Dry Matter Accumulation and Partitioning of Swithgrass Genotypes in Response to Temperature.

Growing temperature affects species distribution, dry matter accumulation and partitioning. The objective of this study was to evaluate the response to temperature of switchgrass (Panicum virgatum L.), a promising bioenergy crop, genotypes on development, growth, reproduction, partitioning, net photosynthesis rate (PN) and fluorescence (F). Three lowland (SL-91-2001, Alamo, Kanlow) and two upland (Caddo and Cave-in-Rock) ecotypes of switchgrass were grown in pots filled with pure, fine sand providing nutrients with Hoagland’s nutrient solution. Four growth chambers at the Controlled-Environment Research Laboratory (CERL) facility at Oklahoma State University were used for this study and four different day/night temperature treatments of 23/15, 28/20, 33/25, and 38/30^oC with 14 hours daylight and 10 hours night condition was imposed at four leaf stages. Genotype SL93-2001-1 had higher stem elongation, tillering and photosynthetic rate across the temperature treatments compared to other gentotypes. Plant height and dry matter accumulation decreased sharply in 38/30^oC for all genotypes but total number of tillers per plant increased. Leaf /stem ratio increase with increase of temperature. Node numbers and Specific Leaf Area were not affected by temperature.  Lowland genotypes had higher photosynthetic rates at high temperatures while uplands at low temperatures. Photosynthetic Light response curve showed that lowland lowland ecotypes have lower light saturation point compared to upland ecotypes in all temperature regimes. Upland ecotypes produced panicles earlier than lowland ecotypes in all temperature. Total number of panicle bearing tillers, panicle length and spikelets per panicle decreased significantly in highest temperatures which indicate a reduction of population and dominance of the switchgrass genotypes in tall grass prairie in future. The temperature response study of swithgrass genotype will be useful not only for selection of traits that are important for present and future climatic condition but it will also be important to quantify the biomass yield under projected higher temperature as a result of global change.