Glutamate-gated receptor that probably acts as non-selective cation channel, at least in hypocotyls (Probable). Can be triggered by Asn, Ser, Gly and, to a lower extent, Ala, Cys and Glu (PubMed:18162597, PubMed:22447719). May be involved in light-signal transduction and calcium homeostasis via the regulation of calcium influx into cells (Probable). Plays an important role in the calcium-based fast transmission of environmental stress (PubMed:15864638). Acts as negative regulator of lateral root initiation and development (PubMed:23590882). May restrict primordia numbers and position along the root axis by a signaling process originating in the phloem (PubMed:23590882). AtGLR3.4-mediated cytosolic calcium influx may be involved in the regulation of seed germination under salt stress by modulating sodium accumulation through the SOS pathway (PubMed:29432559). Forms a heteromeric channel with GLR3.2. Localizes to the plasma membrane. Highly expressed in roots and at lower levels in leaves and siliques (PubMed:12082126). Expressed in seedlings, cotyledons, roots (e.g. root hairs, epidermis and cortex cells), stems, leaves (e.g. vascular bundles and hydathodes), and siliques (PubMed:15864638). Expressed in root phloem (PubMed:23590882). The induction by glutamate, gamma-amino butiric acid (GABA), malate, aspartate, acetate, wounding, touch, and cold stress stimuli is abscisic acid (ABA)-independent, but calcium-dependent. Cold-mediated induction is rapid but transient. Impaired glutamate-triggered (and Ala, Asn, Cys, Gly, Ser-triggered) membrane depolarization and calcium rise (PubMed:18162597). Slight reduction of photosynthetic yield of Photosystem II (PubMed:21110940). Overproduction and aberrant placement of lateral root primordia (PubMed:23590882). May be due to an intron retention. Belongs to the glutamate-gated ion channel (TC 1.A.10.1) family. Truncated C-terminus.