Timing of atrazine application for control of quackgrass (Agropyron repens)

L'application foliaire ou au sol de l'atrazine dans la lutte au chiendent (Agropyron repens) dans le maïs (Zea mays) a été étudiée. Les traitements d'atrazine pour la lutte au chiendent ont augmenté significativement le rendement du maïs. Le labour printanier sans atrazine a eu peu ou aucun effet à long terme sur la population de chiendent. Une seule application de 4,5 kg m.a. d'atrazine ha-1 à l'automne ou au printemps n'a pas procuré une meilleure lutte au chiendent qu'une application fractionnée de 2,25 kg m.a. d'atrazine ha-1 dans les expériences en application foliaire ou sur sol dénudé. La repousse du chiendent et le rendement en soya (Glycine max) ont été mesurés pendant 2 ans après la dernière application d'atrazine. Le chiendent ne s'est pas réimplanté de façon appréciable en-dedans de 2 ans après l'arrêt des traitements sur n'importe laquelle des parcelles traitées à l'atrazine. Les résidus d'atrazine des applications automnales antérieures ont réduit significativement le rendement en soya. Deux ans après le dernier traitement à l'atrazine, les rendements du soya étaient similaires, peu importe si les applications antérieures d'atrazine avaient été effectuées au printemps ou à l'automne.The use of foliar or soil applied atrazine to control quackgrass (Agropyron repens) in corn (Zea mays) was investigated. Atrazine treatments to control quackgrass significantly increased corn yield. Spring tillage without atrazine had little or no long term effect on quackgrass stand. A single application of 4.5 kg a.i. atrazine ha-1 applied in the fall or spring provided no better control of quackgrass than a split application of 2.25 kg a.i. atrazine ha-1 in either the foliage or bare soil experiments. Quackgrass recovery and soybean (Glycine max) yield were measured for 2 yr afterthe last atrazine application. Quackgrass did not recover to any significant extent within 2 yr after the cessation of the treatments on any of the atrazine treated plots. Atrazine residues from the previous fall applications significantly reduced soybean yield. Two years after the last atrazine treatment, soybean yields were similar, regardiess of former spring or fall atrazine application

Morphological, pharmacokinetic, and hematological studies of lead-exposed pigeons

Adult white Carneaux pigeons were orally dosed with inorganic lead (6.25 mg Pb/kg/day, gastric intubation) for up to 64 weeks and the following studies were carried out: (1) the subcellular distribution of lead in erythrocytes; (2) the changes in tissue lead levels with time; (3) morphological assessment of tissue responses to lead; and (4) hematological effects of lead, the major systemic evidence of toxicity. In the early stage of exposure, there is some lead accumulation in the erythrocyte nucleus relative to its proportion of total cell volume, but such accumulation disappears with time. The kinetic behavior of lead in seven tissues—blood, brain, kidney, liver, femur, sciatic nerve, and crop—was seen to conform to two mathematical methods of lead distribution; brain, kidney, and femur lead increased with dosing time and reached or appeared to approach an upper plateau; lead in blood, liver, sciatic nerve, and crop increased to a maximum, followed by a decline to a lower plateau level. Morphologically, renal tubule cells showed the presence of lead-containing inclusion bodies while CNS mitochondria appeared to have accumulated lead. No evidence of segmental demyelination was seen. Lead exposure induced a marked and rapid hypochromic normocytic anemia in these birds, as well as an elevation in erythrocyte porphyrin. No disturbance in mechanical fragility or osmotic resistance was noted

Infanticide and expulsion of females in a cooperative mammal

In cooperative groups of suricates (Suricata suricatta), helpers of both sexes assist breeding adults in defending and feeding pups, and survival rises in larger groups. Despite this, dominant breeding females expel subordinate females from the group in the latter half of their (own) pregnancy, apparently because adult females sometimes kill their pups. Some of the females that have been expelled are allowed to rejoin the group soon after the dominant female's pups are born and subsequently assist in rearing the pups. Female helpers initially resist expulsion and repeatedly attempt to return to their natal group, indicating that it is unlikely that dominant females need to grant them reproductive concessions to retain them in the group