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Franco Tognoni and Roberto Lorenzi

Abstract

The acid phase of methanolic extracts of Picea glauca var. albertiana cv. Conica tissue, a difficult-to-root cultivar, had a high content of substances, at Rf 0.9 – 1.0, which inhibited the growth of Avena first internode. Chamaecyparis lawsoniana var. fletcheri, an easy-to-root variety, had a lower content of these substances. The substances stimulated root formation in mung bean cuttings, but no synergistic root-promoting effect was found when they were supplied to mung bean cuttings in the presence of 5 × 10−6M indoleacetic acid (IAA).

The substances at Rf 0.9 – 1.0 showed a dose-response effect over a concn range of 0 to 1.106 g fresh wt. Concn higher than 1.106 g did not further increase the number of roots in either species. An additive effect between extract and IAA was found in Picea at concn below 0.276 g and in Chamaecyparis at concn lower than 0.110 g and higher than 1.106 g fresh wt. The possibility that root initiation may be determined by hormone balance rather than a single substance is discussed.

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Erin C. Hill and Mathieu Ngouajio

Hairy vetch (Vicia villosa Roth) (HV) and cowpea [Vigna unguiculata (L.) Walp.] (CP) are two leguminous cover crops used in vegetable production systems. The residues of both species have been shown to suppress weeds via allelopathic interactions; however, they may also carry a risk of crop injury. A laboratory experiment was designed to study the dose response of carrot, sweet corn, cucumber, lettuce, onion, pepper, and tomato germination and radicle elongation to the aqueous extracts of both HV and CP. Aqueous extracts of fresh, whole plants were lyophilized to obtain a dry powder. Treatments of 0.00, 0.25, 0.50, 1.00, 2.00, 4.00, and 8.00 g dry extract/L of distilled water were applied to 10 seeds on filter paper in petri dishes. The petri dishes were then sealed and placed in the dark at 21 °C for 4 to 7 days, depending on the species germination. After the incubation period, germination rates and radicle lengths were recorded. Each treatment had 4 replications and the full experiment was executed twice. Pepper germination was reduced by increasing concentrations of HV extract; however, all other crops were not affected by HV or CP extracts. The HV extract had a significant effect on radicle elongation in carrot, corn, cucumber, lettuce, onion, and tomato. Inhibition of radical growth at 8 g·L-1 ranged from 42% in cucumber to as high as 81% in carrot. The CP extract had a negative effect on the radicle elongation of carrot, corn, lettuce, and tomato. Inhibition at 8 g·L-1 ranged from 42% in carrot to 67% in tomato. This study shows that both HV and CP extracts hold the potential to negatively affect the listed crops. Therefore, studies need to be done on the persistence of these effects in the field to maximize weed control while avoiding crop injury.

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Chad Hutchinson, Milt McGiffen Jr., James Sims, and J. Ole Becker

As of 2005, methyl bromide will no longer be produced or imported for agricultural use in industrialized countries. The uncertain future of methyl bromide as a soil fumigant has stimulated research into the use of other soil fumigants for weed control. Laboratory experiments were conducted to determine the efficacy of methyl bromide (MB), methyl iodide (MI), propargyl bromide (PB), 1,3-dichloropropene (1,3-D), and metham sodium (MS) alone and in combination with chloropicrin (PIC) against Cyperus esculentus L (yellow nutsedge). The experimental design was a randomized complete block with three replications. All experiments were repeated. Tubers were imbibed for 24 h and mixed with soil adjusted to 14% moisture (w/w). Soil/tuber samples were fumigated for 48 h with MB, MI, 1,3-D, and PIC at 0.0, 3.1, 6.3, 12.5, 25, 50, 100, and 200 μm of active ingredient. Samples were fumigated with PB and MS at 0.0, 0.8, 1.6, 3.1, 6.3, 12.5, 25, and 50 μm of active ingredient. After fumigation and venting, each soil/tuber sample was wetted and placed in a Petri plate for 5 days. Shoot emergence was recorded. Additionally, to determine synergism response with PIC, 17% PIC was added to each fumigant/rate combination. Fumigation and data collection were performed as described above. Dose-response curves were constructed to determine the effective dose to control 50% of nutsedge emergence (ED50). PB and MS were the most efficacious fumigants with ED50's of 3.7 and 6.5 μm, respectively. EC50 values for all the fumigants were significantly lower than MB except for 1,3-D. All the fumigant-PIC combinations resulted in synergistic control of nutsedge.

