University of Maryland, College Park
Title of presentation: Effects of Water Availability and Temperature on CAM Expression and Water Use Efficiency by Sedum Album and Sedum Kamtschaticum
Advisors: Mark van Iersel and John D. Lea-Cox
Abstract: Though varying degrees of CAM have been documented for Sedum species, less is known about the implications of this variation for total water and carbon budgets. This study tracks the carbon gain and water use for the more extensively studied Sedum album and for Sedum kamtschaticum, for which CAM has been sparsely documented. Whole plant gas exchange chambers were used to document the diurnal flux of CO2 and evapotranspiration from four replicates of each species. Plants were watered at the beginning of the experiment and again after 21 days. Whole plant gas exchange and evapotranspiration was continuously measured within eight acrylic chambers, placed in one of two Conviron (Winnipeg, Canada) growth chambers, using a datalogger (CR10T; Campbell Scientific, Logan, UT). Air flow through each gas exchange chamber (≈17 mmol·s−1) was measured with mass flow meters (HFM200; Teledyne Hasting Inst., Hampton, VA) and the difference in CO2 concentration between the air entering and exiting the gas exchange chambers was measured with an infrared gas analyzer in differential mode (LI-6262; LI-COR, Lincoln, NE). Most likely as a result of differential Crassuleacean Acid metabolism (CAM), S. album fixed C at 2.55 (± 0.30) mmol and S. kamtschaticum fixed C at 4.68 (± 0.74) mmol. During this same period, S. kamtschticum used 68.87 (± 8.15) grams of water in contrast to 45.82 (± 4.15) grams of water used by S. album. Malic acid analysis indicated that S. album was in CAM throughout the course of the study, but S. kamtschticum only began CAM idling weakly around day 9. These findings suggest that S. album was the more drought tolerant species under the environmental conditions of this experiment. For geographic areas with extended dry periods, S. album may be the preferred species compared to S. kamtschaticum. In cooler, wetter climates, this species may not transpire water fast enough to contribute substantially to green roof stormwater efficiency. Nevertheless, having a species that can tolerate periods of drought stress is important for overall system function, especially when ongoing green roof management or renovation costs are considered.
Authors: Olyssa Starry, University of Maryland, College Park; Jongyun Kim, Pai Chai University, Daejeon, Korea; Sue Dove, University of Georgia, Athens; Marc van Iersel, University of Georgia, Athens; John D. Lea-Cox, University of Maryland, College Park
Specified Source(s) of Funding: USDA–NIFA, SCRI Award no. 2009-51181-05768
Title of presentation: Comparison of Light-Emitting Diode Towers Vs. High-Pressure Sodium Lamps for Year-Round Production of High-Wire Greenhouse-Grown Tomatoes
Advisor: Cary A. Mitchell
Abstract: Intensive year-round local production of greenhouse-grown vegetables requires the use of supplemental lighting to complement solar radiation in light-limited northern climates. Intracanopy light-emitting diode (ICL-LED) towers were compared to overhead high-pressure sodium lamps (HPS-OH) as an alternative supplemental light source for high-wire greenhouse tomato (Solanum lycopersicum L.) production. Two consecutive experiments evaluating growth, yield, and energy consumption from winter-to-summer (increasing natural daily light integral (DLI); Expt. 1) and summer-to-winter (decreasing natural DLI; Expt. 2) were conducted in a northern climate (West Lafayette, IN, USA) to evaluate climatic responses to supplemental photosynthetic lighting. Cultivars Komeett and Success were grown in a glass-glazed greenhouse for five months. Plants were grown under one of three lighting treatments which included: 1000-W (Expt. 1) or 600-W (Expt. 2) HPS-OH lamps vs. LED-ICL towers (95% red and 5% blue) vs. no supplemental lighting (control). No differences were observed between cultivars for any of the parameters evaluated. Our findings indicate that equivalent increases in fruit number and yield can be achieved with the two supplemental light treatments compared to the unsupplemented control. Furthermore, significant energy savings can be achieved using the ICL-LED compared to the standard OH-HPS lamps (75% and 55% for Experiment. 1 and Experiment 2, respectively). Our results suggest that ICL-LED is a viable alternative to the widely adopted HPS-OH lighting.
Authors: Celina Gomez and Cary A. Mitchell, Purdue University, West Lafayette, IN
Specified Source(s) of Funding: NIFA SCRI grant 2010-51181-21369
Title of presentation: Determining the Effectiveness of Red and Blue Light-emitting Diodes As Supplemental Lighting During Seedling (plug) Propagation
Advisor: Roberto G. Lopez
Abstract: Annual bedding plant seedlings (plugs) are considered high-quality when they are compact, fully rooted transplants with a large stem caliper and high root dry mass. The objectives of this study were to: 1) quantify the effects of light emitting diodes (LEDs) and high pressure sodium lamps (HPS) as supplemental light sources to produce annual bedding plant seedlings; and 2) determine what red (R) to blue (B) light ratio produces the highest quality seedlings. Ten bedding plant species (Antirrhinum majus L., Begonia xsemperflorens L., Catharanthus roseus L., Celosia argentea L. var. plumosa L., Impatiens walleriana Hook. f., Pelargonium xhortorum, Petunia xhybrida Vilm.-Andr., Salvia splendens Sellow ex J.A. Shultes, Tagetes patula L., and Viola xwittrockiana Gams.) were grown under 100 μmol·m–2·s–1 delivered from HPS lamps or LED arrays with varying proportions (%) of red:blue light (100:0, 85:15, 70:30, and HPS) with a 16-h photoperiod. Seedling of Antirrhinum, Begonia, Impatiens, Petunia, and Tagetes grown under the 85:15 light treatment were generally more compact with a larger stem caliper and higher relative chlorophyll content than plants grown under HPS lamps. For example, stem caliper increased by 13.6%, 6.5%, 3.5%, 5.1%, and 11.5% compared to seedlings grown under HPS lamps for Antirrhinum, Begonia, Impatiens, Petunia, and Tagetes, respectively. Relative chlorophyll content of Antirrhinum and Begonia increased by 11.6% and 14.0%, respectively, compared to seedlings grown under HPS lamps. Stem length of Antirrhinum, Impatiens, and Tagetes was 5.7%, 30.6%, and 20.8% shorter, respectively, compared to seedlings grown under HPS lamps. Seedlings grown under LED light treatments generally had higher quality parameters than those grown under HPS lamps.