Monitoring moderate Cu and Cd toxicity by chlorophyll fluorescence and P₇₀₀ absorbance in pea leaves

Abstract

We investigated the effect of moderate Cu 2+ and Cd 2+ stress by applying chlorophyll (Chl) fluorescence and P 700 absorbance measurements to monitor the photosynthetic electron transport activity of 3-week-old Pisum sativum L. cv. Petit Provençal plants grown in a modified Hoagland solution containing 50 µM CuSO 4 or 5 µM CdCl 2 . Both heavy metals caused a slight inhibition in PSII photochemistry as indicated by the decrease in the effective quantum efficiency of PSII (Φ PSII ), the maximum electron transport capacity (ETR max ), and the maximum quantum yield for electron transport (α). PSI photochemistry was also affected by these heavy metals. Cu 2+ and Cd 2+ decreased the quantum efficiency of PSI (Φ PSI ) as well as the number of electrons in the intersystem chain, and the Cu 2+ treatment significantly reduced the number of electrons from stromal donors available for PSI. These results indicate that PSII and PSI photochemistry of pea plants are both sensitive to moderate Cu 2+ and Cd 2+ stress, which in turn is easily detected and monitored by Chl fluorescence and P 700 absorbance measurements. Therefore, monitoring the photochemistry of pea plants with these noninvasive, yet sensitive techniques offers a promising strategy to study heavy metal toxicity in the environment.

The effect of excess copper on growth and physiology of important food crops: a review

“…Excess Cu also decreased the active PS II centres of illuminated leaves (Patsikka et al 2002) and resulted in lower photosynthetic electron transport activities (Yruela 2009). Moreover, 50 μM Cu affected the PS II and PS I photochemistry of pea plants (Wodala et al 2012). Additionally, excess Cu decreased the net photosynthetic rate and photosynthetic capacity of barley plants which might be related to mesophyll limitations (Vassilev et al 2002) as well as disturbances of the chloroplast membranes and PS II activity (Vassilev et al 2003).…”

“…There is strong evidence that reduction in chlorophyll biosynthesis is related to structural damages of the photosynthetic apparatus at the thylakoid level under Cu stress (Cisato et al 1997) and interference of Cu with chlorophyll organization (Caspi et al 1999;Wodala et al 2012). Excess Cu also decreased the active PS II centres of illuminated leaves (Patsikka et al 2002) and resulted in lower photosynthetic electron transport activities (Yruela 2009).…”

Characterization of the structural changes and photochemical activity of photosystem I under Al3+ effect

“…PSI is considered to be sensitive to various environmental stresses [18][19][20][21][22][23][24][27][28][29]. Farhat et al [23] reported that the Mg 2+ deficiency stress applied to Sulla carnosa plants leaves causes an impairment of PSI photochemical activity accompanied by a significant reduction in the abundance of the LHCI antenna and PsaA polypeptides of PSI RC.…”

“…Further, several studies showed that PSI complex is also one of the targets of several toxic divalent metal cations such as Cd 2+ , Cu 2+ , Hg 2+ and Pb 2+ . It has been reported that these cations affect photochemical activity, inhibit electron transport between PC and P700 at the donor side, decreased the active P700 content, alter the LHCI antenna and cause a conformational changes of the secondary structure polypeptides of PSI [18,22,[25][26][27][28][29].…”

Potential for Phytoextraction of Cu by Sesamum indicum L. and Cyamopsis tetragonoloba L.: A Green Solution to Decontaminate Soil

“…The reduction in photosynthetic pigments is likely because of chloroplast damage during development phase upon exposure of Cu in soil system (Ali et al 2015). Kabata-Pendias and Pendias (2001) have presented a strong evidence regarding the chlorophyll biosynthesis reduction which might be linked with the destruction of photosynthetic organization at thylakoid level and also the hindrance of Cu with organized system of chlorophyll (Wodala et al 2012). …”