Introduction: In Mexico, there is a lack of information on morphological, physical and chemical characteristics of acorns of Quercus, which makes it difficult to make decisions on the use that can be made to the fruits.

Objectives: To identify the morphological, physical and chemical characteristics of Quercus rugosa Née, Q. sideroxyla Humb. & Bonpl. and Q. deserticola Trel. acorns.

Materials and methods: From each species, 10 trees were selected and 30 acorns per tree were collected. Mature acorns were characterized morphologically (polar and equatorial diameter, shell weight and total weight) and in physicochemical characterization (moisture, dry matter, ash, crude fiber and protein, ethereal extract and tannins) green and mature acorns were used. Differences among species and among maturity stages were determined with an analysis of variance (P ≤ 0.05) and subsequent Tukey’s test.

Results and discussion: Morphology varied among species and among trees of the same species (P < 0.05); Q. deserticola had the largest acorn size (15.69 mm) and weight (1.94 g), and Q. sideroxyla produced the smallest acorns. Maturity stage and species significantly (P < 0.05) influenced chemical composition; mature acorns had higher content of ethereal extract (8.88 %) and protein (8.40 %). Pearson’s correlation indicated that acorn weight was strongly associated with crown diameter and diameter at breast height.

Conclusion: Significant differences were found in morphology and chemical composition of acorns of each species, although they inhabit sites with similar characteristics.

Introduction: Nutritional potential of wild edible mushrooms and loss of their nutraceutical properties during cooking have been little examined.

Objective: To evaluate the nutritional content and effect of heat treatment on nutraceutical properties in the wild species Lactarius indigo (Schwein.) Fr. (blue mushroom), Ramaria flava (Schaeff.) Quél. (changle) and Hypomyces lactifluorum (Schwein.) Tul. & C. Tul. (lobster mushroom), collected in temperate pine and oak forests of the Sierra Norte de Puebla.

Materials and methods: The mushrooms were collected in the company of “traditional mushroom collectors”. Proximal composition was quantified according to AOAC methods. The effect of heat treatment was evaluated at 50 and 92 °C at 10 to 60 min intervals. Total phenolic content was determined by the Folin-Ciocalteu method and antioxidant capacity by ABTS and FRAP assays.

Results and discussion: R. flava and L. indigo had the highest percentages of protein (24.02 %) and crude fiber (14.64 %) on dry basis, respectively. R. flava had the highest phenolic content (4.40 mg gallic acid equivalents per gram dry basis) and the highest antioxidant capacity (23.65 µmol trolox equivalents per gram dry basis). Degradation kinetics of the compounds was first order; H. lactifluorum and R. flava had the highest loss of phenols and antioxidants, respectively.

Conclusion: The mushrooms studied showed high nutritional value and retained more than 50 % of their antioxidant properties after thermal processing.

Introduction: Standing leaf litter represent an essential source of organic matter and nutrients to dynamize biogeochemical processes at the ecosystem level.

Objectives: To characterize the accumulation and decomposition of organic materials and flow of nutrients from standing litter in an urban dry tropical forest in a successional stage, after 10 years of abandonment of agricultural activities, and to determine the potential use of three species in future active restoration activities.

Materials and methods: Standing litter samples were collected from a forest fragment in Santa Marta, Colombia, separating leaves, reproductive material, woody material and other residues. Additionally, leaves of three species of interest for ecological restoration (Albizia niopoides Spruce ex Benth., Cordia alba [Jacq.] Roem. & Schult. and Machaerium milleflorum Dugand G. A.) were separated and Ca, Mg, K, N and P concentrations were determined.

Results and discussion: Total standing litter was 8.3 Mg∙ha-1 with a mean residence time of two years. The leaves represented 20% of the standing litter, with a mean residence time of 1.4 years. Based on the decomposition constant (kj = 0.73) and the rate of leaf litterfall, organic matter returns accounted for 3.4 Mg∙ha-1∙year-1. Leaf decomposition rate decreased in the following order C. alba > M. milleflorum > A. niopoides. P represented the greatest limitation with low release rates (0.1 to 1.2 kg∙ha-1∙year-1).

Conclusions: The passive restoration strategy allowed reactivation of biogeochemical cycle via fine leaf litter. Cordia alba showed potential for inclusion in restoration activities, with lower values for leaf N/P ratio, and higher rates for leaf litterfall, litter decomposition and nutrient release.

Introduction: Mexican oregano (Lippia graveolens Kunth) leaves are marketed for use in food and for essential oil extraction. Phenolic compounds with antioxidant properties can be obtained from the residues (leaves without oil and stems) under appropriate extraction conditions.

