Flower formation and pod/flower ratio in canola (Brassica napus L.) affected by assimilates supply around flowering

An alternative means by which to examine the importance of assimilates supply to flower and pod formation is to analyze the relationships of leaf area index (LAI), above-ground dry matter (ADM), leaf area duration (LAD) and crop growth rate (CGR) around flowering with flower number and pod/flower ratio. For this objective, an experiment was conducted at Agricultural Research Station of Gonbad, Iran in 2005-2006 and 2006-2007. The experiment was a randomized complete block design arranged in split plot. Two cultivars of spring type canola (Hyola401 and RGS003) as subplots were grown at 5 sowing dates as main plots, spaced approximately 30 days apart, to obtain different environmental conditions and assimilates availability around flowering. The experiment was conducted at two conditions, i.e. supplemental irrigation and rainfed. In both main (MR) and branch (MR) racemes, flower number increased as LAI and ADM at the beginning of flowering increased. The reduction in flower number with reduction of LAI and ADM is evidence that canola plants can adjust to carbohydrates availability by altering the number of potential resource demanding sinks. Pod/flower ratio was quadratically related to ADM at the beginning of flowering. A significant positive linear relationship was found between LAD and CGR during flowering period and pod/flower ratio. Therefore, potential and actual pod number was related to cumulative dry matter production of the crop until the beginning of flowering and until the end of flowering, respectively.