Effects of Paraquat on the Ultrastructure of Mesquite Mesophyll Cells*

Abstract

Summary. The effect of paraquat (l,1′‐dimethyl‐4,4′‐bipyridylium‐24) on the ultra‐structure of mesophyll cells of honey mesquite (Prosopis juliftora (Swartz) DC. var. glandulosa (Torr.) Cockerell) was studied by means of electron microscopic techniques. The first visible change induced by the herbicide was a rapid disintegration of the plasmalemma, followed by rupturing of the chloroplast membranes and loss of chloroplast turgor. Changes that occurred in plants treated and sampled in the dark were similar to those in plants treated and sampled in the light. The only change of a biochemical nature detected was a marked reduction in the quantity of starch deposits in chloroplasts. No changes were noted in the mitochondria, Golgi bodies, endoplasmic reticulum or nucleus, or in the composition of the cytoplasm or cell walls of treated tissues. Effets du paraquat sur I'ultrastructure des cellules du mésophylle de Prosopis Resume L'action du paraquat (1,1′‐diméthyle‐4,4′‐bipyridylium‐2A) sur l'ultrastructure des cellules de mésophylle de Prosopis (P. juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell) a été eatudiée au moyen des techniques de microscopie électronique. Le premier effet visible provoqué par l'herbicide fut une deasintegration rapide de la membrane cytoplasmique suivie de la rupture des membranes des chloroplastes et de la perte de la turgescence des chloroplastes. Les transformations qui apparurent dans les plantes traitées et conservées a l'obscurité, furent analogues á ceux des plantes traitées et exposées a la lumière. Le seul changement de nature biochimique deacelé fut une reduction marquée de la quantité des dépôts d'amidon dans les chloroplastes. Aucun changement ne fut observe dans les mitochondries, l'appareil de Golgi, le réticulum endoplasmique ou le noyau, pas plus que dans la composition du cytoplasme ou des parois cellulaires des tissus traités. Der Einfluss von Paraquat auf die Feinstruktur von Mesophyllzellen des Honig‐Mesquitebaums

Detection and Significance of Symptomless Latent Infections of Monilinia Fructicola in Plums

“…The toxic reaction may be complete within a few hours of illumination (Dodge 1971), but in the honey mesquite, mesophyll cells were damaged by paraquat as much in the dark as in the light (Baur et al 1969). The response of symptomless latent infections in paraquat-treated plum tissue in the dark lagged behind the light response by only two days, indicating either that light was only partially stimulatory, or that the light requirement was almost completely satisfied during the treatment process under subdued light (PAR 15 uE/m 2 /sec) lasting 90 minutes.…”

Effects of root zone temperature and paraquat in the induction of oxidative stress in Trichosanthes cucumerina L.

“…The entire process occurs so quickly that there is no measurable translocation of paraquat (Syngenta Crop Protection AG 2005). In a study of the effect of paraquat on plant ultra structure, Baur et al (1969) reported that the first visible change induced by the herbicide was a rapid disintegration of the plasmalemma, followed by rupturing of the chloroplast membranes and loss of chloroplast turgor. These are physiological disturbances that could result in drastic decline in the net photosynthetic recorded at 48 h after paraquat treatment.…”

Studies of herbicide toxicity and mode of action using isolated mesophyll cells and callus-derived cell suspensions

“…It was expected that both diquat and paraquat would destroy totally the cellular membranes, since extensive damage to plant cells occurred with intact plants treated with bipyridilium herbicides (Stokes et al 1970;Harris and Dodge 1972a, 19726). A lOmM solution of paraquat in 0.1% surfactant caused extensive damage of mesquite within 5 min (Baur et al 1969). Since all of the cells in our study were bathed continuously in the water-soluble herbicides we assumed the herbicides would enter the cells quickly and destroy the membranes.…”