Search Results
Abstract
Herbicidal efficacy of 0%, 1%, 4%, 7%, and 10% Roundup incorporated in carboxymethyl cellulose (CMC) and starch-grafted polymer (SGP) gels was evaluated after topical application (2 ml gel/plant) to leaves of Canada thistle, field bindweed, and Japanese honeysuckle. Increasing Roundup concentration caused a quadratic injury rating response in Canada thistle, with 7% Roundup giving maximal injury. Complete shoot necrosis and minimal regrowth of field bindweed resulted from 4%, 7%, or 10% Roundup. Injury ratings in Japanese honeysuckle increased linearly with increasing Roundup concentration, although no concentration gave complete control with one application. After a 2nd application, complete shoot necrosis occurred in only 50% of the plants treated with 10% Roundup. Although efficacy of gel-incorporated Roundup was not appreciably affected by gel type, SGP shelf life at room temperature was superior to that of CMC.
Abstract
Emergence and growth of ‘Heinz 1350’ seedlings of tomato (Lycopersieon esculentum Mill.) in magnesium silicate (Laponite 445) gel was compared with that in a commercial peat-lite. The gel was prepared in 0, 0.5, 1.0, 2.0, and 3.0-fold Hoagland solution (version 1). Emergence was decreased by the highest gel nutrient concentration. Seedling growth ceased 8 days after sowing seed onto gel with no nutrients. Seedling growth rate was greatest in peat-lite and least in gel prepared from 0.5-fold Hoagland solution. Shoot:root dry weight ratio was increased by gels relative to peat-lite and by decreasing gel nutrient concentration.
Abstract
Fertilization of tomato (Lycopersicon esculentum Mill.) in solution culture with NH4-N resulted in reduced shoot and root concentration of Ca, Mg, K, P, and NO3, increased leaf and root resistances to water flux, and decreased water use efficiency as compared to plants cultured with NO3-N. Solution adjustment to pH 6.5 decreased shoot/root fresh weight ratio with both N forms; decreased leaf diffusive resistance and water stress but increased root resistance to water flux and shoot NH4 concentration under NH4-N nutrition. Solution pH had little effect on tissue ion concentration.
Abstract
Decreasing soil water potential (minima of −0.3, −2.0 and −6.0 bars) reduced fruit number, set, and mean and total fruit weight of tomato (Lycopersicon esculentum Mill). Under the 2 wettest soil water regimes, NH4-N compared to NO3-N fertilization reduced total and mean fruit weights but increased fruit number whereas no differences in these variables were found between N-forms under the driest regime. Incidence and severity of blossom-end rot (BER) were increased by NH4 nutrition and by decreasing soil water potential (SWP). Decreasing SWP either had no effect or increased leaf Ca, Mg, and K concentrations but decreased fruit concentration of these ions. At any soil water regime, NH4 fertilization decreased leaf Ca and Mg concentration but generally increased leaf K and fruit Ca, Mg, and K concentrations. While BER incidence and severity did not appear to be related to fruit Ca, Mg, and K concentration, the disorder was associated with increased stylar to calyx fruit-half concentration ratios of these ions. Basal (pre-dawn) leaf xylem pressure potential (ψ p) was unaffected by N nutrition but was greater (less negative) under the wettest regime. Compared to plants supplied with NO3-N whose minimal and mean light-saturation ψ p values decreased with decreasing SWP, plants given NH4-N reached a constant ψ p level regardless of soil water regime. Since leaf diffusive resistance (RL) values increased with decreasing SWP, but were unaffected by N form, the lower transpiration and transpiration rates under NH4-N might be explained by increased non-leaf resistances to water flux and/or by reduced soil-plant water potential gradients.
Tomato (Lycopersicon esculentum Mill.) and asparagus (Asparagus officinalis L.) seeds were primed for 1 week in –0.8 MPa (20C, dark) polyethylene glycol 8000 (PEG), synthetic seawater (INO), or combinations of Ca+2, K+, or Na+ with Cl−,
Seeds of `Ace 55' tomato (Lycopersicon esculentum Mill.) and `Mary Washington' asparagus (Asparagus officinalis L.) were primed in -0.8 MPa (20C, 1 week, dark) polyethylene glycol 8000 (PEG), synthetic seawater (INO), or NaNO3. Primed seeds of both species had a higher percentage of germination than untreated seeds only at 10C in nonsaline (– 0.05 MPa) medium, while in saline medium (– 0.6 MPa) priming increased the percentage of germination of tomato seeds at 10 and 30C, and of primed asparagus seeds at 10 and 20C. Sodium nitrate was superior to PEG or IN0 for priming tomato seeds since it resulted in fewer days to 50% germination and higher final germination percentage in saline media at all temperatures. IN0 was a satisfactory alternative to PEG or NaNO3 for priming asparagus seeds since priming agent had little or no effect on germination. Seedling emergence from NaNO3-primed seeds of both species sown in a seedbed provided saline (– 0.39 MPa) irrigation was faster than from untreated dry-sown seeds. In the saline seedbed, priming increased final emergence percentage (FEP) from asparagus seeds, provided they were not subsequently dried, but had no effect on the percentage emergence of tomato seeds. Fluid-drilling primed or germinated seeds of either species enhanced seedling establishment in the saline seedbed by reducing time to 50% emergence and/or increasing FEP relative to primed, dried-b&k or untreated seeds.
`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.
Abstract
Ammonium nutrition, in comparison to NO3–N nutrition, of tomato in sand culture reduced shoot growth, total and mean fruit weight, fruit number, leaf xylem pressure potential, leaf CA, Mg, and NO3 concentration, and normal fruit Ca, Mg, K, and NO3 concentration. Leaf diffusive resistance, leaf NH4 concentration, and blossom-end rot incidence were increased by NH4–N nutrition. Increasing substrate NO3 level increased shoot growth, fruit number per plant, and fruit NO3 concentration. Increasing substrate NH4 level increased leaf diffusive resistance, and leaf xylem pressure potential, but had no effect on shoot growth. Under both N forms, increasing N level did not affect fruit yield or normal fruit Ca, K, or P concentration, but decreased leaf Ca, Mg, and P concentration, and increased normal fruit Mg. Blossom-end rot occurred only under NH4–N nutrition. Affected fruit had lower Ca, Mg, NO3, and NH4 concentration and higher fruit K/Ca ratio. Fruit condition exerted no effect on fruit P or K concentration.
'Maffei 15' baby lima bean seeds were sown every 6 cm in rows 76 cm apart to yield a nominal stand of 215,000 plants/ha at two locations in Delaware over 2 years. Seedlings were thinned within 2 weeks of planting to provide 0%, 16.7%, 33.3%, and 50.0% stand reduction at two in-row spacing patterns to determine subsequent effects on vegetative and reproductive growth. Shoot fresh weight per square meter was decreased only in 2003 by 21% and bean fresh weight per square meter was decreased only in 2004 by 13.8% when plant stand decreased to 50%. This disproportional vegetative and reproductive growth response to stand reduction resulted from a compensatory linear increase in shoot fresh weight, usable pod number, and bean fresh weight of individual plants. Thus, 'Maffei 15' lima bean tolerates a considerable loss of plant stand with little or no effect on yield.