Rhythmical Changes in the Sensitivity of Cotton Seedlings to Herbicides

Abstract

Cotton (Gossypiam hiruutam L) seedlings that were grown under a photoperiod of 12 hours darkness and 12 hours light showed oscillations in their sensitivity to the herbicides sodium 5(2-chloro4-trifluoromethyl)-phenoxy)-2-nitrobenzoate (acifluorfen), butyl 2-(4-((5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy)propanoate (fluazifop) and 3-isopropyl-lH-2,1,3-benzothiadiin-4(3H)-oe 2,2-dioxide (bentazon). Sensi The herbicides sodium 5-(2-chloro4-trifluoromethyl)-phenoxy)-2-nitrobenzoate (acifluorfen), butyl 2-(4-((5-(trifluoromethyl)-2-pyridinyl) oxy)phenoxy)propanoate (fluazifop) and 3-isopropyl-1H-2,1,3-benzothiad in4(3H)-one 2,2-dioxide (bentazon) were applied by spraying the seedlings until run-off. The injury caused by the herbicides was evaluated by degree of damage to the cotyledons as expressed by appearance of necrotic areas after several days. It was scored from 1 which represents no visible necrotic areas on the cotyledons to 5 which represents completely necrotic cotyledons. At the time of herbicide application, the seedlings had only two cotyledons and had not yet developed shoots. Resumption of growth was determined by measuring the shoot weight several days after the herbicide application.Humans and other animals show oscillations in their sensitivity to many chemical agents such as pyrethrum, atropin, pentobarbitol sodium, ethanol and histamine (12). There are also reports on oscillations in the sensitivity of plants to chemical agents. For example, changes in membrane potential in Samanea pulvini by sucrose (1 1) and inhibition of flowering in Lemna by ions (5) were related to the time ofday that sucrose or ions were applied. Of special importance are the relations between the response of plants to herbicides and the time of day when the herbicides are applied. Many studies demonstrated such relations between herbicides with various mechanisms ofaction and many plant species (1-4, 7, 8, 14). However, it is not yet clear what contributes to the daily oscillation in the sensitivity to herbicides.The aim of the present work was to test whether such daily oscillations in the sensitivity to herbicides were rhythmical changes which must be entrained by a certain photoperiod and were regulated by an endogenous clock.

Relationships between circadian rhythm of chilling resistance and acclimation to chilling in cotton seedlings

“…There are other examples of plant responses to external factors that are longer than one LDC but are dependent on the time of the beginning of the exposure. Cotton seedlings show daily changes in their resistance to several herbicides although the differential injury symptoms do not appear until after more than one LDC from herbicide application (Rikin et al 1984b), In bean seedlings, treatment with exogenous ethylene stimulates ethylene production, the degree of ethylene stimulation by ethylene treatment depending on the time in the LDC when treatment begins, and the differential ethylene production lasting more than one LDC (Rikin and Anderson 1990).…”

Working Time Society consensus statements: Circadian time structure impacts vulnerability to xenobiotics—relevance to industrial toxicology and nonstandard work schedules

“…Hundreds of animal and human research studies corroborate the CTS mediates the responses to and consequences of a wide variety of toxic challenges. Investigations involving other species, such as insects, fish, and plants, also document prominent disparity in vulnerability according to the circadian time of exposure to insecticides and pesticides—β-cyfluthrin, chlorfenapyr, dichlorodiphenyltrichloroethane, dursban, malathion, permethrin, and trichlorfon—and herbicides—glyphosate, glufosinate, fomesafen, and chlorimuron ethyl24, 57,58,59,60,61,62,63,64,65 ) —thus demonstrating the ubiquity across species of the phenomenon of chronotoxicity.…”