Abstract The sequence of abiotic stresses profoundly influences plant acclimation responses, yet studies directly comparing the advantages of sequential versus simultaneous stress exposure remain limited, particularly in medicinal non-model species. This study elucidated how the temporal sequence and combination mode (sequential versus simultaneous) of abiotic stresses shape chloroplast-mediated adaptation in licorice (Glycyrrhiza uralensis) seedlings, comparing simultaneous and sequential drought (D) and cold (C) stress. Seedlings were subjected to single (D, C), simultaneous (D&C), and sequential (C-then-D, C7D7; D-then-C, D7C7) stresses, followed by a 3-day recovery phase. Simultaneous stress caused severe synergistic damage. Chloroplastic reactive oxygen species (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\text{O}}_{2}^{ - }\)</EquationSource>  </InlineEquation> and H2O2) increased significantly. Lipid peroxidation (MDA) rose. Photosystem II photochemistry (Fv/Fm, qp, ETR) was severely impaired. In contrast, both sequential treatments conferred clear physiological advantages based on measurements from isolated chloroplasts. They preemptively suppressed chloroplastic ROS generation, preserved photosynthetic integrity, and enabled rapid recovery. In addition, sequential stress reprogrammed carbon allocation, with root soluble sugars being depleted during the stress period and rapidly replenished upon recovery, thereby fueling compensatory shoot growth. No significant differences in growth parameters were observed between the two sequential treatments during either the stress or recovery phases. However, the recovery of PSII efficiency differed markedly: Fv/Fm in C7D7 fully returned to control levels within 3 days, whereas D7C7 showed no significant recovery during the recovery phase. These findings demonstrate that stress history is a pivotal determinant of multi-stress tolerance in licorice seedlings. Sequential exposure, rather than simultaneous stress, enables proactive chloroplastic redox management and adaptive carbon reallocation. The more pronounced recovery observed in C7D7 further indicates that the order of stress application can fine-tune physiological outcomes, although the primary benefit derives from sequential rather than simultaneous exposure.

Chloroplast-Centered Acclimation to Sequential Stress Superior Drought Tolerance in Licorice via ROS Attenuation and Enhanced Recovery Sink

期刊论文
发表日期：

2026年6月29日

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Y.-H. Xie,
J. Gao,
N. Wang,
G. Zhang,
Y. Chen,
F. Yan,
Y.-G. Yan,
G.-C. Cui

摘要

Abstract

The sequence of abiotic stresses profoundly influences plant acclimation responses, yet studies directly comparing the advantages of sequential versus simultaneous stress exposure remain limited, particularly in medicinal non-model species. This study elucidated how the temporal sequence and combination mode (sequential versus simultaneous) of abiotic stresses shape chloroplast-mediated adaptation in licorice (Glycyrrhiza uralensis) seedlings, comparing simultaneous and sequential drought (D) and cold (C) stress. Seedlings were subjected to single (D, C), simultaneous (D&C), and sequential (C-then-D, C₇D₇; D-then-C, D₇C₇) stresses, followed by a 3-day recovery phase. Simultaneous stress caused severe synergistic damage. Chloroplastic reactive oxygen species ( \({\text{O}}_{2}^{ - }\) and H₂O₂) increased significantly. Lipid peroxidation (MDA) rose. Photosystem II photochemistry (F_v/F_m, q_p, ETR) was severely impaired. In contrast, both sequential treatments conferred clear physiological advantages based on measurements from isolated chloroplasts. They preemptively suppressed chloroplastic ROS generation, preserved photosynthetic integrity, and enabled rapid recovery. In addition, sequential stress reprogrammed carbon allocation, with root soluble sugars being depleted during the stress period and rapidly replenished upon recovery, thereby fueling compensatory shoot growth. No significant differences in growth parameters were observed between the two sequential treatments during either the stress or recovery phases. However, the recovery of PSII efficiency differed markedly: F_v/F_m in C₇D₇ fully returned to control levels within 3 days, whereas D₇C₇ showed no significant recovery during the recovery phase. These findings demonstrate that stress history is a pivotal determinant of multi-stress tolerance in licorice seedlings. Sequential exposure, rather than simultaneous stress, enables proactive chloroplastic redox management and adaptive carbon reallocation. The more pronounced recovery observed in C₇D₇ further indicates that the order of stress application can fine-tune physiological outcomes, although the primary benefit derives from sequential rather than simultaneous exposure.