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Introduction: Communities dominated in the canopy by pinyon pines harbor species richness and have complex physiognomy because they form an ecotone between arid and temperate zones. Objectives: To describe the floristic attributes that distinguish four communities dominated by pinyon pines; define units based on floristic composition and structure; and determine the influence of edaphic factors. Materials and methods: The flora of four communities in the state of Zacatecas was recorded. The arboreal and shrub vegetation was analyzed quantitatively using the point-centered quarter technique. Semi-realistic physiognomic profiles were made for each site. The groups resulting from cluster analysis were ordered with edaphic factors through a canonical correspondence analysis. Results and discussion: Floristic richness was 244 species; each community contains between 60 and 80 species. Structurally, three physiognomic variants were recorded: forests dominated by Pinus cembroides Zucc.; association of P. cembroides - P. cembroides var. bicolor Little; and forest dominated by P. maximartinezii Rzed. The pH, electrical conductivity and soil texture have a great influence on the structure and plant composition of the communities. The P. cembroides - P. cembroides var. bicolor association and its accompanying species develop in nutrient-poor soils, while P. maximartinezii forests prefer shallow soils. Conclusion: The floristic similarity among communities was low. Each community must be managed differently, meeting the particular requirements of the species that develop there.

Most terrestrial plants form specialized mycorrhizal structures with symbiotic fungi. These improve the establishment and development of the associated plants, through the modification of the root system, by facilitating greater uptake of water and nutrients from the environment, especially when resources are scarce. An additional biotic factor is the use of mycorrhizal helper bacteria, whose beneficial functions increase the benefits of mycorrhizae. For this reason, its potential use as a biotechnological tool in agricultural and forestry applications has been actively studied, particularly for future management practices and recovery of forest populations. Pinus maximartinezii Rzed. is an endemic species of Mexico of economic and ecological importance, considered in danger of extinction, due to its restricted distribution and low population density. Therefore, it is considered of great importance to increase the knowledge of important interactions such as ectomycorrhizal symbiosis and associated microorganisms for the development of management strategies in order to conserve and increase their population. In the present work, the abundance and richness of EcM morphotypes associated with P. maximartinezii were determined in their natural distribution areas. The morphological characterization of the EcM morphotypes collected was carried out. Additionally, the effect of the inoculation of four sources of ectomycorrhizal inoculum (Laccaria proxima, Helvella lacunosa, native soil and burned native soil) and the co-inoculation of the rhizobacteria Azospirillum brasilense on the growth, nutritional content and percentage of mycorrhization of the trees was evaluated. In total, 18 EcM morphotypes associated with adult P. maximartinezii trees were recorded during two sampling seasons of which three (MZac2, MZac5 and MZac8) represented approximately 90% of the total number of tips of ectomycorrhizal apices. According to the set of distinctive morphoanatomical features, the MZac5 morphotype was reliably identified as Cenococcum geophilum. This morphotype was the most abundant, given that it was recorded in 42.5% of the total live ectomycorrhizal roots (18.3 and 24.2% for dry and rainy seasons respectively). A synergistic effect of the fungus (L. proxima and H. lacunosa) and the bacterium (A. brasilense) was observed in terms of biomass, diameter and height, although in some of these the value was similar or higher when the HEcM were implemented without the bacteria. The plants inoculated with H. lacunosa and H. lacunosa + A. brasilense showed better physiological quality than the plants non inoculated or those inoculated exclusively with the bacteria. In the same way, these co-inoculated plants presented higher contents of macronutrients and micronutrients, although the greater nutrimental mobilization to aerial part (P, K, Fe, Na and Zn) was observed in the plants inoculated with L. proxima. The mycorrhizal colonization varied from 68.69 to 92.73%, registering the highest percentage in plants inoculated with native soil + A. brasilense. A total of eight EcM morphotypes associated with young blue pine plants in which native soil was inoculated were recorded. Therefore, it is concluded that the individual inoculation of EcM and dual fungi of bacteria such as A. brasilense can improve the physiological and nutritional quality of plants of P. maximartinezii, since their implementation and knowledge of native HEMCs represent an enormous biotechnological potential in the production of plants of said forest species in danger of extinction., Thesis. M. Sc. in Innovation in Natural Resources Management, Colegio de Postgraduados, Campus San Luis Potosí, 2019

