Variation in relative growth rate and growth traits in wild and cultivated Capsicum accessions grown under different temperatures

Differences in environmental conditions are known to influence plant growth and growth-related traits. The aim of this study was to identify the variation in relative growth rate (RGR), and its underlying physiological and morphological traits, in a group of ten wild and cultivated Capsicum accessions of four Capsicum species at two contrasting temperatures. Therefore, a growth analysis was performed at two temperature regimes (21.1 degrees/18.7 degrees C and 17.3 degrees/14.7 degrees C; day/night). Variation in RGR, growth-related traits and their mutual relationships were analysed at the start of branching. RGR at branching proved to be a reliable predictor for the development of dry mass pre-anthesis in Capsicum. The reduction in RGR and growth-related traits, in response to lowered temperatures, varied between these Capsicum accessions; some being better adapted to low temperatures than others. The variation in the reduction of RGR under lowered temperatures was due to changes in both net assimilation rate (NAR) and leaf area ratio (LAR). Dry mass allocation to the leaves (leaf mass fraction) was not influenced by temperature. Specific leaf area (SLA) was correlated with RGR under standard temperatures, but not under lowered temperatures. At both temperatures, NAR was the most important factor to explain variations in RGR between the different Capsicum accessions. From this study, and the work of others, it was concluded that NAR was the most important factor to explain variations in RGR in plants of the same genus or species, and even between closely-related plant species.