| 1. |
- Mangora, M. M., et al.
(författare)
-
Effects of waterlogging, salinity and light on the productivity of Bruguiera gymnorrhiza and Heritiera littoralis seedlings
- 2017
-
Ingår i: African Journal of Marine Science. - 1814-232X .- 1814-2338. ; 39:2, s. 167-174
-
Tidskriftsartikel (refereegranskat)abstract
- This study aimed to establish the effects of waterlogging, salinity and light on the early development of mangroves. Seedlings of Bruguiera gymnorrhiza (L.) Lamk. and Heritiera littoralis Dryand were exposed to 12 weeks of waterlogging, during which time growth and photosynthesis were measured every two weeks. The salinity of the water inundation ranged from fresh water to full-strength sea water (salinity 35). Seedlings were exposed to either full sunlight of 1 500 mu mol photon m(-2) s(-1) (SD 397) at midday or shade conditions of 325 mu mol photon m(-2) s(-1) (SD 40) of light at midday, to explore whether the plants would be differently affected by prolonged waterlogging in increased salinities and under different light conditions. Heritiera littoralis was more sensitive to waterlogging, salinity and light, displaying a least relative growth rate of 0.127 g g(-1) week(-1) (SE 0.032) under shade, and 0.025 g g(-1) week(-1) (SE 0.021) in full light; while under shade, photosynthesis continued only in fresh water, but photosynthetic yield decreased from 0.7 to 0.4 with increasing duration of waterlogging. By 12 weeks, all H. littoralis seedlings treated with any saltwater mixture had died. Bruguiera gymnorrhiza seedlings maintained a moderate rate of photosynthesis throughout inundation in both shade and full light, with yields of 0.7 and 0.3, respectively. Furthermore, B. gymnorrhiza survived waterlogging in up to 66% seawater, and maintained comparable relative growth rates of 0.164 g g(-1) week(-1) (SE 0.066) with 0.083 g g(-1) week(-1) (SE 0.065) and 0.074 g g(-1) week(-1) (SE 0.036) with 0.052 g g(-1) week(-1) (SE 0.037) under shade and in full light between fresh water and the highest salinity conditions, respectively. These results suggest that B. gymnorrhiza is broadly tolerant, making it a potential candidate species for restoring vulnerable mangrove forests.
|
|
| 2. |
- George, Rushingisha, et al.
(författare)
-
High midday temperature stress has stronger effects on biomass than on photosynthesis : A mesocosm experiment on four tropical seagrass species
- 2018
-
Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 8:9, s. 4508-4517
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of repeated midday temperature stress on the photosynthetic performance and biomass production of seagrass was studied in a mesocosm setup with four common tropical species, including Thalassia hemprichii, Cymodocea serrulata, Enhalus acoroides, and Thalassodendron ciliatum. To mimic natural conditions during low tides, the plants were exposed to temperature spikes of different maximal temperatures, that is, ambient (29-33 degrees C), 34, 36, 40, and 45 degrees C, during three midday hours for seven consecutive days. At temperatures of up to 36 degrees C, all species could maintain full photosynthetic rates (measured as the electron transport rate, ETR) throughout the experiment without displaying any obvious photosynthetic stress responses (measured as declining maximal quantum yield, Fv/Fm). All species except T.ciliatum could also withstand 40 degrees C, and only at 45 degrees C did all species display significantly lower photosynthetic rates and declining Fv/Fm. Biomass estimation, however, revealed a different pattern, where significant losses of both above- and belowground seagrass biomass occurred in all species at both 40 and 45 degrees C (except for C.serrulata in the 40 degrees C treatment). Biomass losses were clearly higher in the shoots than in the belowground root-rhizome complex. The findings indicate that, although tropical seagrasses presently can cope with high midday temperature stress, a few degrees increase in maximum daily temperature could cause significant losses in seagrass biomass and productivity.
|
|
