Abstract:Tree species are potential hosts for epiphytes; however in some forests epiphytes have a biased distribution among hosts. In a tropical dry forest of Mexico, previous research showed that there are trees with few epiphytes. It is possible that the bark of these hosts contain allelochemicals that influence epiphyte seed germination. The aims of this study were (1) to determine whether hosts with low epiphyte abundance (Ipomoea murucoides, I. pauciflora and Lysiloma acapulcense) would inhibit seed germination of Tillandsia recurvata through aqueous and organic bark extracts, (2) to determine whether germination of T. recurvata would differ among the hosts with low epiphyte abundance and a host with high epiphyte abundance (Bursera copallifera) and (3) to relate the chemical composition of organic bark extracts with inhibition of T. recurvata seed germination. Hexanic and dichloromethanic extracts were partially chemically characterized. Total phenolics and flavonoids concentrations of methanolic extracts were analysed. Aqueous and organic bark extracts from hosts with few epiphytes inhibited T. recurvata seed germination. Aqueous and dichloromethanic extracts of B. copallifera inhibited slightly the germination of T. recurvata. There was a positive correlation between concentration of flavonoids and inhibition of seed germination. Results suggest that a combination of compounds may be responsible for affecting the germination of T. recurvata. This study demonstrates the chemical effect of aqueous and organic bark extracts from hosts on germination of an epiphytic bromeliad.

According to the Food and Agriculture Organization of the United Nations, the world population will reach nine billion people in 2050, of which 75% will live in urban settlements. One of the biggest challenges will be meeting the demand for food, as farmland is being lost to climate change, water scarcity, soil pollution, among other factors. In this context, hydroponics, an agricultural method that dispenses with soil, provides a viable alternative to address this problem. Although hydroponics has proven its effectiveness on a large scale, there are still challenges in implementing this technique on a small scale, specifically in urban and suburban settings. Also, in rural communities, where the availability of suitable technologies is scarce. Paradigms such as the Internet of Things and Industry 4.0, promote Precision Agriculture on a small scale, allowing the control of variables such as pH, electrical conductivity, temperature, among others, resulting in higher production and resource savings.

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Ursolic acid (1) and a new flavanone, 5-O-(6-rhamnosylglucoside)-7-hydroxy-4'-methoxyflavanone (2), were isolated from the leaves of Salvia elegans Vahl. These natural products displayed antidepressant activity in mice as determined by means of a forced swimming test (FST) evaluation. Structural elucidation was carried out by chemical derivatization (acetylation) and spectroscopic analyses, such as 1 H-and 13 C-NMR and two-dimensional (2-D) COSY, heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple-bond correlation (HMBC) spectroscopy experiments.

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Ten Hyptis suaveolens hairy root lines were established by infecting nodal explants with K599+pGus-GFP+ and ATCC15834+pTDT strains from Agrobacterium rhizogenes. Genetic transformation was confirmed by epifluorescence and plagiotropic hairy root growth in absence of growth regulators. Cytotoxicity was determined using the sulforhodamine B method, and the production of podophyllotoxin (PTOX) was measured by high performance thin layer chromatography scanning. Through these methodologies, HsTD10 was identified as the hairy root line with the highest cytotoxicity and PTOX production, which was corroborated by liquid chromatography-mass spectrometry and micrOTOF-Q II. A suspension culture of HsTD10 was established in which PTOX and carbohydrate consumption during growth kinetics were quantified by high-performance liquid chromatography. Procedures to increase the production and retrieval of PTOX in the HsTD10 line included selection of culture medium, addition of thiamine, and modification of the PTOX extraction method. The best combination of these variables was MS medium at 75% of its components with the addition of 2 mg L-1 of thiamine, extraction with methanol-dichloromethane, and sonication at 40 ± 5°C. During kinetics, growth-associated PTOX accumulation was observed. The specific growth rate (μ) was 0.11 d-1. The highest concentration of PTOX obtained with HsTD10 (5.6 mg g-1 DW) was 100 times higher than that reported for roots of wild plants and 56 times higher than that for in vitro nontransformed roots of H. suaveolens.

Castilleja tenuiflora is a medicinal plant that grows in pine-oak woods primarily in southern and central Mexico. It is highly valued for its medicinal properties, which have been attributed to aucubin-like iridoids. In the present study, we developed an efficient protocol for in vitro shoot proliferation and ex vitro rooting of C. tenuiflora. Using a colorimetric method, we determined total iridoid contents of various different tissues of propagated plants. The shoots were induced from nodal explants cultured on Murashige and Skoog (MS) (1962) medium supplemented with indole-3-butyric acid (IBA) (0 and 0.5 lM) and different concentrations of thidiazuron (TDZ), 6-benzyladenine (BA), or kinetin (KIN) (0-20 lM). Of the cytokinins tested, KIN was more effective for shoot induction than TDZ or BA, and the highest shoot proliferation rate was achieved with 5 lM KIN (4 shoots per explant). Plantlets were rooted on MS medium, nutrient solution, or potting mix, alone or in combination with auxins. The best responses (100% rooting efficiency) were obtained by dipping shoots in half-strength MS medium containing 7.5 lM IBA before transfer to potting mix. On average, each shoot formed 9 roots of 39.3 ± 3.8 mm in length after 21 days. These roots appeared to be more functional than those that developed in nutrient solution, and were associated with a high survival rate (95%) during acclimatization and cultivation in a greenhouse, where flowering occurred after 4 months. Propagated plants accumulated iridoids, thus representing a potential source of pharmacologically useful compounds.