The nature and kinetics of reactions in dry seeds determines how long the seeds survive. We used gas chromatography to assay volatile organic compounds (VOCs) emitted from seeds of three unrelated species as a means to non-invasively probe chemical changes during very dry, dry, and humid storage (seeds were dried to 5.5, 33, and 75% relative humidity at room temperature). VOCs emitted from seeds stored in humid conditions reflected fermentation-type reactions, with methanol and ethanol being predominant in Lactuca sativa and Carum carvi, and acetaldehyde and acetone being predominant in Eruca vesicaria. Dried C. carvi seeds continued to emit fermentation-type products, although at slower rates than the seeds stored in humid conditions. In contrast, drying caused a switch in VOC emission in L. sativa and E. vesicaria seeds towards higher emission of pentane and hexanal, molecules considered to be byproducts from the peroxidation of polyunsaturated fatty acids. Longevity correlated best with the rate of fermentation-type reactions and appeared unrelated to the rate of lipid peroxidation. Emission of VOCs decreased when seed species were mixed together, indicating that seeds adsorbed VOCs. Adsorption of VOCs did not appear to damage seeds, as longevity was not affected in seed mixtures. Collectively, the study shows similarity among species in the types of reactions that occur in dry seeds, but high diversity in the substrates, and hence the byproducts, of the reactions. Moreover, the study suggests that the most abundant VOCs arise from degradation of storage reserves within seed cells, and that these reactions and their byproducts are not, in themselves, damaging.

This work compared the quantification of soluble fibre in feeds using different chemical and in vitro approaches, and studied the potential interference between soluble fibre and mucin determinations. Six ingredients: sugar beet pulp (SBP), SBP pectins, insoluble SBP, wheat straw, sunflower hulls and lignocellulose, and seven rabbit diets, differing in soluble fibre content, were evaluated. In experiment 1, ingredients and diets were analyzed for total dietary fibre (TDF), insoluble dietary fibre (IDF), soluble dietary fibre (SDF), aNDFom (corrected for protein, aNDFom-cp) and 2-step pepsin/pancreatin in vitro DM indigestibility (corrected for ash and protein, ivDMi2). Soluble fibre was estimated by difference using three procedures: TDF–IDF (SDF_IDF), TDF–ivDMi2 (SDF_ivDMi2), and TDF–aNDFom-cp (SDF_aNDFom-cp). Soluble fibre determined directly (SDF) or by difference as SDF_ivDMi2 were not different (109 g/kg DM, on average). However, when it was calculated as SDF_aNDFom-cp the value was 40% higher (153 g/kg DM, P < 0.05), whereas SDF_IDF (124 g/kg DM) did not differ from any of the other methods. The correlation between the four methods was high (r ≥ 0.96; P ≤ 0.001; n = 13), but it decreased or even disappeared when SBP pectins and SBP were excluded and a lower and more narrow range of variation of soluble fibre was used. In experiment 2, the ivDMi2 using crucibles (reference method) were compared to those made using individual or collective ankom bags in order to simplify the determination of SDF_ivDMi2. The ivDMi2 was not different when using crucibles or individual or collective ankom bags. In experiment 3, the potential interference between soluble fibre and intestinal mucin determinations was studied using rabbit intestinal raw mucus, digesta and SBP pectins, lignocelluloses and a rabbit diet. An interference was observed between the determinations of soluble fibre and crude mucin, as contents of TDF and apparent crude mucin were high in SBP pectins (994 and 709 g/kg DM) and rabbit intestinal raw mucus (571 and 739 g/kg DM). After a pectinase treatment, the coefficient of apparent mucin recovery of SBP pectins was close to zero, whereas that of rabbit mucus was not modified. An estimation of the crude mucin carbohydrates retained in digesta TDF is proposed to correct TDF and soluble fibre digestibility. In conclusion, the values of soluble fibre depend on the methodology used. The contamination of crude mucin with soluble fibre is avoided using pectinase.

The aim of this paper is to examine the environmental effect of different chemical characteristics of Zinc (Zn) sources, assessing the transport, leaching and accumulation in the environment in sand, acidic (AS) and calcareous (CS) soils. Comparative short- and long-term studies applying ZnO sources [bulk, laboratory-synthesized and commercial nanoparticles (NP)], ZnSO₄, complexed Zn (Zn-lignosulfonate) and chelated Zn (Zn-diethylenetriamine-pentaacetate, Zn-hydroxy-ethylenediamine-tetraacetate and Zn-ethylenediamine-tetraacetate) were carried out. For all treatments and media, the medium- and long-term dissolution kinetic model was fitted to a logistic function. The applied Zn in the form of ZnO was mainly retained at the upper half (0–7.5 cm) of the columns and in very available form (ranging 40–61% of added Zn in AS and 29–31% in CS). Leached Zn reached values below 6% in AS and 3% in CS. The use of chelated Zn in both soils and complexed Zn, and ZnSO₄ in AS resulted in excessive leaching of Zn (around 70%). The amount of Zn available at the upper half of the column was less than 5%. In the CS, these fertilizers showed a higher aging than ZnO sources, negatively affecting its availability as a nutrient for crops. ZnO NP showed short- and medium-term dissolution kinetics that allow gradual nutrient release and high availability at the medium-term. These products provide an effective solution for plant nutrition while mitigating the environmental problems observed with more traditional sources related to leaching. Graphical Abstract

The effect of antioxidants applied in one step of a cryopreservation protocol by encapsulation–dehydration on recovery and genetic stability of mint shoot tips has been studied. Glutathione (0.16 or 0.24 mM), ascorbic acid (0.28 or 0.43 mM) and α-tocopherol (vitamin E) were added to the preculture medium (0.3 M sucrose). DNA was extracted from three different types of samples: leaves from shoots, callus at the base of shoots and callus. RAPD and AFLP markers were used to assess the genetic stability. The use of antioxidants did not improve recovery after cryopreservation. One of the genotypes, ‘MEN 198’, showed higher percentage of stable samples than the other one, ‘MEN 186’ (56 vs. 37 %; considering all treatments and types of explant). The use of vitamin E improved the percentage of stable samples with respect to control treatment (no antioxidant) in ‘MEN 186’. No differences in the percentages of stable samples were observed among cryopreserved and non-cryopreserved (treated similarly without immersion in liquid nitrogen) plant material. Recovered shoots of both genotypes showed higher stability (76–80 % stable samples) than callus samples (14–22 %).