Root silicification of grasses and crops from Pampean region, Argentina

PAOLICCHI, MICAELA; FERNÁNDEZ HONAINE, MARIANA; OSTERRIETH, MARGARITA; BENVENUTO, MARIA LAURA; ALTAMIRANO, STELLA MARIS

Rio de Janeiro

Congreso; 68º Congresso Nacional de Botânica e XXXVI Jornada Fluminense de Botânica.; 2017

Plants can accumulate amorphous silica (SiO2) in intra or intercellular spaces of different tissues. Roots, as well as the rest of the organs, produce amorphous silica biomineralizations (silicophytoliths) in their tissues; however, there are scarce studies that analyzed root silicification. In Poaceae family, silica can be restricted to the endodermis, spread throughout all root tissues or deposited into intercellular spaces. Once roots are decomposed, the deposits of amorphous silica are incorporated to the rest of the soil components. The aims of this study were 1) to analyze the silica content in roots of typical grasses and some crops (soybean, maize and wheat) from Pampean region, Argentina; 2) to identify the location of the amorphous silica deposits; 3) to evaluate the potential input of silica and silicophytoliths from roots to soils. Roots from seven typical pampean grasses and three crops were collected from natural and cultivated areas from SE Buenos Aires province, Argentina. Silicophytoliths were extracted through a calcination technique, theirs morphologies were described under light and electron scanning microscopes. In order to identify the location of silica deposits, roots were transverse or longitudinal sectioned, cleared and stained with phenol. Silicophytolith content ranged between 4-11% in pampean grasses and 0.8-4.20% in crops. Bothriochloa laguroides produces silica aggregates in endodermal walls; while the rest of the pampean grasses produce silicifications of endodermal walls and xylem. In crops, silica is deposited in xylem, endodermal cells and into intercellular spaces of epidermal cells. The results obtained revealed that 1) silicophytolith production in roots from pampean grasses and crops is abundant; 2) the morphologies found are coincident with previous studies in relation to Poaceae 3) the input of silica and silicophytoliths from roots to soils may be more relevant in natural than in cultivated areas, due to the higher production of silicophytoliths in native grasses. The abundant production of silicophytoliths by roots of plants represents an important contribution of amorphous silica to soils and, in consequence to the Si cycle. Finally, the results contribute to the understanding of the silicification process in native and cultivated species from Argentina