Cycas revoluta, an important ornamental palm-like plant of warmer regions of the world, often exhibits a foliar chlorotic/necrotic dieback in landscapes. Despite a weak correlation (r2 ≤ 0.28) of percent symptoms with soil nutrient levels or pH, symptom severity was correlated more notably (r2 =0.49) with Mn and had even a higher correlation (r2 = 0.61) with the Fe : Mn ratio. Anatomical examination of chlorotic leaflets indicated an accumulation of tanniniferous cells but did not provide direct evidence of Mn deficiency. Although field surveys indicated a link between low Mn levels and Fe : Mn ratio in the plant and appearance of the disorder, the manifestation of symptoms could not be directly correlated with any edaphic factors. However, identical symptoms were induced in young plants by withholding Mn in a solution culture experiment. Application of chelated Mn on expanding leaves alleviated the disorder, but only for the current growth flush. Irrigation frequency in concert with other cultural practices probably are more responsible for development of symptoms than actual soil Mn inadequacy. In consideration of acute susceptibility of cycads to micronutrient deficiencies, plants should be supplied with a complete micronutrient fertilizer during growth in containers and before field planting.
Bijan Dehgan, Joseph E. Durando, and Thomas H. Yeager
R. L. Morris and B. T. Swanson
Chlorotic silver maples (Acer saccharinum L.) were treated during bud break with soil-applied EDDHA (ethylenediaminedi-0-hydroxyphenylacetate) and trunk implants of encapsulated FAC (ferric ammonium citrate), EDTA (ethylenediaminetetracetate) and DTPA (diethylenetriaminepentaacetate). Foliar levels of Ca were higher in chlorotic than green tissue. Chlorophyll levels and twig growth of treated trees were not significantly different from chlorotic controls after treatment. Soil Fe levels were different under chlorotic and green control plants. However, foliar Fe analyses demonstrated that Fe levels were not different in green and chlorotic leaf tissue.
Richard T. Poole and Charles A. Conover
Simulated shipping of Chrysalidocarpus lutescens H. Wendl., Dracaena marginata Lam., Ficus benjamina L., and Schefflera arboricola Endl. for 7, 14, 21, or 28 days at 10°, 13°, 16°, or 19°C indicated that long-term shipping is possible while maintaining plant quality. Schefflera shipped best at 10°, Ficus at 10° or 13°, and Chrysalidocarpus and Dracaena at 13°, 16°, or 19°. Simulated shipping durations of up to 21 days were obtained on all species without significant loss of quality, and 28-day durations were possible at selected temperatures without severe quality reductions.
F. J. Marousky and B. K. Harbaugh
Plants of Philodendron scandens subsp. oxycardium (Schott) Bunt. were exposed to ethylene-air mixtures at various temperatures and levels of light and CO2. Plants held in ethylene (2.5 to 10μl/liter air) abscised leaves and stipules, developed chlorotic foliage, and grew poorly. As the levels and duration of exposure to ethylene increased, the rate of leaf abscission increased. Plants exposed to 5μl ethylene/liter air at 23.5°C for 3 days in light abscised more than 50% of their leaves, whereas plants similarly handled but held in darkness lost 20%. At a given level of ethylene, the lower the temperature the fewer the number of leaves abscised. Plants held at 27° at 10 μl/liter air had total leaf abscission. Plants held in ethylene with 5% CO2 or with lanolin-coated leaves abscised fewer leaves than plants without added CO2 or non-coated leaves.
