Biological Rhythms Research (1995) 26(1), 48-54
Studies on Halimeda
V. Effect of Temperature on Chloroplast Migration in this Siphonous Green Alga*
Edward A Drew and K M Abel
Australian Institute of Marine Science, PMB No 3, MSO, Townsville,
Queensland 4810, Australia
*Contribution No 697 from the Australian Institute of Marine Science
Abstract
The effect of temperatures between 15 and 30 C on the daily cycle of chloroplast migration in Halimeda distorta and Halimeda tuna was determined from changes in surface pigmentation recorded by time-lapse videography throughout the experiments. An un-named opuntioid species was also tested between 20 and 35 C. Both the daily pattern and the amplitude of change in surface pigmentation, which were sustained for at least 5 days at 25 C, were unchanged at the higher temperatures. At 20 C the amplitude was considerably reduced but cyclical changes in surface pigmentation continued to occur throughout the 3-day low temperature period. However, at 15 C even greater reduction in amplitude was observed together with a reduced rate of paling at the onset of darkness and absence of pre-dawn re-greening. Furthermore, at 15 C all daily changes in surface pigmentation has ceased by the second day in H tuna and by the third day in H distorta. These effects of lower temperatures were reversed when the plants were returned to 25 C, although after the 15 C treatment of H tuna the amplitude of the change in surface pigmentation in two of the three replicate plants was small on the first night back at 25 C whilst the third plant lost pigmentation progressively and was completely white, and apparently dead, two days later.