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- Author or Editor: Robert D. Wright x
- Journal of the American Society for Horticultural Science x
Abstract
Rooted cuttings of Ilex crenata Thunb. ‘Helleri’ were grown in sand culture with varied Ca and Mg levels in a factorial experiment. No increase in total dry weight was achieved by increasing Ca or Mg rates above 5–10 ppm. Necrosis of shoot apices occurred at 0 ppm Ca. The tissue level of Ca required for optimal growth (0.23–0.38%) was lower than has been reported for broadleaf evergreens. In a 2nd experiment with pine bark, Ca was supplied at 0 and 120 ppm and Mg at 0 and 60 ppm. No differences in dry weight due to added Ca and Mg were observed. In a 3rd experiment, the influence of dolomitic limestone (0, 2, 4, and 8 kg m−3) and gypsum (1 and 2 kg m−3), added to pine bark, on Ca and Mg availability over time was determined. The addition of dolomitic limestone increased Ca and Mg in the growing medium solution, but unamended bark supplied both elements in quantities sufficient for growth of I. crenata ‘Helleri’ The addition of gypsum caused a large initial increase in Ca in the growing medium solution, but levels dropped precipitously thereafter.
Abstract
Rooted cuttings of Ilex crenata Thunb. ‘Helleri’, Rhododendron obtusum Planch. ‘Rosebud’, and Juniperus chinensis L. ‘San Jose’ were grown in a 100% pine-bark medium amended with dolomitic limestone at 0 to 8 kg m-3 with resulting pH from 3.4 to 7.2. Except for juniper at 2 kg m-3, growth was not increased by liming, and 8 kg m-3 tended to reduce shoot and root growth. This reduced growth was attributed in part to greater NH4 adsorption by the bark, reducing the amount available for plant uptake, and a higher nitrification rate, leading to an elevated NO3 to NH4 ratio in the medium. Liming pine bark to improve growth of these woody plants may be unnecessary.
Abstract
Three genera of woody plants were container-grown in a pine bark medium. Pine bark was amended or unamended with nitrapyrin (NI) and fertilized with an NH4-N fertilizer. Medium solution NH4-N concentrations of bark without NI decreased rapidly for the first 3 to 5 weeks with a concomitant increase in NO3-N concentrations. Medium solution pH at 0 NI decreased 0.8 unit during periods of rapid NO3-N accumulation. The low medium solution pH of the 0 NI treatment resulted in solution Ca, Mg, and Mn concentrations that were several times greater than at 82 μg of NI. Correspondingly, tissue concentrations of these ions were generally greater at the 0 NI treatment than at the 82 μg NI treatment. In general, there were no differences in shoot dry weight in response to NI treatment. Results indicate that nitrification is important in the nutrition of container-grown plants.
Abstract
A 100% pine bark medium was amended with dolomitic lime at 0, 3, or 6 kg·m−3 and periodically fertilized with 210 ml of a nutrient solution containing 100 ppm N as (NH4)2S04. At the 3- and 6-kg lime treatments, medium solution NH4-N concentrations decreased rapidly while N03-N concentrations increased. At 0 kg lime, the NH4-N decrease was slower than at the 3- and 6-kg lime treatments and N03-N was not found. Similarly treated bark without plants was used to determine a N03-N accumulation rate (NAR). NAR was greatest at 6 kg of lime, except at the last 2 sampling dates, when NAR did not differ between 3 and 6 kg of lime. This lack of difference was attributed to a limiting NH4-N supply at 6 kg of lime. In a 2nd experiment, NAR of bark treated with 6 kg of lime per m3 and fertilized with 300 ppm NH4-N was 3 times greater than with bark treated with 100 ppm NH4-N, thus supporting the contention that, over time, the NH4-N supply of the 100-ppm treatment limited nitrification. These results indicate that the stimulative influence of lime on nitrification is subject to medium pH and NH4-N status that changes over time.
The influence of K nutrition (25, 75, 150, 300, 450, and 600 mg K/liter) and moisture stress conditioning (MSC) (exposing plants to four sublethal dry-down cycles) on leaf water relations, evapotranspiration, growth, and nutrient content was determined for salvia (Salvia splendens F. Sellow `Bonfire'). Potassium concentration and MSC had an interactive influence on osmotic potential at full (π100) and zero (π0) turgor. Differences in osmotic potential between MSC and non-MSC plants for π100 and π0 increased with increasing K concentration. Increasing K concentration and MSC resulted in active osmotic adjustment and, consequently, increased cellular turgor potentials. Foliar K content increased with increasing K concentration and MSC. High K concentrations and MSC both reduced plant evapotranspiration on a per-plant and per-unit-leaf-area basis. Greatest shoot dry weight occurred for plants grown with 300 mg K/liter and non-MSC. Total leaf area increased with increasing K concentration, but MSC had little effect.
