Aluminum-induced decrease in CO2 assimilation in citrus seedlings is unaccompanied by decreased activities of key enzymes involved in CO2 assimilation

Abstract

'Cleopatra' tangerine (Citrus reshni Hort. ex Tanaka) seedlings were irrigated daily for 8 weeks with 1/4 strength Hoagland's nutrient solution containing 0 (control) or 2 mM aluminum (Al). Leaves from Al-treated plants had decreased CO2 assimilation and stomatal conductance, but increased intercellular CO2 concentrations compared with control leaves. On a leaf area basis, 2 mM Al increased activities of key enzymes in the Calvin cycle, including ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoribulokinase (PRK), stromal fructose-1,6-bisphosphatase (FBPase), and a key enzyme in starch synthesis, ADP-glucose pyrophosphorylase (AGPase), compared with control leaves. Aluminum had no effect on cytosolic FBPase activity, but it decreased sucrose phosphate synthase (SPS) activity. Aluminum had no effect on area-based concentrations of carbohydrates, glucose-6-phosphate (G6P) and fructose 6-phosphate (F6P) or the G6P:F6P ratio, but it decreased the area-based concentration of 3-phosphoglycerate (PGA). Photochemical quenching coefficient (qP) and electron transport rate through PSII were greatly reduced by Al. Non-photochemical quenching coefficient (NPQ) was less affected by Al than qP and electron transport rate through PSII. We conclude that the reduced rate of CO2 assimilation in Al-treated leaves was probably caused by a combination of factors such as reduced electron transport rate through PSII, increased closure of PSII reaction centers and increased photorespiration.

Gas exchange, photosystem II photochemistry, and the antioxidant system of longan plant (Dimocarpus longan Lour.) leaves in response to lead (Pb) stress

“…The plant materials were extensively washed with deionized water. They were then dried at 80 °C for 48 h and DM was measured according to Chen et al (2005). The Pb concentrations were determined according to Fang (1991).…”

Effects of Aluminum on Light Energy Utilization and Photoprotective Systems in Citrus Leaves

“…Since CO 2 assimilation decreases in leaves supplied with Al (Pereira et al, 2000;Chen et al, 2005), only a fraction of the absorbed light energy is used in electron transport. As a result, there is more excess excitation energy in leaves with large Al content than in normal leaves, particularly under high photon flux (PF).…”

“…Low pH and high Al concentration are the factors contributing to poor citrus growth and shortened lifespan of trees (Lin and Myhre, 1990). Although the effects of Al on mineral nutrient (Lin and Myhre, 1991b) and CO 2 assimilation (Pereira et al, 2000;Chen et al, 2005) of citrus have been investigated by a few researchers, very little is known about the effects of Al on the photoprotectives system of citrus leaves. Therefore it is a useful plant to analyse the responses of different mechanisms of energy dissipation in photosynthetic metabolism to Al.…”

Productivity of Indigofera zollingeriana under different canopy and soil acidity level in oil palm estate

“…Then, Qifu et al (2002) said that A1 content in high acid soil might disturb soy growth and ruined plant roots leading to low production of plant due to inefficiency of nutrient and water absorption by roots. Chen et al (2005) said that A1 decreased CO2 intake useful in assimilation of tangerine (Citrus rehhni) affecting enzyme activities involved in Calvin cycle. Nutrients supply decreased by the assimilation process disruption decreasing production and quality of plants, especially in plants sensitive to A1 stress.…”