Calcium and Silicon Precipitation in Pinus taeda Needles in Response to Soil Application of Cellulosic Residue

Abstract

The use of biosolids as a sustainable alternative in the management of planted Pinus taeda forests affects availability of nutrients and beneficial elements. Calcium (Ca) and Silicon (Si) play important roles in plant regulatory and protective systems; therefore, our objective was to use scanning electron microscopy combined with energy-dispersive spectroscopy (SEM-EDS) to analyze the accumulation of elements in P. taeda needles grown in soil that received 0 to 60 Mg ha^-1 applications of cellulosic waste. Microanalyses of needle sections were performed using a SEM with elemental detection by EDS. Mapping mode allowed for detection and analysis of Ca, Si, and C distributions in needle sections. Calcium and Si precipitation occurred in needles, with Ca accumulating in the phloem and Si in the epidermal cells. Application of 60 Mg ha^-1 changed the availability and accumulation of elements, which resulted in more Ca crystals and fewer Si crystals.

Keywords:
Calcium oxalate; phytoliths; electron microscopy

Key message:

Different patterns of Ca and Si accumulation (with possible physiological and ecological roles) as function of cellulosic waste application were detected in P. taeda by using SEM - EDS microanalysis.