Environmental stress in plants impacts many biological processes, including male gametogenesis, and affects several cytological mechanisms that are strongly interrelated. To understand the likely impact of rising temperature on reproductive fitness in the climate change regime, a study of tapetal mitosis and its accompanying meiosis over seasons was made to elucidate the influence of temperature change on the cytological events occurring during microsporogenesis. For this we used two species of an environmentally sensitive plant system, i.e., genus Cymbopogon Sprengel (Poaceae), namely Cymbopogon nardus (L.) Rendle var. confertiflorus (Steud.) Bor (2n = 20) and Cymbopogon jwaruncusha (Jones) Schult. (2n = 20). Both species flower profusely during extreme summer (48 °C) and mild winter (15 °C) but support low and high seed fertility, respectively, in the two seasons. We have shown that tapetal mitotic patterns over seasons entail differential behavior for tapetal mitosis. During the process of tapetum development there are episodes of endomitosis that form either (i) an endopolyploid genomically imbalanced uninucleate and multinucleate tapetum, and (or) (ii) an acytokinetic multinucleate genomically balanced tapetum, with the progression of meiosis in the accompanying sporogenous tissue. The relative frequency of occurrence of the two types of tapetum mitosis patterns is significantly different in the two seasons, and it is found to be correlated with the temperature conditions. Whereas, the former (genomically imbalanced tapetum) are prevalent during the hot summer, the latter (genomically balanced tapetum) are frequent under optimal conditions. Such a differential behaviour in tapetal mitosis vis-à-vis temperature change is also correspondingly accompanied by substantial disturbances or regularity in meiotic anaphase disjunction. Both species show similar patterns. The study underpins that tapetal mitotic behaviour per se could be a reasonable indicator to elucidate the effect of climate change on reproductive fitness.

Plant molecular systematics relies on using DNA barcodes for studying the evolutionary relationship between species Sequences of the nuclear internal transcribed spacer (ITS) regions have been used widely in molecular phylogenetic studies because of their high variability compared to plastid sequences. Elaeocarpus is a diverse genus within the family Elaeocarpaceae and is widely distributed worldwide among tropical and subtropical climatic zones. Elaeocarpus ganitrus has important medicinal and religious values in India. However, Elaeocarpus ganitrus evolutionary relationship with other Elaeocarpus species is not much explored, especially at the molecular and phylogenetic levels. The present research successfully amplified the nuclear gene ITS2, sequenced and submitted it to NCBI Genbank after using Basic Local Alignment Search Tool (BLAST). Automatic Barcode Gap Discovery (ABGD) and Assemble Species by Automatic Partitioning (ASAP) resulted in different numbers of molecular operational taxonomic units (MOTUs). The lowest score of ASAP (4.5) segregated the sequences into 31 MOTUs with the Threshold dist. value of 0.003524. This study establishes an evolutionary relationship between Elaeocarpus ganitrus and other species belonging to the same genus through the neighbor-joining method. The 38 Elaeocarpus samples were clustered into seven major groups based on ITS2 sequence: Group I is represented by Elaeocarpus ganitrus along with Elaeocarpus sylvestris, Elaeocarpus glabripetalus, Elaeocarpus duclouxii, Elaeocarpus decipiens, and Elaeocarpus zollingeri. Group II is characterized by Elaeocarpus austroyunnanensis and Elaeocarpus glaber. Group III comprises Elaeocarpus sphaericus, Elaeocarpus angustifolius, Elaeocarpus grandis, Elaeocarpus ptilanthus, and Elaeocarpus sphaerocarpus. Three accessions of Elaeocarpus hookerianus are placed in group IV. Elaeocarpus largiflorens and Elaeocarpus thelmae represent group V. Groupr VI contains three species: Elaeocarpus sylvestris, Elaeocarpus dubius, and Elaeocarpus johnsonii. Group VII comprises five species which include Elaeocarpus glabripetalus, Elaeocarpus rugosus, Elaeocarpus tuberculatus, Elaeocarpus hainanensis, and Elaeocarpus angustifolius. The study concludes with the possibility of correctly using the ITS2 gene to identify, discriminate, and documentation of Elaeocarpus ganitrus and other species of the same genus.