Agricultural byproducts are a major source of biomass for biofuel/bioenergy conversion. The southeastern
U.S. produces a great amount of nutshells from pecan, walnut, and peanut processing. In this study, walnut
shells were selected as a representative agricultural byproduct, and a hydrothermal process catalyzed by both
bases and acid was applied to convert the walnut shells into liquefied organic compounds. Conversion rate,
major organic products, and their distribution were measured under different concentration of bases (0−1.0
M) and reaction temperature (200−300 °C, corresponding to a pressure range of 1.5−8.6 MPa). An increase
in base concentration (KOH and Na2CO3 ) or reaction temperature generally resulted in higher conversation
rates and was more favorable to the generation of organic compounds of lower molecular weights. HCl as a
catalyst promoted the generation of levulinic acid, but the conversion rates were very low. Major compounds
from hydrothermal process catalyzed by bases were phenol derivatives. Small amounts of cyclopenten derivatives
and C12−18 fatty acids were detected. The effects of reaction conditions on the distribution of products were
characterized by the relative abundance of each compound group categorized based on the GC retention time.
Freshly harvested Florida pusley (Richardia scabraL.) seeds do not germinate in continuous dark, but do germinate if exposed to more than 2 hr of light each day. Increasing periods of illumination up to 16 hr per day increases the germination percentages. Scarification increases the rate of germination in the presence of light. Scarification also causes germination of seeds stored for 8 months or longer in total darkness. The seeds fail to germinate at constant temperatures of 15 C or less and at 40 C. Almost complete germination occurs at a constant temperature of 30 C, or at alternating temperatures of 20 and 30 C. The seeds germinate equally well in the pH range of 3 to 8. Increasing depths of planting reduces percent emergence, and none of the seedlings emerge from a depth of 1.5 cm or more. Air-dried seeds can be stored either at 5 or at 25 C without losing viability, at least up to a period of 1 year after harvest. Moist storage of seeds at 5 C reduces germinability.
The objective of this study was to investigate the effects of water stress in sweet potato {Ipomoea batatas L.[Lam] 'Georgia Jet') on biomass production and plant-water relationships in an enriched CO2 atmosphere. Plants were grown in pots containing sandy loam soil (Typic Paleudult) at two concentrations of elevated CO2 and two water regimes in open-top field chambers. During the first 12 d of water stress, leaf xylem potentials were higher in plants grown in a CO2 concentration of 438 and 666/zmol mol"' than in plants grown at 364)umol mol"'. The 364 /xmol mol"" CO2 grown plants had to be rewatered 2d earlier than the high CO2-grown plants in response to water stress. For plants grown under water stress, the yield of storage roots and root: shoot ratio were greater at high CO2 than at 364/^mol mol"'; the increase, however, was not linear with increasing CO2 concentrations. In well-watered plants, biomass production and storage root yield increased at elevated CO2, and these were greater as compared to water-stressed plants grown at the same CO2 concentration.
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