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Abstract <p>Under conditions of increasing climate aridity in the southern regions, research into the adaptive mechanisms of forest-forming oak species has important prognostic significance. The aim of this work was a comparative assessment of resistance to water deficit and recovery ability in seedlings of the native deciduous <i>Quercus pubescens</i> Willd. and the introduced evergreen <i>Quercus ilex</i> L. based on the analysis of the fast chlorophyll <i>a</i> fluorescence induction kinetics (JIP-test). The experiment simulated progressive soil drought (moderate and severe) with subsequent rehydration under controlled conditions. The results revealed two contrasting physiological survival strategies in response to drought stress. <i>Q. pubescens</i> seedlings exhibited a conservative-plastic response aimed at maintaining functional homeostasis. They showed a moderate decrease in the maximum quantum yield of primary PSII photochemistry (φ<sub>Po</sub>) and the performance index (PI<sub>ABS</sub>) under drought, but the recovery of photochemical parameters after watering was slow. In contrast, <i>Q.&#xa0;ilex</i> demonstrated a stress-avoidance “deep dormancy” strategy: the photosynthetic apparatus responded to water deficit with radical suppression of PSII activity, pronounced inactivation of reaction centers, and a sharp increase in thermal dissipation (DIo/RC). A critically important adaptive element for this species was the stable operation of photosystem I, the indicators of which (δ<sub>Ro</sub>, ψ<sub>Ro</sub>) were maintained or even increased under stress, ensuring basic energy metabolism. This allowed <i>Q.&#xa0;ilex</i> to achieve rapid and nearly complete recovery after the water limitation was removed. Thus, <i>Q. pubescens</i> has an advantage under short-term droughts due to mechanisms of operational regulation, while <i>Q. ilex</i> is more resistant to prolonged and intense water stress due to a strategy of temporary shutdown followed by effective regeneration. JIP-test parameters (PI<sub>total</sub>, ABS/RC, δ<sub>Ro</sub>, ψ<sub>Ro</sub>) proved their high diagnostic value for identifying species-specific differences in adaptation to hydrothermal stress.</p>

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Features of Photosynthetic Apparatus Functioning under Progressive Drought in Seedlings of Quercus pubescens and Quercus ilex

  • 期刊论文

  • 发表日期：

    2026年5月7日

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  • S. P. Korsakova,
  • M. S. Kovalev,
  • T. M. Sakhno,
  • M. L. Novitsky

摘要

Abstract

Under conditions of increasing climate aridity in the southern regions, research into the adaptive mechanisms of forest-forming oak species has important prognostic significance. The aim of this work was a comparative assessment of resistance to water deficit and recovery ability in seedlings of the native deciduous Quercus pubescens Willd. and the introduced evergreen Quercus ilex L. based on the analysis of the fast chlorophyll a fluorescence induction kinetics (JIP-test). The experiment simulated progressive soil drought (moderate and severe) with subsequent rehydration under controlled conditions. The results revealed two contrasting physiological survival strategies in response to drought stress. Q. pubescens seedlings exhibited a conservative-plastic response aimed at maintaining functional homeostasis. They showed a moderate decrease in the maximum quantum yield of primary PSII photochemistry (φPo) and the performance index (PIABS) under drought, but the recovery of photochemical parameters after watering was slow. In contrast, Q. ilex demonstrated a stress-avoidance “deep dormancy” strategy: the photosynthetic apparatus responded to water deficit with radical suppression of PSII activity, pronounced inactivation of reaction centers, and a sharp increase in thermal dissipation (DIo/RC). A critically important adaptive element for this species was the stable operation of photosystem I, the indicators of which (δRo, ψRo) were maintained or even increased under stress, ensuring basic energy metabolism. This allowed Q. ilex to achieve rapid and nearly complete recovery after the water limitation was removed. Thus, Q. pubescens has an advantage under short-term droughts due to mechanisms of operational regulation, while Q. ilex is more resistant to prolonged and intense water stress due to a strategy of temporary shutdown followed by effective regeneration. JIP-test parameters (PItotal, ABS/RC, δRo, ψRo) proved their high diagnostic value for identifying species-specific differences in adaptation to hydrothermal stress.