Abstract

Aluminum (Al) toxicity is the major factor limiting plant growth in acidic soils, which comprise up to 70% of the world’s potentially arable lands. Although, Al toxicity and tolerance in plant roots have been extensively studied during the past decades because inhibition of root growth is one of the earliest symptoms of Al injury and the most easily recognized symptom in solution culture, limited data are available on the effects of Al toxicity on leaf photosynthesis. In this paper we review the effects of Al on stomatal conductance, ultrastructure, pigments and light absorption, water relations, photochemistry, lipid peroxidation, photosynthetic enzymes, carbohydrates and their relations to the Al-induced photosynthesis inhibition in plant leaves. Al appears to preferentially impair thylakoids and photosynthetic electron transport chain in most plants. In addition to decreasing light absorption by lowering pigment concentration, both energy dissipation and antioxidant systems in Al-stressed leaves are enhanced to protect them from photo-oxidative damage under high light. The amelioration of brassinosteroids, boron (B), phosphorus (P) and mycorrhizas on the Al-induced decrease in CO₂ assimilation, as well as some aspects needed to be further studied are also discussed.

Key words: Aluminum toxicity, photosynthesis, photochemistry, photoprotective system.