A temperature‐sensitive nodulation mutant (<i>sym</i> 5) of <i>Pisum sativum</i> L.

Abstract

Abstract. In peas ( Pisum sativum L.) homozygous for sym 5, nodulation has an unusual temperature dependence. These sym 5 mutants nodulate poorly at a root temperature of 20°C but nodulate better at 12°C. By lowering the root temperature of the sym 5 mutants from a lightroom temperature of 20/15°C to a constant 12°C, 8d after planting, the number of nodules can be further increased. A cool period (12°C) as short as 6h, early in the infection process, is sufficient to significantly increase nodulation of plants otherwise growing at 20/15°C. This temperature‐sensitivity of nodulation is not due to a temperature induced change of a sym 5‐related, 66‐kD peptide but may involve accumulation of a gas in the rhizosphere.