Soil structure and stability in the spermosphere of myxosdiaspore chia (Salvia hispanica L.)

Mucilage produced by myxodiaspores has been mainly studied for its role in seed ecology. This work investigates changes due to mucilage in soil structure and stability in the spermosphere of the myxodiaspore crop chia (Salvia hispanica L.). In sandy-loam repacked soil sown with chia and subjected to wetting-drying, Computer Assisted X-ray micro tomography (X-ray micro CT) shows that extrusion of a mucilage capsule leaves a pore of volume 3 times larger than the seed, surrounded by a shell of particles with lower pore size than the bulk soil. In three soils (sandy loam- S, loam-L, and clay loam-C) the aggregate stability index to wet sieving (Stw) decreased with one and two drying-wetting cycles (DW). Application of 2% w/w mucilage increased Stw before and after DW, from 29% in C to more than 60-fold in S. Mucilage amended samples after DW had higher or equal Stw than unamended soil before DW. Soil retained at the surface of hydrated diaspores exposed to water flow changed with soil texture (11.3, 90.5, 91.7 mg on each hydrated seed for S, L and C respectively) and chia genotype (6.7, 9.9 and 12.8 mg per hydrated seed in BC and G8 log-day flowering mutants and commercial Black chia respectively). Based our results myxodiaspores affect soil structure by providing a microenvironment of altered porosity and high stability around the mucilage capsule extruded by hydrated seed. This finding is relevant to characterizing a transient but crucial time of crop production around sowing.