The effect was studied of sunlight and far‐red (FR) light during seed development, on seed quality and germination of Sicyos deppei G. Don. Seeds exposed to FR during development were lighter in colour and their weight, size and water content were significantly lower. Less than 10% of non‐scarified freshly harvested seeds germinated. Scarified, freshly harvested seeds developed under sunlight had a partially negative photoblastic response; both red (R) and FR light inhibited germination. The highest and fastest germination occurred in darkness, probably due to the effect of the high photon flux densities on the phytochrome during seed development. Scarified seeds ripened under FR light, germinated well in FR light and in darkness, but R light inhibited germination. After 6 months of storage, the permeability of S. deppei seeds increased, the partially negative photoblastic response was lost and germination of scarified seeds increased. Specifically, in seeds developed under FR, germination in darkness was faster than for the other light treatments, but slow in darkness for seeds developed under sunlight. The physiological and morphological heteroblastic responses in S. deppei probably extend its seed germination and seedling recruitment periods.

Argentatin B has been shown to inhibit the growth of colon HCT-15, and prostate PC-3 cancer cells. However, the mechanism by which argentatin B inhibits cell proliferation is still unknown. We aimed to investigate the mechanism by which argentatin B inhibits cell proliferation. The cell cycle was studied by flow cytometry. Apoptosis was evaluated by Annexin-V-Fluos, and Hoechst 33342 dye staining. Cell senescence was evaluated by proliferation tests, and staining for SA-β-galactosidase. Senescence-related proteins (PCNA, p21, and p27) were analyzed by Western blotting. Potential toxicity of argentatin B was evaluated in CD-1 mice. Its effect on tumor growth was tested in a HCT-15 and PC-3 xenograft model. Argentatin B induced an increment of cells in sub G1, but did not produce apoptosis. Proliferation of both cell lines was inhibited by argentatin B. Forty-three percent HCT-15, and 66% PC-3 cells showed positive SA-β-galactosidase staining. The expression of PCNA was decreased, p21 expression was increased in both cell lines, but p27 expression increased only in PC-3 cells after treatment. Administration of argentatin B to healthy mice did not produce treatment-associated pathologies. However, it restricted the growth of HCT-15 and PC-3 tumors. These results indicate that treatment with argentatin B induces cell senescence.

Annonaceous acetogenins (ACGs) are molecules with carbon numbers C35-C37, usually with tetrahydrofuran and tetrahydropyran rings and one terminal γ-lactone (usually α,β-unsaturated), in a large aliphatic chain that is varyingly hydroxylated, acetoxylated or ketonized. ACGs have ecological functions as insecticides and are pharmacologically promising due to their cytotoxic and antitumoral properties. They are found in the seeds, leaves, roots, flowers and fruits of annonaceous plants and can be detected during isolation via thin-layer chromatography using Kedde's reagent, which reacts with the unsaturated lactone. This chapter describes the location in situ of ACGs in fresh sections of annonaceous seeds using Kedde's reagent.The acetogenins are located in the idioblasts, in the endosperm and in the embryonic axis during differentiation. This method can aid in the detection of ACGs with a terminal unsaturated γ-lactone in organs and tissues.

Acetogenins (ACGs) are bioactive compounds with cytotoxic properties in different cell lines. They are antitumoural, antiparasitic, antimalarial, insecticidal, antimicrobial, anti-fungal and antibacterial. These secondary metabolites function in plant defence and are found in specific organelles and specific cells, thereby preventing toxicity to the plant itself and permitting site-specific defence. The aim of this work was to histochemically determine the in situ localisation of ACGs in the endosperm of Annona macroprophyllata seeds using Kedde’s reagent. Additionally, the co-localisation of ACGs with other storage molecules was analysed. The seeds were analysed after 6 and 10 days of imbibition, when 1 or 2 cm of the radicle had emerged and metabolism was fully established. The seeds were then transversally cut in half at the midline and processed using different histological and histochemical techniques. Positive reactions with Kedde’s reagent were only observed in fresh, unfixed sections that were preserved in water, and staining was found only in the large cells (the idioblasts) at the periphery of the endosperm. The ACGs’ positive reaction with Sudan III corroborated their lipid nature. Paraffin sections stained with Naphthol Blue Black showed reactions in the endosperm parenchyma cells and stained the proteoplasts blue, indicating that they might correspond to storage sites for albumin-like proteins. Lugol’s iodine, which is similar in chemical composition to Wagner’s reagent, caused a golden brown reaction product in the cytoplasm of the idioblasts, which may indicate the presence of alkaloids.Based on these results, we propose that Kedde’s reagent is an appropriate histochemical stain for detecting ACGs in situ in idioblasts and that idioblasts store ACGs and probably alkaloids. ACGs that are located in idioblasts found in restricted, peripheral areas of the endosperm could serve as a barrier that protects the seeds against insects and pathogen attack.

Resumen. Se determinaron las características y calidad de las semi llas de Ch. pentadactylon, de dos localidades en Guerrero y Oaxaca, su germinación bajo los factores de escarificación, temperatura y luz y la viabilidad d e semillas de Gu errero almacenadas 6 meses a 5º C. Las semillas resultaron ortodoxas y con latencia por cubie rta sem in al impermeable. Las semillas de Guerrero presentaron mayor peso, longitud y contenido de humedad respecto a las de Oaxaca , pero las semi llas escarificadas de Oaxaca germinaron con mayor porcen taje. La germinación de sem illas escarificadas de ambos siti os fue mejor en temperatura flu ctuante y se inhibió bajo rojo lej ano . No hu bo diferencias en la capacidad germinativa bajo obscuridad, luz roja y b lanca. Una fracción d e la población de semi llas podría permanecer latente en bajas relaciones de rojo:rojo lej a no transmitidas por la hojarasca. Las diferencias entre poblaciones pudieron deberse a un efecto materno inducido por temperatura y la humedad de sus localidad es. Palabras clave: germinación, almacenamiento, fotoblastismo, semi llas ortodoxas, temperatura de germ in ación. Abstract. Seed quality and seed germination with scarificatio n and n on scarification and variab le temperature and light were determined in Ch. pentadactylon seeds form two pladces of Guerrero and Oaxaca. Also seed viability was determined in seeds from Guerrero stored 6 months at 5º C. Seeds showed to be orthodox a nd dorman t dueto an impervious seed coat. The seeds from Guerrero had higher weight, length and water content tha n those from Oaxaca, however the scarified seeds from Oaxaca reached a higher germination percentages. Germination of scarified seeds of the two popu lations was enhanced by alternated temperatures and in hibite d by far red light. Germ in ation under darkness, red light and wh ite light did not differ significan tly. In soil sorne seeds could be dormant under a low ratio red:far red light transmitted by litter. The differences between the two populations might be due to a maternal effect induced by weather conditions in their geographic localiti es.