Effect of growth temperature on Aster flower development

Little is known about the effect of growth temperature on Aster (Compositae, Asteraceae) flower development. In this study, we report on this effect for two aster lines, 'Suntana' and 'Sungal'. Growth temperature had a dramatic effect on the duration of flower development, ranging from 22 days for plants growing at 29 degrees C up to 32 days for plants grown at 17 degrees C. Flower longevity was approximate to 40% shorter under the higher temperature for both lines. Growth temperature also affected flowerhead form: 'Suntana' flowerhead diameter was 20% larger at 17 degrees C than at 29 degrees C. The number of 'Sungal' florets per flowerhead was four times greater at the lower temperature. Shading (30%) under temperature-controlled conditions had no effect on any of the parameters measured. For plants grown outdoors, our results suggest that shading plants may increase quality by reducing the growth temperature.