Supra-optimal temperatures induce photochemical leaf damage and reduce photosynthetic O2 evolution in Carica papaya L

• Published in: Environmental and experimental botany Vol. 203; p. 105051
• Main Authors: Souza, Guilherme Augusto Rodrigues de, Neves, Diesily de Andrade, Ruas, Katherine Fraga, Baroni, Danilo Força, Santos, Késia Dias dos, Bernado, Wallace de Paula, Miranda, Rosana Maria dos Santos Nani de, Almeida, Claudio Martins de, Santos, Anne Reis, Rodrigues, Weverton Pereira, Rakocevic, Miroslava, Campostrini, Eliemar
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2022
• Subjects: Chlorophyll a fluorescence; Climatic changes; Heat stress; JIPTest; Membrane fluidity; NADPH; PAR; DAE; Climatic changes; OEC; RuBisCO; JIPTest; HDPE; Membrane fluidity; ANOVA; ETC; LHCII; DPVar; Chlorophyll a fluorescence; Heat stress; ATP; ChlF
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2022.105051

Carica papaya L. is a tropical and subtropical fruit tree. In such climatic regions, cultivation frequently includes exposure to supra-optimal temperatures, which may affect the leaf photosynthetic capacity. Two papaya genotypes, 'Candy' and 'Golden THB', were used to study the effects of supra-optimal temperatures on photochemical responses. The seedlings were cultivated in a greenhouse in 40 L pots. After 100 days, excised leaf discs were incubated at 25, 35, 40, 45, 50 or 55 °C, for 15, 30, 45 or 60 min. Emissions of chlorophyll a fluorescence and photosynthetic O2 evolution rates were measured. In both genotypes, F0 increased, while Fm decreased after 15 min at 45 °C or above, indicating photochemical damage. An increase in non-photochemical dissipation in relation to photochemical dissipation (Fv/F0) was noted, resulting in decreased maximum (ΦP0) and effective (QYLss) quantum yields of the PSII. A reduction in the probability of the electrons being transported beyond QA- (Ψ0), and in the efficiency of electron transport through the chain (ΦE0) were observed, indicating an increase in the quantum efficiency of energy dissipation (ΦD0). The high rate of reaction center deactivation (increase in RC/CS0) in supra-optimal temperatures resulted in elevated absorption (ABS/RC), capture (TR0/RC), transport (ET0/RC), and dissipation (DI0/RC) of energy per active reaction center. An increase in energy absorption by the PSII antenna complex (ABS/CS0) occurred above 40 °C. However, this additional energy was not effectively captured (TR0/CS0), or transported (ET0/CS0), resulting in high excess energy dissipation (DI0/CS0, NPQLss, NPQD). An increase in ΔV/Δt0 reflected a reduction in the rate of photosynthetic O2 evolution rate at temperatures above 30 °C. The reduction of three key parameters PIAbs, SFIabs and RfdLss occurred in leaf disks incubated at 40 °C for a period of 15 min, indicating a reduction in photochemical efficiency in both genotypes. Therefore, severe damage to the photosynthetic capacity of C. papaya L. can be observed at temperatures above 40 °C.
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•Temperatures higher than 40 °C cause photochemical damage to papaya leaves.•Chlorophyll fluorescence images show heterogeneity of photochemical damage.•Energy capture and transport are more sensitive than absorption by the LHCII.•Moderate temperatures excite PSI and optimize electron transport.•Reduction in the rate of evolution of photosynthetic O2 from 35 °C.