Foliar anthocyanin accumulation may be a useful indicator of hardiness in eucalypt seedlings

Anthocyanin as an indicator of seedling hardiness was tested in field trials at 350 m above sea level (a.s.l.) (Watson’s Block with Eucalyptus globulus Labill. and E. nitens [Deane and Maiden] Maiden) and at 700 m a.s.l. (Moory Rd. with E. nitens only). Nutrients were withheld (nutrient-deprived) or added (nutrient-loaded) to seedlings in the nursery and shaded or non-shaded in the field. The photochemical efficiency of photosystem II (Fv/Fm) decreased with average minimum temperature in non-shaded, but not shaded, treatments. At Watson’s Block this decrease was most pronounced in nutrient-loaded E. globulus and nutrient-deprived E. nitens seedlings and at Moory Rd. in nutrientdeprived non-shaded E. nitens. Shading reduced the rate of decrease of Fv/Fm, or there was no change, with average minimum temperature at Moory Rd. Trends of changes in light-saturated net photosynthesis (Amax) with decreasing average minimum temperature at Moory Rd. were generally similar to that of Fv/Fm. Boundary-line analysis indicated that Fv/Fm was optimal (ca. 0.8) whilst foliar anthocyanin concentration was <=0.5 mmol m^-2 and then decreased exponentially with increasing foliar anthocyanin concentration. A similar analysis showed that Amax decreased exponentially from a maximum of 20 (mu)mol m^-2 s^-1 at 0.2 mmol m^-2 to a minimum of 1 (mu)mol m^-2 s^-1 at 0.8 mmol m^-2 foliar anthocyanin concentration. Seedlings high in anthocyanin were associated with low stomatal conductance and low specific leaf area before planting. It was concluded that foliar anthocyanin concentration in the nursery is a potential indicator of eucalypt seedling hardiness to low temperatures experienced after transplanting.