Elongation of Eucalyptus roots during day and night

Abstract

Root elongation was measured in mature Eucalyptus pauciflora Sieber ex Sprengel subsp. pauciflora trees in a high-elevation stand, and in seedlings of E. pauciflora and E. nitens (Deane and Maiden') grown in a glasshouse. Elongation of non-mycorrhizal roots (> 10 mm long) was measured at 0600 and 1800 h on several consecutive days. Root elongation of seedlings of both species in the glasshouse was greater than that of mature E. pauciflora trees in the forest. For seedlings of comparable size, roots of E. nitens elongated faster than roots of E. pauciflora. Root elongation was always greater during the night than during the day in both species, in both the glasshouse and forest environment. Both water and osmotic potentials of root tips of E. pauciflora seedlings were lower during the night than during the day. The derived turgor pressure value of root tips was greater during the night than during the day and there was no difference in turgor pressure above the yield threshold.