Light-grown mung bean (Phaseolus aureus Roxb.) cuttings were treated with buffered and nonbuffered solutions of Ethephon, indole butyric acid (IBA), and the combination of both. Ethephon treatment resulted in increased tissue ethylene levels with increasing solution pH, but had no effect on rooting. IBA treatment had no effect on tissue ethylene levels, but strongly promoted rooting. Combinations of Ethephon and IBA had no effect on rooting of mung bean cuttings beyond that obtained by IBA alone.
Fourteen herbicides or herbicide combinations, wood chip mulch, chipped rubber tire mulch, and newspaper mulch were evaluated for weed control efficacy and phytotoxicity using 12 species of herbaceous perennials under field growing conditions. The effect of herbicide application time was monitored by applying herbicides to dormant and actively growing plants. Herbicide and mulch treatments were compared to weeded and non-weeded controls. Herbicide phytotoxicity was dependent on age and species of herbaceous perennial and time of herbicide application. Herbicide injury was generally greater for young plants compared to established plants and phytotoxicity was usually reduced when herbicides were applied to dormant rather than actively growing plants. Injury was sometimes greater when herbicides were applied in early spring compared to applications made after complete herbaceous perennial emergence. Injury to young shoots that had emerged prior to the earliest possible time that herbicides could be applied in the spring was probably involved. Applying herbicides in the fall may avoid such injury. Mulching field grown perennials with wood chips provided the most effective weed control and often the best quality plants. With the exceptions of Hemerocallis ‘After Dark’ and Phlox maculata ‘Omega’, the herbaceous perennials evaluated were tolerant of most of the herbicides applied. Several herbicides, including Balan 2.5G at 3.36 kg ai/ha (3.0 lb ai/A), Snapshot 80DF at 4.48 kg ai/ha (4.0 lb ai/A), and Stomp 60WDG at 4.48 kg ai/ha (4.0 lb ai/A), demonstrated potential for weed control in herbaceous perennial production systems and landscape plantings. Goal 1.6EC at 1.68 kg ai/ha (1.5 lb ai/A) and Ronstar 50WP at 3.92 kg ai/ha (3.5 lb ai/A) were often phytotoxic when applied to herbaceous perennials.
Endogenous production of ethylene and endogenous levels of abscisic acid were measured from Hibiscus rosa-si nensis L. abscission zone explants at six stages of development: tight bud, open flower, closed flower, petal abscission, calyx abscission, and peduncle abscission.Explants acropetal and basipetal to the abscission zone produced less ethylene than the abscission zone explants. Ethylene production increased with time both prior to and during abscission, reaching a peak in the later stages of senescence after abscission was complete.Bound abscisic acid was greatest in segments acropetal to the abscission zone at the closed flower stage. Free abscisic acid was double that of bound abscisic acid in the tight bud stage with the basipetal level exceeding that of the acropetal level until flower closure. Acropetal-free abscisic acid began to rise at petal abscission increasing sharply to a peak at calyx abscission. both. However, ABA has exhibited ethylene production in pea seedlings and stimulated its production in orange peel (24). Ethylene has also been shown to enhance the effect of ABA (50). Some interactions have been observed between ethylene and other growth regulators (1,10,11,23,32,39,47,50). An investigation of endogenous levels of ABA relative to endogenous ethylene production is in order. The objective of this study was to characterize the endogenous levels of ethylene and ABA in Hibiscius rosa-sinensis L. abscission zones to determine possible cause and effect relationships during floral development. MATERIALS AND METHODSHibiscuts rosa-sinienisis L. flower stem explants were used because the abscission zone is accessible and senescence and abscission are rapid. Ethylene and ABA determinations were made from abscission zone No. 2 (Fig. 1) (Fig. 2), as defined according to the development, senescence, and abscission of the flower petals, calyx, and peduncle. Explants 1.5 cm long, with the abscission zone centered. were used for ethylene analysis (Fig. la). Explants were surface-sterilized in 0.5% sodium hypochlorite for 4 min, blotted dry, and aseptically transferred to sterile flow chambers.The flow chamber consisted of a 7 cm X 1.5 cm (i.d.) glass tube fitted at each end with a 5 cm X 4 mm (i.d.) glass tubing in a rubber stopper. The 20 explants rested on a gauze pad placed in the bottom of each chamber. The glass tubing at the top of the chamber was attached to a humidified air flow system (0.35 ml/min) similar to that described by Pratt et al. (42). Controls consisted of 1.5-cm explants acropetal to and basipetal to the abscission zone explant (Fig. la). Empty chambers were used as a check on the system. One-milliliter gas-tight plastic syringes were attached to the exhaust port of the flow chamber. The syringes remained attached without the plunger. At sampling time, a plunger was started into the syringe, the syringe was removed from the flow system, and the 1-ml sample was injected into a gas chromatograph. Gas samples were taken at 6 AM, 10 AM. and 4 PM daily for 7 days. Explant fres...
Soil cultivation (3 to 5 times/yr) and herbicide management (oxadiazon, 3.92 kg ai/ha), agricultural standards for reducing weed competition, were compared to three alternative nursery field management systems regarding weed suppression: ‘Norcen’ bird's-foot trefoil companion crop, ‘Wheeler’ winter rye cover crop/mulch, and grass sod (80% ‘Eton’ perennial ryegrass and 20% ‘Ruby’ red fescue). Field management treatment had a significant effect on observed weed populations. Weed densities were also subject to yearly variations caused by climate and endogenous weed life cycles. Herbicide management (oxadiazon) consistently provided the best control of undesired vegetation (0.3 weeds/m2) followed by the grass sod (0.7 weeds/m2), Wheeler rye cover crop/mulch (1.7 weeds/m2), Norcen bird's-foot trefoil companion crop (8.6 weeds/m2), and cultivated (55.7 weeds/m2) treatments, respectively. Although the grass sod treatment provided excellent control of undesired vegetation, as an alternative to cultivation and herbicide use, it proved to be excessively competitive with the nursery crop. The bird's-foot trefoil treatment quickly became infested with broadleaf weeds the eradication of which proved difficult. The Wheeler winter rye cover crop/mulch field management system provided acceptable weed control combined with other beneficial effects on the plant/soil environment. Results support the effectiveness of Wheeler winter rye and perhaps other allelopathic cover crop/mulch systems in controlling undesired vegetation in horticultural field production systems.
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