9S-lipoxygenase that can use linoleic acid or linolenic acid as substrates. Plant lipoxygenases may be involved in a number of diverse aspects of plant physiology including growth and development, pest resistance, and senescence or responses to wounding. Catalyzes the hydroperoxidation of lipids containing a cis,cis-1,4-pentadiene structure. Function as regulators of root development by controlling the emergence of lateral roots (PubMed:17369372, PubMed:18949503). 9S-lypoxygenase-derived oxylipins may play an antagonistic role to ethylene signaling in the control of responses involving oxidative stress, lipid peroxidation and plant defense (PubMed:21481031). LOX5-derived oxylipins may facilitate performance of green peach aphid (Myzus persicae) on foliage (PubMed:21481031). 9S-lypoxygenase-derived oxylipins are engaged during infection to control the balance between salicylic acid (SA) and jasmonate (JA) signaling to facilitate infection by the fungal pathogen Fusarium graminearum (PubMed:26075826). 9S-lypoxygenase-derived oxylipins activate brassinosteroid signaling to promote cell wall-based defense and limit pathogen infection (PubMed:26417008). Does not seem to contribute to the oxidation of free fatty acids during seed aging (PubMed:28371855). (9Z,12Z)-octadecadienoate + O2 = (9S)-hydroperoxy-(10E,12Z)-octadecadienoate (9Z,12Z,15Z)-octadecatrienoate + O2 = (9S)-hydroperoxy-(10E,12Z,15Z)-octadecatrienoate Binds 1 Fe cation per subunit. Lipid metabolism; oxylipin biosynthesis. Expressed in roots. First observed in lateral root primordia (LRP), from the first pericycle divisions. Disappears before root emergence. Induced by the green peach aphid (Myzus persicae) (PubMed:22474183). Induced by infection with the fungal pathogen Fusarium graminearum (PubMed:26075826). Increment in the number of lateral roots, and moderate increase in the length of the primary root (PubMed:17369372). Reduced performance of green peach aphid (Myzus persicae) on foliage (PubMed:22474183). Enhanced disease resistance to the fungal pathogen Fusarium graminearum (PubMed:26075826). The double mutant plants lox1 and lox5 exhibit enhanced susceptibility to the bacterial pathogen Pseudomonas syringae pv tomato DC3000 and the biotrophic powdery mildew pathogen Golovinomyces cichoracearum (PubMed:26417008). Belongs to the lipoxygenase family.