Plant Silicon and Phytolith Contents as Affected by Water Availability and Herbivory: Integrating Laboratory Experimentation and Natural Habitat Studies

Purpose When studying the effects of environmental variables on plant Si contents, results of laboratory and field experiments do not always agree with each other. However, new insights into the roles silicon plays in plant life can be gained if both approaches are integrated. Methods Experimental and natural-habitat studies of the effects of water availability and herbivory on plant silicon contents are reviewed and integrated. Results Although higher water availability is expected to have a positive effect on plant silicon contents, naturally-growing plants often have high silicon contents when grown under drought conditions. Likewise, although experimentation suggests that herbivory has a positive effect on plant silicon contents, such a correlation is not often found in nature. Conclusions Stronger effects of multiple environmental variables or selection in favour of constitutive silicon uptake and deposition as protection from drought and grazing stresses are the reasonable causes of discrepancies between experimental and natural-habitat studies.