Effects of A1 on growth, nodulation and polyphenol oxidase activities in groundnut

Al toxicity is a complex growth-limiting factor. Glasshouse studies using solution culture were carried out to examine the effects of Al on: (a) growth and nodulation of groundnut (Arachis hypogaea L.) and (b) the activities of polyphenol oxidase (PPO) of the youngest expanded leaves (YEL). Results showed that root elongation and dry weight in Al-treated plants were significantly reduced. At 20 and 30 days after planting (DAP), there was a decrease in nodule number (30%) and dry weight (45%) with an increase in the sum of activities of monomeric Al from 10 to 30 μ m. The PPO activities in YEL extracts of Al-treated plants remained higher than the control at all stages of plant growth with a maximum at 30 DAP.