High temperature stress might hamper the success of sexual reproduction in Hizikia fusiformis from Shantou, China: a photosynthetic perspective

Abstract

:Comparative studies of photosynthetic physiology were carried out to evaluate high light and temperature stresses in reproductive (receptacles) and vegetative (blades) tissues of fertile thalli of Hizikia fusiformis from Nanao Island, China. Receptacles had much higher rates of photosynthesis than blades, and temperature sensitivity was much higher for photosynthesis than for respiration. Both receptacles and blades survived extended exposure to 1500 μmol photons m−2 s−1; however, above 30°C, photosynthetic activity declined rapidly. Prolonged exposure to high temperature sharply depressed photosynthesis, and extended exposure to 40°C was more detrimental to photosynthesis than exposure to 30°C. Moreover, photosynthesis of receptacles was more susceptible to heat than photosynthesis in blades. Following 15 min at 40°C, receptacle photosynthesis declined to 28% of initial value and recovered to only 60% of initial value within 1 h in recovery conditions. However, after 30 min at 40°C, receptacle photosynthesis did not recover within 4 h, suggesting that the photosynthetic apparatus had suffered irreversible injury. Respiration was not affected by high temperature. Our study shows that high temperature but not high light stress might hamper sexual reproduction in H. fusiformis.