Masters Theses

Date of Award

12-1985

Degree Type

Thesis

Degree Name

Master of Science

Major

Landscape Architecture

Major Professor

Gary L. McDaniel

Committee Members

Effin T. Graham, G. Douglas Crater

Abstract

The role of nitrogen and calcium fertilization in stem strength of potted poinsettia was assessed. 'Annette Hegg Dark Red', 'Gutbier V-14 (Glory)', and 'Eckespoint C-1', were provided with the following fertilizer formulations: 1) 15-16-17 Peter's Peat-lite Special, 2) 15-0-15 Peter's Dark Weather Feed, 3) 15-16-17 plus foliar sprays of calcium chloride, and 4) 15-0-15 plus calcium sprays. The 15-16-17 fertilizer formulation is currently used in commercial poinsettia production. It is a higher ammoniacal nitrogen formulation (21% NH4-N, 26% urea, 53% NO3-N) than 15-0-15 (13% urea, 87% NO3-N, primarily as CaNO3). Calcium chloride foliar sprays provided additional Calcium.

Preliminary results of the first study, in which the plants were fertilized with 20-20-20 Peter's General Purpose Fertilizer (87% NH4-N) initially and the above treatments were begun following the pinch date, showed no differences in branch retention due to the nitrogen source or additional calcium. Subsequent studies began nutritional regimes after potting the rooted cuttings. Generally, branch retention is enhanced by use of calcium nitrate as the nitrogen source. Additional calcium as foliar sprays did not significantly increase branch retention. However, further investigations of calcium chloride spray applications at higher rates, more frequent application dates and for a longer duration may be warranted.

Histological investigation of anatomical structure was also conducted. The poinsettia tissue was sampled at maturity when the stems were very woody and processing by the conventional paraffin technique was impractical. A new method of tissue sectioning was developed. Infiltration with polyethylene glycol (PEG) 400 and sectioning with a disposable rotary microtome blade attached to a standard sliding microtome blade provided a satisfactory method of working with this difficult tissue. While sections obtained in this manner were quite thick, (40 micrometers), there was very good differentiation of the vascular, cortical and epidermal tissue systems, nuclei, and starch when the sections were stained with toluidine blue or Gill's hematoxylin counterstained with safranin. Further investigations refining this technique to produce thinner sections and involving histochemical tests and polarized light microscopy are warranted.

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