Agarose hydrogel composite supports microgreen cultivation with enhanced porosity and continuous water supply under terrestrial and microgravitational conditions

• Published in: International journal of biological macromolecules Vol. 220; pp. 135 - 146
• Main Authors: Teng, Zi, Luo, Yaguang, Pearlstein, Daniel J., Zhou, Bin, Johnson, Christina M., Mowery, Joseph, Wang, Qin, Fonseca, Jorge M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2022
• Subjects: Agarose; Hydrogel; Microgravity; Microgreens; Pore size distribution; Soilless culture medium; Soilless culture medium; Hydrogel; Pore size distribution; Microgravity; Microgreens; Agarose
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2022.08.046

Hydrogels are attractive soilless media for plant cultivation with strong water and nutrient retention. However, pristine hydrogels contain mostly ultra-micro pores and lack air-filled porosity for root zone aeration. Herein we report a porous hydrogel composite comprising an agarose network and porous growing mix particle (GMP) fillers. The agarose backbone allowed the composite to sustain a 12-d growth cycle for red cabbage microgreens without the need for watering or crew interaction. Moreover, the GMP induced greater total pore volume and increased the prevalence of pores >30 μm by 8-fold. Further investigation suggested that the nutrients from GMP accounted for a 54 % increase in microgreen yield over pristine hydrogel, while the porous structure introduced by GMP improved the yield by another 44 %. Increased air-filled porosity accelerated the water transport and loss of hydrogel but maintained favorable water potential levels for plant extraction. Finally, the hydrogel composite supported microgreen growth satisfyingly under simulated microgravity despite some morphological changes. Results of this study reveal a novel growth substrate that is lightweight, convenient, and water-efficient, while effectively sustaining plant growth for multiple applications including indoor farming and space farming.
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•Novel plant growth medium comprising agarose hydrogel and porous fillers.•The agarose backbone allowed continuous water supply to microgreens for 12 d.•The added fillers introduced a significant percentage of air-filled pores.•The extra porosity caused 44 % better fresh yield at similar nutrient levels.•Satisfactory growth despite morphological changes was observed under microgravity.