Temperature response of early foliar expansion of potato and wheat

Abstract

We studied the course of early leaf area expansion and specific leaf area (S(LA)) in potato (Solanum tuberosum L.) and wheat (Triticum aestivum L.) genotypes and tested whether air temperature explains differences in these courses within different environments. Such knowledge can be used to improve crop growth modelling. The relative rate of leaf area expansion (R(L)) of potato and wheat decreased with thermal time, but was nearly linear up to a leaf area index (L) of 1·0. The R(L) (L < 1; mean: 17·9 x 10-3°C-1 d-1) of potato showed an interaction between genotype and environment, and varied with year. The R(L) (L < 1; mean: 7·1 x 10-3°C-1 d-1) of winter wheat was lower than that of spring wheat (mean: 10·9 x 10-3°C-1 d-1), and both varied with year. S(LA) of potato increased nearly linearly with thermal time from 5 to 15 m2 kg-1 at 50% emergence, to 20 to 25 m2 kg-1 at 155°Cd, and then decreased slightly. The S(LA) of both winter and spring wheat began at 16 to 23 m2 kg-1 and in most cases increased slightly with thermal time. In potato, regression parameters of S(LA) with thermal time were affected by environment (management conditions and year) and genotype; in wheat they were affected by environment (year and site). Treatment effects on R(L) of potato were not correlated with those on S(LA), and were only partly correlated for wheat. Therefore we conclude that the early foliar expansion of potato is associated with a strong increase in S(LA), and not so for wheat. For both crops the course of early leaf area expansion and of S(LA) with air temperature is not robust over environments and genotypes. The consequences of these results for modelling are discussed. (C) 2000 Annals of Botany Company.