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  • Author or Editor: Wallace Pill x
  • Journal of the American Society for Horticultural Science x
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Abstract

Nitrapyrin (NI) incorporation into a peat-vermiculite medium reduced shoot growth of tomato (Lycopersicon esculentum Mill. cv. Marglobe) but this reduction was less pronounced at higher NO3-N fertilization levels. An initial 50 ppm NI application caused less growth reduction than 7, weekly 7.14 ppm applications. While increasing NO3 level had little effect on shoot ion concentration, with the exception of increasing shoot K and NO3 concentration, the increased shoot total N, Mg, and K concentrations with NI were attributed to the concentrating effect of reduced growth. Single and multiple NI applications decreased and increased, respectively, both plant water stress and medium NO3 retention. Nitrapyrin consistently increased medium NO3 concentration at the 2 highest NO3 fertilization levels. With time, however, medium NO3 concentration decreased and increased with single and multiple NI applications, respectively, relative to each other. Nitrapyrin initially decreased leaf xylem pressure potential (ψp), but with time, water stress decreased below that of the control plants with the single NI application but remained consistently high with multiple applications. Since leaf diffusive resistance and ψp were lower and transpiration rate was initially higher with the single NI application relative to the control, and since plants given the multiple NI applications had the lowest ψp and transpiration rate values throughout the study, it is hypothesized that NI reduced water uptake. That NI decreased both NO3 assimilation and uptake was evidenced by decreased shoot total N content, increased shoot NO3 content, and increased medium NO3 concentration.

Open Access

The influence of two drying regimes and two storage temperatures of primed asparagus (Asparagus officinalis L.) and tomato (Lycopersicon esculentum Mill.) seeds on germination after storage up to 3 months was examined. Seeds of `Mary Washington' asparagus and `Ace 55' tomato primed in synthetic seawater (-1.0 MPa, 20C, 1 week, dark) were surface-dried at 20C and 50% relative humidity (RH) for 2 h (42% to 49% moisture) or dried-back at 20C and 32.5% RH for 48 h (moisture = 13% tomato and 22% asparagus). These and nonprimed seeds were stored in tight-lidded metal cans and heat-sealed plastic pouches at 4 or 20C for up to 3 months before germination at 20C. After 3-month storage, primed surface-dried asparagus seeds stored at 4C had greater germination percentage and rate than nonprimed seeds, surface-dried seeds stored at 20C, or primed dried-back seeds. Dried-back primed tomato seeds had higher germination percentage than surface-dried primed seeds after 2 or 3 months of storage, with storage temperature having no effect on germination perecentage or rate. In a further study, primed surface-dried and primed dried-back seeds stored at 4 or 20C for 1.5 months in sealed containers were germinated at 15, 25, or 35C under low (-0.05 MPa) or high osmotic stress (-0.4 MPa). Primed surface-dried asparagus seeds stored at 4C, compared to nonprimed seeds, surface-dried seed stored at 20C, or primed dried-back seeds, had greater germination percentage at 15 and 35C and low osmotic stress, and higher germination rate at 15 or 25C. Primed tomato seeds had greater germination percentage than nonprimed seeds only at 35C and low osmotic stress, and higher germination rate at 15 or 25C. Storage of primed tomato seeds at 4C rather than 20C increased germination rate at 15 or 25C, and increased germination percentage at 35C and low osmotic stress. For maximal seed viability and germination rate after 1.5 to 3 months of storage, primed asparagus and tomato seeds should be stored at 4C rather than 20C; however, asparagus seeds should be surface-dried, and tomato seeds should be dried-back.

Free access

Abstract

Nitrapyrin (NI) at 10 ppm, compared to water control, added to a soil-sand-peat medium decreased shoot growth of tomatoes (Lycopersicon esculentum Mill. cv. Marglobe) grown with NO3-N nutrition but had no effect on growth with NH4-N nutrition. While plant water stress was decreased by NI compared to the control with NO3-N nutrition, the toxic effect of increased uncombined NH4 concentration in the shoots may have caused the growth reduction. Denitrification suppression by NI with NO3-N nutrition was evidenced by increased media and shoot NO3 concentrations. Nitrification suppression by NI with NH4-N nutrition was evidenced by increased media and shoot NH4 concentrations. Nitrapyrin, irrespective of N form, decreased shoot Ca concentration, increased shoot K and uncombined NH4 concentrations, and had no effect on shoot Mg concentration. Plant water stress was decreased by NI with both N forms at the third and fifth weeks after final transplanting. While NI decreased the differential effect of N form on transpiration rate and leaf diffusive resistance (RL), in NI’s absence, NH4-N nutrition decreased transpiration and increased RL relative to NO3-N. Decreased shoot growth with NH4-N relative to NO3-N nutrition, both in the presence and absence of NI, was associated with increases in plant water stress, root hydraulic resistance, and shoot uncombined NH4 concentration, but a decrease in shoot Ca concentration.

Open Access

Abstract

The effects of 0.02, 0.06, 0.18, and 0.54 kg P/m3 incorporation as superphosphate (0-9-0) in peat–vermiculite and of NO3-N and NH4-H liquid feeds were investigated with tomato (Lycopersicon esculentum Mill. cv. Marglobe). Increasing P rate decreased shoot and root dry weights but increased total fruit fresh weight. NH4-N, relative to NO3-N nutrition, decreased shoot growth but had no effect on fruit yield. Decreased vegetative growth with increasing P rate and NH4-N nutrition was associated with decreased leaflet xylem pressure potential, increased transpiration rate, and increased leaf NH4-N concentration. Leaf P and medium water-soluble P concentrations increased with increasing P rate but were unaffected by N form. During time of fruit development, leaf P content decreased at the 2 lowest P rates but increased at higher P rates. Net P export from leaves ceased and luxury P consumption began between 0.06 and 0.18 kg P/m3.

