Leaf silicification in grasses — A review

Abstract

Silica is absorbed from the soil by many grasses in an active or passive manner depending upon the species involved. It is carried upwards in the transpiration stream and deposited throughout the plant where it polymerizes to form amorphous silica gel. Deposition appears to be a passive process but some active mechanism may be involved. Deposition follows a set sequence and may be initiated before leaf expansion. Silica benefits most plants but may have adverse effects upon herbivores ingesting this plant silica. A number of possible roles have been suggested for silica deposition in plants such as the “light window” hypothesis or as a defence against large herbivores and these are discussed in the light of the available evidence. It is concluded that leaf silicification evolved in response to invertebrate herbivory and is primarily aimed at reducing tissue loss to these herbivores.

Uittreksel

Silika word deur verskeie grasse uit die grond op ‘n aktiewe of passiewe wyse geabsorbeer, afhangend van die betrokke spesie. Dit word opwaarts in die transpirasie stroom vervoer en oor die hele plant neergelê waar dit polimeriseer om ‘n struktuurlose silikajel te vorm. Dit skyn asof neerlegging ‘n passiewe proses is, maar aktiewe meganismes mag ook betrokke wees. Neerlegging geskied volgens ‘n vaste volgorde en mag reeds voor blaarontwikkeling ‘n aanvang neem. Die meeste plante word deur silika bevoordeel, maar dit mag ‘n negatiewe uitwerking op herbivore hê wat hierdie plantsilika inneem. Verskeie moontlike funksies vir silikaneerlegging is al oorweeg, byvoorbeeld die “lig inlaat” hipotese, of as ‘n verweer teen groot herbivore. Dit word in die lig van bestaande bewyse bespreek. Die gevolgtrekking word gemaak dot blaar‐silisifikasie as reaksie tot ongewerwelde herbivo‐rie ontwikkel is, en primêr gemik is op verminderde weefselverlies by hierdie herbivore.

Additional index words:

• Uptake
• distribution
• functions
• adaptive significance