Iron enhances aluminum-incluced leaf necrosis and plant growth inhibition in Eucalyptus camaldulensis

Nguyen Tran Nguyenl, Ngo Duc Hiep2 & Kounosuke Pujital’3

lgraduate School ofbiosphere Sciences. Hiroshima Umversity, 739-8528, Hiroshima, Japan. 2forest Science Sub-/nstitute ofsouth Vietnam, Hochiminh city, Vietnam. 3corresponding author*

Key words: aluminum, antioxidant, chlorophyll, Eucalyptus camaldulensis, iron, necrosis

Abstract

The combined effects of exeess Fe and Al on Eucalyptus camaldulensis Dehnh. were studied by investigating time course and visible symptoms of Ieaf necrosis, plant biomass, the status of some antioxidants and pigments and nutrient concentrations. Seedlings were grown hydroponically in nutrient solutions containing 0 or 500 µM AICI3′ each with a FESO4 range of 1, 12 and 120 µM at ph 4.2. Leaf necrosis and plant growth inhibition were induced by Al and enhanced by the increase in Fe concentration. The process from the first appearance of necrotic spots to leaf death (shedding) of a leaf proceeded from a few days to about 20 days after the leaf had fully expanded. Either 120 µM Fe without Al or Al reduced plant growth ta.a similar extent but 120 µM Fe without Al did not cause leaf necrosis. In leaves, excess Fe (12 and 12e µM) without Al reduced concentration of ASC and GSH, while concentration of Fe, DHA and GSSG and DHA:ASC and GSSG:GSH ratios tended to increase with the increase in Fe concentration in treatment solution with or without Al. At 1 µM Fe, Al increased concentration of DHA and DHA:ASC and GSSG:GSH ratios. Catalase activity in leaves reduced with the increase in leaf Al concentration. At 1 µM Fe, Al greatly reduced concentrations of Fe and chlorophylls in leaves but increase two times Fe concentration in stems. These suggest that the enhancement effects of Fe on Al-induced leaf necrosis and plant growth inhibition can be discussed in context of the excess Fe itself weakens antioxidant capability of ASC-GSH cycle in leaves and greatly reduces plant growth; and the increase in Fe accumulation in stems is involved in Al-induced leaf chlorosis.

Abbreviations: ASC – ascorbate; DHA – dehydroascorbate; GSH – reduced glutathione; GSSG – oxidized glutathione

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