Variations in heterotrophic seedling growth parameters of 28 plant species and their relationships with seed traits

The timing of seedling emergence, influenced by heterotrophic growth, is a critical determinant for the competitive success of annual plants in arable cropping systems under temperate climates. While the heterotrophic growth phase is crucial for seedling establishment under field conditions, it has been much less explored compared to other growth phases. We address this gap by: i) analyzing the heterotrophic growth of primary seminal roots and shoots, focusing on their inter- and intra-specific diversity and growth synchrony, and ii) investigating the relationship between seed traits and heterotrophic growth parameters to explore how these traits influence growth dynamics. We synthesized data from 28 plant species, including 13 crops, 11 weeds, and four model plants, combining new datasets and published data. Inter-specific variation in heterotrophic root growth was assessed across all 28 species, while intra-specific variation in heterotrophic growth was examined in detail for seven species. We also explored the relationships between heterotrophic growth parameters (for both root and shoot) and seed traits, including seed mass and hydrothermal time model parameters — base water potential (Ψ b ) and base temperature (T b ) for germination. Our results showed that the maximum seedling length increased with an increase in seed mass or a decrease in either Ψ b or T b . The thermal time to mid-elongation, maximal shoot growth rate, and growth synchrony were significantly correlated to seed mass in weeds. This study enhances our ability to predict plant performance in agricultural systems, informs weed management strategies, and supports ecological forecasting in changing environments. • Thermal time required for heterotrophic growth differs among species. • Both inter- and intra-specific variations in root/shoot growth exist. • A positive correlation was observed between maximal growth length and seed mass. • Base temperature was negatively correlated with the maximal root length. • Base water potential was negatively correlated with the maximal growth length.