Hema Kasinathan Thesis May 1 2012.pdf - Atrium - University of ...

2.3.4 Temperature and pHIn both studies, pH treatments of 6.0, 6.5, 7.0, 7.5 and 8.0 were assessed. Theplants were watered with deionized water adjusted to the desired pH using 5% acetic acidor 10% sodium hydroxide. Fresh pH-adjusted water was prepared and applied every day.The pH meter (Hanna instruments, Woonsocket, RI) was calibrated before each use,using standard buffer solutions (Fisher Scientific, Nepean, ON). To achieve the desiredpH of the sand growth medium, water of the target pH was added to each pipette tip /Falcon tube or conetainer. The water that drained from the pipette tips / Falcon tubes orconetainers was collected and the pH of the drain water was measured for each treatment.Based on this result, the pH of the watering solution was adjusted up or down and thewatering solution was re-applied until the desired pH was attained in the drain water.The temperatures assessed in both studies were 10°, 15°, 20°, 25° and 30°C,provided by standard growth cabinets. Temperature was measured at plant height. AHOBO temperature sensor (ProSeries Temp RH 2009 ONSET Computer Corporation,MA) was placed inside each growth cabinet. Temperatures were recorded at 5-minintervals and the daily mean temperature was calculated from the day after inoculation tothe day before harvest.Both studies were repeated, with the following modifications: treatments at pH5.0 and 5.5 were added to assess clubroot development at lower pH values. Also, thetreatments at 10° and 30°C were dropped because very low levels of clubroot haddeveloped at 10°C and many of the plants at 30°C had died before reaching 6 weeks ofage in the symptom development trial or 1 week in the root hair infection trial. Finally,38