Growth and nutrient use efficiency of water tupelo seedlings in flooded and well-drained soil.

Growth characteristics and nutrient utilization rate of Nyssa aquatica L. seedlings grown in pots containing flooded or well-drained soil were compared in a greenhouse study. For most of the growing season, relative height and diameter growth rates, and biomass accumulation rates were greater for seedlings in flooded soil than for seedlings in well-drained soil. The concentration of Fe in the roots of seedlings in flooded soil was almost tenfold greater than that of seedlings in well-drained soil. However, flooding had no effect on foliar Fe concentrations. The flooding treatment resulted in decreased concentrations of N in all component parts and increased concentrations of P in the roots and stem, but it had no effect on foliar P concentrations. In response to flooding, foliar K concentrations decreased, whereas the concentration of K in the roots increased. Flooding had no effect on the K concentration of the stem. Seedlings in flooded soil produced more total biomass per milligram of nutrient absorbed than seedlings in well-drained soil, suggesting that N. aquatica seedlings are more efficient at producing biomass and height growth under hydric conditions than under mesic conditions.

Histocompatibility screening by molecular techniques: use of polymerase chain reaction products and heteroduplex formation.

Novel molecular approaches have recently become available allowing improved major histocompatibility complex (MHC) matching of potential allogeneic bone marrow donors and recipients. Current cellular and serological assays are hindered by aberrant cell populations and limited reagents which only detect an individuals' phenotype. Therefore, a molecular screening protocol which discriminates at the genotypic level would be advantageous. Here we describe a two-step DNA-based approach that can be applied to large-scale screening of potential donors. A primary screen, utilizing polymerase chain reaction (PCR), reduces the potential donor population, whereas a secondary or fine resolution screen uses DNA heteroduplex analysis to determine identity or non-identity at specific loci. Heteroduplex analysis generates a DNA migration pattern that is unique for alleles at a given locus, and is more sensitive than serology in discriminating among individuals. Here we demonstrate the potential feasibility of this approach by analyzing results at one MHC locus, HLA-DQ. Since this method does not rely on typing sera or viable lymphocytes, it is not subject to the variability found in the traditional methods. In contrast to traditional methods, these molecular techniques can provide the critical information needed to select a potential bone marrow donor.