Agarose hydrogel composite supports microgreen growth with continuous water supply under terrestrial and microgravitational conditions

Authors: TENG, ZI - University Of Maryland; Luo, Yaguang - Sunny; Pearlstein, Daniel; Zhou, Bin; JOHNSON, CHRISTINA - National Aeronautics And Space Administration (NASA); WANG, QIN - University Of Maryland; Fonseca, Jorge

Submitted to: International Journal of Biological Macromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2022
Publication Date: 11/1/2022
Citation: Teng, Z., Luo, Y., Pearlstein, D.J., Zhou, B., Johnson, C.M., Wang, Q., Fonseca, J.M. 2022. Agarose hydrogel composite supports microgreen growth with continuous water supply under terrestrial and microgravitational conditions. International Journal of Biological Macromolecules. 220:135-146. https://doi.org/10.1016/j.ijbiomac.2022.08.046.
DOI: https://doi.org/10.1016/j.ijbiomac.2022.08.046

Interpretive Summary: Feeding the increasing world population with shrinking arable land and water resources requires novel alternatives to soil-based cultivation systems and efficient water usage. Ultralight substance that support plant growth in microgravity is critical to ensure Astronauts’ healthy diet during their space mission. Hereby, scientists at USDA-ARS, in collaboration with University of Maryland and NASA, developed and tested a hydrogel composite material as a novel plant growth substrate. Consisting of a biodegradable hydrogel and porous organic particles, this substrate features ultra-lightweight, convenient operation, and remarkable water holding and delivering capabilities. It sustained a full 12-d growth cycle for red cabbage microgreens under normal and microgravitational conditions without the need for watering or attendance. The developed substrate may find its use in various applications such as controlled environment agriculture and space farming.

Technical Abstract: Shrinking arable land and freshwater resources makes feeding future generations increasingly challenging. Controlled environment agriculture (CEA) has tremendous growth potential because it offers an efficient and sustainable forum for plant growth. Herein we report a porous hydrogel/growing mix composite (HGC) as a potential substrate for growing vegetables in CEA systems. Both pristine hydrogel and HGC sustained a 12-d growth cycle for red cabbage microgreens without the need for watering or attendance. Moreover, blending growing mix particles with hydrogel led to a significant increase in average pore size (evidenced by mercury intrusion porosimetry) and total dissolved solid level. Further investigation suggested that the dissolved solids from growing mix particles accounted for a 54% increase in microgreen yield over pristine hydrogel, while the porosity of the particles resulted another 44% increase in yield. The HGC underwent more rapid water loss than pristine hydrogel, but the water remained readily extractable by plants per water potential measurement. Furthermore, an evaluation using a random positioning machine suggested satisfactory plant growth on HGC under simulated microgravity. The results of this study reveal a novel growth substrate that is lightweight, convenient, and water-efficient, which effectively sustains plant growth for various applications including indoor farming and space farming.