Jonathan Egilla

Ph.D.
Assistant Professor of Horticulture & Crop Physiology
Lincoln University of Missouri · Agriculture & Environmental Sciences

Publications

  • Jonathan N. Egilla
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    ABSTRACT: The yield and leaf elemental concentration of beetroot was determined in a Nutrient Film Technique (NFT) hydroponic experiment. The nutrient solutions contained in mg L: 108 nitrogen (N) and 12.0 calcium (Ca) (N1Ca1), or 200 N and 66.7 Ca (N2Ca2), respectively. Edible root fresh weight (RFW [g/plant]), was significantly (P = 0.0308) increased with N2Ca2 over N1Ca1. The higher RFW yield of N2Ca2 grown beetroot corresponded with significantly (P = 0.05) higher leaf concentrations of Ca, magnesium (Mg), manganese (Mn), molybdenum (Mo), aluminum (Al) and sodium (Na), but not zinc (Zn). Lower tissue Ca and B concentration probably contributed to the reduced yield observed, and Na can be beneficial to the growth of beetroot in hydroponic culture. Adequate supply and enhanced uptake of Ca and B in balance with K, Mg and the other elements are essential in nutrient source selection and management during hydroponic culture of beetroot, and probably other members of Beta species.
    Journal of Plant Nutrition - J PLANT NUTR. 01/2012; 35(2):203-214.
  • Jonathan N. Egilla, Abua Ikem
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    ABSTRACT: Complete fertilizers formulated for fertigation and soil application are commonly used in hydroponic production. However, these are unsuitable for hydroponic culture of many crops because of imbalances in mineral nutrient composition. Currently, research information about the effect of nonhydroponic fertilizers and the confounding effects of crop type and culture condition on crop yield is limited. The influence of mineral nutrient source (FERT) and growing environment (two controlled environment hydroponic greenhouses; CEHG) with different temperature and relative humidity (RH) regimes on mineral elemental concentration and yield of cos lettuce (Lactuca sativa L. var. longifolia Lam.), cv. Cimmaron, were determined in a nutrient film technique (NFT) hydroponic culture. With the exception of calcium, both CEHG and FERT had a significant effect on the tissue concentration of all the macronutrients, and the concentration of micronutrients in lettuce tissue were optimum, regardless of FERT and CEHG, except for Fe (APHN and CAMG) and Mo (APHN). However, low tissue concentration of macronutrients may have contributed to reducing the marketable yield, which was also significantly affected by FERT.
    International Journal of Vegetable Science 01/2011; 17(1):83-103.
  • Abua Ikem, Jonathan Egilla
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    ABSTRACT: Trace element content of fish feed and bluegill sunfish muscles (Lepomis macrochirus) from aquaculture and natural pond in Missouri were determined using the inductively coupled-plasma optical emission spectrometer (ICP-OES) and the direct mercury analyzer (DMA). Dietary intake rates of trace elements were estimated. Dogfish muscle (DORM-2) and lobster hepatopancreas (TORT-2) reference standards were used in trace element recovery and method validations. The average elemental concentrations (mg/kg diet, dry wt.) of fish feed were: As 1.81, Cd 2.37, Co 0.10, Cr 1.42, Cu 8.0, Fe 404, Mn 35.9, Ni 0.51, Pb 9.16, Se 1.71, Sn 20.7, V 0.09, Zn 118 and Hg 0.07. The mean elemental concentrations (μg/kg wet wt.) in bluegill muscles from both aquaculture and wild (in parenthesis) sources were: As 0.36 (0.06), Cd 0.28 (0.01), Co 0.0 (0.0), Cr 0.52 (0.05), Cu 0.38 (0.18), Fe 17.5 (2.43), Mn 0.18 (0.24), Ni 0.18 (0.04), Pb 1.03 (0.04), Se 0.34 (0.30), Sn 0.66 (0.42), V 0.02 (0.01), Zn 6.97 (9.13) and Hg 0.06 (0.24). Kruskal–Wallis chi square indicated significant differences in As, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sn, V, Zn and Hg (P < 0.001), Se (P < 0.01) and Mn (P < 0.05) across the sampling locations. Dietary intake rates, estimated from weekly consumption of 228 g of aquaculture and wild bluegills, posed no health risks for approximately 85% of all samples.
