The effects of 6-benzylamino purine (BA) concentration and timing of BA application at various phases of bud development of Ilex crenata Thunb. 'Rotundifolia' were studied. Foliar applications of BA at 800 ppm to unbranched rooted cuttings enhanced axillary bud development resulting in well branched Iiners. Axillary bud development of rooted cuttings was enhanced when applications were made when buds were swelIing preceding a flush of growth. Applications made prior to bud swelling or made during a flush of growth were ineffective in stimulating additional axillary bud development. Combined applications of BA at 800 ppm to liners preceding two successive flushes of growth resulted in a 68% increase in total numbers of shoots per plant over control plants. Applications of BA at 600 ppm and 800 ppm to individual shoots resulted in swelling of the terminal 4-5 cm section of treated stems and development of a red pigment followed by growth of numerous axillary shoots on the stem produced by the apical bud. Applications of BA at 1000 ppm and 1200 ppm to individual shoots acted as chemical pinching agents inhibiting apical buds. Leaves on shoots which developed from liners treated with BA at 1200 ppm were 46% smaller than those on control plants. These suppressed leaves contained 60% fewer upper epidermal cells than leaves of control plants, and average epidermal cell size was 24% larger than those of control plants. / Ph. D.

Medium solution N and electrical conductivity (EC), and foliar N levels were measured to determine criteria which signal the need for reapplication of a controlled-release fertilizer (CRF) in order to maximize growth of container-grown Ilex crenata Thunb. ‘Helleri’. Rooted cuttings of ‘Helleri’ holly were initially fertilized (7 Mar. 1991) with 8-9 month (18N-2.6P-9.9K) or 12-14 month (17N-3.1P-9.9K) Osmocote. A subset of 12 plants received a CRF reapplication (half rate) of the respective Osmocote formulation on 19 July, 2 Aug., or 16 Aug. In addition to reapplication treatments, 12 plants received a liquid fertilizer (LF) solution with each irrigation starting on 19 July. Canopy widths of plants receiving LF or CRF reapplication on 19 July and 2 Aug. were greater than those plants without supplemental fertilizer (control). At the time of the second reapplication date (2 Aug.), medium solution N and EC, and foliar N levels of control plants were = 40 mg liter⁻¹, 0.4 d m⁻¹ and 2.3%, respectively. Since growth of control plants was less than those of LF, CRF 19 July and 2 Aug. reapplications, medium solution N and EC, and foliar N values at the time of the second reapplication (2 Aug.) signaled the need for CRF reapplication or LF supplementation. There was a strong relationship between medium solution EC and N (NO₃ + NH₄) (r² = 0.91, P = 0.05), indicating that growers could use EC measurements to predict medium solution N concentration, as well as to assess the adequacy of the fertilizer regime. / Master of Science

Rooted cuttings of Ilex crenata 'Helleri' were grown in sand culture with four rates of Ca and Mg (0, 5, 10, and 40 ppm) in a factorial experiment. No increase in total dry weight was achieved by increasing Ca and Mg rates above 5 ppm. Necrosis of shoot apices occurred at the 0 ppm Ca rate. A second rate experiment supported the results of the initial research. In addition to symptoms of Ca deficiency on the 0 Ca treatments, symptoms of severe Mg deficiency appeared on the 0 Mg treatments. These began as a discoloration of the lower leaves followed by abscission. A third experiment was performed on 'Helleri' holly growing in pine bark. Calcium was supplied at 0 and 120 ppm and Mg at 0 and 60 ppm. No differences in dry weight were observed. A third experiment studied the influence of four dolomitic limestone rates (0, 2, 4, and 8 kg/m³) and two gypsum rates (1 and 2 kg/m³) mixed with pine bark on Ca availability, Mg availability, and pH over time. Although the addition of dolomitic limestone increased Ca and Mg in the medium solution, unamended bark supplied sufficient quantities of both elements for the growth of Ilex crenata 'Helleri'. The addition of gypsum caused a large initial increase in Ca in the medium solution, but supplies dropped drastically thereafter. / M.S.