Heat inhibition of tuber development in potato (Solanum tuberosum L.): effects on microtuber formation in vitro

Summary Microtuber formation by single node stem segments of in vitro grown potato plantlets was used as a model system for investigation of heat inhibition of tuber development. The stem segments were incubated in darkness at 20°C or 26°C on a tuberisation medium containing benzyl aminopurine (140 μg 1⁻¹) and sucrose (80 g 1⁻¹). Continuous incubation at 26°C strongly inhibited tuberisation and exposure to 26°C for only 1 week before transfer to 20°C significantly reduced microtuber fresh weight. Inclusion of a gibberellin synthesis inhibitor, paclobutrazol (10⁻⁵ M), in the tuberisation medium counteracted the heat inhibition of tuber initiation but not the reduction of microtuber fresh weight. Thus, consistent with previous reports, inhibition of tuber initiation appears attributable to increased endogenous levels of gibberellins. Possible causes of the reduction in microtuber fresh weight are discussed.     

Hematology of healthy Florida manatees (Trichechus manatus)

Background: Hematologic analysis is an important tool in evaluating the general health status of free‐ranging manatees and in the diagnosis and monitoring of rehabilitating animals. Objectives: The purpose of this study was to evaluate diagnostically important hematologic analytes in healthy manatees (Trichechus manatus) and to assess variations with respect to location (free ranging vs captive), age class (small calves, large calves, subadults, and adults), and gender. Methods: Blood was collected from 55 free‐ranging and 63 captive healthy manatees. Most analytes were measured using a CELL‐DYN 3500R; automated reticulocytes were measured with an ADVIA 120. Standard manual methods were used for differential leukocyte counts, reticulocyte and Heinz body counts, and plasma protein and fibrinogen concentrations. Results: Rouleaux, slight polychromasia, stomatocytosis, and low numbers of schistocytes and nucleated RBCs (NRBCs) were seen often in stained blood films. Manual reticulocyte counts were higher than automated reticulocyte counts. Heinz bodies were present in erythrocytes of most manatees. Compared with free‐ranging manatees, captive animals had slightly lower MCV, MCH, and eosinophil counts and slightly higher heterophil and NRBC counts, and fibrinogen concentration. Total leukocyte, heterophil, and monocyte counts tended to be lower in adults than in younger animals. Small calves tended to have higher reticulocyte counts and NRBC counts than older animals. Conclusions: Hematologic findings were generally similar between captive and free‐ranging manatees. Higher manual reticulocyte counts suggest the ADVIA detects only reticulocytes containing large amounts of RNA. Higher reticulocyte and NRBC counts in young calves probably reflect an increased rate of erythropoiesis compared with older animals.     

Evaluation of Cellular Uptake and Removal of Chlorpropham in the Treatment of Dunaliella salina for Phytoene Production

Chlorpropham is a carbamate herbicide that inhibits cell division and has been widely used as a potato sprout suppressant. Recently we showed that the microalga Dunaliella salina treated with chlorpropham massively accumulated the colourless carotenoids phytoene and phytofluene. Phytoene and phytofluene are valued for their antioxidant, UV-absorption and skin protectant properties; however, they are present in very low quantities in nature. The low toxicity herbicide chlorpropham seems a promising catalyst to produce phytoene in large quantities from CO₂ and solar energy with D. salina. This study explored chlorpropham uptake by the algal cells, the formation of potential intermediate metabolites, and the removal of residual chlorpropham from harvested D. salina biomass. Algal biomass rapidly concentrated chlorpropham from culture media. However, washing the harvested biomass with fresh culture medium twice and five times removed ~83 and ~97% of the chlorpropham from the biomass, respectively, and retained algal cell integrity. Furthermore, chloroaniline, a common metabolite of chlorpropham degradation, was not detected in chlorpropham-treated cultures, which were monitored every two days for thirty days. Cells treated with chlorpropham for either 10 min or 24 h continued to over-accumulate phytoene after resuspension in an herbicide-free medium. These data imply that whilst Dunaliella cells do not possess the intracellular capacity to degrade chlorpropham to chloroaniline, the effect of chlorpropham is irreversible on cell nuclear division and hence on carotenoid metabolism.