SPECTRAL PROPERTIES OF MICROWAVE-POWERED SULFUR LAMPS IN COMPARISON TO SUNLIGHT AND HIGH PRESSURE SODIUM/METAL HALIDE LAMPS

The spectral properties of 3.4kW microwave-powered sulfur (MPS) lamps were compared with sunlight and with a combination of high-pressure sodium (HPS) and metal halide (MH) lamps. Photosynthetic photon flux (PPF) levels at 1.2m from the MPS lamps (half and full power) and the HPS/MH lamps were 565, 1650, and 875μmol m^s^, respectively, versus 2000μmol m^s^ for sunlight. The percent of spectral irradiance from bare MPS lamps operated at full power was comparable to that of sunlight in the 400-500nm (blue) and 600-700nm (red) regions but was 60% higher in the 500-600nm (yellow) region. On a percent distribution basis, HPS/MH lamps had 50% less blue, nearly 25% more red, and twice as much yellow irradiance as sunlight. On a percent basis, MPS and HPS/MH lamps emitted one third to one half as much 700-792nm (far-red) irradiance as sunlight. At half power, there was a significant shift in spectral output of the MPS lamps from the red to the blue region. Measurements taken with a pyranometer and a pyrgeometer indicate that the biggest difference between MPS and HPS/MH lamps was in the 0.8 to 3.0μm (near infrared, NIR) region; MPS lamps emitted one quarter as much NIR as HPS/MH lamps or the sun on a normalized basis (Jμmol^). There was no appreciable difference in far IR (3 to 50μm) between half power MPS and HPS/MH lamps, while at full power, MPS lamps had only one half as much far IR. Based on their spectral characteristics and high PPF, MPS lamps should provide an excellent source of radiant energy for use in plant growth chambers

SPECTRAL PROPERTIES OF MICROWAVE-POWERED SULFUR LAMPS IN COMPARISON TO SUNLIGHT AND HIGH PRESSURE SODIUM/METAL HALIDE LAMPS

The spectral properties of 3.4kW microwave-powered sulfur (MPS) lamps were compared with sunlight and with a combination of high-pressure sodium (HPS) and metal halide (MH) lamps. Photosynthetic photon flux (PPF) levels at 1.2m from the MPS lamps (half and full power) and the HPS/MH lamps were 565, 1650, and 875μmol m^<-2>s^<-1>, respectively, versus 2000μmol m^<-2>s^<-1> for sunlight. The percent of spectral irradiance from bare MPS lamps operated at full power was comparable to that of sunlight in the 400-500nm (blue) and 600-700nm (red) regions but was 60% higher in the 500-600nm (yellow) region. On a percent distribution basis, HPS/MH lamps had 50% less blue, nearly 25% more red, and twice as much yellow irradiance as sunlight. On a percent basis, MPS and HPS/MH lamps emitted one third to one half as much 700-792nm (far-red) irradiance as sunlight. At half power, there was a significant shift in spectral output of the MPS lamps from the red to the blue region. Measurements taken with a pyranometer and a pyrgeometer indicate that the biggest difference between MPS and HPS/MH lamps was in the 0.8 to 3.0μm (near infrared, NIR) region; MPS lamps emitted one quarter as much NIR as HPS/MH lamps or the sun on a normalized basis (Jμmol^<-1>). There was no appreciable difference in far IR (3 to 50μm) between half power MPS and HPS/MH lamps, while at full power, MPS lamps had only one half as much far IR. Based on their spectral characteristics and high PPF, MPS lamps should provide an excellent source of radiant energy for use in plant growth chambers

Effects of light and temperature on the growth of Takayama helix

Takayama helix is a mixotrophic dinoflagellate that can feed on diverse algal prey. We explored the effects of light intensity and water temperature, two important physical factors, on its autotrophic and mixotrophic growth rates when fed on Alexandrium minutum CCMP1888. Both the autotrophic and mixotrophic growth rates and ingestion rates of T. helix on A. minutum were significantly affected by photon flux density. Positive growth rates of T. helix at 6-58 mu mol photons center dot m(-2) center dot s(-1) were observed in both the autotrophic (maximum rate = 0.2 center dot d(-1)) and mixotrophic modes (0.4 center dot d(-1)). Of course, it did not grow both autotrophically and mixotrophically in complete darkness. At &gt;= 247 mu mol photons center dot m(-2) center dot s(-1), the autotrophic growth rates were negative (i.e., photoinhibition), but mixotrophy turned these negative rates to positive. Both autotrophic and mixotrophic growth and ingestion rates were significantly affected by water temperature. Under both autotrophic and mixotrophic conditions, it grew at 15-28 degrees C, but not at &lt;= 10 or 30 degrees C. Therefore, both light intensity and temperature are critical factors affecting the survival and growth of T. helix.N

Mangrove microclimates alter seedling dynamics at the range edge

Recent climate warming has led to asynchronous species migrations, with major consequences for ecosystems worldwide. In woody communities, localized microclimates have the potential to create feedback mechanisms that can alter the rate of species range shifts attributed to macroclimate drivers alone. Mangrove encroachment into saltmarsh in many areas is driven by a reduction in freeze events, and this encroachment can further modify local climate, but the subsequent impacts on mangrove seedling dynamics are unknown. We monitored microclimate conditions beneath mangrove canopies and adjacent open saltmarsh at a freeze-sensitive mangrove-saltmarsh ecotone and assessed survival of experimentally transplanted mangrove seedlings. Mangrove canopies buffered night time cooling during the winter, leading to interspecific differences in freeze damage on mangrove seedlings. However, mangrove canopies also altered biotic interactions. Herbivore damage was higher under canopies, leading to greater mangrove seedling mortality beneath canopies relative to saltmarsh. While warming-induced expansion of mangroves can lead to positive microclimate feedbacks, simultaneous fluctuations in biotic drivers can also alter seedling dynamics. Thus, climate change can drive divergent feedback mechanisms through both abiotic and biotic channels, highlighting the importance of vegetation-microclimate interactions as important moderators of climate driven range shifts