Trade-Offs Between Growth, Longevity, and Storage Carbohydrates in Herbs and Shrubs: Evidence for Active Carbon Allocation Strategies.

Abstract

Plants store nonstructural carbohydrates (NSCs) like starch, fructans and soluble sugars to support metabolism, stress tolerance and defence during low photosynthesis, ultimately influencing their growth and longevity. However, the relationship between NSC composition and growth or persistence in wild plants remains unclear. This study explores trade-offs between growth, longevity and NSCs in 201 plant species across diverse climates in the Western USA, spanning 500-4300 m in elevation and 80-1000 mm in precipitation. Annual growth rates and plant ages were derived from the ring widths of semidesert, steppe and alpine herbs and shrubs, along with NSC profiles in their roots and rhizomes. Results showed an inverse relationship between growth and age, with total NSC, starch and fructan levels negatively correlated with growth, supporting the growth-longevity and growth-storage trade-off hypotheses. Conversely, higher growth rates were linked to soluble sugars, suggesting that climate-driven growth limitations alone do not explain increased NSCs. Fructans were positively associated with longevity, especially in long-lived desert shrubs and alpine herbs, underscoring NSCs' active role in survival strategies. These findings challenge the carbon surplus hypothesis, suggesting that plants actively use specific NSCs to balance growth and persistence, with energy-rich sugars promoting growth and osmoprotective fructans enhancing longevity.