    Food Chemistry. 01/2008;
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    J. N. Egilla, F. T. Davies, T. W. Boutton
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    ABSTRACT: The influence of drought stress (DS) upon whole-plant water content, water relations, photosynthesis, and water-use efficiency of Hibiscus rosa-sinensis cv. Leprechaun (Hibiscus) plants at three levels of potassium (K) nutritional status were determined after a 21-d gradually imposed DS treatment. Compared to K-deficient plants, adequate K supply improved the leaf water content (LWC) and leaf water relations of Hibiscus by decreasing the , and generally sustained rates of net photosynthesis (P N) and transpiration (E), and stomatal conductance (g s), both in DS and non-DS plants. In K-deficient Hibiscus, LWC, turgor potential ( P), and P N, E, and g s as well as instantaneous water-use efficiency, WUE (P N/E) were consistently lower, compared to K-sufficient plants. Carbon isotope discrimination () was lower (i.e. longterm WUE was greatest) in DS than non-DS plants, but K had no effect on during the 21-d drought treatment period under glasshouse conditions. However, the trend in the value of DS plants suggests that could be a useful index of the response of Hibiscus to DS under glasshouse growing conditions. Thus the incorporation of a properly controlled fertilization regime involving sufficient levels of K can improve the acclimation of P N to low leaf, increase P N/E of Hibiscus, and may have potential benefit for other woody plants species.
    Photosynthetica 01/2005; 43(1):135-140. · 0.86 Impact Factor
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    01/2003;
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    ABSTRACT: As a potential phytoremediation system for phytoextraction of chromium (Cr), we evaluated the influence of the arbuscular mycorrhizal fungus Glomus intraradices on leaf tissue elemen-tal composition, growth and gas exchange of sunflower (Helianthus annuus L.). Sunflower seedlings were either inocu-lated with mycorrhizal fungi (AM) or non-inoculated (Non-AM) and then exposed to two Cr species: {12 mmol of trivalent cation (Cr þ3) [Cr(III)] or 0.1 mmol of divalent dichromate anion (Cr 2 O 7 À) [Cr(VI)]}. Both Cr species depressed plant growth, decreased stomatal conductance (g s) and net photosynthesis (A).
    Journal of Plant Nutrition - J PLANT NUTR. 01/2002; 25(11).
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    ABSTRACT: Little is known about physiological changes that occur with micropropagated chile ancho pepper (Capsicum annuum L. cv. San Luis) plantlets during acclimatization. Plantlets were transferred to ex vitro conditions to study selected physiological changes and growth performance during acclimatization and post-acclimatization. The physiology of the plantlets was characterized by measuring leaf gas exchange and water status. Plant growth was determined by assessing plant height, leaf number, total leaf area, relative growth rate (RGR), and leaf, root, and stem dry matter (DM). Chile pepper plantlets became acclimatized within 6 days after transplantation. During this period, physiological adjustments occurred, which were critical for plantlet survival. After initial ex vitro transplanting, plantlets experienced water deficit [leaf wilting and reduced relative water content (RWC)], which corresponded with reduced stomatal conductance (g s) and transpiration (E), and an increase in stomatal resistance (r s). Thus, leaf stomata that developed in vitro were functional ex vitro. Because of this stomatal control, plantlets minimized transplant shock, recovered and survived. Prior to transplanting, plantlets were photomixotrophic, as indicated by low photosynthetic rates (A). During acclimatization, RWC, g s, E, and A were significantly lower two days after transplanting. However, within 6 days after transplanting, plantlets recovered and became photoautotrophic – attaining high A, g s, and E. Water use efficiency was initially low during the first days after transplanting, but increased dramatically at the end of the acclimatization period in part due to increased A. The stabilization and improvement of plantlet water status and gas exchange during acclimatization and post-acclimatization closely correlated with increased plantlet growth.
    Plant Cell Tissue and Organ Culture 01/2001; 66(1):17-24. · 2.61 Impact Factor
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    ABSTRACT: Chromium (Cr) is a heavy metal risk to human health, and a contaminant found in agricultural soils and industrial sites. Phytoremediation, which relies on phytoextraction of Cr with biological organisms, is an important alternative to costly physical and chemical methods of treating contaminated sites. The ability of the arbuscular mycorrhizal fungus (AM), Glomus intraradices, to enhance Cr uptake and plant tolerance was tested on the growth and gas exchange of sunflower (Helianthus annuus L.). Mycorrhizal-colonized (AM) and non-inoculated (Non-AM) sunflower plants were subjected to two Cr species [trivalent cation (Cr3+) {Cr(III)}, and divalent dichromate anion (Cr2O7-) {Cr(VI)}]. Both Cr species depressed plant growth, decreased net photosynthesis (A) and increased the vapor pressure difference; however, Cr(VI) was more toxic. Chromium accumulation was greatest in roots, intermediate in stems and leaves, and lowest in flowers. Greater Cr accumulation occurred with Cr(VI) than Cr(III). AM enhanced the ability of sunflower plants to tolerate and hyperaccumulate Cr. At higher Cr levels greater mycorrhizal dependency occurred, as indicated by proportionally greater growth, higher A and reduced visual symptoms of stress, compared to Non-AM plants. AM plants had greater Cr-accumulating ability than Non-AM plants at the highest concentrations of Cr(III) and Cr(VI), as indicated by the greater Cr phytoextraction coefficient. Mycorrhizal colonization (arbuscule, vesicle, and hyphae formation) was more adversely affected by Cr(VI) than Cr(III), however high levels of colonization still occurred at even the most toxic levels. Arbuscules, which play an important role in mineral ion exchange in root cortical cells, had the greatest sensitivity to Cr toxicity. Higher levels of both Cr species reduced leaf tissue phosphorus (P). While tissue P was higher in AM plants at the highest Cr(III) level, tissue P did not account for mycorrhizal benefits observed with Cr(VI) plants.