Objective: To evaluate the effect of extraction solvent and mass/volume ratio on phenolic compounds concentration and their antioxidant capacity in oregano residues.

Materials and methods: Residual leaf (without oil) and stems of oregano were used to obtain extracts with 30, 50 and 80 % aqueous ethanol (ET30, ET50, ET80, respectively) and solvent mass/ volume ratios (1:10, 1:20 and 1:30). Yield in solids, total phenols concentration and flavonoids, and antioxidant capacity were evaluated in the extracts. Similarity analysis between extracts was performed by HPLC-DAD and the main phenols were identified by UPLC-MS.

Results and discussion: Extract yields, phenol concentrations and flavonoids and antioxidant capacity for leaves were higher than for stems. The maximum concentration of phenols was obtained with ET80 and 1:30 ratio, which indicates better dissolution in ethanol than in water. The extracts ET50 and ET80 had chromatographic similarity of phenols in both residues; naringenin, taxifolin, eriodictyol, caffeic acid and luteolin were the major compounds.

Conclusion: Ethanol-water concentrations and mass/solvent ratios are feasible for obtaining flavonoid and non-flavonoid phenolic compounds with antioxidant capacity from oil-free leaves and stems of oregano.

Introduction: Tropical forests represent complex and dynamic ecosystems that cover extensive areas, hence the importance of determining biomass content and representing spatial variability.

Objective: Estimating and mapping aboveground biomass and its associated uncertainty for medium-stature semi-evergreen (SMSP) and semi-deciduous (SMSC) tropical forests of the Yucatan Peninsula.

Materials and methods: Aboveground biomass was estimated as a function of explanatory variables taken from Landsat images and climatic variables, using the random Forest algorithm. Aboveground biomass was mapped from previous biomass estimates for stripes of the territory with the presence of LiDAR (Light Detection And Ranging) and field data. Uncertainty at the pixel level was estimated as the coefficient of variation.

Results and discussion: A combination of climatic and spectral variables showed acceptable capacity to estimate biomass in the medium-stature semi-evergreen and semi-deciduous tropical forest with an explained variance of 50 % and RMSE (root mean squared error) of 34.2 Mg·ha -1 and 26.2 Mg·ha -1 , respectively, prevailing climate variables. SMSP biomass ranged from 4.0 to 185.7 Mg·ha -1 and SMSC ranged from 11.7 to 117 Mg·ha -1 . The lowest values of uncertainty were recorded for the medium-stature semi-evergreen tropical forest, being higher in areas with lower amounts of aboveground biomass.

Conclusion: Aboveground biomass was estimated and mapped by the combined use of auxiliary variables with an acceptable accuracy, against uncertainty of predictions, which represents an opportunity for future improvement.

Introduction: Determining growth and yield potential of a forest species is a requirement for management planning. One of the important forest species for the Tumaco region is Carapa guianensis (Aubl.), due to its high timber potential.

Objective: To evaluate the growth potential of the native species C. guianensis (andiroba or tangare) in Tumaco, Colombia.

Materials and methods: Permanent plots were established in which tree measurement variables were recorded for 90 even-aged individuals for 60 months. Mean annual increments were estimated and an allometric equation was fitted to estimate height from the diameter at 1.30 m (DBH).

Results and discussion: At 60 months of age, C. guianensis trees showed survival between 70 and 87 %. Mean annual increase in diameter and height was 2.9 cm∙yr -1 and 2.3 cm∙yr -1 , respectively. By fitting linear and nonlinear models, we determine the following allometric equation . The species showed rapid diameter growth compared to other regions where it can take more than 50 years to reach a minimum usable diameter of 40 cm.

Conclusion: Based on mean annual growth increments, and under the agroecological conditions of the region, C. guianensis is expected to reach maturity at an early age (before 50 years of age).

Introduction: Prosopis laevigata (Humb. & Bonpl. ex Willd.) M. C. Johnst, P. glandulosa Torr., Vachellia schaffneri (S. Watson) Seigler & Eibinger, V. pennatula (S. Watson) Seigler & Eibinger and V. farnesiana (L.) Wight & Arn. are characteristic species of semi-arid areas. Their seeds show physical dormancy and are naturally scarified by chewing, trampling, digestive tract of fauna, fire, or washing away during rains.

Objective: To describe the morphology of the seed coat of three species of Vachellia and two of Prosopis, and to assess the chemical, mechanical and thermal scarification of seeds.

Materials and methods: Chemical (HCl for 30, 120, 150 and 180 min), thermal (80, 100, 120 and 140 °C for 3 min) and mechanical (sanding) scarification were applied. Resistance to breaking by compression was measured. The experimental design was randomized complete blocks per species.

