Catalyzes the transfer of a phosphate group from ATP to the 5-hydroxylmethyl group of pyridoxal to form the biologically active pyridoxal phosphate, an active form of vitamin B6 (PubMed:12068103, PubMed:12244454). Required for Na(+) and K(+) homeostasis and for salt tolerance (PubMed:11910005). Involved in root hair development, both for initiation and tip growth (PubMed:12068103). ATP + pyridoxal = ADP + H(+) + pyridoxal 5'-phosphate Divalent metal cations. Zn(2+) >> Co(2+) > Mg(2+) > Mn(2+) > Ca(2+). Optimum pH is 6.0. Active from pH 4.5 to 10.5. Cofactor metabolism; pyridoxal 5'-phosphate salvage; pyridoxal 5'-phosphate from pyridoxal: step 1/1. Homodimer. Expressed ubiquitously in leaves, stems, roots, flowers and siliques (PubMed:12244454). Present in root hairs and other tip-growing cells such as papillar cells on the top of stigma (PubMed:12068103). Becomes detectable 60 hours after imbibition of the seeds and remains constant up to 101 hours after imbibition. Both long and short transcripts are down-regulated in roots but not in shoots by NaCl and abscisic acid treatment (PubMed:11910005). Under cold stress, the expression of the short transcript is increased while the long one becomes undetectable (PubMed:11910005). Defective pyridoxal kinase results in both salt hypersensitive and root hairless phenotypes (PubMed:11910005, PubMed:12068103). Hypersensitivity to Na(+), K(+) and Li(+) ions (PubMed:11910005). Increased accumulation of Na(+) ions but reduced K(+) retaining under NaCl stress (PubMed:11910005). Belongs to the pyridoxine kinase family.