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  • Author or Editor: J.A. Taylor x
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In 1992, a cultivar trial was initiated in Columbus, Ohio to evaluate differences in establishment and long-term performance of cultivars of tall fescue (Festuca arundinacea), creeping red fescue (F. rubra), chewings fescue (F. rubra ssp. fallax), hard fescue (F. brevipila), kentucky bluegrass (Poa pratensis), rough bluegrass (P. trivialis), and perennial ryegrass (Lolium perenne) under low maintenance conditions in a shaded environment. Fertilizer and supplemental irrigation were applied until 1994 to establish the grasses, after which no supplemental irrigation, or pesticides were applied and fertilizer rates were reduced to 48.8 kg·ha-1 (1 lb/1000 ft2) of N per year. Percentage cover and overall quality data were collected in 2000 and compared with data collected in 1994. Initial establishment success does not appear to be a good predictor of long-term success of a cultivar in a shaded environment. There was some variability in cultivar performance under shade within a given turfgrass species. The tall fescue cultivars, as a group, had the highest overall quality and percentage cover under shade, followed by the fine fescues, kentucky bluegrass, rough bluegrass, and perennial ryegrass cultivars.

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The effect of rootzone salinity (0 to 90 mM NaCl) on shoot growth of 6 grape cultivars [‘Sultana’ (syn. ‘Thompson Seedless’), ‘Carbernet Sauvignon’, ‘Crouchen’, ‘Shiraz’, ‘Doradillo’ and ‘Palomino’] grown as rooted cuttings was determined in sand cultures. Relative shoot growth values over 23 days with salt were ‘Palomino’ 100, ‘Sultana’ 94, ‘Shiraz’ 87, ‘Crouchen’ 83, ‘Cabernet Sauvignon’ 63, and ‘Doradillo’ 59. Application of concurrent waterlogging (anaerobiosis) stress on the root system depressed shoot growth more than salt stress alone and changed the ranking for shoot growth. Waterlogging increased total uptake of Na and Cl, increased the amount of Na and Cl transported into the shoots, and resulted in visible leaf damage within 5 days of the onset of the waterlogging.

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Imbibed nonviable lettuce (Lactuca sativa L.) seeds have been shown to have lower density than imbibed control seeds. The purpose of this study was to investigate density differences associated with seed death. The relationship between endosperm integrity and the volume, density, and leakage of imbibed control and heat-killed ‘Montello’ lettuce seeds was studied. After an 8-hr soak, heat-killed seeds imbibed 23% more water than control seeds. The percentage of heat-killed seeds with density of 1.08 g·cm-3 was 2%, compared to 90% for the control. Mean electrical conductivity of the steep water was similar for heat-killed and control seeds. Seeds were punctured to rupture the endosperm layer surrounding the embryo. Puncturing the heat-killed seeds decreased total water uptake, as measured by decreased swelling, and increased density compared to intact heat-killed seeds. Leachate from punctured heat-killed seed had a 41% higher mean conductivity than that from punctured control seed. These data suggest that the undamaged endosperm restricted leakage of electrolytes from the embryo to the soak water. We speculate that the endosperm caused osmotically active solutes to accumulate in the extra-embryonic fluid of heat-killed seeds. This accumulation of solutes decreases the water potential inside the embryonic pouch, resulting in a greater uptake of water from the environment. The additional water uptake by heat-killed seeds would increase seed swelling and decrease seed density relative to control seeds.

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Abstract

Germinated seeds of ‘King Cole’ cabbage (Brassica oleracea L. ‘Capitata’) were separated on a float-sink basis from nongerminated seeds by density differences. Aqueous solutions of varying densities were prepared from Maltrin 250. Brief exposures (<2 min) of the germinated seeds to 1.10 g cc−1 solution did not affect the percentage of seedling growth. The percentage of recovery of germinated seeds increased, and the percentage of germinated seeds decreased as the solution density increased from 1.06 to 1.09 g cc−1. Sowing density-separated germinated seeds improved both the percentage of emergence and time to 50% emergence for nonaged and artificially aged seeds. The greatest improvement in emergence was observed from the aged seeds. Dry seeds were separated into density lots of 0.95 to 1.05 g cc−1 in 0.05 increments with solutions of hexane and chloroform. Each dry seed density lot then was germinated and separated. The dry seed density separation did not improve the percentage of germinated seeds or recovery. No correlation was found between the densities of dry and imbibed seeds.

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Greenhouse-grown root, foliage, fruit, and seed crops were exposed to peroxyacetyl nitrate (PAN) at 0, 5, 10, 20, and 40 ppb, 4 hours per day, twice per week, from germination to maturity of harvestable product. A response of PAN dose and growth or yield parameters was significant only for lettuce (Lactuca sativa L. cv. Empire) and Swiss chard (Beta vulgaris L. var. cicla, cv. Fordhook). Leaf fresh weight was reduced by 13% in ‘Empire’ lettuce and by 23% in chard in the 40 ppb PAN treatments relative to 0 ppb PAN controls. Peroxyacetyl nitrate at 10 ppb appeared to stimulate the growth of most crops. The threshold for inhibition of growth by PAN, under conditions of 2 exposures per week, appeared to be between 10 and 20 ppb. These results suggest that PAN, at concentrations below the threshold for visible injury, can alter the growth of plants, but that significant reductions in growth or yield may occur only in highly susceptible cultivars of leafy crops.

