(169h) Modeling Water Absorption of Hydrogel Coated Seeds
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Environmental Division
Advanced Treatment Technologies for Water II
Wednesday, November 8, 2023 - 5:43pm to 6:02pm
Plant species that grow naturally in semi-arid environments have developed various survival
strategies to capture water. One of them is to produce mucilage: a hydrogel seed coat that
absorbs soil moisture and helps maintain hydration during drought events. Inspired by these
mucilage-producing seeds, hydrogel coatings have been developed to improve drought
resistance in other seed species. Some field tests showed encouraging results, such as
increased growth by 16% in wheatgrass, 50% in cucumber, 77% in corn, and 100% in pea
shrub. However, other tests showed conflicting results as the seed coatings reduced
germination rates, especially with thin seed coats (hydrogel mass < 50% of seed mass).
Unfortunately, the reason behind the dichotomy of these germination rates is unknown. To
investigate the effect of a hydrogel seed coat on water transport, we designed artificial
seeds made of clay and coated them with an alginate hydrogel. We then measured the
associated imbibition rate and examined how the permeability variation in the flow direction
in this spherical geometry affects the dynamics of water moving into the clay core. We
found that the hydrogel coating did not delay the imbibition of the clay core and could be
captured by the Lucas Washburn theory. We then successfully confronted our model with
experiments conducted on coated soy seeds. Further, we tested the germination rate of our
coated soy seeds and observed that (1) the seeds coated in the hydrogel had fewer yields,
but (2) the ones that germinated had a more extensive root system, and (3) the hydrogel-
coated seeds that did not germinate were beginning to decay, indicating an overly wet
surrounding environment. Together, our results further help to elucidate the reasons behind
the conflicting yields reported when coating seeds with hydrogel.
strategies to capture water. One of them is to produce mucilage: a hydrogel seed coat that
absorbs soil moisture and helps maintain hydration during drought events. Inspired by these
mucilage-producing seeds, hydrogel coatings have been developed to improve drought
resistance in other seed species. Some field tests showed encouraging results, such as
increased growth by 16% in wheatgrass, 50% in cucumber, 77% in corn, and 100% in pea
shrub. However, other tests showed conflicting results as the seed coatings reduced
germination rates, especially with thin seed coats (hydrogel mass < 50% of seed mass).
Unfortunately, the reason behind the dichotomy of these germination rates is unknown. To
investigate the effect of a hydrogel seed coat on water transport, we designed artificial
seeds made of clay and coated them with an alginate hydrogel. We then measured the
associated imbibition rate and examined how the permeability variation in the flow direction
in this spherical geometry affects the dynamics of water moving into the clay core. We
found that the hydrogel coating did not delay the imbibition of the clay core and could be
captured by the Lucas Washburn theory. We then successfully confronted our model with
experiments conducted on coated soy seeds. Further, we tested the germination rate of our
coated soy seeds and observed that (1) the seeds coated in the hydrogel had fewer yields,
but (2) the ones that germinated had a more extensive root system, and (3) the hydrogel-
coated seeds that did not germinate were beginning to decay, indicating an overly wet
surrounding environment. Together, our results further help to elucidate the reasons behind
the conflicting yields reported when coating seeds with hydrogel.