Results and discussion: Seeds showed a layer of lignified and impermeable macrosclereids, but the aleurone layer could not be detected. Sanding allowed germination from 81.2 to 100 %. Chemical and thermal treatments showed no differences, only in the case of P. laevigata, chemical scarification for 180 min caused higher germination (72.5 %) compared to the control. Vachellia schaffneri seeds were more resistant to compression (669 N) and had more intense dormancy (0.83), while P. glandulosa had the lowest dormancy (0.42).

Conclusions: Mechanical scarification was the best method to eliminate dormancy in Vachellia and Prosopis seeds.

Introduction: The list of threatened species is enhancing and needs to be revised by integrating plant tissue culture tools with conventional techniques that support the appropriate management of these species.

Objective: To assess the effects of the growth regulators for the induction of somatic embryos from mature seeds, shoots, and compact green callus of Echinocactus parryi Engelm. and the histological analysis of the embryogenic structures.

Materials and methods: A completely randomized design was utilized to evaluate three types of explants (apical, medium, and basal) cultured on basal Murashige & Skoog media (MS) with different growth regulators concentrations (2, 4-D [dichlorophenoxy acetic acid], BAP [6-benzylaminopurine] and kinetin, at four levels: 0.5, 1, 1.5, and 2 mg∙L -1 ). Histological analysis of the embryogenic structures was performed.

Results and discussion: The 2, 4-D induced both embryogenic and organogenic callus from seeds and shoot explants. The globular stage did not evolve to their maturity, presumably because of 2, 4-D accumulation. The compact callus explants were the more efficient to induce 19.2 somatic embryos per explant when they were cultured in the medium with 0.5 mg∙L -1 kinetin. However, the latest phases did not germinate, probably due to abnormalities generated by genetic and epigenetic changes in the DNA that can cause abnormal somatic embryos. The histology image demonstrated that the globular and torpedo structures were visible under a microscope showing stained nucleus and numerous starch grains.

Conclusions: E. parryi is a species that can produce a high number of embryogenic structures, which represents a great potential to grow massive plants.

Introduction: Metal pollution is one of the major environmental problems. Some metals are toxic at very low concentrations, bioaccumulate and do not decompose to non-toxic forms.

Objective: To isolate a strain of microscopic fungus in a site contaminated with toxic metals and to evaluate the tolerance to these substances.

Materials and methods: Fungi were isolated from the soil of an abandoned lead mine. Tolerance index of fungi to cadmium, mercury and lead was evaluated individually at concentrations of 50, 100, 250, 350 and 500 ppm; in addition, a multimetal system (mixture) with cadmium, chromium, mercury and lead was evaluated at 4, 8, 16, 64, 80, 120, 200 and 400 ppm. The minimum inhibitory concentration (MIC) was also determined.

Results and discussion: The isolated fungi were identified as Aspergillus terreus, which showed high tolerance indices for lead (0.9) at all concentrations tested and indices of 0.8 at most mercury concentrations. Cadmium was the most toxic metal; tolerance indices of 0.56 and 0.2 were observed at 50 ppm and 100 ppm, respectively. High tolerance indices (0.9) were observed in the multimetal system up to 64 ppm. MIC was greater than 500 ppm with lead and mercury, less than 250 ppm with cadmium and greater than 400 ppm with the multimetal system.

Conclusion: A. terreus showed high tolerance to lead at all concentrations tested. The level of tolerance is influenced by the type of metal.

Introduction: Ochroma pyramidale (Cav. ex Lam.) Urb. is a species with high potential for use in commercial reforestation. Knowledge of nutrient requirements in nursery increases the chances of success in the field by generating plants with adequate morphological and physiological characteristics.

Objective: To identify the key nutrients for O. pyramidale growth in nursery and to characterize the associated visual symptoms of deficiency.

Materials and methods: The design was completely randomized with 10 treatments: one treatment without fertilization, one treatment with complete fertilization (CF), and eight resulting from the CF treatment with suppression of N, P, K, Ca, Mg, S, B and cationic microelements (Mn, Fe, Cu and Zn). The effect of each treatment was determined by height, root collar diameter, aboveground dry biomass, root dry biomass, leaf area and relative growth rate. An analysis of variance and separation of means was performed using the Tukey's test (P < 0.05).

Results and discussion: Nutrient suppression had significant effects (P < 0.05) on growth after six months in nursery. P was the most limiting element, followed by N. The other treatments showed no significant differences compared to the FC treatment. N suppression caused yellowing, and lack of P caused necrosis with subsequent death and detachment in leaves. B suppression showed no clear deficiency symptoms.

Conclusion: O. pyramidale showed high nutrient uptake efficiency. Only N and P strongly limited its development, which represent the key nutrients for the species.