The role of lignotubers (basal burls) in the stress recovery of messmate stringybark, Eucalyptus obliqua L'Herit. seedlings and its arboricultural implications

Abstract

Dormant buds such as lignotuberous and epicormic buds are adaptations possessed by plants growing in stressful environments. Eucalyptus obliqua is a species occupying a wide range of habitats in south-eastern Australia, which displays ecotypic diversity. Seedlings of E. obliqua from provenances with and without lignotubers were subject to heat stress at 40–100°C for durations ranging from 2 to 128 min. Seedlings from a single population were also stressed by decapitation, which left two, four or eight leaves intact. While the upper stems and leaves of the heated seedlings from different provenances reacted in the same way to the treatments imposed, seedlings that lacked lignotubers died at lower temperatures and at shorter durations than seedlings that possessed lignotubers. Production of lignotuberous shoots did not necessarily guarantee seedling survival as the mortality rates of lignotuberous shoots were high, ranging from 55% to 100%. The recoveries of the heated and decapitated seedlings were similar, but the possession of foliage enhanced the survival of lignotuberous shoots that were produced after treatment. The possession of lignotuberous and epicormic buds by tree species is an important adaptation to stress that has implications for urban tree management. Lignotuberous shoot production is usually a last-resort survival mechanism.