BACKGROUND AND AIMS: Understanding interspecific differences in plant growth rates and their internal and external drivers is key to predicting species responses to ongoing environmental changes. Annual growth rates vary among plants based on their ecological preferences, growth forms, ecophysiological adaptations and evolutionary history. However, the relative importance of these factors remains unclear, particularly in high-mountain ecosystems experiencing rapid changes. METHODS: We examined how habitat associations, elevational optima, growth forms, and ecophysiological and anatomical traits influence interspecific differences in radial growth rates among 324 vascular dicot species naturally occurring in the western Himalayas. Growth rates were determined from annual ring width measurements on the oldest plant sections of over 7800 individuals from a range of habitats (desert, steppe, wetland, alpine, subnival), growth forms (perennial tap-rooted, rhizomatous, cushiony, woody) and climatic gradients (elevations of 2650-6150 m). KEY RESULTS: Habitat associations accounted for 24 % of the variability in interspecific growth rates. Adding growth form and height increased the explanation to 42 %, and incorporating plant functional traits further improved predictions to 46 %. Growth rates were higher in warmer, drier conditions and lower in cold, wet environments. Subnival cushion plants had the slowest growth, while ruderal plants grew the fastest. Desert plants showed higher growth rates, reflecting their drought adaptive strategies, while wetland forbs had lower growth rates due to increased resource competition. Growth was positively correlated with leaf nitrogen content and non-structural carbohydrates (mainly fructans), due to enhanced photosynthesis and stress tolerance, and negatively correlated with leaf carbon and root nitrogen content. CONCLUSION: Our study of 324 dicot species in the western Himalayas suggests that plant growth in high elevations is determined by a combination of habitat conditions, morphological traits and ecophysiological adaptations. Growth variations among the highest-growing angiosperms reflect adaptive strategies along the global 'fast-slow' and 'acquisitive-conservative' spectrums. These results underscore the importance of habitat-specific studies for predicting plant growth responses to environmental changes, emphasizing a species-specific approach for effective conservation in fragile ecosystems.

• Klíčová slova
• Fast–slow economics spectrum, Himalayan plants, ecophysiology, functional traits, herbchronology, high-elevation plants, plant growth,
• MeSH
• druhová specificita MeSH
• ekosystém * MeSH
• fyziologická adaptace * MeSH
• nadmořská výška MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Indie MeSH

Plants in extreme environments face pronounced seasonal variations in abiotic conditions, influencing their growth and carbon gain. However, our understanding of how plants in cold-arid mountains sustain carbon assimilation during short growing seasons remains limited. Here, we investigate seasonal dynamics and interspecific variability in photochemical performance of 310 individuals, comprising 10 different dicotyledon plant species across 3100-5300 m in the NW Himalayas, spanning semi-deserts to subnival zones. From early June to late September, we measured Fv/Fm and ΦPSII, assessing ΦPSII relationships with leaf traits (N, P, C, C:N ratio, LMA, and LDMC) and environmental factors (temperature, soil moisture content, etc.). Our findings revealed that high-Himalayan plants maintained relatively stable photosynthetic performance (Fv/Fm = 0.7-0.85), indicating optimal function even under potential stress. Contrary to our hypothesis that ΦPSII peaks mid-season in alpine and subnival zones and early season in steppes and semi-deserts, it declined by 33% across species and habitats throughout the season. This decline was closely associated with nutrient depletion, leaf senescence, and energy-water limitations. Species exhibited distinct strategies, with some prioritising structural resilience over photosynthesis, while others optimised photochemical performance despite environmental constraints. Alpine and subnival plant performance was constrained more by soil moisture deficits and high temperatures than cold temperatures, while deep-rooted steppe and semi-desert plants were primarily constrained by high temperatures and evaporative forcing rather than soil moisture deficit. These results provide new insights into how Himalayan plants adapt to extreme environmental conditions, highlighting the crucial interplay between moisture and temperature in shaping their performance within cold-arid mountains.

• Klíčová slova
• Fv/Fm, Himalayas, alpine and subnival ecosystems, chlorophyll fluorescence, cold‐arid mountains, leaf traits, photochemical performance of PSII, seasonal dynamics,
• MeSH
• ekosystém MeSH
• fotosyntéza * fyziologie   MeSH
• listy rostlin fyziologie   MeSH
• nízká teplota MeSH
• půda chemie   MeSH
• roční období MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Himálaj MeSH
• Názvy látek
• půda MeSH

BACKGROUND AND AIMS: Understanding biomass allocation among plant organs is crucial for comprehending plant growth optimization, survival and responses to the drivers of global change. Yet, the mechanisms governing mass allocation in vascular plants from extreme elevations exposed to cold and drought stresses remain poorly understood. METHODOLOGY: We analysed organ mass weights and fractions in 258 Himalayan herbaceous species across diverse habitats (wetland, steppe, alpine), growth forms (annual, perennial taprooted, rhizomatous and cushiony) and climatic gradients (3500-6150 m elevation) to explore whether biomass distribution adhered to fixed allometric or optimal partitioning rules, and how variations in size, phylogeny and ecological preferences influence their strategies for resource allocation. KEY FINDINGS: Following optimal partitioning theory, Himalayan plants distribute more biomass to key organs vital for acquiring and preserving limited resources necessary for their growth and survival. Allocation strategies are mainly influenced by plant growth forms and habitat conditions, notably temperature, water availability and evaporative demands. Alpine plants invest primarily in below-ground stem bases for storage and regeneration, reducing above-ground stems while increasing leaf mass fraction to maximize carbon assimilation in their short growing season. Conversely, arid steppe plants prioritize deep roots over leaves to secure water and minimize transpiration. Wetland plants allocate resources to above-ground stems and below-ground rhizomes, enabling them to resist competition and grazing in fertile environments. CONCLUSIONS: Himalayan plants from extreme elevations optimize their allocation strategies to acquire scarce resources under specific conditions, efficiently investing carbon from supportive to acquisitive and protective functions with increasing cold and drought. Intraspecific variation and shared ancestry have not significantly altered biomass allocation strategies of Himalayan plants. Despite diverse evolutionary histories, plants from similar habitats have developed comparable phenotypic structures to adapt to their specific environments. This study offers new insights into plant adaptations in diverse Himalayan environments and underscores the importance of efficient resource allocation for survival and growth in challenging conditions.

• Klíčová slova
• Biomass allocation, Himalayas, allometric partitioning theory, environmental gradients, optimal partitioning theory, phylogeny,
• MeSH
• biomasa * MeSH
• ekosystém MeSH
• fyziologická adaptace * MeSH
• Magnoliopsida * fyziologie   růst a vývoj   MeSH
• nízká teplota * MeSH
• období sucha * MeSH
• Publikační typ
• časopisecké články MeSH