Role of microstructure of cellulosic mucilage in seed anchorage: A mechanical interpretation of antitelechory in plants

Abstract

Aims and Background

Cellulosic, hemicellulosic and pectinaceous mucilages produced by certain angiosperms as adaptation in myxodiaspory are investigated in the past to understand their role in seed dispersal. The present understanding of zoochory and telechory are based on mucilage amount, state of hydration and to a limited extent, role of mucilage microstructure studied using adhesion and friction. However, in the case of cellulosic mucilages, the role played by the cellulosic fibrils in seed dispersal is not clear, especially since they have a negative correlation with endozoochory.

Methods

Using fresh cellulosic seed mucilages from sweet basil (Ocimum basilicum) and chia (Salvia hispanica) we investigate the role of microstructure of the mucilage in two key behaviours: anchoring and adhesion properties of the seeds through Large Amplitude Oscillatory Shear (LAOS) rheological experiments carried out on seed mucilages along with wet tack strength studies.

Results

We report a special large deformation mechanism operational in these cellulosic mucilages triggered through ‘strain stiffening’. In comparison to pectin gels which also exhibit strain stiffening at lower strains, these mucilages show strain stiffening under large deformations along with higher wet adhesion strength. From the LAOS rheological studies and microstructure, we have shown that cellulosic components have a significant role towards the observed behaviour.

Conclusions

The unique strain stiffening behaviour and strong wet adhesion characteristics observed in basil and chia seed mucilage strongly point to the plausible role of cellulosic components in supporting the antitelechory found commonly in plants of arid habitats.