The root system dominates the growth balance between the aboveground and belowground parts of cotton

Abstract

Growth balance is very important for plants, which is the coordination of resource acquisition between the aboveground and belowground parts. Extensive research has focused on the aboveground portion, and less attention has been given to the root system. Furthermore, the specific regulatory mechanisms responsible for maintaining the growth balance between aboveground and belowground in crops are still unclear. We examined the root/shoot ratio and leaf area/root length ratio in 19 pima cotton (Gossypium barbadense) and 19 upland cotton (Gossypium hirsutum) accessions, and the effects of root traits on the growth balance were explored. The results indicated that growth balance could affect the biomass accumulation of cotton, and the root system was the core part of controlling growth balance. The difference was that the specific root length played a major role in pima cotton, while the root mass fraction was more important in upland cotton. Despite these differences, both types of cotton achieved similar resource acquisition capability through the synergistic effect of mass fraction and morphological characteristics of leaves and roots. Our study is the first to demonstrate that the root system dominates the growth balance in pima and upland cotton. Selecting accessions with similar phenotypes may represent a promising new direction for increasing the success probability of interspecific hybridization and introgression breeding. These findings expand our understanding of the resource acquisition and utilization of crops and provide a valuable perspective for ecological research and crop breeding.