The effect of different temperatures (14, 20 and 30 degrees C) and photoperiods (10 and 16 h) on the photosynthesis, growth and reproduction of Ruppia drepanensis Tineo plants from the Donana National Park (SW Spain) were studied. After 84-91 days of growth under a 16 h photoperiod, the plants showed maximal biomass yield at 20 degrees C (395 mg ash-free dry weight per plant), with lower yields at 14 and 30 degrees C (216 and 284 mg ash-free dry weight per plant respectively). A short photoperiod resulted in a lower biomass yield when combined with low temperatures (59 mg afdw per plant, at 10 h and 14 degrees C). Reproduction was also optimal at 20 degrees C, while low temperatures (14 degrees C) inhibited flower induction, No seed was produced at 30 degrees C. Photoperiod had little effect on flowering, as compared with temperature. According to the photosynthetic performance of R. drepanensis, we can define this species as cold-adapted but also capable of acclimating to higher temperatures (30 degrees C). Net photosynthesis at 250 mu mol photons m(-2) s(-1) (P-250) was maximal at 20 degrees C (72 to 82 mu g O-2 g(-1) afdw min(-1)). Photosynthetic plasticity allowed for high net production rates at 10 degrees C (P-250=65 to 68 mu g O-2 g(-1) afdw min(-1)), independently of the temperature experienced during growth. At 30 degrees C, however, net photosynthetic rates were lower in plants grown at 20 degrees C than at 30 degrees C (P-250 = 6.5 and 55.9 mu g O-2 g(-1) afdw min(-1) respectively). The cold- adapted character of this Mediterranean endemism is finely tuned to the requirements of its winter-annual life cycle, while its acclimation capacity is suited to cope with the rapidly increasing temperatures along late spring in the temporary wetlands it inhabits. [KEYWORDS: photoperiod; thermal response; acclimation; flower induction; seed production Fresh-water macrophytes; maritima l; light; ecology]
Original languageEnglish
JournalAquatic Botany
Journal publication date1998

ID: 354781