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Mark J. Arena, Otto J. Schwarz, and Willard T. Witte

Aqueous diffusates of either Salix erythroflexus (contorted willow) or Robinia pseudoacacia (black locust) were tested as a root-promoting substance on woody plants and Vigna radiata (mung bean). On 8 July 1995 water diffusates were prepared from fresh chopped terminal stems of either willow or locust (680 g) that were steeped in 4 liters of water for 24 hours. Semihardwood cuttings of Chionanthus retusus were double wounded, steeped in either willow, locust, or water for 24 hours followed by a treatment with 3.0% IBA in talc. One additional group of cuttings was treated with 3.0% IBA only. After 75 days, cuttings treated with willow diffusate and IBA produced the greatest number of roots, followed by the locust diffusate and IBA treatments. A similar test using willow diffusate and IBA on softwood cuttings of Chionanthus virginicus resulted in an 80% success rate. A modified mung bean bioassay was used to partially characterize and verify the effects of the diffusates. Diffusates were made from chopped frozen locust or willow terminal stems (10 g/300 ml H2O), stirred for 24 hours. Mung bean cuttings treated with either locust or willow diffusate (5 ml/10 ml H2O) plus 80 ppm IBA produced more roots than IBA or either diffusate alone. A dose response test showed a significant increase in rooting as concentrations increased (H2O,10%, 50%, 75%, and 100%) for both diffusates. Ethyl acetate extractions of each diffusate at pH 3.0 produced more roots than extracts at pH 7.0. A thermal stability test (20 min at 100 °C) on the diffusates showed willow maintained its root-promoting activity, while locust did not.

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W.H. Briggs, H. Xiao, K.L. Parkin, and I.L. Goldman

The acute syndromes associated with many human diseases of the cardiovascular system such as myocardial infarction, angina, and some forms of stroke are caused by thrombosis. Platelet aggregation plays a central role in thrombus formation. Dietary intake of inhibitors of aggregation may provide protection against these disorders, which effect millions of Americans. Previous research in our laboratory has shown that juice from onion (Allium cepa) inhibits platelet aggregation ex vivo. Various sulfur-containing compounds are largely responsible for the distinctive aromas, flavors, and platelet inhibitory actions of onion. Among these is the thiosulfinate (TS) family of compounds formed upon maceration of the vegetable. In this study, several pure Allium compounds were evaluated for antiplatelet activity. TSs were synthesized in model reaction mixtures containing the enzyme allinase and S-alk(en)yl-L-cysteine sulfoxides (ACSOs), their natural precursors, or purified from garlic juice. Antiplatelet activity of each compound was determined by dose response using whole blood from human donors. A minimum of 0.4 mM methyl methaneTS, a compound found in freshly cut onion and garlic (Allium sativum), was needed to significantly inhibit aggregation relative to a non-TS control. By contrast, a lower concentration (0.05 mM) of 2-propenyl 2-propeneTS (allicin) and propyl propraneTS, compounds found in garlic but not onion, was required. The garlic compound methyl 2-propeneTS significantly inhibited at 0.2 mM. These data imply a role of alk(en)yl groups in TS antiplatelet efficacy. Variability in ACSO-derived TS composition in cut onion tissue may explain differential antiplatelet activity of onion cultivars. Results from this investigation suggest that ACSO and TS composition profiles may be useful for evaluating the medicinal value of Alliums.

