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<p>Desert winter ephemerals are short-lived herbaceous species that exploit brief periods of rainfall to complete their life cycles rapidly. This study investigated the photosynthetic adaptations of five such annual forb species, <i>Malva parviflora</i>,<i> Lactuca serriola</i>,<i> Sisymbrium irio</i>,<i> Rumex pulcher</i>, and <i>Chenopodiastrum murale</i>, naturally growing under shaded, low-light conditions beneath date palm canopies. Gas exchange measurements and chlorophyll <i>a</i> fluorescence quenching analysis revealed that all species maintained high rates of CO₂ assimilation and exhibited efficient photosystem II (PSII) photochemistry, as evidenced by elevated maximum and effective quantum yields and a substantial proportion of open PSII reaction centers. Among the species evaluated, the heliotropic <i>M. parviflora</i> achieved the greatest above-ground biomass, exceeding that of the other forbs by 62–400%. This superior growth coincided with markedly enhanced energy conservation performance indices: efficiencies associated with the reduction of intersystem electron acceptors were 20–53% higher, while those linked to terminal acceptor reduction were 45–68% higher in <i>M. parviflora</i>. These enhancements corresponded with elevated parameters derived from polyphasic chlorophyll <i>a</i> fluorescence transients, indicating more efficient PSII photochemistry and electron transport relative to the other species. Additionally, <i>M. parviflora</i> exhibited optimized pigment composition and distinctive photoprotective behavior, including slow non-photochemical quenching (NPQ) induction but rapid relaxation, suggesting a highly responsive shift between thermal energy dissipation and photochemical use. Together, these traits reveal a coordinated suite of photosynthetic adjustments that underpin the species’ exceptional biomass production and help explain its competitive dominance in low-light desert understory microhabitats.</p>

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Casting Shadows Over Competitor Species: Photosynthetic Strategies of Heliotropic Malva parviflora To Outgrow Desert Winter Ephemerals in low-light Environments

  • 期刊论文

  • 发表日期：

    2025年12月10日

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  • Ahmad Zia

摘要

Desert winter ephemerals are short-lived herbaceous species that exploit brief periods of rainfall to complete their life cycles rapidly. This study investigated the photosynthetic adaptations of five such annual forb species, Malva parviflora, Lactuca serriola, Sisymbrium irio, Rumex pulcher, and Chenopodiastrum murale, naturally growing under shaded, low-light conditions beneath date palm canopies. Gas exchange measurements and chlorophyll a fluorescence quenching analysis revealed that all species maintained high rates of CO₂ assimilation and exhibited efficient photosystem II (PSII) photochemistry, as evidenced by elevated maximum and effective quantum yields and a substantial proportion of open PSII reaction centers. Among the species evaluated, the heliotropic M. parviflora achieved the greatest above-ground biomass, exceeding that of the other forbs by 62–400%. This superior growth coincided with markedly enhanced energy conservation performance indices: efficiencies associated with the reduction of intersystem electron acceptors were 20–53% higher, while those linked to terminal acceptor reduction were 45–68% higher in M. parviflora. These enhancements corresponded with elevated parameters derived from polyphasic chlorophyll a fluorescence transients, indicating more efficient PSII photochemistry and electron transport relative to the other species. Additionally, M. parviflora exhibited optimized pigment composition and distinctive photoprotective behavior, including slow non-photochemical quenching (NPQ) induction but rapid relaxation, suggesting a highly responsive shift between thermal energy dissipation and photochemical use. Together, these traits reveal a coordinated suite of photosynthetic adjustments that underpin the species’ exceptional biomass production and help explain its competitive dominance in low-light desert understory microhabitats.