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  • Author or Editor: Wallace Pill x
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Ten 10 wildflower species grew satisfactorily in a 1:1 (vol.) mix of Ironrich (IR, mineral co-product of the titanium dioxide industry) and Fairgrow (FG, co-composted sewage sludge and solid waste). Shoot fresh weights in the low fertility IR and in the high fertility FG averaged 35% and 157%, respectively, those grown in IR+FG. Wildflower establishment in 10cm-deep outdoor seedbeds of IR, FG, or IR+FG were compared to those in soil (control) plots. Maximum percentage seedling emergence and emergence rate and synchrony were lower in FG than in IR, values in IR+FG being intermediate and similar to those for control plots. Shoot fresh weights, however, were greater from the IR+FG than from IR, FG or the control plots. Total shoot dry weights of wildflowers from 1 m2 subplots after 3 months were FG > IR = IR+FG > control, being respectively 8.4, 8.5, 5.1 and 1.1% those of total shoot dry weights of weeds.

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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

Matrically priming seeds of common Kentucky bluegrass (Poa pratensis L.) and `SR8300' tall fescue (Festuca arundinacea Schreb.) in fine, exfoliated vermiculite (-1.5 MPa, 20 °C, 4 days) increased subsequent germination rate but did not increase germination percentage or synchrony. The lowest seed: vermiculite ratio (dry weight basis) to provide full priming benefit for seeds of Kentucky bluegrass and tall fescue was 1:10 and 1:20, respectively. Storing Kentucky bluegrass seeds primed in 1:10 (seed:vermiculite) in moist vermiculite for 10 days at either 5 or 20 °C did not reduce germination rate in comparison to primed seeds that were not stored. Primed tall fescue seeds could be stored in moist vermiculite (1:20, seed:vermiculite) for up to 10 days at 5 °C with no loss of priming benefit, but storage for only 2 days at 20 °C resulted in germination. Primed seeds of Kentucky bluegrass (stored for 0 or 10 days at 5 or 20 °C) or tall fescue (stored 0 or 10 days at 5 °C or 2 days at 20 °C) resulted in more rapid germination and seedling emergence, and greater seedling shoot fresh and dry masses than was the case for nonprimed seeds.

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Switchgrass (Panicum virgatum L.) is one of the perennial, native, warm-season grasses recommended as a component of wildflower meadows. Seed treatments to alleviate low seed vigor and seed dormancy of switchgrass would enhance establishment of either plug transplants or seedlings after direct sowing into the meadow. “Heavy” seeds (45.5 mg/50 seeds) of open-pollinated switchgrass stored under cool and dry conditions (average 13 °C, 30% relative humidity) for 24 months had higher germination percentage than “light” seeds (26.0 mg per 50 seeds). In factorial combination, the heavy seeds were subjected to acid scarification (8 M H2SO4 for 5 min), sodium hypochlorite treatment (5.25% NaOCl for 15 min), and moist chilling (prechilling in 0.2% KNO3, for 14 days). Acid scarification followed by NaOCl treatment additively increased germination, a response that was associated with marked corrosion of the lemma margin in the distal region of the caryopsis, as observed by scanning electron microscopy. Prechilling the seeds following acid scarification and NaOCl further increased germination. All three treatments combined (acid scarification, NaOCl, and prechilling) almost doubled the final emergence and greatly increased seedling shoot dry mass in both a warm and cool postsowing environment. However, the effectiveness of these seed treatments was lost after 32 months of dry storage.

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The effect of seed germination rate, or of seedling emergence rate, was studied in relation to subsequent plant growth of `Cortina' lettuce (Lactuca sativa L.). Seedling growth response to selection by time of germination was assessed by imbibing seeds at 5 °C to increase the time range for germination. Germinated seeds were removed daily and transferred to “slants” (germination paper held at 20° from vertical) at 15 °C. Five days after each transfer, root and hypocotyl lengths were measured. As days required for germination increased, root lengths decreased and hypocotyl lengths increased, resulting in no change in total seedling length. The relation between rate of seedling emergence from raw or pelleted seeds of the same lot and shoot fresh weight was examined using commercially practiced hydroponic techniques. Shoot fresh weight at 10 and 21 days after planting was related inversely and linearly to the day of emergence for both seed treatments. In the same study, the coefficient of variation of shoot fresh weight was positively related to time of seedling emergence only at 10 days. Germinated seeds were selected after 1 and 2 days of imbibition; subsequent seedling emergence rate and shoot fresh weight at 25 days were recorded. First-day germinated seeds had faster and more synchronous emergence, and produced heavier and more uniform shoots. Discarding slow-to-germinate seeds should enhance seedling emergence and growth.

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The percentage of normal grain amaranth seedlings decreased and that of abnormal seedlings increased as threshing cylinder speed increased from 8.1 to 30.7 m·s-1. At the highest threshing speed, seed deterioration (loss of germination and increase in the percentage of abnormal seedlings) was exacerbated by increasing seed storage from 7 to 47 months. Threshing cylinder speeds of 8.1 to 12.8 m·s-1 resulted in similar percentages of normal seedlings as those achieved with hand-harvesting and threshing. Although injury to hand-harvested seeds or seeds threshed at 8.1 m·s-1 was not apparent, scanning electron micrographs of seeds threshed at 12.8 or 22.4 m·s-1 revealed damage to the seedcoat and the endosperm. Damage extended to the embryo when threshing cylinder speed was increased to 30.7 m·s-1.

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Hand-harvested and threshed grain amaranth seeds stored for 6.5 years and combine-harvested and threshed seeds (cylinder speed 26.4 m·s-1) stored for 9.5 years were subjected to several osmotic priming treatment. The selected priming treatment (–1.25 MPa polyethylene glycol at 15C for 10 days) increased percent radicle emergence of hand-harvested seeds and mechanically damaged, combine-harvested seeds and resulted in germination rates that were at least as high as those achieved with other priming treatments. In an incubator test, priming increased percent radicle emergence of hand-harvested seeds only at 15C; however, it increased percent radicle emergence of combine-harvested seeds at 15 and 35C. Priming also increased radicle emergence rate, but this response was more pronounced and exerted over a wider temperature range for the older, lower-vigor, combine-harvested seeds than for the younger, higher-vigor, hand-harvested seeds. In a greenhouse test, hand-harvested seeds had a higher percentage of normal seedlings and a lower percentage of abnormal seedlings than combine-harvested seeds. Priming had no effect on these variables. As a result of priming, normal seedling emergence rate and shoot fresh weight were higher from combine-harvested seeds than from hand-harvested seeds, such that values of these variables for primed, combine-harvested seeds were at least equal to those for nonprimed, hand-harvested seeds. Thus, the invigorating effect of priming was more pronounced for the lower-vigor, mechanically damaged, combine-harvested seeds than for the higher-vigor, hand-harvested seeds.

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