Water supply influences boron uptake by transplanted oilseed rape (Brassica napus cv. Eureka) grown in low boron soil

Abstract

Previous studies have shown that low soil water supply depresses boron (B) uptake and may induce B deficiency in crops at low soil B. The present study was conducted to assess the possibility that increases in root/shoot ratio induced by water stress might offset the negative effect of water stress on B absorption in low B soil. Oilseed rape (Brassica napus cv. Eureka) plants were subject to a factorial combination of two levels of B: +B (0.45 mg B kg-1 air dry soil) and -B (without added B); and three levels of water supply: adequate (Wet), subsoil dry (Wet-Dry) and surface soil dry (Dry). In -B soil, the water stress treatments significantly increased root dry weights, but decreased shoot dry weights, resulting in a decrease in shoot/root ratio. By contrast, water stress had no effect on shoot/root ratios of plants in +B soil. Decreasing water supply in the soil significantly decreased B absorption per unit root mass in -B soil but not in +B soil. The increase in root/shoot ratio was unable to significantly offset the decrease in B uptake induced by dry soil conditions and water stress still strongly depressed B concentrations in young leaves.