Open Access

Abstract

Germinated seeds of ‘Heinz 1350 VF’ tomato (Lycopersicon esculentum Mill.) were subjected to short-term (through 5 days) low temperature (0° or 5°C) storage suspended in 2 fluid-drilling gels (Natrosol 250 HHR or Laponite 445). Following storage, a greenhouse emergence assay and respiratory characterization via double inhibitor titrations (0.4/mM KCN and 10.0/mM salicylhydroxamic acid) were conducted. After 3-day storage in Natrosol or moist cheesecloth, emergence was about 90% but had decreased to <60% following 3-day storage in Laponite. With 5-day storage in Natrosol, 0° drastically reduced seedling vigor relative to that at 5°. Total O2 consumption by all stored germinated seeds was less than that of unstored germinated seeds. Consumption of O2 via both the cytochrome and alternative respiratory pathways was not affected differentially by storage temperature or gel. The maximum inducible rate of oxygen consumption via the alternative pathway decreased during storage in Natrosol at 0° or Laponite at 5° relative to that of unstored seeds or seeds stored in Natrosol at 5°.

Open Access

Abstract

The effects of storage of pregerminated tomato seed (Lycopersicon esculentum Mill. cv. Marglobe) at 0° and 5°C for 0, 4, 8, 12, 16, and 20 days in 4 gels or in moist cheesecloth on percentage emergence (PE) and emergence rate index (ERI) were examined. The PE and ERI values of freshly germinated (unstored) seeds were statistically equal and high in all gels and much greater than the values of dry seed. After 4 days storage, both PE and ERI were unaffected by storage temperature but were significantly affected by gels in order of emergence magnitude: Moist cheesecloth = Natrosol 250 HHR > Laponite 508 = SGP104K > Vittera II Hydrogel. With ≥ 8-day storage, storage temperature interacted with gels so that 0° compared to 5° storage gave greater PE and ERI in Natrosol 250 HHR and Laponite 508 but lower values in moist cheesecloth. Pregerminated tomato seed storage in Natrosol 250 HHR at 0° is an acceptable alternative to 5° moist storage providing, even after 12 days of storage, a distinctly higher PE and ERI than dry seed. To avoid unacceptably low emergence, chitted seed storage in Vittera II hydrogel should be avoided and storage in Laponite 508 or SGP104K should not exceed 4 days.

Open Access

Germination studies indicated that increasing priming duration (-1.0 MPa at 20 °C for 7, 14, or 21 days) increased `Moss Curled' parsley [Petroselinum crispum (Mill.) Nyman ex A.W. Hill] germination rate quadratically and seed moisture content linearly. A histological and anatomical study was conducted to identify and/or quantify principle mericarp organ or tissue volume changes influenced by priming duration. Embryo volume increased as priming duration increased from 7 to 21 days (0.014 to 0.034 mm3), and this was due more to radicle (0.007 to 0.022 mm3) than to cotyledon (0.006 to 0.011 mm3) growth. Concomitant with increased embryo volume was increased volume of the depleted layer (space formation, surrounding the embryo), from 0.038 after 7 days to 0.071 mm3 after 21 days, and increased hydrolysis of central endosperm (a thick-walled endosperm type). In nonprimed mericarps, central endosperm cells constituted 97% of the endosperm volume. The remaining 3% was comprised of 1% depleted layer and 2% distal endosperm (small, thin-walled, and irregularly shaped endosperm cells). During 7 or 21 days of priming, ≈10% or 40%, respectively, of central endosperm cells were hydrolyzed centrifugally around the embryo with a corresponding decrease in volume of central endosperm with thick cell walls. In addition, distal endosperm cells adjacent to the depleted layer, containing reserve materials, were digested of contents following 21 days priming, and sometimes, following 7 days priming. A long priming duration resulted in degradation of pericarp tissues, as indicated visually and by a decline in pericarp volume. We hypothesize that priming duration of parsley primarily influences radicle growth and centrifugal digestion and utilization of central and distal endosperm, resulting in a larger depleted layer required for embryo volume increases. Secondary events influenced by priming duration include cotyledon growth and degradation of pericarp tissues.

Free access

`Moss Curled' parsley [Petroselinum crispum (Mill.) Nyman ex. A.W. Hill] schizocarps were osmotically primed in polyethylene glycol at -1.0 MPa for 7 days at 20 °C. The smaller of the two mericarps within a parsley schizocarp had lower germination percentage, but similar rate and synchrony of germination. Osmotic priming increased germination percentage, rate, and synchrony, irrespective of mericarp half. This promotive effect of priming on germination was associated with embryonic advancement as indicated by a doubling of radicle and cotyledon volumes, without changes in lengths of these organs. Periclinal divisions of the lateral expansion meristem, distinct in primed radicles but indistinct in nonprimed radicles, led to radial alignment of the cortical cells and a doubling of cortical volume and thereby increased radicle volume. Each embryonic cotyledon of primed mericarps had three distinct procambial bundles that differentiated along most of the cotyledon length, while nonprimed cotyledons had from zero to three that differentiated only a short way into the cotyledon. Priming increased coyledonary procambium length by 5-fold and volume by 11-fold. Increased embryonic growth due to priming was associated with greater endosperm depletion adjacent to the embryo. The schizocarps frequently separated or partially separated into component mericarps during priming, indicating a weakening of pericarp tissue along the commissural suture and possibly elsewhere.

Free access