Brassica phrnology depends on time gap between phases and local temperature. You may take an approximation from Kjellstrom and refs therein, http://pubs.aic.ca/doi/pdf/10.4141/cjps93-102

If you are doing a large scale farm experiment, you might want to do some destructive sampling per sub-plot for each treatment/replication to measure fresh and dry weight.

I did similar study:

1.measure the leaf surface area (cm2)

2. Plant height (cm)

3. Root Mass (%)

4. Fresh Weight (kg) or Dry Weight (k) 

5. Number of leaves per plant

6. Number of Shoot per Plant

Considering the task (parameters of reproductive stages), I would recommend to measure the parameters from previous list at least twice (before or at start of  bolting and at the time of 50% flowers) + some more traits:

1) time to bolting stage

2) time to the first open flower

3) time to 50% of open flowers at the main stem

4) number of flowers per plant (main stem), flower size

5) pods number per plant (main stem), pod size at mature stage

6) seeds number per pod and per plant (main stem)

7) 1000 seeds weight

Dear Kumar

This depends on the nature plant growth and its condition. Many herbaceous plants that have no woody structure growth rapidly and plant properties could be measure every two, three (or every) day. Other woody plants which growth slowly and along the time can be measure every one or two week to achieve the significant difference. It seems the Brasica ssp. belongs to the herbaceous plants and growths rapidly.

Best regards,

Thanks everyone for their kind suggestions