Root system architecture of Kosteletzkya pentacarpos (Malvaceae) and belowground environmental influences on root and aerial growth dynamics

Abstract

Root growth and architecture of Kosteletzkya pentacarpos and its response to nutrients and soil texture were studied to facilitate domestication of this plant as a biofuel crop (seeds for oil, stems for ethanol). Because it is salt tolerant, it does not compete with food crops for land. Four soil treatments in the bottom chambers of two-chambered growing units (three nutrient levels in sandy loam and saline, dredged material) were used to test substrate influences on root structure and aerial growth in a greenhouse study. Simultaneously, underground reserves were determined by collecting aerial biomass of dark-grown plants. Root cores (15 × 50 cm) were taken to determine root architecture of 2-year-old field-grown plants. High nutrient availability increased the coarse root biomass (≥2 mm diameter) and increased capsule production. Plants grown in dredged sediment had no substantial growth differences from the controls. Underground reserves were significant. Field cores demonstrated that roots extended more than 50 cm with most of the coarse roots in the upper 20 cm and the coarse to fine root ratio decreasing with depth. Fine root surface area, measured using image-analysis software, was substantially greater than many other crops, as was root mass density. Root architecture of K. pentacarpos and its responses to various nutrient levels and soil types demonstrate that it is a promising species for further development as a crop on coastal saline land including dredged material sites. Its perennial taproot system stores carbon and will perform buffer functions between upland and wetlands as sea level rises.