You don't have a problem..

then how to take the od. if i am taking 3 replications its giving 3 different ods because of clumps. i have tried couple of times. everytime i am getting clumps

Bacterial broth should  be shaken but not very strongly (adjust rpm), in order to ensure ventilation, and nutrient availability and  prevents bacterial clumps . 

or you can change your broth and incubate by shaking all the time.

or addition of Glycerol  can inhibit clumping.

I hope this helps.

In shaken liquid cultures, clumps of cells can be easily visualized in the medium. It has been observed that even in very light cultures that appear clear, there are high numbers of cells likely attributable to this clumping and perhaps smaller cell size.

or keep samples cold and use a sterile stick, loop or needle to remove a small clump of cells (1–5 μl) and inoculate directly into liquid or solid media.

or add glycerol to prevent clumping

thank you all. i shall be trying the options you suggested in the next round of experiment?

how much glycerol is to be added in the broth of 100ml?

plz suggest

Thank you

Take a single colony using a tooth pick and inoculate in 50 ml LB. Keep it in shaker overnight at 26 to 28 and less than 50 rpm. What I do is I centrifuge it for pellet in swing rotor centrifuge and dissolve the pellet in 1/2 MS+ 10 micromolar acetosyringone and then take the OD in a cuvette. Since you will get a suspension it's difficult to pipette. Use pasteur pipette with tips cut or 1ml tip with cuts.