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A. Jeremy Bishko, Paul. R. Fisher, and William R. Argo

The objective was to systematically quantify the dose response from applications of several alkaline materials recommended for raising pH in acidic media. A 70 peat: 30 perlite (by volume) medium was mixed with a pre-plant nutrient charge, a wetting agent, and between 0 and 1.5 kg·m3 of a dolomitic hydrated lime resulting in six starting-pHs between 3.4 and 6.4. The supernatant from a solution of Ca(OH)2, 2.5 to 40 mL·L-1 of a flowable dolomitic limestone suspension, 99.5% KHCO3 between 0.6 to 9.6 g·L-1, 85% KOH between 0.056 and 0.56 g·L-1, 15N-0P-12K water-soluble fertilizer at 50 to 400 mg·L-1 N, and a distilled water control were applied at 60 mL per 126-mL container with minimal leaching as a single drench (except the 15N-0P-12K that was applied about every three days). All chemicals increased medium-pH within one day, and pH remained stable until day 28 except for Ca(OH)2 which showed a 0.2 unit decrease in pH from day 1 to 28. The Ca(OH)2 and KOH drenches raised medium-pH by less than 0.5 units, and there was a slight decrease in pH from the 15N-0P-12K for starting-pHs lower than 5.0. Flowable dolomitic lime and KHCO3 raised pH by up to 2 pH units, averaged across starting pHs and 1-28 days after application. The effect on medium-pH increased as concentration of flowable lime and KHCO3 increased. Effect of flowable lime was greater (up to 2.9 units) at lower starting-pHs, whereas KHCO3 was less affected by starting-pH. Medium-EC increased by <0.6 dS·m-1 following single applications of all solutions.

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A. Jeremy Bishko, Paul R. Fisher, and William R. Argo

Medium-pH above 6.4 is a common cause of micronutrient deficiency for container-grown plants, and technologies are required to correct an excessively high medium-pH. The objective was to quantify the dose response from application of several acidic materials that have been recommended for lowering medium-pH in soilless media. A 70% peat/30% perlite (by volume) medium was mixed with a preplant nutrient charge, a wetting agent and 1.5, 1.8, 2.1, or 2.4 kg·m-3 of a dolomitic hydrated lime resulting in four starting pH levels ranging from 6.4 to 7.6. Aluminum sulfate (17% Al) at 1.8-28.8 g·L-1, flowable elemental sulfur (52% S) at 3.55-56.8 mL·L-1, ferrous sulfate (20.8% Fe) at 1.8-28.8 g·L-1, Seplex-L organic acid at 0.32-5.12 mL·L-1, sulfuric acid (93%) at 0.08-2.56 mL·L-1, 21.1N-3.1P-5.8K water-soluble fertilizer at 50-400 mg·L-1 N (potential acidity 780 g CaCO3 equivalents/kg), and a deionized water control were applied at 60 mL per 126-cm3 container with minimal leaching as a single drench (except repeat sulfuric acid applications at 0.08 or 0.16 mL·L-1 and 21.1N-3.1P-5.8K treatments that were applied about every 3 days). Medium-pH and electrical conductivity (EC) were tested over 28 days using the saturated medium extract method using deionized water as the extractant. One day after application, aluminum sulfate, ferrous sulfate, and sulfuric acid lowered pH by up to 3 pH units at the highest concentrations and medium-pH remained fairly stable for the following 27 days. Flowable sulfur lowered pH gradually over the course of the experiment by up to 3.3 pH units, with no difference across the wide range in concentrations. Organic acid had minimal impact on medium-pH, and 21.1N-3.1P-5.8K did not lower medium-pH despite the fact that all nitrogen was supplied in the ammonium and urea form. At recommended concentrations, chemicals tested raised medium-EC, but not above acceptable levels for plant growth. The highest rates of aluminum and ferrous sulfates, and sulfuric acid, however, increased medium-EC by 2.0 dS·m-1 on day 1. Medium-pH-responses to acid-reaction chemicals would be expected to vary in commercial practices depending on additional factors such as lime type and incorporation rate, water alkalinity, media components, and plant interactions.

