Seed weight in canola as a function of assimilate supply and source-sink ratio during seed filling period

Understanding variation in SW (seed weigh) is of major importance in
understanding SY (seed yield) variation. The objective of this study was to
determine factors such as SN (seed number) per unit area, SFD (seed filling
duration) and SFR (seed filling rate) and temperature, LAI (leaf area index), LAD
(leaf area duration), above-ground dry matter, CGR (crop growth rate), leaf dry
matter remobilization and efficiency and SSR (source-sink ratio) around SFP (seed
filling period), affecting SW in canola (Brassica napus L.). The experiment was
conducted at Agricultural Research Station of Gonbad, Iran, during 2005-7. Two
cultivars of spring type canola (Hyola401 and RGS003) as subplots were grown at
5 sowing dates (SDs) as main plots, spaced approximately 30 days apart, to obtain
a wide range of environmental conditions during SFP. The experiment was
arranged in two conditions, i.e. supplemental irrigation (SI) and rainfed (RF). SW
was influenced by the growing season rainfall and temperature. The availability of
the crop to produce and to remobilize photosynthetic assimilates to developing
seeds was a good determinant factor for SW. SW increased with increase in LAI,
above-ground dry matter production and remobilization and SSR around SFP,
leading to an increased SY, suggested that SW primarily depends on the resource
availability. The relationships of SW with SFR and SFD and above-ground dry
matter, LAI, leaf dry matter remobilization and efficiency and SSR around SFP,
over environmental conditions, sowing dates and cultivars, showed these variables
to be generally applicable in canola SW determination.
Keywords: Canola; Cultivar; Seed weight; Assimilate supply; Seed filling period.