Multi‐trophic metacommunity interactions mediate asynchrony and stability in fluctuating environments

Abstract The induction and relaxation of photochemistry and non-photochemical quenching (NPQ) are not instantaneous and require time to respond to fluctuating environments. There is a lack of integrated understanding on how photochemistry and NPQ influence photosynthesis in fluctuating environments. We measured the induction and relaxation of chlorophyll a fluorescence and gas exchange in poplar and cotton at varying temperatures under saturating and fluctuating lights. When the light shifted from dark to high, the fraction of open reaction centers in photosystem II (qL) gradually increased while NPQ increased suddenly and then remained stable. Temperature significantly changed the response of qL but not that of NPQ during the dark to high light transition. Increased qL led to higher photosynthesis but their precise relationship was affected by NPQ and temperature. qL was significantly related to biochemical capacity. Thus, qL appears to be a strong indicator of the activation of carboxylase, leading to the similar dynamics between qL and photosynthesis. When the light shifted from high to low intensity, NPQ is still engaged at a high level, causing a stronger decline in photosynthesis. Our finding suggests that the dynamic effects of photochemistry and NPQ on photosynthesis depend on the phases of environmental fluctuations and interactive effects of light and temperature. Across the full spectra of light fluctuation, the slow induction of qL is a more important limiting factor than the slow relaxation of NPQ for photosynthesis in typical ranges of temperature for photosynthesis. The findings provided a new perspective to improve photosynthetic productivity with molecular biology under natural fluctuating environments.

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Selective Oviposition by Oriental Fire-bellied Toads in Temporally Fluctuating Environments

Current Herpetology ◽

10.5358/hsj.40.120 ◽

2021 ◽

Vol 40 (2) ◽

Cited By ~ 1

Author(s):

Seung-Yun Baek ◽

Min-Hyun Lee ◽

Yong-Su Kim ◽

Sang-Ryong Bae ◽

Uh-Ram Song ◽

...

Keyword(s):

Fluctuating Environments

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Make and break the alarmone: regulation of (p)ppGpp synthetase/hydrolase enzymes in bacteria

FEMS Microbiology Reviews ◽

10.1093/femsre/fuz009 ◽

2019 ◽

Vol 43 (4) ◽

pp. 389-400 ◽

Cited By ~ 37

Author(s):

Séverin Ronneau ◽

Régis Hallez

Keyword(s):

Cell Cycle ◽

Stress Response ◽

Stress Responses ◽

Biofilm Formation ◽

Pathogenic Bacteria ◽

Second Messengers ◽

Molecular Devices ◽

Environmental Cues ◽

Fluctuating Environments ◽

Harsh Conditions

ABSTRACTBacteria use dedicated mechanisms to respond adequately to fluctuating environments and to optimize their chances of survival in harsh conditions. One of the major stress responses used by virtually all bacteria relies on the sharp accumulation of an alarmone, the guanosine penta- or tetra-phosphate commonly referred to as (p)ppGpp. Under stressful conditions, essentially nutrient starvation, these second messengers completely reshape the metabolism and physiology by coordinately modulating growth, transcription, translation and cell cycle. As a central regulator of bacterial stress response, the alarmone is also involved in biofilm formation, virulence, antibiotics tolerance and resistance in many pathogenic bacteria. Intracellular concentrations of (p)ppGpp are determined by a highly conserved and widely distributed family of proteins called RelA-SpoT Homologs (RSH). Recently, several studies uncovering mechanisms that regulate RSH activities have renewed a strong interest in this field. In this review, we outline the diversity of the RSH protein family as well as the molecular devices used by bacteria to integrate and transform environmental cues into intracellular (p)ppGpp levels.

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