Effects of the herbicides Lindex and Simazine on chloroplast and nodule development, nodule activity, and grain yield inLupinus albus L.

Abstract

Field and laboratory investigations were carried out to determine the influence of two commercial herbicides Lindex and Simazine on symbiotic N2 fixation, the photosynthetic apparatus, percentage of proteins, and grain yield of lupins (Lupinus albus L. cv. Multolupa). The herbicides were added (3 kg commercial product in 9001 per ha) two weeks after sowing. The nodulated roots were tested for nitrogenase activity by the acetylene reduction assay (ARA) at the first and second flowering. The ARA values decreased with herbicide application. The decrease was smaller in the Simazine treatments with inoculated seeds. The ARA for plants treated with Lindex did not increase with inoculation. Nitrogenase activity was greater in the non-inoculated plants growing together with weeds. The effect of Simazine on the photosynthetic apparatus proved to be more toxic than that of Lindex, not only considerably reducing the size of the chloroplasts but also affecting the grana structure. The latter appeared as an electron-dense compact mass. There were no visible alterations in the photosynthetic apparatus of plants treated with Lindex. However starch, which was not present in the control leaves, accumulated.No ultrastructural changes were observed in the nodule cells treated with Lindex. Simazine altered nodule cells by causing vesicle formation, degeneration of bacteria, and by decreasing the number of N2-fixing bacteroids.The grain yield decreased with both herbicide treatments, the decrease being lower in the inoculated plants, especially in the Simazine treatment.Our results suggest that each herbicide had a different effect on N 2 fixation, the photosynthetic apparatus and grain yield. Laboratory studies indicated that cyanazine and simazine did not adversely affect the growth of Bradyrhizobium.

Effect of weed management on weeds, and on the nodulation, nitrogenase activity, growth and yield of pea (Pisum sativum)

“…Kumar et al (1981) reported poor nodulation in chickpea with 1.6 and 3.2 kg/ha each of simazine and prometryn. Simazine at 1.38 kg/ha markedly decreased the specific nitrogenase activity in lupins (De Felipe et al, 1987), while Kumar et al (1981) could not detect nitrogenase activity in simazine-treated (at 1.6 and 3.2 kg/ha) chickpea plants, as leghaemoglobin did not develop at all in the nodules. Bentazone is known to decrease specific nitrogenase activity in kidney bean (Bethlenfalvay et al, 1979;Schnelle and Hensley, 1990) and soybean (Ozair and Moshier, 1988;Yueh and Hensley, 1993).…”

“…Thus, the plants were dependent for nodulation on the native strains of Rhizobium in the soil. The higher nitrogenase activity found at some sampling dates in the unweeded treatment compared to the hand-weeded treatment might be due to the reasons proposed by De Felipe et al (1987) and Brockwell et al (1995).…”

“…Sandhu et al (1991) observed higher specific nitrogenase activity in a hand-weeded treatment over an unweeded control in inoculated lentils and they were of the view that this might have resulted from the better availability of space, nutrients, water and solar energy due to the removal of weeds. However, in lupins De Felipe et al (1987) and Pozuelo et al (1989) found higher specific nitrogenase activity in weedy plots and they were of the view that the greater activity observed in non-inoculated plants may be due to less nitrate being available to lupins as a consequence of competition for nutrients. Brockwell et al (1995) also supported this view.…”

“…The lower yields observed in the unweeded as compared to the hand-weeded treatment were probably due to crop-weed competition for nutrients, light and space (De Felipe et al, 1987;Kumar and Kolar, 1989;Sandhu et al, 1991), rather than competition for moisture, as the crop received enough rainfall during the whole growing season.…”

Nodulation and Yield Response of Chickpea (Cicer arietinum L) to Pre and Post Emergence Herbicides

“…Similar results reported by Singh and Wright (2002) that the adverse effect of herbicides on nodulation and nitrogen fixation in legumes by affecting the nitrogen-fixing Rhizobia (Rhizobium leguminosarum population). Whereas, Felipe et al, (1987) suggested that, the direct effects of herbicides on the plant, decreased the number of nitrogen-fixing bacteroids.…”