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Beth Ann A. Workmaster and Jiwan P. Palta

`Stevens' cranberry (Vaccinium macrocarpon Ait.) terminal bud freezing stress resistance was assessed by nonlinear regression utilizing relative scoring of the post-thaw bud growth and development based on defined bud stages 2 weeks following controlled freezing tests. Bud stages tested were chosen based on a phenology profile from each sampling date throughout the spring season. Previous year (overwintering) leaf freezing stress resistance was evaluated after both 2 days (injury) and 2 weeks (survival). The Gompertz function with a bootstrapping method was used to estimate the tissues' relative freezing stress resistance as the LT50. Bud injury levels (LT50) were expressed as the temperatures at which the mean potential regrowth capability was impaired by 50%, as compared with the unfrozen controls. In leaves, the LT50 is the temperature at which 50% injury (2-day evaluation) or survival (2-week evaluation) was modeled to occur. Dramatic changes in terminal bud relative freezing stress resistance occurred both within and between the tight and swollen bud stages. These results clearly show that seasonal changes in freezing stress resistance do not necessarily parallel changes in crop phenology and bud development. These results indicate that some physiological, biochemical, or fine anatomical changes may explain the seasonal loss in hardiness within a visual bud stage. Previous year leaves may possess the ability to recover from freeze-induced injury, as leaf survival was found to be the most reliable indicator of cranberry leaf hardiness. Major shifts in phenology and bud and leaf hardiness coincided with the rise of minimum canopy-level air temperatures to above freezing. The nonlinear regression technique utilized made it possible to estimate LT50 with data points comprising half or more of the sigmoidal dose response curve. Our study provides precise and quantitative estimates of the cold hardiness changes in cranberry terminal buds and leaves in spring. From precise estimates we were able to define critical temperatures for the impairment of cranberry bud growth. This is the first systematic study of cranberry terminal bud cold hardiness and spring bud development in relation to changes in the soil and air temperatures under natural conditions. Our study shows that regrowth assessment of the cranberry upright inherently describes the composite effects of freezing stress on plant health.

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Wenqi You and Allen V. Barker

The herbicidal action of foliar applications of glufosinate-ammonium (GLA) is due to toxic accumulation of unassimilated NH4 + in leaves; however, the effects of root-applied GLA on NH4 + accumulation and plant growth are unknown. In a dose-response hydroponics experiment, tomato (Lycopersicon esculentum Mill.) plants were grown in nitrate-based solutions with GLA added at 0, 6, 12, 25, or 50 mg·L-1. To observe plant responses to an exogenous NH4 + source with herbicide-induced responses, plants were grown in an NH4 +-based solution without GLA addition. At 6 days after treatment (DAT), GLA in solution at 25 mg·L-1 produced partial leaf wilting, chlorosis, and necrosis of foliage, and at 50 mg·L-1, plants were fully wilted and necrotic. Ammonium (NH4 +-N) concentration in shoots at 6 DAT increased from 0 to 6 mg·g-1 fresh weight with increasing GLA in the nutrient solution. Ethylene evolution doubled (from 4 to 8 nL·g-1·h-1, fresh weight) with increases in GLA from 0 to 25 mg·L-1 but declined with apparent plant death with GLA at 50 mg·L-1. Other treatments, including NH4 + nutrition, did not induce toxicity symptoms in leaves or give increases in NH4 + accumulation or ethylene evolution during the 6 days of the experiment. In a time-course experiment, tomato plants treated with GLA at 25 mg·L-1 were chlorotic at 4 DAT. Ethylene evolution (fresh weight basis) rose from an initial rate of 2.6 nL·g-1·h-1 to 8.3 nL·g-1·h-1 after 4 days. At 9 DAT, all plants receiving this treatment died. In the time-course experiment, an exogenous NH4 + treatment caused a slight inhibition in shoot fresh weight relative to NO3 - nutrition with no GLA but caused no visible symptoms and only slight enhancements in NH4 + accumulation and ethylene evolution over the 9-day period. Following GLA treatment, NH4 + accumulated in the shoots and increased sharply with time, whereas exogenous NH4 + led to NH4 + accumulation primarily in roots. Results suggest that GLA was absorbed by roots and translocated to shoots, where it initiated accumulation of NH4 + and ethylene evolution as indications of herbicidal action. Chemical name used: glufosinate-ammonium, GLA.

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James R. Schupp, Thomas M. Kon, and H. Edwin Winzeler

Discussion In both 2010 and 2011, ACC application at the 20-mm growth stage was effective at reducing fruit set and ineffective at 10 mm ( Table 1 ). There was a linear dose response at 20 mm for reduction in yield and increase in fruit size. Fruit size