Effects of temperature, radiation and crop growth rate on seed weight in canola (B. napus)

Seed weight (SW) in canola is a function of environmental factors, such as temperature and photothermal quotient (PTQ) during seed filling period (SFP), and duration and rate of SFP. The objective of this experiment was to determine environmental factors influencing SW, during SFP. The experiment was a randomized complete block design, arranged in a split-plot in two conditions, i.e. supplemental irrigation and rainfed. The experiment was conducted at Agricultural Research Station of Gonbad, during 2005-7. Two cultivars of canola (Hyola401 and RGS003) as subplots were grown at 5 sowing dates (SDs) as main plots, spaced approximately 30 days apart. For an each degree increase of mean air temperature during SFP, 1000-SW of Hyola401 and RGS003 decreased 0.171 and 0.144 g, respectively. There was a quadratic relationship between 1000-SW and PTQ during SFP. Also, there was a linear relationship between 1000-SW and seed filling rate, explaining 67 and 74% of the variation for Hyola401 and RGS003, respectively. The strong relationships of SW with temperature, PTQ and CGR during SFP, and the duration and rate of SFP over different environmental conditions, SDs and cultivars, showed these variables to be generally applicable in SW determination.