Interspecific variation in leaf traits, photosynthetic light response, and whole- plant productivity in amaranths (Amaranthus spp. L.)

Photosynthetic light response curve parameters help us understand the interspecific variation in photosynthetic traits, leaf acclimation status, carbon uptake, and plant productivity in specific environments. These parameters are also influenced by leaf traits which rely on species and growth environment. In accessions of four amaranth species (Amaranthus. hybridus, A. dubius, A. hypochondriacus, and A. cruentus), we determined variations in the net photosynthetic light response curves and leaf traits, and analysed the relationships between maximum gross photosynthetic rate, leaf traits, and whole-plant productivity. Non-rectangular hyperbolae were used for the net photosynthesis light response curves. Maximum gross photosynthetic rate (P-gmax) was the only variant parameter among the species, ranging from 22.29 to 34.21 mu mol m(-2) s(-1). Interspecific variation existed for all the leaf traits except leaf mass per area and leaf inclination angle. Stomatal conductance, nitrogen, chlorophyll, and carotenoid contents, as well as leaf area correlated with P-gmax. Stomatal conductance and leaf nitrogen explained much of the variation in P-gmax at the leaf level. At the plant level, the slope between absolute growth rate and leaf area showed a strong linear relationship with P-gmax. Overall, A. hybridus and A. cruentus exhibited higher P-gmax at the leaf level and light use efficiency at the whole-plant level than A. dubius, and A. hypochondriacus. Thus, A. hybridus and A. cruentus tended to be more efficient with respect to carbon assimilation. These findings highlight the correlation between leaf photosynthetic characteristics, other leaf traits, and whole plant productivity in amaranths. Future studies may explore more species and accessions of Amaranthus at different locations or light environments.

Automated summary

Photosynthetic light response curve parameters are important for understanding the variation in photosynthetic traits, leaf acclimation status, carbon uptake, and plant productivity among different species. In this study, we analyzed the net photosynthetic light response curves and leaf traits of four amaranth species and found that maximum gross photosynthetic rate and leaf traits were correlated with plant productivity. We also observed that A. hybridus and A. cruentus had higher photosynthetic rates and light use efficiency compared to A. dubius and A. hypochondriacus. These findings highlight the importance of leaf photosynthetic characteristics and other leaf traits in determining plant productivity in amaranths.