Photosystem II Is More Sensitive than Photosystem I to Al3+ Induced Phytotoxicity

Abstract

Aluminium (Al) the most abundant metal in the earth’s crust is toxic in acid soils (pH < 5.5) mainly in the ionic form of Al3+ species. The ability of crops to overcome Al toxicity varies among crop species and cultivars. Here, we report for a first time the simultaneous responses of photosystem II (PSII) and photosystem I (PSI) to Al3+ phytotoxicity. The responses of PSII and PSI in the durum wheat (Triticum turgidum L. cv. ‘Appulo E’) and the triticale (X Triticosecale Witmark cv. ‘Dada’) were evaluated by chlorophyll fluorescence quenching analysis and reflection spectroscopy respectively, under control (−Al, pH 6.5) and 148 μM Al (+Al, pH 4.5) conditions. During control growth conditions the high activity of PSII in ‘Appulo E’ led to a rather higher electron flow to PSI, which induced a higher PSI excitation pressure in ‘Appulo E’ than in ‘Dada’ that presented a lower PSII activity. However, under 148 μM Al the triticale ‘Dada’ presented a lower PSII and PSI excitation pressure than ‘Appulo E’. In conclusion, both photosystems of ‘Dada’ displayed a superior performance than ‘Appulo E’ under Al exposure, while in both cultivars PSII was more affected than PSI from Al3+ phytotoxicity.

Light Energy Partitioning under Various Environmental Stresses Combined with Elevated CO2 in Three Deciduous Broadleaf Tree Species in Japan

“…Similar to the present study, a stable or even lower Y(NO) due to the decline in Y(II), accompanied with the increase in Y(NPQ), was also reported in paraquat-exposed Arabidopsis thaliana [11,18] and in Al-exposed A. thaliana [12]. The decrease in J NO may denote also decreased ROS production [17].…”

“…Non-regulated, non-photochemical quenching consists of chlorophyll fluorescence internal conversions and intersystem crossing, which leads to the formation of singlet oxygen ( 1 O 2 ) via the triplet state of chlorophyll ( 3 chl*) [10,11,13]. Since J NO declined, it seems that J NPQ was sufficient enough to protect plants from ROS, by exhibiting lower 1 O 2 production, and preventing the photosynthetic apparatus from oxidative damage [12].…”

Arbuscular Mycorrhizal Symbiosis Enhances Photosynthesis in the Medicinal Herb Salvia fruticosa by Improving Photosystem II Photochemistry

“…Since plant production is driven by photosynthesis, evaluating photosynthetic function is a reasonable way to estimate the fate of plant growth and development [ 26 , 27 ], while variations in the efficiency or capacity of photosynthesis can lead to variation in growth rate, productivity and crop yield [ 28 ]. Photosynthesis is a highly regulated process in which the absorbed solar energy as photons by the light-harvesting complexes (LHCs) is transferred to the reaction centers (RCs) where through charge separation the electrons flow from photosystem II (PSII) to photosystem I (PSI) [ 26 , 27 , 29 ] (for details see Figure 1 ). The two photosystems work coordinately, and the result is the formation of ATP and reducing power (reduced ferredoxin and NADPH) that need to be coordinated with the activity of metabolic processes for carbohydrate synthesis [ 26 , 29 ].…”

“…Photosynthesis is a highly regulated process in which the absorbed solar energy as photons by the light-harvesting complexes (LHCs) is transferred to the reaction centers (RCs) where through charge separation the electrons flow from photosystem II (PSII) to photosystem I (PSI) [ 26 , 27 , 29 ] (for details see Figure 1 ). The two photosystems work coordinately, and the result is the formation of ATP and reducing power (reduced ferredoxin and NADPH) that need to be coordinated with the activity of metabolic processes for carbohydrate synthesis [ 26 , 29 ]. The disturbance of photosynthesis at the molecular level is associated with low electron transport through PSII (ETR) and/or with structural injury to PSII and the LHCs [ 30 ].…”

Rapid Hormetic Responses of Photosystem II Photochemistry to Cadmium Exposure

“…In accordance, S. sclarea plants exposed to 100 μM Cd show an increased capacity to keep quinone (QA) oxidized, thus, to have a higher fraction of open PSII reaction centers (qP) compared to controls. In other words, S. sclarea plants exposed to 100 μM Cd show a low PSII excitation pressure associated with toxicity tolerance mechanisms [99,100]. High excitation pressure defines excess energy and consequently a disproportion between energy resource and requirement [101].…”