Histone demethylase that demethylates 'Lys-36' (H3K36me) of histone H3 with a specific activity for H3K36me3 and H3K36me2 (PubMed:25132385, PubMed:30774641). Also active on 'Lys-27' (H3K27me) of histone H3 with a specific activity for H3K27me3 and H3K27me2 (PubMed:25267112, PubMed:33324437, PubMed:30774641). No activity on H3K36me1 and H3K27me1 (PubMed:25132385, PubMed:25267112). Involved in the control of flowering time by demethylating H3K36me2 at the FT locus and repressing its expression (PubMed:25132385). Acts within the central clock and contributes, in parallel with LUX, to temperature compensation, probably as a component of the evening complex, to maintain circadian period at increasing temperatures; this mechanism involves binding to and regulation of CCA1 and PRR7 promoters (PubMed:21358285, PubMed:30774641). Works in concert with TOC1 to promote the morning-phased clock genes CCA1 and LHY which function as components of the central oscillator (PubMed:21358285). Together with JMJ32, regulates the flowering-repressor FLOWERING LOCUS C (FLC) locus by removing the repressive histone modification H3 lysine 27 trimethylation (H3K27me3), especially at elevated temperatures (e.g. 29 degrees Celsius), thus preventing extreme precocious flowering (PubMed:25267112). JMJ30 and JMJ32 are regulators involved in the integration of abscisic acid (ABA) and brassinosteroids (BR) signaling pathways (PubMed:33324437). Together with JMJ32, controls ABA-mediated growth arrest during the post-germination stage in unfavorable conditions, and responses to ABA during root development, via the removal of repressive histone mark (H3K27me3) from the SnRK2.8 promoter, thus promoting SnRK2.8 expression and subsequent kinase-dependent ABI3 activation (PubMed:30983495, PubMed:30859592). In addition, removes the repressive histone marks (H3K27me3) from the BZR1 locus in response to stress and ABA, thus activating the BR signaling pathway which, in turn, inhibits the ABA signaling pathway (PubMed:33324437). Able to drive tissue identity changes to promote callus formation form somatic cells via a massive genome-wide chromatin remodeling (e.g. H3K9me3 demethylation) leading to the induction of Lateral organ Boundaries-Domain (LBD) genes (e.g. LBD16 and LBD29) that establish root primordia; when in complex with ARF proteins (e.g. ARF7 and ARF19), recruits ATXR2 which promotes the deposition of H3K36me3 at LBD genes promoters, thus ensuring their stable activation during callus formation (PubMed:29923261). 2 2-oxoglutarate + N(6),N(6),N(6)-trimethyl-L-lysyl(36)-[histone H3] + 2 O2 = 2 CO2 + 2 formaldehyde + N(6)-methyl-L-lysyl(36)-[histone H3] + 2 succinate 2 2-oxoglutarate + N(6),N(6),N(6)-trimethyl-L-lysyl(27)-[histone H3] + 2 O2 = 2 CO2 + 2 formaldehyde + N(6)-methyl-L-lysyl(27)-[histone H3] + 2 succinate 2 2-oxoglutarate + N(6),N(6)-dimethyl-L-lysyl(36)-[histone H3] + 2 O2 = 2 CO2 + 2 formaldehyde + L-lysyl(36)-[histone H3] + 2 succinate Binds 1 Fe(2+) ion per subunit. Interacts with EFM (PubMed:25132385). Binds to ATXR2, ARF7 and ARF19 (PubMed:29923261). Predominantly localized in the nucleus, especially in euchromatin. Expressed ubiquitously in vasculatures, roots, rosette leaves, stems, inflorescences and siliques (PubMed:18713399, PubMed:25267112). Mainly present in the root meristem and root differentiation area (PubMed:30859592, PubMed:33324437). Observed at high level in callus (PubMed:29923261). Accumulates progressively during seedling growth (PubMed:33324437). Expressed during callus formation (PubMed:29923261). Circadian-regulation with a broad peak in the late day and early night (PubMed:21115819, PubMed:21139085, PubMed:25132385). Stabilized at elevated temperatures (at protein level) (PubMed:25267112). Induced by abscisic acid (ABA) specifically during the post-germination stage in an ABI3-dependent manner (PubMed:30859592). Repressed by brassinosteroids (BR) during the post-germination stage (PubMed:33324437). Altered overall H3K36me3 modifications (PubMed:30774641). No visible phenotype under normal growth conditions, but mutant plants have a short-period circadian phenotype (PubMed:21115819, PubMed:21139085, PubMed:30859592, PubMed:21358285, PubMed:30774641). Defective temperature compensation leading to shorter circadian period at increasing temperatures with altered expression levels of clock genes at 27 degrees Celsius (PubMed:30774641). Reduced callus formation from somatic cells associated with low Lateral organ Boundaries-Domain (LBD) transcript levels (e.g. LBD16, LBD17, LBD18 and LBD29) associated with an impaired reduction of H3K9me3 deposition and altered H3K36me3 accumulation at their loci during leaf-to-callus transition (PubMed:29923261). The double mutant jmj30-2 atxr2-1 is strongly impaired in callus formation (PubMed:29923261). Reduced abscisic acid (ABA)-mediated growth arrest during the post-germination stage, with stronger effect in plants lacking both JMJ30 and JMJ32 (PubMed:30859592). The double mutant missing JMJ30 and JMJ32 exhibits an early-flowering phenotype at elevated temperatures (e.g. 29 degrees Celsius), associated with increased H3K27me3 levels at the FLC locus and decreased FLC expression (PubMed:25267112). The double mutant jmj30 jmj32 has longer primary roots (PubMed:30983495). In jmj30-2 jmj32-1 double mutants, reduced brassinosteroids (BR) mediated repression of ABA-inducible genes (e.g. ABI5, ABF2, ABF3 and ABF4) (PubMed:33324437). Plants over-expressing JMJD5 show delayed flowering. Belongs to the JARID1 histone demethylase family.