Growth analyses of tomato genotypes grown under low night temperatures and low light intensity

Summary In three experiments the growth of 16 genotypes of tomato was examined. The plants were raised in growth rooms at a day temperature of 19°C and night temperatures of 14, 10 or 6°C respectively under a light intensity of 24 Wm^-2 visible radiation and a daylength of 8 hours. The results were analysed by a multivariate analysis of variance.Relative growth rate (RGR), leaf area ratio (LAR), specific leaf area (SLA) and leaf weight ratio (LWR) decreased with time. The change in net assimilation rate (NAR) was small. The decrease in RGR was mainly due to the decrease in LAR.RGR, LAR and SLA were lower and LWR slightly higher at lower night temperatures. NAR was hardly affected. The lower RGR at lower night temperatures was mainly due to a lower SLA.Significant differences between genotypes were found in total dry weight, NAR, LAR, SLA and LWR, but hardly in RGR. Significant genotype × temperature interactions occurred.LAR and SLA were positively, NAR and LAR, and NAR and SLA negatively correlated.