Silicon en route - from loam to leaf

The beneficial effects of silicon (Si) in higher plants are widely recognized under stress (abiotic and biotic), specifically in plants with a relatively higher ability to absorb and accumulate the element. The capability of plants to take up, transport and accumulate Si varies considerably across and within species, so do the Si derived benefits. This variation has been attributed to differences in plant species’ anatomical, physiological, and morphological features, the presence of functional Si transporters, the quantity and type of silicic acid supply and the interaction of deposition and dissolution processes between distinct silicon fractions in soil. Si mobility is also strongly influenced by the plant’s biocycling and rhizosphere effects. However, the understanding of the actual mechanism of Si’s journey from soil to leaf is still farfetched and complicated by the contradictory reports in the voluminous literature. Moreover, crosstalk between Si and other signaling molecules, particularly under stress, further confounds the results. Therefore, a thorough understanding of various factors and processes influencing Si uptake, transport, and deposition (silicification) is crucial for maximizing the Si derived benefits in stressful environments. Here we document the current state of knowledge about Si uptake, mechanisms of Si transport and its role in stress tolerance within plants. We also highlight the knowledge gaps in Si mobilization and describe future research priorities.