and stomatal conductance but lower water-use efficiency.

Increased leaf tissue nitrogen in aquaponics correlated with higher photosynthesis rates.

Abstract

As human population size continues to increase and climate change effects worsen, future food security has become a primary concern for agricultural industries worldwide. Yields of traditional agricultural methods are commonly limited by water and nutrient availability and many crop yields are predicted to decline. Alternative farming practices like aquaponics, which can alleviate these negative yield pressures, may become critical to reaching food production targets. Aquaponics approaches involve the cyclic joint production of fish and hydroponic plants where the fish efflux provides nutrients to plants that then purify the water to be recycled to the fish tanks. In this study, we investigated the acclimation of physiology and functional traits of plants grown in aquaponics versus soil for three leafy green species. We compared gas exchange, stomatal anatomy, water-use efficiency, and foliar chemistry on newly formed leaves across weekly measurements. Increased photosynthetic rate, driven by higher stomatal conductance and increases in tissue nitrogen, led to higher biomass production in aquaponics for all species. Aquaponics plants adjusted stomatal behavior and to a lesser degree stomatal anatomy to become less water-use efficient than plants grown in soil. Collectively, our findings demonstrate the ability of plants to acclimate quickly to aquaponics growing systems that largely remove water and nutrient limitations to plant growth. The increased biomass production of broccoli, pak choi, and salanova by 185%, 116%, and 362% in aquaponics compared to soil-grown plants demonstrates the potential of small-scale aquaponics systems as an efficient and sustainable alternative farming practice.

As aspects of our food system are under pressure from population growth and global change, the need to investigate the efficacy of alternate agriculture practices is imminently important. Our study examined the capacity of leafy green species grown in aquaponics to acclimate to unlimited access to water and consistent supplies of nitrogen from fish efflux, compared to the same species grown in soil. We found biomass production, rates of photosynthesis, and stomatal conductance to be higher in aquaponics, while water use efficiency was lower in aquaponics for all species. Our study also found nitrogen supply to be higher in leaf tissues in plants grown in aquaponics, which correlated with the observed higher rates of photosynthesis. Our findings offer mechanistic insights into the future of sustainable farming that utilizes aquaponics to produce non-staple crops that meaningfully contribute to feed insecurity.

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