plant assignment to vendor

Hi,

I am using ECC 6.0 When i try to assign plant to vendor master in add purchasing data, the field plant is not coming there.I tried with different vendor, but its not coming for any of the vendors. It is only showing vendor,city,data retention at VSR and plant level..thatsall..i could not do STO..

Kindly tell me what could be the problem please...??

regards,

JanaMM