The effects of different external nitrate concentrations on growth of Phaseolus vulgaris cv. Seafarer at chilling temperatures

Abstract

SummaryThe effects of different applied nitrate concentrations (1 to 50 mol m3) on growth of Phaseolus vulgaris cv. Seafarer at temperatures around 15°C was examined. Total plant dry weight and carbon content decreased sharply with increased applied nitrate 1 to 10 mol m‐3 then decreased slightly with further increases in applied N. Total plant reduced ‐N content increased sharply with increased applied nitrate concentration from 1 to 5 mol m‐3, changed little with increased applied nitrate from 5 to 25 mol m‐3, then increased when applied nitrate was increased from 25 to 50 mol m‐3. Nitrate concentration in all tissues increased sharply with applied nitrate increased from 1 to 10 mol m3 and showed a further increase at 50 mol m3 applied nitrate.Fresh weight to dry weight ratio for all leaves and specific leaf area for all secondary leaves increased sharply with applied nitrate concentration from 1 to 5 mol m‐3 then decreased with applied nitrate 25 to 50 mol m3 Secondary leaf chlorophyll concentration decreased sharply when applied nitrate increased from 1 to 5 mol m‐3 but increased with applied nitrate from 25 to 50 mol m‐3. Initially, the rate of leaf extension was greater at 20 mol m‐3 applied nitrate than 1 mol m‐3 applied nitrate.It is proposed that decreased growth with increased applied nitrate in the range 1 to 10 mol m‐3 is due to increased leaf damage caused by a greater rate of leaf expansion.