Kin recognition in plants has attracted considerable attention following evidence that plants can distinguish neighbors based on genetic relatedness. Previous studies have primarily focused on morphological responses such as biomass allocation and spatial arrangement of roots and leaves. However, less is known about how kin recognition influences physiological responses and how these effects vary across developmental stages.
In this study, we investigated both physiological and life-history responses to kin and non-kin interactions in Arabidopsis thaliana using a temporal framework. The focal genotype was Col-0, which was grown under three conditions: solitary (Col-0 alone), kin pairs (Col-0 vs. Col-0), and non-kin pairs (Col-0 vs. Ler). Plants were cultivated for two months after transplanting. From 4.5 to 8 weeks after transplanting, physiological traits—including SPAD (chlorophyll content index), stomatal conductance, electron transport rate (ETR),—were measured twice weekly. In parallel, shoot, root, and reproductive organ biomass, as well as pod mass and diameter, were recorded repeatedly up to 7.5 weeks. At the end of the experiment, total seed mass and mean seed mass were measured.
Physiologically, SPAD values declined earlier and more strongly in non-kin pairs than in solitary or kin pairs. This decline was accompanied by significant reductions in ETR, suggesting decreased photosynthetic performance under non-kin competition. In contrast, no significant differences were observed in shoot or root biomass among treatments. However, reproductive organ biomass and pod mass were significantly greater in non-kin pairs compared to solitary and kin treatments. Total seed mass was significantly lower in kin pairs than in the other treatments, whereas mean seed mass per seed did not differ among treatments.
Taken together, our results indicate that A. thaliana alters both physiological performance and reproductive allocation depending on the genetic relatedness of neighboring conspecifics. Importantly, these responses are not static but vary across life stages: physiological suppression under non-kin interactions coincided with enhanced reproductive allocation, whereas kin interactions were associated with reduced total reproductive output. By integrating physiological and life-history perspectives, this study demonstrates that kin recognition shapes plant strategies dynamically throughout development, potentially influencing competitive interactions and fitness outcomes.