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Dharmalingam S. Pitchay, Jonathan M. Frantz and James C. Locke

Geranium (Pelargonium ×hortorum) is considered to be one of the top-selling floriculture plants, and is highly responsive to increased macro- and micronutrient bioavailability. In spite of its economic importance, there are few nutrient disorder symptoms reported for this species. The lack of nutritional information contributes to suboptimal geranium production quality. Understanding the bioenergetic construction costs during nutrient deficiency can provide insight into the significance of that element predisposing plants to other stress. Therefore, this study was conducted to investigate the impact of nutrient deficiency on plant growth. Pelargonium plants were grown hydroponically in a glass greenhouse. The treatment consisted of a complete modified Hoagland's millimolar concentrations of macronutrients (15 NO3-N, 1.0 PO4-P, 6.0 K, 5.0 Ca, 2.0 Mg, and 2.0 SO4-S) and micromolar concentrations of micronutrients (72 Fe, 9.0 Mn, 1.5 Cu, 1.5 Zn, 45.0 B, and 0.1 Mo) and 10 additional solutions each devoid of one essential nutrient (N, P, Ca, Mg, S, Fe, Mn, Cu, Zn, or B). The plants were photographed and divided into young, maturing, and old leaves, the respective petioles, young and old stems, flowers, buds, and roots at “hidden hunger,” incipient, mid- and advanced-stages of nutrient stress. Unique visual deficiency symptoms of interveinal red pigmentation were noted on the matured leaves of P- and Mg-deficient plants, while N-deficient plants developed chlorotic leaf margins. Tissue N concentration greatly influenced bioenergetic construction costs, probably due to differences in protein content. This information will provide an additional tool in producing premium geraniums for the greenhouse industry.

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Timothy K. Broschat

Ixoras (Ixora L.) growing in calcareous sandy soils are highly susceptible to a reddish leaf spot disorder. Symptoms appear on the oldest leaves of a shoot and consist of irregular diffuse brownish-red blotches on slightly chlorotic leaves. Symptoms of K deficiency, P deficiency, and both K and P deficiency were induced in container-grown Ixora `Nora Grant' by withholding the appropriate element from the fertilization regime. Potassium-deficient ixoras showed sharply delimited necrotic spotting on the oldest leaves, were stunted in overall size, and retained fewer leaves per shoot than control plants. Phosphorus-deficient plants showed no spotting, but had uniformly brownish-red older leaves and olive-green younger foliage. Plants deficient in both elements displayed symptoms similar to those observed on landscape plants. Symptomatic experimental and landscape ixoras all had low foliar concentrations of both K and P.

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Catherine S.M. Ku and David R. Hershey

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Valéria Santos Cavalcante, Renato de Mello Prado, Ricardo de Lima Vasconcelos, Hilário Júnior de Almeida and Thais Ramos da Silva

improve fruit visual, nutritional, and flavor quality. The identification of nutrient deficiency symptoms is relatively complex, due to the various biological functions and interactions that occur between nutrients and the environment, and even similar

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Dariusz Swietlik and Linsen Zhang

Chelator-buffered nutrient solutions were used to study the effect of different levels of Zn activity in the rhizosphere on growth and nutritive responses of various tissues of sour orange seedlings. The seedlings were grown for 3 months in a growth chamber in a hydroponic culture containing from 5 to 69 μm and 5 to 101 μm total Zn in Expts. 1 and 2, respectively. Zn+2 activities were calculated with a computerized chemical equilibrium model (Geochem-PC), and buffered by inclusion of a chelator, diethylenetriamine pentaacetate (DTPA), at 74 and 44 μm in excess of the sum of Fe, Mn, Zn, Cu, Ni, and Co in Expts. 1 and 2, respectively. The use of DTPA-buffered solutions proved successful in imposing varying degrees of Zn deficiency. The deficiency was confirmed by leaf symptomatology, leaf chemical analyses, i.e., <16 mg·kg-1 Zn, and responses to foliar sprays and application of Zn to the roots. Growth parameters varied in their sensitivity to Zn deficiency, i.e., root dry weight < leaf number and white root growth < stem dry weight < leaf dry weight < shoot elongation and leaf area. The critical activities, expressed as pZn = -log(Zn+2), were ≈10.2±0.2 for root dry weight, 10.1±0.2 for leaf number and white root growth, 10.0±0.2 for stem dry weight, 9.9±0.2 for leaf dry weight, and 9.8±0.2 for shoot growth and leaf area. Increases in growth were observed in response to Zn applications even in the absence of visible Zn-deficiency symptoms. Seedlings containing >23 mg·kg-1 Zn in leaves did not respond to further additions of Zn to the nutrient solution. Zinc foliar sprays were less effective than Zn applications to the roots in alleviating severe Zn deficiency because foliar-absorbed Zn was not translocated from the top to the roots and thus could not correct Zn deficiency in the roots.

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Timothy K. Broschat

develop moderate to severe K, Mg or both deficiency symptoms on south Florida’s sandy, nutrient-poor soils. These deficiencies are not only unsightly, but also cause premature senescence of the older leaves, leading to complete defoliation by April. Thus

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Bijan Dehgan, Joseph E. Durando and Thomas H. Yeager

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.

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Brian A. Krug, Brian E. Whipker, Jonathan Frantz and Ingram McCall

( Clarkson, 1984 ). Because of these characteristics of Ca, shoot deficiency symptoms appear primarily on the upper leaves. Visual symptoms include deformed, strap-like leaves; chlorosis; and leaves that develop yellow-to-tan margins, eventually becoming

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Josh B. Henry, Ingram McCall, Brian Jackson and Brian E. Whipker

have the potential to deplete the initial P concentration in the substrate and may begin reallocating P from older plant tissues, leading to the development of deficiency symptoms on the lower leaves ( Mengel et al., 2001 ). Deficiency symptoms

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Yong Zhang, Chunxia Fu, Yujing Yan, Yan’an Wang, Ming Li, Meixiang Chen, Jianping Qian, Xinting Yang and Shuhan Cheng

plant, thus deficiency symptoms are first observed in the youngest leaves ( Fageria et al., 2003 ). Zn deficiency results in reduced leaf and shoot size and photosynthetic rates, ultimately influencing the apple yield and quality ( Wang and Jin, 2005