Effects of aluminum on the growth and distribution of calcium in roots of an aluminum-sensitive cultivar of barley (Hordeum vulgare)

Abstract

Aluminum-induced inhibition of root growth in the Al-sensitive cultivar Kearney of barley (Hordeum vulgare L.) is the result of disruption of both cell division in the meristematic region and cell expansion in the zone of elongation of the roots. In seedlings directly germinated in 50 μM Al, inhibition of root growth is detected 48 h after initiation of germination and it results primarily from the disruption of cell elongation. In seedlings germinated for 2 days under Al-free conditions, inhibition of root growth is apparent 8 h after transfer to 50 μM Al. In this instance, root growth inhibition is mainly the result of disruption of cell division in the meristematic region of the root. The calcium indicator dyes chlorotetracycline and Fluo-3 are used to study the distribution of intracellular calcium and its relationship to aluminum phototoxicity. Aluminum increases both chlorotetracycline and Fluo-3 fluorescence intensities. Fluorescence of the cytosolic calcium indicator dye Fluo-3 increases primarily in the zone of elongation of the roots of seedlings directly germinated in 50 μM aluminum. The increase in Fluo-3 fluorescence occurs concomitantly with major changes in both the length and width of the cells in the zone of elongation. The evidence suggests that changes in calcium homeostasis occurring in cells of the zone of elongation may be a major factor in the disruption of cell expansion and consequently root growth in seedlings directly germinated in 50 μM aluminum. Key words: aluminum, calcium, barley, chlorotetracycline, Fluo-3.