Ellen T. Paparozzi, Walter W. Stroup, and M. Elizabeth Conley
Response surface methods refer to a set of experimental design and analysis methods to study the effect of quantitative treatments on a response of interest. In theory, these methods have a broad range of applicability. While they have gained widespread acceptance and application in manufacturing and quality improvement research, they have never caught on in the agricultural sciences. We propose that this is because there has not been specific research demonstrating their usage. In this paper, two 34 factorial experiments were performed using 100 poinsettia plants (Euphorbia pulcherrima Willd. ex Klotzsch) to measure nutrient element concentrations in leaves at three rates each of nitrogen (N), sulfur (S), iron (Fe), and manganese (Mn). Three different methods of analysis were compared—the standard analysis of variance with no regression model, the quadratic regression model commonly assumed for most standard response surface methods and the Hoerl model regression, a nonlinear alternative to quadratic response. Actual nutrient element values were compared with the values predicted by each regression model and then also evaluated to see if the visual symptomology of yellowing related to those nutrient concentrations in leaves. The Hoerl model demonstrated better ability to detect biologically relevant nonlinear two-, three-, and four-way nutrient interactions. Though there was minimal replication this model characterized the treatment effects while keeping the size of the experiment manageable both in terms of time (labor) and cost of plant analyses. Additionally, it was shown that when S, Fe, and/or Mn were deficient along with N, their visual deficiency symptoms were masked by the overall yellowing associated with N deficiency. This model is recommended as the initial experiment in a series where scientists are looking to expand information already determined for two factors. Other treatment systems that this can be used with include: levels of irrigation, pesticides, and plant growth regulators.
Ron M. Wik, Paul. R. Fisher, Dean A. Kopsell, and William R. Argo
Two experiments were completed to determine whether the form and concentration of iron (Fe) affected Fe toxicity in the Fe-efficient species Pelargonium ×hortorum `Ringo Deep Scarlet' L.H. Bail. grown at a horticulturally low substrate pH of 4.1 to 4.9 or Fe deficiency in the Fe-inefficient species Calibrachoa ×hybrida `Trailing White' Cerv. grown at a horticulturally high substrate pH of 6.3 to 6.9. Ferric ethylenediaminedi(o-hydroxyphenylacetic) acid (Fe-EDDHA), ferric ethylenediamine tetraacetic acid (Fe-EDTA), and ferrous sulfate heptahydrate (FeSO4·7H2O) were applied at 0.0, 0.5, 1.0, 2.0, or 4.0 mg ·L–1 Fe in the nutrient solution. Pelargonium showed micronutrient toxicity symptoms with all treatments, including the zero Fe control. Contaminant sources of Fe and Mn were found in the peat/perlite medium, fungicide, and lime, which probably contributed to widespread toxicity in Pelargonium. Calibrachoa receiving 0 mg Fe/L exhibited severe Fe deficiency symptoms. Calibrachoa grown with Fe-EDDHA resulted in vigorous growth and dark green foliage, with no difference from 1 to 4 mg·L–1 Fe. Using Fe-EDTA, 4 mg Fe/L was required for acceptable growth of Calibrachoa, and all plants grown with FeSO4 were stunted and chlorotic. Use of Fe-EDDHA in water-soluble fertilizer may increase the upper acceptable limit for media pH in Fe-inefficient species. However, iron and Mn present as contaminants in peat, irrigation water, or other sources can be highly soluble at low pH. Therefore, it is important to maintain a pH above 6 for Fe-efficient species regardless of applied Fe form or concentration, in order to avoid the potential for micronutrient toxicity.
Nicole L. Waterland, Craig A. Campbell, John J. Finer, and Michelle L. Jones
determine if the stressed plants would recover. Visual observations were taken daily and data are the average of four replications. Evaluations of wilt status and leaf chlorosis. Whole plant wilt status and leaf chlorosis ratings were collected daily
Thomas E. Marler, Ruben dela Cruz, and Andrea L. Blas
We thank Howard Gabe of Novartis Seeds, Inc., Golden Valley, Minn., for donation of soybean seeds and providing field evaluation data on soybean irondeficiency chlorosis. We thank David W. Reed for advice on assay procedures, Rick Wood for use of
Geoffrey M. Weaver and Marc W. van Iersel
wilting ( Blanchard et al., 2007 ; Kim and van Iersel, 2011 ; Waterland et al., 2010a , 2010b ; Weaver and van Iersel, 2014 ). However, ABA application also causes unwanted phytotoxic effects such as chlorosis and leaf abscission in some species
Ricardo Goenaga, A. Graves Gillaspie Jr, and Adolfo Quiles
African nations ( Food and Agriculture Organization, 2009 ). Calcareous soils, where cowpea is often grown, cover more than 25% of the earth's soil surface ( Marschner, 2003 ). When grown at pH greater than 7.5, cowpea develops severe leaf chlorosis caused