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Abstract

Seed of germinated celery, Apium graveolens L. (Dulce group) and pepper, Capsicum annuum L. were separated from ungerminated seed by density differences in a sucrose and water solution. The top (floating) fraction in both species had the highest percentage germination and percent and rate of emergence compared to either the bottom fraction or unseparated seed.

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Abstract

The effects of water deficits were examined on osmotic regulation of germinating seedlings of tomato (Lycopersicon esculentum Mill cv. Campbell 1327). Seed were germinated in aerated water and then grown for an additional 2 days in Petri dishes. The germinated seeds were then transferred to water potentials of 0 to −6 bars in 2-bar increments. Mannitol and water was used to obtain the desired water potential of the media. Water relations, growth rates and reducing sugars, non-reducing sugars, amino acids, proline, nitrates, phosphates, potassium, and electrical conductivity were determined for roots and shoots at different water stresses. As water stress increased, osmotic adjustment occurred in the roots which accounted for the maintenance of turgor and growth. During the same period, little adjustment occurred in the shoots and consequently growth decreased. Turgor potential was highly correlated with growth rates for both plant parts. All solutes measured, except proline, generally increased in the roots and decreased in the shoots as water stress increased. Proline increased in both plant parts during the same period. Thus, solute regulation occurred during water deficits. Osmotic regulation in germinating tomato seedlings appears to be an adaptive feature during periods of water stress.

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Abstract

Two species of tomato, Lycopersicon chilense Dun. and Solanum pennellii Corr., which have drought-resistant characteristics, were compared to the commercial tomato, Lycopersicon esculentum Mill. cv. Campbell 1327, to evaluate the effects of water deficits on germination and early seedling growth at 25, 30, and 35°C. Five levels or water stress (0, −2, −4, −6, and −8 bars) were maintained by solutions of polyethylene glycol (PEG) 6000. Germination of dry seed was inhibited more by water stress than by growth of the germinated seedlings of each species. Germinated seed of all species were able to continue growth at 35° plus water stress at all levels, while germination under the same conditions was totally suppressed. The water-sensitive phase of germination occurred just prior to radicle emergence. Emergence was not affected by sowing germinated seed in a drying soil; but sowing dry seed under the same conditions resulted in a decrease in emergence. Germination and seedling growth of L. chilense and S. pennellii were more sensitive to water stress than L. esculentum at 25°. At 30 and 35°, L chilense, S. pennellii and L. esculentum had similar rates of germination and similar amounts of early seedling growth.

Open Access

Abstract

The objective of this study was to determine the relationship between seed density and seed quality of vegetable seeds hydrated by imbibing or priming procedures. Species studied were: lettuce (Lactuca sativa L.), tomato (Lycopersicon esculentum Mill.), onion (Allium cepa L.), cabbage (Brassica oleracea var. capitata L.), and carrot (Daucus carota L.). Seeds of each crop were soaked in either aerated distilled water at 25C (imbibed seeds) or polyethylene glycol (PEG) 8000 at 15C (primed seeds). After soaking, seeds were separated into density classes with a float-sink procedure using aqueous solutions of Maltrin 600 (Maltrin 500 for lettuce) with 0.02 g·cm−3 density increments. Significant (P > 0.01) positive relationships were determined between seed density classes and germination percentages for lettuce, tomato, and onion seeds, whether separated after imbibition (R 2 = 0.93, 0.83, and 0.66, respectively) or after priming (R 2 = 0.95, 0.94, and 0.91, respectively). High-density classes of hydrated lettuce, tomato, and onion seeds in either the imbibed or primed treatment usually exhibited faster and more uniform rates of radicle emergence and, after 6 days, had longer hypocotyls (cotyledon for onions) than low-density classes. The significant quality differences exhibited among the density classes of lettuce, tomato, and onion seeds after priming will enable seedlots of these species to be upgraded by discarding the low-density, poor-quality seeds.

Open Access

Abstract

‘Troyer’ citrange [Poncirus trifoliata (L.) Raf. × Citrus sinensis (L.) Osbeck] seedlings were exposed to 82 ppm HCl for 20 minutes or 100 pphm ozone for 4 hours at 5, 12, and 16 weeks after inoculation with the vesicular-arbuscular mycorrhizal fungus, Glomus fasciculatus (Thaxter) Gerd. & Trappe. One group of citrange seedlings was exposed in a 2nd experiment to ozone at 90 pphm for 6 hours, once weekly, and a second group was exposed to 45 pphm for 3 hours, twice weekly for a period of 19 weeks beginning 1 week after fungal inoculation. Intermittent HCl and ozone exposures significantly reduced height and dry weight of mycorrhizal, but not of non-mycorrhizal plants. Fungal chlamydospore production was reduced 57% in ozone treatments but was not reduced by HCl exposures. Weekly exposures to 90 pphm ozone levels significantly reduced total dry weight in mycorrhizal plants by 42%, but reduced that of non-mycorrhizal plants by only 19%. However, 45 pphm ozone levels did not cause a similar reduction in either mycorrhizal or non-mycorrhizal plants. Mycorrhizal infection was reduced 15% and spore production 39% at 90 pphm ozone. The lower ozone level (45 pphm) reduced infection 22%, but had no effect on spore production. Absorption of phosphorus was not reduced by ozone treatments in either mycorrhizal or non-mycorrhizal plants.

Open Access