02781nam a2200265 a 450000100080000000500110000800800410001910000160006024500550007626000470013130000100017850000240018852021440021265000110235665000110236765000190237865000200239765000130241765000120243065000160244265000230245865000090248165300090249065300160249915638492000-01-06       1983    bl uuuu  m   00u1 u    #d1 aBOVI, O. A.  aEstimating carbon balance of field-grown soybeans.  a[Gainesville]: University of Floridac1983  a127p.  aPh.D. Dissertation.  aDaily total canopy photosynthesis estimated throughout the whole season in field-grown soybean (Glycine max (L.) Merr., 'Cobb'), was input into the Florida Soybean Crop Growth Simulator (SOYGRO) which was allowed to estimate respiration costs (growth and maintenance respiration) and allocate assimilate to dry matter production. Simulated results were compared with field dry-matter measurements. The soybean crop was subjected to three water regimes (vegetetive phase water deficit, reproductive phase water deficit, and well-irrigated) and two levels of insect defoliation (non-defoliated and approximately 30 percent defoliated), in a split-plot design with four field replications. These treatments provided a range in seasonal carbon input to compare with induced variations in dry matter production and yield. Carbon exchange rate was measured in the field once or twice weekly at mid-day, using a portable assimilation chamber. Efflux of CO2 from crop and soil in darkness was also measured to allow calculation of total canopy photosynthesis. Photosynthesis-light response equations were developed and used with hourly values of photosynthetic photon flux to give daily integrated total canopy photosynthesis for every day of the season. Total seasonal photosynthesis was reduced in all treatments when compared to the well-irrigated (non-defoliated) plants. Water deficit treatments reduced total seasonal photosynthesis by 16.2 and 12.5 percent, compared to the well-irrigated plants. Defoliation causedreductions of 4.8, 4.8 and 4.5 percent in total seasonal photosynthesis when compared within the respective main plot water treatments. Final seed yield was best correlated with the cumulative photosynthesis during the linear phase of the seed filling period. Dry matter accumulation in plant parts estimated by SOYGRO (inputing field-measured photosynthesis) stayed within 15 percent of the equivalent field measured dry weights. This study suggests the feasibility of using a portable chamber technique to measure canopy photosynthesis, making possible the study and validations of simulation model parameters, in soybeans.  acanopy  acarbon  aphotosynthesis  aplant nutrition  asoybeans  aCarbono  aGlycine Max  aNutrição Vegetal  aSoja  aCopa  aFotosintese