Effects of Manganese Level and Nitrogen Form on the Growth of Lowbush Blueberry (Vaccinium angustifolium Ait.)

This thesis involved several studies to examine the effect of Manganese (Mn) levels on lowbush blueberry {Vaccinium angustifolium Ait.) either under field conditions or with in vitro methods; nitrogen (N) form and concentrations in tissue culture media were also examined to improve the composition of tissue culture media for lowbush blueberry. A commercial lowbush blueberry field in Cherryfield, Maine, with leaf tissue Mn levels below 750 mg-kg \u27 was fertilized with foliar-applied Sequestered 5% Manganese at 0, 0.234, 0.468, or 0.702 kg-ha \u27 Mn in June. A split-split plot design with eight replications was used. Diammonium phosphate (DAP) at 0 or 224 kg-ha 1 was applied pre-emergently to determine the effect of N availability on Mn absorption. Neither Mn fertilizer nor DAP affected foliar Mn concentrations. DAP increased leaf N and P levels but lowered soil iron (Fe). Stem branching and the number of branched stems increased by DAP. Manganese fertilizer at applied rates had no effect on plant growth. Seven lowbush blueberry clones with leaf tissue Mn levels below 750 mg-kg \u27 were selected in a commercial lowbush blueberry field in Belfast, Maine. Sixteen 0.61 m x 0.61 m treatment plots established on each clone received a soil drench of Citraplex 20% Manganese at 0, 1.12, 2.24, or 3.36 kg-ha \u27 manganese in May. Manganese soil drench did not affect Mn levels in either soil or leaf tissue concentrations in July of the crop year, and large clonal variation existed. Stems collected after leaf drop did not show any growth change due to the application of Mn fertilizer. First subculture of \u27Blomidon\u27 and \u27TC No.1\u27 lowbush blueberry was used as explant to evaluate the effect of Mn on plant growth in tissue culture. Z-2 media were adjusted to contain 0 (control), 7.5, 15 (standard), 30, 60, 90, 120, or 150 mg-kg\u271 Mn. Growth regulator 6-(y,7-Dimethylallylamino)purine (2iP) in treatment media was reduced to 10 mg-kg-1 to obtain measurable shoots. The level of Mn did not affect plant survival rate. Cultures grown on treatment medium with 90 mg-kg 1 Mn produced more shoots and unbranched shoots than those grown on the standard medium and the control group with no Mn. Manganese in Z-2 medium is within the satisfactory range. Manganese concentration higher than 120 mg-kg 1 were toxic for shoot generation. First subculture of \u27Blomidon\u27 and \u27TC No.l\u27 lowbush blueberry was used as explant to evaluate the effect of N form and concentration on plant growth in tissue culture. Eight treatment media containing ammonium nitrogen (NH4-N)and nitrate nitrogen (NCyN) were compared based on plant growth. Results showed that the presense of both forms of N is necessary for plant survival. Explants had better growth when the medium contained more NO,-N rather than more NFL-N