Abstract:

Objective: This study aims to investigate the effects of continuous drought on the functional traits and trait networks of Daemonorops jenkinsiana seedlings, and elucidate the underlying adaptive mechanisms to drought stress, so as to provide a scientific basis for the conservation and utilization of this rattan resource. Method: A continuous drought experiment was conducted on 3-year-old potted D. jenkinsiana seedlings. Based on soil relative humidity (relative to field capacity) and plant growth status, four treatments were established: control (non-drought), light drought, medium drought, and severe drought. Upon reaching each stress level, a total of 47 functional traits were measured, including leaf gas exchange, chlorophyll fluorescence, leaf resistance-related physiological substances, leaf morphology, non-structural carbohydrates in roots and leaves, root and leaf anatomy, and biomass. Result: 1) The functional traits of D. jenkinsiana seedlings in response to drought exhibited a temporal sequence. As drought intensified, the order of trait type response was: photosynthetic physiological traits, followed by biochemical traits, morphological and anatomical traits, and finally biomass traits. 2) Soil moisture indirectly promoted biomass accumulation through the pathways of photosynthetic physiological traits and biochemical traits, with both jointly dominating formation of biomass in D. jenkinsiana seedlings. In contrast, organ morphological and anatomical traits had no significant effect on biomass. 3) Compared with non-drought conditions, the modularity and average path length of D. jenkinsiana increased under drought stress, whereas edge density decreased. Under light and medium drought, network diameter and average clustering coefficient increased. However, under severe drought, network diameter and average clustering coefficient showed little change. 4) Regardless of drought or non-drought conditions, photosynthetic physiological traits exhibited high network degree and consistently served as the central traits of the network. The betweenness centrality of superoxide dismutase (SOD) activity remained relatively high before severe drought, indicating that it was a key trait connecting different trait modules within the network. The closeness centrality of maximum fluorescence under dark adaptation (F_m) was relatively high across all three continuous drought durations, reaching its maximum value (0.46) under severe drought. Conclusion: The drought resistance strategy of D. jenkinsiana dynamically shifts with drought severity. Under non-drought and light drought conditions, the strategy is characterized by photosynthetic optimization and biomass accumulation. Under medium drought, it transitions toward physiological regulation and osmotic protection. Under severe drought, the plant prioritizes the protection of the structural integrity of the photosynthetic apparatus, with resources preferentially allocated to maintaining photosystem function. The common strategy for D. jenkinsiana to cope with different degrees of drought is to maintain the stability of photosystem Ⅱ (PSⅡ) function. Under drought stress, root and leaf traits undergo cross-module integration, reflecting systemic regulation across tissues and levels. Photosynthetic physiological traits consistently remain the core traits of the trait network. Chlorophyll fluorescence traits (e.g., F_m) become key traits under severe drought. SOD activity serves as a key node connecting different trait modules under light to medium drought, but its capacity to regulate the trait network is lost under severe drought.

Key words: Daemonorops jenkinsiana, functional traits, trait network, drought stress, adaptive strategies