Root silicification of grasses and crops from Pampean region and its relevance on silica and silicophytolith content of soils

PAOLICCHI MICAELA; FERNANDEZ HONAINE MARIANA; BENVENUTO MARIA LAURA; OSTERRIETH MARGARITA

Aix en provence

Congreso; 10 th internatinal meeting on phytolith research; 2016

Root silicification of grasses and crops from Pampeanregion and its relevance on silica and silicophytolithcontent of soilsMariana Fern´andez Honaine∗1,2,3, Micaela Paolicchi1,2,3, Margarita Osterrieth1,2, andMaria Laura Benvenuto1,2,31Instituto de Geolog´ıa de Costas y del Cuaternario, Universidad Nacional de Mar del Plata-CIC ? CC722, Correo Central, Mar del Plata, Argentina, Argentina2Instituto de Investigaciones Marinas y Costeras, Universidad Nacional de Mar del Plata-CONICET ?CC 1260, Correo Central, Mar del Plata, Argentina, Argentina3Consejo Nacional de Investigaciones Cient´ıficas y T´ecnicas (CONICET) ? ArgentinaAbstractRoot tissues of grasses and dicots can accumulate amorphous silica. Particularly inPoaceae family, silica can be restricted to the endodermis, spread throughout all tissues ordeposited into intercellular spaces. The aim of the present study were 1) to analyze thesilica content in typical grasses and crops (soybean, maize, wheat) from Pampean region,Argentina; 2) to evaluate the potential input of silica and silicophytoliths from roots to soilsin natural and cultivated areas. Roots from eight typical pampean grasses and three cropswere collected from field. Also, soil samples, including the roots developed within them, werecollected every 10 cm along the profiles from natural and cultivated areas. They were driedand weighted, and the relative contribution of roots to total weight was calculated. Rootsilicophytoliths were extracted following a calcination technique and the content was calculatedas percentage of dry weight. Silicophytolith morphologies were described under lightmicroscope, according previous literature. Silicophytolith content ranged between 4-11% inpampean grasses and between 0.8-4.20% in crops. Bothriochloa laguroides and Sorghastrumpellitum produce silica aggregates in endodermal walls; while the rest of the grasses producesilicifications of endodermal walls and xylem. In crops, silica is deposited in xylem, endodermalcells and epidermal cells. In soils, the abundance of roots was higher at the first 10 cm.In this section the roots represented the 0.39% of the weight of natural soils and 0.03% ofcultivated soils. Towards the base to the profiles the values ranged between 0.0013-0.023%and 0.002-0.001%, in natural and cultivated soils, respectively. Considering a 15% (meanvalue) of silica content of roots obtained from soils, the total silicophytolith input from rootsto soils was 0.0585 gr per 100 gr of soil (at first 10 cm) and between 0.000195-0.00345 grper 100 gr of soil (10-60 cm) in the natural area. Instead, in crop area, where silica in rootswas 11%, the mean value of silica input was 0.0033 gr per 100 gr of soil (first 10cm) and0.00011-0.00022 gr per 100 gr of soil (10-60cm). The main morphologies found in soil rootswere silicified xylem and elongate phytoliths, similar to those found in roots from Pooideaegrasses and crops. The results obtained in this study revealed that 1) silicophytolith productionin roots from pampean grasses and crops is abundant; 2) the morphologies found are∗Speakersciencesconf.org:10thimpr:116660coincident with previous studies in relation to Poaceae; 3) the input of silica and silicophytolithsfrom roots to soils may be more relevant in natural than in cultivated areas, due tothe higher development of roots but also due to the higher production of silicophytoliths innative grasses. Since the root silicophytolith morphologies seem to be more labile than themorphologies produced by other grass organs, it may be possible that they have a strongestinfluence on silica cycle in soils, due to a higher/faster dissolution rate; and also it maycontribute to preservation of soil aggregates, due to the role that silica has on soil structure.Acknowledgments: PICT 2036, PICT 1583, EXA 741/15Keywords: root silicophytolith content, endodermis silicification, amorphous silica, input, Pampeanregion, Argentina, soil