    Journal of Plant Physiology 01/2001; 158(6). · 2.77 Impact Factor
  • J.N. Egilla, F.T. Davies Jr, M.C. Drew
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    ABSTRACT: As competition for the limited water supply available for irrigation of horticultural crops increases, research into crop management practices that enhance drought resistance, plant water-use efficiency and plant growth when water supply is limited has become increasingly essential. This experiment was conducted to determine the effect of potassium (K) nutritional status on the drought resistance of Hibiscus rosa-sinensis L. cv. Leprechaun (Hibiscus). All the treatments were fertilized with Hoagland's nutrient solution, modified to supply K as K_2SO_4, at 0 mM K (K_0), 2.5 mM K (K_2.5), and 10 mM K (K_10), under two irrigation regimes (drought stressed [DS] and non-drought stressed [non-DS]). Regular irrigation and fertigation were adopted for 54 days, and drought stress treatment (initiated on day 55) lasted for 21 days; while non-DS control plants continued to receive regular irrigation and fertigation. Following the 21-day drought stress period, plants were labeled with ^86Rb^+ to determine the percentage of post-drought stress live roots. Both K deficiency (K_0) and drought stress reduced shoot growth, but drought stress increased root growth and thus the root:shoot ratio. At K_0, plants were K-deficient and had the lowest leaf K, Fe, Mn, Zn, Cu, B, Mo and Al, and highest Ca concentrations. Although the percentage of live roots was decreased by drought stress, K_2.5 and K_10 plants (with similar percent live roots) had greater root survival ratio after drought treatment than the K-deficient plants. These observations indicate that adequate K nutrition can improve drought resistance and root longevity in Hibiscus rosa-sinensis.
    Plant and Soil 01/2001; 229(2). · 3.24 Impact Factor
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    ABSTRACT: L.) plantlets was determined during acclimatization and plant establishment. Guava plantlets were asexually propagated through tissue culture and grown in a glasshouse for 18 weeks. Half of the plantlets were inoculated with a mixed endomycorrhiza isolate from Mexico, ZAC-19, containing Glomus diaphanum, G. albidum and G. claroides. Plantlets were fertilized with modified Long Ashton nutrient solution that supplied 11 μg P ml−1. Gas exchange measurements were taken at 2, 4, 8, and 18 weeks after inoculation using a portable photosynthesis system. All micropropagated guava plantlets survived transplant shock. After 6 weeks, mycorrhizal plantlets had greater shoot growth rates and leaf production than non-mycorrhizal plantlets. This also corresponded with increased photosynthetic rates and stomatal conductance of mycorrhizal plants. By 18 weeks, mycorrhizal plantlets had greater shoot length, leaf area, leaf, stem, and root dry mass. However, gas exchange was comparable among treatments, in part because the container size was restricting growth of the larger mycorrhizal plantlets. Non-mycorrhizal plantlets had greater leaf area ratios and specific leaf areas than mycorrhizal plantlets. Increased leaf tissue mineral levels of P, Mg, Cu, and Mo also occurred with mycorrhizal plantlets. Roots of inoculated guava plantlets were heavily colonized with arbuscules, vesicles and endospores. Guava plantlets were highly mycotrophic with a mycorrhizal dependency index of 103%.
    Mycorrhiza 01/2000; 10(1):1-8. · 2.96 Impact Factor
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    ABSTRACT: Crinum lilies (Crinum spp. L.) are tropical and sub-tropical bulbous plants with excellent potential for southern US landscapes. Unfortunately, the more desirable crinum cultivars are slow and expensive to propagate by traditional offsets. The objective of this research was to develop reliable procedures for multiplying Crinum `Ellen Bosanquet' by tissue culture. A sterilization procedure for cleaning explants was developed in which bulb chips containing a basal plate were submersed and agitated in 0.525% hypochlorite for 1h. For shoot formation, tri-scales (three scales attached to a section of the basal plate) were used as the explant source and grown on MS-based media containing five levels of benzyladenine (BA) (0–22.2μM) and five levels of naphthaleneacetic acid (NAA) (0–5.3μM). The greatest shoot formation was obtained from the highest level of BA (22.2μM) without NAA. In a subsequent experiment, explants were cultured for 4 months on media containing 35.5–88.8μM BA, and then transferred to hormone-free media for 3 months. BA at 35.5μM stimulated optimal shoot (8.4) and bulblet (2.8) formation. Plantlets were successfully acclimatized and rooted ex vitro.
