SOIL MANAGEMENT, FERTILIZATION, & IRRIGATION HORTSCIENCE 37(1):126–129. 2002. metric compared to roots of cranberry (Vaccinium macrocarpon Ait. ‘Searles’) fer- + tilized with NH4 that had rectangular epider- Nitrogen Form Affects Growth, Mineral mal cells (Finn et al., 1990). These differences in epidermal cell development were probably – Nutrient Content, and Root Anatomy a result of less cell elongation with NO3 . Alterations in the phytohormone balance of of Cotoneaster and Rudbeckia the plant and differences in the assimilation + – pathways of NH4 and NO3 in the root may Helen T. Kraus and Stuart L. Warren account for the effect of N form on root mor- phology (Marschner, 1986). Department of Horticultural Science, North Carolina State University, Raleigh, As N form affects growth and may alter NC 27695-7609 root growth, thereby impacting establishment in landscape plantings, there is need for more Charles E. Anderson research on the effects of N form on landscape Department of Botany, North Carolina State University, Raleigh, NC 27695-7612 plants. Additionally, results of N form impacts on cotoneaster growth were conflicting, and Additional index words. root growth, Cotoneaster dammeri ‘Skogholm’, Rudbeckia fulgida no reports of the effect of N form on rudbeckia ‘Goldsturm’, ammonium, nitrate, container-grown growth were found, nor were any reports found + – describing the anatomy of cotoneaster and Abstract. Five ratios of NH4 : NO3 (100:0, 75:25, 50:50, 25:75, and 0:100) were evaluated for impact on growth of Cotoneaster dammeri Schneid. ‘Skogholm’ (cotoneaster), a woody rudbeckia roots. Therefore, our objective was ornamental shrub, and Rudbeckia fulgida Ait. ‘Goldsturm’ (rudbeckia), an herbaceous to evaluate the effects of N form and ratio on perennial. Nitrate alone decreased dry weight and leaf area of cotoneaster and rudbeckia growth, mineral nutrient accumulation, and + – + – root anatomy of cotoneaster, a woody orna- compared with mixtures of NH4 and NO3 and NH4 alone. Additionally, NO3 alone + mental shrub, and rudbeckia, a popular herba- suppressed accumulation of cationic nutrients and N in cotoneaster, while mixes of NH4 – ceous perennial. and NO3 enhanced accumulation of nutrients in roots and shoots of rudbeckia compared + – with solutions containing either NH4 or NO3 alone. The steles of roots of cotoneaster and rudbeckia contained more secondary xylem with larger tracheary elements with a mix of Materials and Methods 25 NH + : 75 NO – than with NO – alone. 4 3 3 An experiment was conducted for 12 weeks (14 Oct. 1994 to 4 Jan. 1995) in a glass green- Developing a fertility program involves perlite (Bigg and Daniel, 1978). Reports con- house in Raleigh, N.C. The experiment used a selecting fertilizer rates, and sources and ra- flict on the effect of N form on growth of randomized complete-block design with seven + – tios of nutrients, especially the form of N cotoneaster. Growth of cotoneaster ‘Royal replications (seven plants per NH4 : NO3 + – (NH4 or NO3 ). Nitrogen form affects mineral Beauty’ was not affected when grown in sand treatment) and two species, cotoneaster nutrient concentration of shoots and roots that was supplied daily with nutrient solutions ‘Skogholm’ and rudbeckia ‘Goldsturm’. Ni- + – (Edwards and Horton, 1982; Rosen et al., with different N forms (Gilliam et al., 1980). trogen treatments included five NH4 : NO3 1990), growth rate and N uptake (Edwards and In contrast, when cotoneaster ‘Royal Beauty’ ratios (100:0, 75:25, 50:50, 25:75, and 0:100) Horton, 1982), and root anatomy (Finn et al., was grown in 4 pine bark : 1 sand (by volume) (Table 1). 1990) of ornamental plants. Generally, in- and supplied with weekly applications of nu- Cultural conditions. To facilitate complete – – creasing NO3 in fertilizer solutions stimulates trient solution, NO3 produced greater shoot recovery of root systems at harvest, rooted + organic anion synthesis and cation accumula- growth than NH4 , but root growth was not cotoneaster cuttings and rudbeckia seedlings tion by the plant (Mengel and Kirkby, 1982). effected by N form (Gilliam et al., 1982/83). were grown in 3.8-L containers filled with a – Active uptake of NO3 is believed to induce Frequency of nutrient solution application and substrate of arcillite (Turface, Aimcor Inc., – symport of cations; however, NO3 uptake pH of nutrient solution, along with differences Deerfield, Ill.), consisting of calcined may also occur in exchange for OH– without in container substrates, may have contributed montmorillite and illite clays. Arcillite was cation symport (Mengel and Kirkby, 1982). In to the diversity of plant growth and nutrient chosen as the container substrate because of its + contrast, NH4 often suppresses the absorption accumulation results. high moisture-holding capacity, good aera- of cations and synthesis of organic anions Root morphology and growth