May be involved in the coordinated dissolution of the cell wall matrix during abscission and in the secondary cell wall formation in xylem vessels. Prefers arabinoxylan, but may also use pectic arabinans as substrates. Hydrolysis of terminal non-reducing alpha-L-arabinofuranoside residues in alpha-L-arabinosides. Optimum pH is 4.3. Optimum temperature is 67 degrees Celsius. Expressed in roots, leaves, flowers, stems, siliques and seedlings. Observed in zones of cell proliferation, the vascular system and floral abscission zones. Expressed in the guard cells in stems, in xylem vessels and parenchyma cells surrounding the vessels, in the cambium and in the phloem, but not in the secondary xylem. Not induced by hormones or during leaf senescence. No visible phenotype; even in asd1 and asd2 double mutant. Belongs to the glycosyl hydrolase 51 family.