Pengaruh pretreatment air dingin, paradichlorobenzene (PDB), hydroxyquinoline (OQ), serta PDB:OQ (1:1) terhadap kromosom hibiscus rosa-sinensis l. = The pretreatment effect of cold water paradichlorobenzene (PDB), hydroxyquinoline (OQ) and combination of PDB:OQ (1:1) to the chromosome of hibiscus rosa sinensis l.