Red light represses the photophysiology of the scleractinian coral Stylophora pistillata

Light spectrum plays a key role in the biology of symbiotic corals, with blue light resulting in higher coral growth, zooxanthellae density, chlorophyll a content and photosynthesis rates as compared to red light. However, it is still unclear whether these physiological processes are blue-enhanced or red-repressed. This study investigated the individual and combined effects of blue and red light on the health, zooxanthellae density, photophysiology and colouration of the scleractinian coral Stylophora pistillata over 6 weeks. Coral fragments were exposed to blue, red, and combined 50/50% blue red light, at two irradiance levels (128 and 256 μmol m⁻² s⁻¹). Light spectrum affected the health/survival, zooxanthellae density, and NDVI (a proxy for chlorophyll a content) of S. pistillata. Blue light resulted in highest survival rates, whereas red light resulted in low survival at 256 μmol m⁻² s⁻¹. Blue light also resulted in higher zooxanthellae densities compared to red light at 256 μmol m⁻² s⁻¹, and a higher NDVI compared to red and combined blue red light. Overall, our results suggest that red light negatively affects the health, survival, symbiont density and NDVI of S. pistillata, with a dominance of red over blue light for NDVI.

Phytotoxicity of tolylfluanid in tomatoes

The use of Euparen Multi (tolylfluanid) for controlling Botrytis cinerea in tomatoes has been decreased the last decade for several reasons. Because of the lack of different fungicides with a good efficacy it is important that growers can use different fungicides to prevent development of resistance of Botrytis cinerea against many fungicides. Tolylfluanid has negative side effects on some insect populations that are used for biological control. It is known that Euparen Multi and Euparen can have a negative effect on some predatory mites (Schmidt and Zeller, 1998) such as Phytoseiulus persimilis and some parasitic wasps like Encarsia formosa, Eretmocerus eremicus, Diglyphus isaea and Dacnusa sibirica. Recently investigation indicates that this fungicide is harmless for the predatory bug Macrolophus caliginosus (Biobest, 2006) frequently used in the cultivation of tomatoes as a predator for whitefly (Trialeurodes vaporariorum). To investigate if tolylfluanid has a phytotoxic effect on tomato plants an experiment was performed. Young tomato plants were used, who are more sensitive. These plants were subdivided in different groups, from which each one was sprayed with a different concentration of tolylfluanid. The highest concentrations of tolylfluanid were used to stimulate the visibility of the possible phytotoxic effects. Results of this experiment demonstrate that there wasn't a difference between the different groups that were sprayed with tolylfluanid or the control group. This indicates that tolylfluanid doesn't seem to be phytotoxic. It is also important to mention that this experiment was done in the fall when the intensity of the sunlight was decreasing. There still exists the possibility that extreme irradiation in combination with tolylfluanid can provoke a phototoxic effect on young tomato plants.