Search Results
Abstract
Total germination of 6 cultivars of perennial ryegrass (Lolium perenne L.) was unaffected by up to 10,000 ppm of salinity in the germination medium, but rate of germination decreased quadratically with increased salinity. No interactions of cultivar × salinity were found.
Abstract
This study evaluated the influence of companion grasses and mulch on warm-season turfgrass establishment. Vegetative plantings of centipedegrass [Eremochloa ophiuroides (Munro) Hack.] and St. Augustinegrass [Stenotaphrum secundatun (Walt.) Kuntze] and seeded plantings of bahiagrass (Paspalum notatum var. saurae Parodi) and centipedegrass were seeded with nine companion grasses, and they were either mulched or not mulched with grass hay. Data were gathered on seedling stand, rate of ground cover development, and ground cover composition at various intervals after planting. Browntop millet (Panicum ramosum L.) was the most rapid companion grass to establish in all plantings, but it was also most competitive to warm-season turfgrasses. Although ‘FL-501’ oats (Avena sativa L.) had a slower establishment rate than Browntop millet, it was less competitive than the latter as warm-season turfgrass cover 63 days after planting was equal to control plots planted without a companion grass. Mulch had a beneficial effect on establishment rate of seeded bahiagrass that negated the need for a companion grass when establishing bahiagrass from seed. Mulch had no detrimental effect on the slow establishment of vegetatively propagated St. Augustinegrass and centipedegrass or on seeded centipedegrass.
Abstract
Carboxin at 0, 22, or 45 kg ha-1 and GA3 at 0, 62, or 124 g ha-1 were evaluated as growth regulators on ‘Tifdwarf bermudagrass (Cynodon spp.) putting greens during winter months. Turf response to both compounds was linear, but the magnitude of top-growth response was related to temperature. Bermudagrass response was greatest near its optimum temperature at 26° to 35°C. A single application of carboxin produced a 7-week response in top-growth clippings and GA3 produced a 2-week growth response, even though weekly mean minimum air temperatures ranged from 8° to 19°C. Although significant growth responses occurred with both compounds, many growth rates were less than 25 kg ha-1 d-1 of fresh clippings, too low to sustain acceptable turf quality on putting greens. Carboxin and GA3 have promise for improving turfgrass color under low traffic situations. Carboxin produced a blue-green turf in 5 or more days, and GA3 produced a yellow-green turf in 1 to 2 days. Both compounds eliminated the purple cast commonly associated with ‘Tifdwarf bermudagrass turfs during suboptimum temperatures. Chemical names used: 5,6-dihydro-2-methyl-N-phenyl-1,4-oxathiin-3-carboxamide (carboxin); gibberellic acid (GA3).
Abstract
Two cultivars of Seashore Paspalum (Paspalum vaginatum Swartz.), ‘Adalayd’ (‘Excaliber’) and ‘FSP-1’, were grown in solution culture at 6 levels of salinity derived from synthetic sea water. Cultivars differed in changes of leaf water potential, leaf water potential components, and in growth responses to increased salinity. ‘Adalayd’ exhibited a linear decrease whereas ‘FSP-1’ exhibited a quadratic decrease in leaf water potential with increasing salinity. Leaf osmotic potentials decreased linearly for both cultivars, but there was a significant interaction. Leaf turgor potential decreased linearly for ‘Adalayd’ but quadratically for ‘FSP-1’. ‘FSP-1’ had greater tolerance to salinity in solution culture than Adalayd.
Salt tolerance in grasses is needed due to increased restrictions on limited fresh water resources and to saltwater intrusion into groundwater. St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is used widely as a lawngrass in states bordering the Gulf of Mexico. We describe the response of four St. Augustinegrass cultivars to solution cultures differentially salinized with synthetic seawater. A sea salt mixture was added to half-strength Hoagland's No. 2 nutrient solution to provide six salinity treatments ranging from 1.1 to 41.5 dS·m-1. Adjustments in leaf water potential, leaf osmotic potential, and leaf turgor potential were measured as salt levels were increased gradually at 2-day intervals over 10 days. Salinity effects on growth of top, crown, and root of each cultivar were measured over 3 months. Turfgrasses differed in their response, but were consistent in adjustment in leaf water potential and in leaf turgor potential as salinity increased. Leaf water potential, leaf osmotic potential, and leaf turgor potential decreased linearly with increased salinity, but a positive turgor of 0.1 MPa was maintained at a salt concentration equal to that of seawater. `Seville', the most salt-tolerant St. Augustinegrass cultivar, exhibited a 50% reduction in top growth at 28.1 dS·m-1, while `Floratam', `Floratine', and `Floralawn' St. Augustinegrasses showed the same reduction in top growth at 22.8 dS·m-1. Differences between cultivars were greatest at salinity levels <10 dS·m-1, where `Seville' was twice as salt-tolerant compared to other cultivars. The grasses did not die, although top growth of all cultivars was severely reduced at a salt level equal to seawater.
This investigation documented growth and nutritional responses of St. Augustinegrass `Floralawn', `Floratam', `Floratine', and `Seville' in salinized (conductivity = 1.1 to 41.5 dS·m-1) solution cultures. Averaged over all cultivars' tissue, Cl concentrations increased linearly as salinity increased, while Na concentrations reached a threshold at 10 dS·m-1 during 3 months of growth. Tissue K concentration decreased nonlinearly with increased salinity to 10 dS·m-1, with `Floratine' being the least affected. All cultivars apparently substituted Na for K until an optimum level was reached. Leaf tissue concentration of P decreased linearly, while Ca and Mg decreased nonlinearly with increased salinity. The salinity level that caused a 50% reduction in Ca concentration was 24% lower for `Floratine' than for other cultivars. Tissue color differences were more strongly correlated with Ca and Mg levels in `Floratine' than `Seville'. Differences in cultivar response were noted for K, P, Ca, and Mg, with `Seville' being the most salt-tolerant among those evaluated, based on overall nutritional and growth responses.
Abstract
A technique using salinized agar as a germination medium in sealed, plastic petri dishes is described. Agar concentrations of 0.5%, 1%, 2%, and 3% solidified with up to 35,000 mg·liter−1 of total salts derived from a formula for full-strength seawater. Water loss from petri dishes sealed with a plastic film after 28 days averaged 1.7% and was negligible. Saline-agar media held more moisture initially and lost less water than standard, double germination blotters after 7 days. Germination of perennial ryegrass (Lolium perenne L. ‘Derby’) on unsalinized agar was not different from germination on unsalinized blotters. Total germination of ‘Derby’ perennial ryegrass averaged 94% and was unaffected by salt concentrations up to 5000 mg·liter−1 but germination rate (days to 50% germination) was progressively delayed from 3.98 ± 0.09 days for the controls having no salinity to 5.15 ± 0.33 days at 5000 mg∙liter−1 of salinity.