Effect of temperature and light on germination of 10 species of Eucalyptus from north-western NSW

Abstract

The effects of temperature and light were examined on the germination of 14 seedlots of 10 Eucalyptus species, which are important for revegetation of native communities in north-western New South Wales. The species tested were E. albens, E. blakelyi, E. chloroclada, E. dealbata, E. camaldulensis, E. melanophloia, E. melliodora, E. pilligaensis, E. populnea and E. sideroxylon. Species were subjected to three alternating day/night temperatures (15/5, 25/15 and 35/25°C), representing winter, spring/autumn and summer conditions, respectively, and two light treatments (light/dark or dark), in growth cabinets. Limited quantities of seed of most seedlots prevented full factorial combinations of most treatments. Overall germination was high but varied significantly between species and seedlots within species. Differences were small, but light combined with winter or spring/autumn temperatures resulted in higher average germination (96%) than darkness and summer temperatures (93%). Seedlots of E. chloroclada, E. blakelyi, E. camaldulensis, E. sideroxylon, E. melliodora and E. melanophloia germinated consistently well under all treatment conditions, whereas germination in seedlots of E. albens, E. dealbata, E. melliodora, E. pilligaensis and E. populnea varied with treatments. Germination of small seeds was higher in the presence of light whereas larger seeds germinated better in continuous darkness. The time to first germination was three times faster under summer and spring/autumn temperatures than winter temperatures. In conclusion, temperature and light can significantly impact germination percentage and rate, depending on the species and provenances, and therefore should be considered in planning restoration projects in both nursery and field.