Exogenous calcium mitigates heat stress effects in common bean: a coordinated impact of photoprotection of PSII, up-regu
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ORIGINAL ARTICLE
Exogenous calcium mitigates heat stress effects in common bean: a coordinated impact of photoprotection of PSII, up‑regulating antioxidants, and carbohydrate metabolism Muhammad Naeem1,2 · Jesse Riaz Traub3 · Habib‑ur‑Rehman Athar4 · Wayne Loescher3 Received: 27 July 2019 / Revised: 1 November 2020 / Accepted: 20 November 2020 © Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Kraków 2020
Abstract Calcium (Ca2+) is involved in mediating anti-stress responses in plants through one or combination of biochemical processes. Thus, the major objective of present study was to assess the protective effect of exogenous Ca2+ (0, 2.5, 5.0, and 7.5 mM) on photosynthetic machinery of cv. Jaguar and SER-16 under heat stress (HS 25–45 °C for 48 h). The applied HS (45 °C) caused substantial reduction in net photosynthetic rate (Pn 73%), photosystem II quantum yield (ΦII 24%), linear electron flow (LEF 13%), and SPAD values (27%) with imbalancing of sugars metabolism and redox potential. At heat stress (40 °C), plants of both cultivars tried to acclimate by regulating leaf temperature through increased stomatal conductance (gs 36%), transpiration rate (E 60%) and by increase in non-photochemical quenching (NPQ 19%). In addition, C a2+ pre-treatment protected the membrane from oxidative damage by up-regulating the enzymatic activities and down-regulation of malondialdehyde (MDA) accumulation and electrolyte leakage in plant leaf tissues. Pre-treatment with Ca2+ enhanced the accumulation of sugars (glucose, fructose, inositol, and raffinose) in both heat stressed bean plants (45 °C). In conclusion, cv. Jaguar had greater tolerance to HS than SER-16, which is associated with Ca2+-induced photo-protective effect on PSII, the balance between LEF and reactive oxygen species (ROS) generation with concomitant up-regulation of antioxidant enzymes, and increase in compatible solutes. Based on changes in physiological attributes, it is speculated that C a2+ application might have mediated 2+ thermo-tolerance in plants via Ca -sensing and signaling pathway, which needs to be verified through molecular studies. Keywords Electrolyte leakage · Chlorophyll fluorescence · photosynQ · Compatible solutes · Membrane stability
Introduction Various climate changing models predicted that earth surface temperature will increase by 2–6 °C across the globe by the next century (Mathur et al. 2014; Seneviratne et al. 2016; Xu et al. 2017). Moreover, frequency of warm days and night Communicated by G. Montanaro. * Muhammad Naeem [email protected] 1
Department of Agronomy, University of Agriculture, Faisalabad 38040, Pakistan
2
Directorate of Agriculture Extension & Adaptive Research, Government of Punjab, Lahore, Pakistan
3
Department of Horticulture, Michigan State University, East Lansing, MI 48824, USA
4
Institute of Pure and Applied Biology, Bahauddin Zakariya University, Multan, Pakistan
will increase due to heat waves (Intergovernmental Panel on Climate Change (IPPC 2014) th
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