determine tion, even retention of irrigation without chan- produced by plants, whereas inorganic anion the ability of a plant to exploit the rooting neling, and ease of removal from plant roots = = – accumulation (SO4 , PO4 , and Cl ) is increased volume for water and nutrients (Mengel and (Hiller and Koller, 1979). Temperatures were (Mengel and Kirkby, 1982). Kirkby, 1982) and may be altered by changes maintained at 24 ± 3 °C day/13 ± 3 °C night Growth of Douglas-fir [Pseudotsuga in the form of available N. Cultivars of peach under natural irradiance. Plants were covered menziesii (Mirb.) Franco], especially root [Prunus persica (L.) Batsch.] produced a with black cloth at 5:00 PM and provided with + growth, was reduced by NH4 as the only N- greater volume of roots with 50:50 and 25:75 a daily night interruption from 11:00 PM to + – – source, while growth of lodgepole pine (Pinus mixtures of NH4 and NO3 than with NO3 2:00 AM using incandescent bulbs (photosyn- contorta Dougl.) and Engelmann spruce (Picea alone (Edwards and Horton, 1982). Epidermal thetic photon flux of 3.6 µmol·m–2·s–1 plus – – –2 engelmanni Parry) was reduced with NO3 as cells of roots from plants fertilized with NO3 photomorphogenic radiation of 0.7 W·m ) the only N-source when grown in sand and had denser cytoplasm and were nearly isodia- and uncovered at 8:00 AM. + – Received for publication 27 Nov. 2000. Accepted Table 1. Nutrient solutions for each NH4 : NO3 ratio. for publication 6 June 2001. Research was funded NH + : NO – Nutrient source in part by the North Carolina Agricultural Research 4 3 ratioz NH NO NH Cl KNO Ca(NO ) KH PO K (SO ) CaSO Service (NCARS), Raleigh, NC 27695-7643. Use 4 3 4 3 3 2 2 4 2 4 4 of trade names in this publication does not imply 100:0 3.5 0.32 0.96 1.25 endorsement by the NCARS of products named nor 75:25 0.875 1.75 0.32 0.96 1.25 criticism of similar ones not mentioned. The techni- 50:50 1.75 0.32 0.96 1.25 cal assistance of William Reece and Diane Mays, 25:75 0.875 0.96 0.442 0.32 0.834 Analytical Service Laboratory, Dept. of Soil Sci- 0:100 0.96 1.27 0.32 z ence, and the statistical guidance of William Swal- 1.03 mM MgSO4, 0.09 mM Fe DTPA, 0.05 mM H3BO3, 0.0003 mM CuSO4, 0.009 mM MnCl, 0.001 mM. low are greatly appreciated. (NH4)6Mo7O24, and 0.0008 mM ZnSO4 supplied to each NH4 : NO3 treatment. 126 HORTSCIENCE, VOL. 37(1), FEBRUARY 2002 6704, p. 126-129 126 1/29/02, 10:22 AM Ammonium : nitrate ratio treatments were samples in a CHN elemental analyzer (Perkin tested for differences using analysis of vari- administered twice daily (9:00 AM and 1:00 Elmer 2400, Perkin Elmer). All tissue nutrient ance and regression analyses (SAS Institute, PM) at 50 mg·L–1 N and 450 mL per application analyses were conducted at the Analytical 1985) and were considered significant at P ≤ (900 mL daily) via individual spray stake Service Laboratory, Dept. of Soil Science. 0.05. Treatment comparisons were made by emitters (Spot-Spitter, Green 160°, Roberts Leaf area of each species was determined at single degree of freedom linear contrast tests + Irrigation Products, San Marcos, Calif.) that harvest with a leaf area meter (LI-3000; LI- testing for differences between NH4 alone, – + dispersed nutrient solution treatments evenly COR, Lincoln, Nebr.). Dry weight and leaf NO3 alone, and the average response of NH4 – over each container. A modified Hoagland area data were used to calculate root : shoot : NO3 mixtures. No statistical analyses were + – ÷ solution was applied with the NH4 : NO3 ratio [RSR (cotoneaster) = root dry weight conducted on the anatomical data and these treatments to provide other mineral nutrients shoot (leaf + stem) dry weight and RSR (rud- data are included for comparison purposes necessary for plant growth (Table 1). Nutrient beckia) = root dry weight ÷ leaf dry weight] only. solutions in stock tanks were changed weekly, and specific leaf dry weight (SLW = leaf dry and pH of nutrient solutions was checked daily weight ÷ leaf area). Tissue nutrient content Results and Discussion and adjusted as needed with NaOH or HCl to (mg) was based on percent concentration of maintain a pH of 6.0. To monitor substrate pH, the nutrient, multiplied by plant part (root or Although pH of the nutrient solutions in substrate solution displaced during the 1:00 PM shoot) dry weight and divided by 100, and was stock tanks was maintained at 6.0, substrate + irrigation with nutrient solution was collected utilized to show absolute differences in nutri- solution pH varied with sample date and NH4 – on 25 Oct., 11 Nov., 23 Nov., 12 Dec., and 2 ent accumulation regardless of plant size. : NO3 ratio, while the interaction between + – Jan. Substrate solution pH was measured for Histological procedures. After washing, sample date and NH4 : NO3 ratio was nonsig- cotoneaster only with an Accumet pH meter two root subsamples (1 cm long) from each nificant (Table 2).