    Scientia Horticulturae 01/1999; 82(1):95-102. · 1.50 Impact Factor
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    Jonathan N. Egilla, Fred T. Davies Jr
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    ABSTRACT: Little is known about the effect of varying levels of potassium (K) on the mineral element concentration, growth, and gas exchange, characteristics of woody ornamental plants. The commercially important woody ornamental species Hibiscus rosa‐sinensis L. cv. Leprechaun was evaluated for K response in a series of three experiments with full strength Hoagland's nutrient solution, which supplied 0 to 10 mM K. Plants grown with 4 mM K in nutrient solution (2.4% leaf tissue K) had the greatest shoot growth and root extension. Gas exchange rates (net photosynthesis, transpiration, and stomatal conductance) were also highest at 4 mM K compared to the control (0 mM K /0.6% leaf tissue K), 0.2, 2.0 and 10 mM K treatments. The application of 4 mM K increased net photosynthesis and tranpiration by 2.1 fold and stomatal conductance by 4.5 fold over 0 mM K controls. Increasing K in nutrient solution correlated positively with tissue K, manganese (Mn), and zinc (Zn), but negatively with nitrogen (N), phosphorus (P), calcium (Ca), and magnesium (Mg). There was a stronger sink for K in yonger leaves (the first to fourth fully expanded leaf from the shoot apex) which had higher K concentration than older leaves (the eighth to twelfth fully expanded leaf from the shoot apex). However, with increasing K in nutrient solution, K concentration in leaf tissue increased regardless of leaf age, and the difference between the younger and older leaf was constant. Daily application of 10 mM K resulted in 6.9% leaf tissue K and caused a decrease in plant total dry matter, net photosynthesis, compared to 4 mM K treated plants. However, these parameters remained higher in 10 mM K plants, which retained high ornamental quality than in 0 mM controls. Plants fertilized with 10 mM K, had the highest leaf tissue K and Zn, but lowest P, Ca, Mg, iron (Fe), copper (Cu) and boron (B). Nevertheless, the 10 mM K treated plants exhibited no morphological differences or deficiency symptoms; rather those plants had similar vegetative vigor and flower bud formation rate as those at 4 mM K.
    Journal of Plant Nutrition - J PLANT NUTR. 01/1995; 18(9):1765-1783.
  • Jonathan Nda Egilla, David H. Byrne, David W. Reed
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    ABSTRACT: Three peach rootstocks were evaluated for their capacity to reduce ferric‐iron (Fe) after iron‐stress treatment. Neither of the rootstocks with tolerance to iron (Fe) chlorosis [Titan x Nemaguard (Prunus dulcis (all.) D. A. Webb x Prunus persica (Batsch) L.] nor ‘Montclar’ (P. persica) showed consistently higher Fe‐stress induced Fe reduction/g root fresh weight (RFW) compared to the less tolerant rootstock Nemaguard [(P. persica)]. However, non‐stressed ‘Titan’ x Nemaguard (TNG) showed higher leaf chlorophyll content than both ‘Montclar’ (MC) and Nemaguard (NG) and higher mean Fe reduction by root released reductants than Nemaguard. The reduction rate by root released reductants was approximately 22–34% for NG, 15% for MC, and 29% by TNG. ‘Titan’ x Nemaguard and Montclar maintained better root growth (i.e., had less root necrosis) under Fe‐stress than NG which resulted in greater Fe reduction per plant. This indicates that the maintenance of a greater root surface area during Fe‐stress may be important for the sustenance of significant Fe reduction capacity under prolonged stress on a per plant basis. Fe‐stressed plants of all three rootstocks showed increased formation of root hairs and slightly enlarged root tips, although these died with prolonged Fe‐deficiency in the nutrient solution (after three weeks). Using the Fe‐BPDS gel medium procedure, Fe reduction sites were localized at approximately 2–10 mm behind the root tips and on the newly formed lateral roots. Although no differences in Fe reduction at the root surface were seen among rootstocks, Fe reduction in gel medium was more localized and developed earlier in roots of Fe‐stressed plants and those which had nitrogen (N) present in the gel medium as nitrate (NO3‐) only [versus NO3‐ + ammonium (NH4+)].
    Journal of Plant Nutrition 11/1994; 17(12):2079-2103. · 0.53 Impact Factor
  • Jonathan Nda. Egilla
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    ABSTRACT: Includes bibliographical references. Vita. Thesis (Ph. D.)--Texas A & M University, 1994. "Major subject: Horticulture."

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