We determined the influence of moisture stress conditioning (MSC) (exposing plants to four nonlethal dry-down cycles) on gas exchange and water loss of Salvia splendens F. Sellow `Bonfire'. During day 1 following final irrigation, no differences in leaf water potentials (ψL) were observed due to MSC. However, MSC plants had lower midday net photosynthesis (Pn), transpiration (E), and leaf conductance (gL) than controls. Stomatal inhibition of photosynthesis (SI) of MSC plants was greater than that of controls. Further, the lack of differences in mesophyll resistance to CO2(rm due to MSC indicate gas exchange differences during day 1 were stomatal in nature. During day 2, MSC plants exhibited greater Pn, E, and gL, while SI and rm were greater for controls. MSC plants maintained positive Pn rates and .turgor and lower ψL than control plants during day 2. Higher water-use efficiency estimates were observed for MSC plants than for controls.
Stem cuttings of Blue Rug juniper (Juniperus horizontalis Moench `Wiltonii'), `Hino-Crimson' azalea [Rhododendron (Lindl.) P1anch `Hino-Crimson'], and `Helleri' holly (Ilex crenata Thunb. `Helleri') were propagated in 1 peat: 1 perlite (v/v) at one of five moisture levels based on medium dry weight (125%, 250%, 375%, 500%, or 625%). Cutting survival and percentage of rooted cuttings were highest at the highest medium moisture level in all three species. Incidence of cutting basal rot was not directly related to medium moisture level, but more to the growth stage of the stock plant. Midday xylem water potential (ψ) of cuttings for each species was highest in the wettest propagation medium and lowest in the driest medium. During propagation, stem cutting ψ below - 2.0 MPa occurred even in the wettest medium tested, and frequently reached - 4.0 MPa in cuttings in the driest treatment (125%). Basal water uptake by cuttings was highest in the wettest medium moisture level. Water uptake was highest during the first few days after insertion, and thereafter decreased until root emergence.
Abstract
Hardwood stem cuttings of Ilex crenata Thunb. ‘Convexa’, treated with and without indolebutyric acid (IBA), were inserted into a perlite rooting medium and misted with deionized water during intermittent mist propagation in a controlled-environment chamber. Initially, and at weekly intervals for 6 weeks, leaves, upper stems (portion of stem above rooting medium), and lower stems (portion of stem in rooting medium) were analyzed for N, P, K, Ca, and Mg. At the conclusion of the study, both nontreated and IBA-treated cuttings showed a slight increase in dry weight with detectable but slight leaching of N and K and no detectable leaching of P, Ca, and Mg. Mineral nutrient mobilization to the lower stem was not detected during root initiation for nontreated and IBA-treated cuttings. Following root initiation and later budbreak on the upper stem, N, P, K, Ca, and Mg were all mobililized from the leaves of nontreated and IBA-treated cuttings to the upper stem, whereas only N, P, and K were mobilized to the lower stem of IBA-treated cuttings. For nontreated cuttings, all nutrients were mobilized from the lower stem to the upper stem, while for IBA-treated cuttings only Ca and Mg were mobilized from the lower stem to the upper stem. Root development as influenced by IBA treatment and budbreak on the upper stem had a strong influence on mineral nutrient mobilization.
Containerized seedlings of eastern redcedar (Juniperus virginiana L.) were fertilized weekly for 175 days with a solution containing 50 ppm P, 150 ppm K, and either 0, 5, 10, 20, 40, 80, 160, 320, or 640 ppm N. Plant height, stem diameter, and shoot and root dry weights increased asymptotically with applied N; 640 ppm N diminished response. Growth after 175 (height, stem diameter) and 180 (shoot and root dry weights) days was optimal (90% of maximum) at N concentrations of 115, 155, 230, and 105 ppm, respectively, 1.5% foliar N optimized height growth. Foliar concentrations of N, P, and K increased in treated plants over the duration of the experiment, while Ca, Mg, and Mn decreased or remained constant. Starch concentration of fertilized plants decreased sharply after initiation of the experiment, but controls showed little change during the first 120 days. Sucrose concentration remained constant over the summer but increased sharply in late fall. At 180 days, foliar concentrations of starch, sucrose, hexose, N, P, K, and B increased asymptotically with applied N; concentrations of Ca, Mg, and Mn decreased.