In order to study the cardinal temperatures of lambsquarter (Chenopodium album), purselane (Protulace oleracea), crab grass (Digitaria sanguinalis) and also predicting their emergence time within the fields an experiment was conducted in Weeds Research Labratory, Faculty of Agriculture, Ferdowsi University of Mashhad in 2005.The type of experiment was a completely randomized design with 9 treatment and three replications was used. Treatments consisted of 9 constant temperatures (5, 10,15,20,25,30,35,40 and 45°C) with 50 percent relative humidity and constant light radiation for 14 days. The germinated seeds were counted everyday and the rate of germination percentage, cumulative germination and cardinal temperatures were calculated. The cardinal temperatures including base temperature (Tb), optimum temperature (To) and cieling temperature (Tc) for lambsquarter was 4,29.5 and 43.3°C for purslane 11.8,35 and 49.3 °C and for crab grass it were 14.16,25/6 and 41.3°C respectively.The results indicated that lambsquarter with lower Tb and To is able to germinate when it is cooler and thus it will be dominant early in the season, Gradually , when the weather is getting warmer, purselane and then crab grass will dominate and invade the fields. On the whole, due to differences in physiologic of aspects and rate of weed growth the germination peak differs within fields.
Keywords: Germination, base temperature, optimum temperature, cieling temperature. |
