Thermoinhibition describes the inability of seeds to germinate at high temperatures, although germination proceeds immediately when the temperature is reduced below a certain threshold level. This phenomenon is distinct from thermodormancy, where some form of dormancy-breaking treatment is required before germination can proceed at the favourable temperature. Like seed dormancy, thermoinhibition is manifested in a number of different ways, ranging from simple high-temperature induced changes to the structures enclosing the embryo which prevent radicle emergence, to the interaction of a number of different factors, and probable expression of certain genes inhibitory to germination which may be temperature regulated. Thermoinhibition occurs in a large number of important crop species, so that an understanding of this phenomenon is both of scientific interest and practical importance

The metabolite profiles of Sutherlandia frutescens populations may vary depending on their geographical location, affecting the quality of plant-based pharmaceutical products generated from this species. This paper aims at using metabolic profiling through liquid chromatography mass spectrometry (LC–MS) to assess the metabolite content of seed pods from populations of the medicinal plant S. frutescens growing in geographically different environments. Terpenoid (retention time: 7.5–9.0min) and flavonoid (retention time: 15.0–19.0min) regions of the chromatograms were useful in distinguishing between samples and five distinct clusters were revealed after principal component analysis (PCA). This may assist in tracing the region where plants actually come from and the identification at the subspecies level. To increase the class separation and simplify interpretation, we focused on those populations from the arid Karoo and the coastal Gansbaai area, applying orthogonal partial least squares discriminant analysis (OPLS-DA) to organize these into two clear groups. The presence or absence of sutherlandioside B (SU1) and its derivatives contributed significantly to the separation of the Karoo plants from those from the Gansbaai cluster. Processing procedures of herbal products require standardization, but this becomes challenging when plants do not contain key chemical principles. Extracts from the Gansbaai population had virtually undetectable levels of SU1; consequently products manufactured from farmed plants originating from this region may lack these compounds, which are now proposed to be anti-cancerous. There were several sutherlandioside-type metabolites that distinguished populations from each other. These chemicals may add new knowledge in terms of the broader metabolomic understanding of Sutherlandia populations and their potential pharmacological action. In vitro plants generated as part of a commercialization–conservation strategy had a similar metabolite profile to non-propagated plants. In fact, these plants could be traced to the West Coast populations, further confirming their identity. This study highlighted that SU1 cannot be used as the only quality control marker for Sutherlandia products, since it does not occur in all populations and there is no conclusive evidence that it is the main active ingredient of the plant. The effect of α-naphthalene acetic acid (NAA) at 1mg l−1 was tested on in vitro plants. Sutherlandiosides and sutherlandins were detectable in treated plants. Although the treatment had impacts on the growth capacity of plants, SU1 did not accumulate at higher levels in auxin-treated plantlets. The similarity of micropropagated plants to wild plants proved that tissue culture does not have deleterious effects on the chemistry of Sutherlandia plants. Metabolomic approaches using LC–MS are thus an important feature as a diagnostic tool and should be integrated into the herbal product manufacturing process utilizing Sutherlandia and its extracts

Symbiosis involves responses that maintain the plant host and symbiotic partner’s genetic program; yet these cues are far from elucidated. Here we describe the effects of lumichrome, a flavin identified from Rhizobium spp., applied to lotus (Lotus japonicus) and tomato (Solanum lycopersicum). Combined transcriptional and metabolite analyses suggest that both species shared common pathways that were altered in response to this application under replete, sterile conditions. These included genes involved in symbiosis, as well as transcriptional and metabolic responses related to enhanced starch accumulation and altered ethylene metabolism. Lumichrome priming also resulted in altered colonization with either Mesorhizobium loti (for lotus) or Glomus intraradices/G. mossea (for tomato). It enhanced nodule number but not nodule formation in lotus; while leading to enhanced hyphae initiation and delayed arbuscule maturation in tomato.

Future climatic scenarios forecast increasingly frequent droughts that will pose substantial consequences on tree mortality. In light of this, drought-tolerant eucalypts have been propagated; however, the severity of these conditions will invoke adaptive responses, impacting the commercially valuable wood properties. To determine what mechanisms govern the wood anatomical adaptive response, highly controlled drought experiments were conducted in Eucalyptus grandis W. Hill ex Maiden, with the tree physiology and transcriptome closely monitored. In response to water deficit, E. grandis displays an isohydric stomatal response to conserve water and enable stem growth to continue, albeit at a reduced rate. Maintaining gaseous exchange is likely a critical short-term response that drives the formation of hydraulically safer xylem. For instance, the development of significantly smaller fibers and vessels was found to increase cellular density, thereby promoting drought tolerance through improved functional redundancy, as well as implosion and cavitation resistance. The transcriptome was explored to identify the molecular mechanisms responsible for controlling xylem cell size during prolonged water deficit. Downregulation of genes associated with cell wall remodeling and the biosynthesis of cellulose, hemicellulose and pectin appeared to coincide with a reduction in cellular enlargement during drought. Furthermore, transcript levels of NAC and MYB transcription factors, vital for cell wall component biosynthesis, were reduced, while those linked to lignification increased. The upregulation of EgCAD and various peroxidases under water deficit did not correlate with an increased lignin composition. However, with the elevated cellular density, a higher lignin content per xylem cross-sectional area was observed, potentially enhancing hydraulic safety. These results support the requirement for higher density, drought-adapted wood as a long-term adaptive response in E. grandis, which is largely influenced by the isohydric stomatal response coupled with cellular expansion-related molecular processes.