Hi Aziz,
i am seeing your issue , till then do onething and check either it is working or not,
plesae pass these exporting parameters too, (marked in bold) and see it works or not.
CALL FUNCTION 'BAPI_MATERIAL_SAVEDATA'
EXPORTING
headdata = lwa_bapihead
clientdata = lwa_mara
clientdatax = lwa_marax
PLANTDATA =
PLANTDATAX =
please see this link, this might gives fruitful result .