Participation of Ethylene in Common Purslane Response to Dicamba

Abstract

The responses of common purslane (Portulaca oleraqea L.) plants to 2-methoxy-3,66-dichlorobenzoic acid (dicamba) were found to be similar in many respects to ethylene fumigation effects. Dicamba and ethylene increased the permeability of celi membranes in purslane tissues. An increased efflux of electrolytes was observed in the bending region of the stems of dicamba-treated plants. Epinastic leaves after dicamba (10 micrograms) and ethylene (microliter per liter) treatments showed an increased efflux of rubidium. The permeability effects were observable within 1 day after dicamba or ethylene application. Protein metabolism in purslane leaves was not influenced by dicamba until 2 days after treatment, as indicated by reduced nitrate reductase activity. Inhibition of phenylalanine-U-YC incorporation into protein was observed 3 days after treatment. Ethylene reduced both phenylalanine-U-"C incorporation into protein and nitrate reductase actvity within 1 day. Dicamba caused a rapid increase in ethylene production in purslane plants to levels many times greater than those observed in untreated plants. It was concluded that the dicamba-enhanced production of ethylene is responsible for many of the observed effects of the herbicide. Dicamba is a systemic herbicide which has been used effectively to control many broad-leaved weeds resistant to other herbicides. Common purslane, a troublesome weed which is extremely drought-resistant, is not easily controlled by 2 ,4-D or 2,4,5-T but is sensitive to dicamba (23,39 The literature suggests that many herbicides act upon protein synthesis (7, 27, 31) and cell membrane permeability (6, 26). Dicamba was reported to inhibit leucine incorporation into protein in soybean hypocotyl sections and to inhibit induction of a-amylase in barley aleurone layers (31). Magalhaes and Ashton (26) found a decrease in the permeability of cell membranes of dicamba-treated nutsedge leaves. There are also a number of reports that some systemic herbicides, apparently acting as synthetic auxins, stimulate ethylene production in treated plants and that their physiological effects can be attributed in part to the effects of this natural hormone (1-3, 16, 20, 28, 32). In this report the action of dicamba is examined by comparing the effects of the herbicide and ethylene on protein synthesis and cell membrane permeability. MATERLALS AND METHODSCommon purslane (Portulaca oleracea L.) seeds were sown in sand in 10-cm plastic pots placed in trays filled with Hoagland's nutrient solution (19) for subirrigation. The plants were grown in a growth room under a 14-hr light (1100 ft-c) and 10-hr dark period at a continuous temperature of 25 + 1 C and 60% relative humidity. At 2 weeks of age the plants were thinned to three plants per pot.Dicamba and Ethylene Treatments. At 4 weeks of age the purslane plants were treated with various levels of dicamba dissolved in water. Foliar application was performed by placing 20-Mxl droplets of a desired concentration on each of five fully developed leaves of ea...

Ethylene effect on kochia (Kochia scoparia) and emission following dicamba application

“…Epinasty was a symptom of auxinic herbicide action in kochia, but ethylene was not the cause. Contrary to results with common purslane and sunflower (Hall et al 1985;Stacewicz-Sapuncakis et al 1973), kochia response to ethylene was not implicated as a source of herbicidal activity. The epinastic response in kochia caused by dicamba or fluroxypyr must result from a plant response other than ethylene production.…”

“…Plant species differ in response to ethylene. Ethylene, induced by dicamba, was determined a cause of epinasty and defoliation in common purslane (Stacewicz-Sapuncakis et al 1973). Chickweed and yellow starthistle, however, were not sensitive to ethylene (Coupland and Jackson 1991;Valenzuela-Valenzuela et al 2002).…”

“…(Holm and Abeles 1968). Dicamba-induced ethylene production caused whole plant responses in common purslane (Portulaca oleracea L.) that resulted in epinasty and defoliation (Stacewicz-Sapuncakis et al 1973). Tomato (Lycopersicon esculentum Mill.…”

Chlorsulfuron Induction of Leaf Abscission in Velvetleaf (Abutilon theophrasti)

“…Herbicides have been reported to stimulate ethylene pro duction in a number of plant species (3,20,25). Increased concentrations of ethylene induce epinasty (1), enhance senescence (6), and reduce the amount of chlorophyll (6,7).…”

An Evaluation of the Role of Ethylene in Herbicidal Injury Induced by Picloram or Clopyralid in Rapeseed and Sunflower Plants

“…Herbicides have been reported to stimulate ethylene production in a number of plant species (1,3,11,13,14,17,18,20,21). In particular, the auxin-type herbicides such as 2,4-D, 2,4,5-T, picloram, 2,5-dichlorophenoxyacetic acid, and dicamba promote ethylene biosynthesis (5,8,(15)(16)(17)(18)(19).…”