| Summary: | Bryophytes are critical components of tropical forest ecosystems and have multiple essential ecological functions. The intense light and often hot environments in tropical regions present some of the greatest challenges for the bryophyte photosynthetic activities. It is critical for us to understand how bryophytes respond to the changing temperatures and light intensities to help predict responses of non-vascular plants to climate change scenarios. To this end, a controlled study was conducted to explore the effects of different temperature increases and light levels on the chlorophyll a/b ratio, health status, effective photochemical quantum yield of PS II and growth of bryophytes species, Hypnum plumaeforme, Brachythecium buchananii, Thuidium glaucinoides, Anomobryum julaceum, Pterobryopsis crassicaulis and Pseudosymblepharis angustata. Chlorophyll a/b ratios varied widely and ranged from 1.0 to 3.0. Chlorophyll a/b ratio was not an ideal indicator of shade plant for the examined species. Physiologically these bryophytes were well-acclimated to the temperature of their habitats during the growing season. Temperature increases of 1.5 and 3 °C had a significantly negative effect on the health status, photosynthetic performance and growth of the selected bryophytes. Excess and low photosynthetically active radiations (PARs) harmed their photochemical efficiency and growth. Vegetation growth carryover (VGC) may explain the subsequent growth of the six bryophyte species under environmental stress. However, prolonged periods of warming and excess/low PARs led to relatively poor thallus health and negative net photosynthetic rates that finally resulted in mortality.
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