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  • Author or Editor: J. A. Taylor x
  • Journal of the American Society for Horticultural Science x
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Abstract

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.

Open Access
Authors: and

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.

Open Access

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.

Open Access

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

Abstract

Tomato seedlings (Lycopersicon esculentum Mill. ‘Heinz 1350’) were inoculated with the vesicular-arbuscular mycorrhizal fungus Glomus fasciculatus (Thaxter) Gerd. & Trappe and either exposed to 30 pphm (589 μg/m3) ozone or to filtered air for 3 hours once weekly, beginning 3 weeks after inoculation, under long photoperiods (12–13.5 hr). Root infection by G. fasciculatus in ozone-exposed plants was retarded from week 3 to 5 compared to controls but recovered by week 7. Growth rates of mycorrhizal control plants were significantly greater than ozone-exposed mycorrhizal plants, but there were no differences in growth rates of nonmycorrhizal controls, mycorrhizal ozone-exposed plants, and nonmycorrhizal ozone-exposed plants. Under short photoperiods (less than 12 hr), growth rates of mycorrhizal controls were less than nonmycorrhizal controls and ozone did not significantly affect growth rates of nonmycorrhizal plants relative to controls. Leaf chlorophyll levels were similar whether plants were mycorrhizal, nonmycorrhizal, or exposed to ozone.

Open Access

Abstract

Table beet (Beta vulgaris L.) ‘Ruby Queen’ seeds were either germinated in aerated water till radicle emergence or osmoconditioned (OC) in –1.2 MPa solutions of polyethylene glycol 6000 or MgSO4 for 7 days at 15°C. Seeds were sown in soil in growth chambers, infested with Pythium spp., and damping-off incidence was evaluated after 14 days. Disease incidence was reduced, compared to dry sown seeds, as a result of presowing treatments. High populations of bacteria (106–108 CFU/ml of solution) developed during the aerated soak, which protected seeds from Pythium damping-off. Seed leaching or osmoconditioning did not decrease susceptibility to damping-off in the absence of high seed bacterial populations. The fluid drilling gel was studied as a delivery system for chemical fungicides. Damping-off in dry-sown seed was reduced by incorporating thiram into a hydroxyethyl cellulose (Natrosol 250 HHW) gel. Gel alone had no effect on damping-off. In field studies, only slight improvements in stand were attributed to the incorporation of thiram in presowing treatments. Fungicide dressing of dry seed resulted in a large improvement in emergence. All presowing treatments had greater field emergence than dry-sown seeds in the absence of thiram, which was attributed to bacterial protection from damping-off.

Open Access