Abstract: Aims This study compares different inflorescence area measurement methods in Fabaceae (subfamily Papilionoideae), aiming to provide methodological references for studies on plant functional traits and reproductive strategies.
Methods Five species of Papilionoideae were selected as research subjects, and the differences among three measurement methods—fully unfolded area, column area, and projected area—were measured and analyzed, along with their correlations with carbon economics and physiological indicators.
Important findings The results demonstrate that: (1) Inflorescence areas obtained by different measurement methods is in the order of fully unfolded area > column area ≈ projected area. Linear regression reveals a significant positive correlation between any two types of areas (p < 0.001). The conversion equation for different areas is: projected area (cm²) = 0.20 × fully unfolded area (cm²); projected area (cm²) = 0.67 × column area (cm²); column area (cm²) = 0.27 × fully unfolded area (cm²); (2) Both fully unfolded area and projected area show significant positive correlations with inflorescence dry weight (p < 0.001; p = 0.006) and total respiration rate (p < 0.001; p = 0.006), whereas column area exhibits no significant correlation with inflorescence dry weight, total transpiration rate, or total respiration rate (p > 0.05). Projected inflorescence area can be measured easily and quickly using image-based methods, making it a convenient and highly repeatable indicator. We therefore recommend projected area as the preferred standard for quantifying inflorescence area. By establishing the conversion relationships between different area indices and verifying the effectiveness of projected area in representing carbon investment and metabolic activity in reproductive organs, this study provides a viable pathway for building trait databases and conducting comparative ecological analyses.

Key words: papilionoideae, raceme area, flower mass per area (FMA), transpiration, respiration