Growth and photosynthetic activity of Sargassum henslowianum (Fucales, Phaeophyta) seedlings in responses to different light intensities, temperatures and CO₂ levels under laboratory conditions

Abstract

The habitat of Sargassum henslowianum (Fucales, Phaeophyta) is currently threatened by rising CO₂ and global warming. Young seedlings of S. henslowianum regenerated from holdfasts were cultured under laboratory conditions with different levels of light intensity, temperature and CO₂ concentration, aiming to examine the influences of these environmental factors on the growth and photosynthesis of this alga in its early growth stage. Young seedlings of Sargassum henslowianum exhibited faster growth under a light intensity of 60 µmol photons·m⁻²·s⁻¹ than other light treatments (20 and 120 µmol photons·m⁻²·s⁻¹). Seedlings growing at low light tended to develop blades and branches. Photosynthesis of seedlings increased with the temperature rising from 15 to 25°C, and the blades or branches tended to develop with rising temperature. High temperature (30°C) depressed the growth of the young seedlings. Elevated CO₂ significantly enhanced the germination vigor of the alga, but reduced net photosynthetic rate and irradiance saturation point. Our results suggest that experimental conditions, such as light intensities, temperature and CO₂ levels each significantly affect the development and physiology of S. henslowianum seedlings. We propose that 60 µmol photons·m⁻²·s⁻¹ and 25°C are preferable light–temperature conditions for the growth of S. henslowianum seedlings.

Key words:

• Climate change
• environmental factors
• photosynthesis
• Sargassum henslowianum
• seedling

Funding

This study was supported by the National Natural Science Foundation of China (41276148 and 41076094).

Editorial responsibility: Mirta Teichberg

Additional information

Funding

Funding: This study was supported by the National Natural Science Foundation of China (41276148 and 41076094).