Pinus maximartinezii is a rare, endemic, threatened species known from a single small population in the state of Zacatecas, Mexico. Among the pine species that produce edible nuts, it produces one of the largest and most nutritious seeds. The seeds of P. maximartinezii have historically been used for human consumption. The cones are harvested directly from the trees, and the seeds are sold illegally in local, national and international markets. However, the effects of seed extraction must be thoroughly evaluated to determine the potential impacts on population stability. To assess the impact of different rates of seed harvesting on the demography of this species, a 2-yr study of population dynamics was conducted in three 0.1-ha plots. A 9 × 9 size-structured matrix model was used to simulate changes in population growth over time in conjunction with increasing stepwise reductions in fecundity. The population growth rate (λ) of P. maximartinezii was 1.1175, with a 95% confidence interval (CI) from 1.1008 to 1.1321, and it was relatively insensitive to changes in fecundity and growth. Under a seed extraction intensity of 99%, λ decreased to 1.0241, with a CI from 1.0177 to 1.0361. Elasticity analysis was then performed to identify the combined effects of proportional changes in fecundities and the largest stasis elements on λ. The results suggest that a sound conservation strategy should focus on improving the survival of juveniles and adults during their first reproductive events and on the largest adults, as well as on protecting the habitat of this threatened endemic species.

Pinus maximartinezii (Rzedowsky) and P. pinceana (Gordon), two endemic species of Pinus from Mexico, were successfully regenerated in vitro by organogenesis starting from mature embryos. In both species, 100% of the explants produced adventitious buds after an 18-day induction period on media containing 6-benzylaminopurine (BA) and a subsequent 8 weeks of incubation on growth regulator-free media. The most successful treatment (13.3 µM BA) resulted in an average of 14.6 and 25.9 buds per explant in P. maximartinezii and P. pinceana, respectively. Rooting was achieved by auxin pulses or by Agrobacterium rhizogenes inoculation. In the first case, roots formed on 13% and 7% of the auxin-treated shoots of P. maximartinezii and P. pinceana, respectively. In the second case, A. rhizogenes induced root formation on 60% and 67% of the inoculated shoots from P. maximartinezii and P. pinceana, respectively. The presence of the foreign genes transferred by A. rhizogenes into these roots was demonstrated by histochemical staining for β-glucuronidase activity, the polymerase chain reaction and Southern blot analysis.

Pinus pinceana) has a restricted and fragmented range, trees are widely scattered within populations, and reproduction is limited. Nevertheless, genetic diversity was high; based on 27 isozyme loci in 18 enzyme systems, unbiased expected heterozygosity averaged 0.174. Differentiation also was high (FST 5 0.152), reflecting isolation between southern, central, and northern fragments of the range. Among populations in the northern fragment, FST was only 0.056, and the number of migrants per generation (Nm) was 4.21, which should preclude fixation. Nm between central and southern populations or between them and populations in the northern fragment was lower, 0.99‐1.66, indicating a degree of genetic isolation. Multilocus outcrossing rates ( tm) ranged from 0.836 in the south to 0.897 in the north. Therefore, selfing is low but statistically significant. The equilibrium inbreeding coefficient

Pinus maximartinezii Rzedowski is a rare pinyon pine known to occur naturally on only one site on the Cerro de Pinones, in the Sierra de Morones, near the town ofJuchipila, in southern Zacatecas, Mexico(21° 21' N, 103° 13' W). P. maximartinezii has been considered one ofthe most rare and endangered ofall pine species(Farjon et a1.1993,Perry 1991, Dvorak et al. 2000). The entire distribution of the species is reported as approximately 400-1000 hectares and the population size about 2000 to 10,000 mature individuals (Donahue and Mar-Lopez 1995, Arteaga et al. 2000, Dvorak et al. 2000). Although trees will grow from 1450-m to 2550-m elevation, most of the population at Cerrode Pinones occurs in a band from 2100 to 2300 m. This species has attracted much attention in recent years due to its limited natural distribution, endangered status, hugeconesand edible nuts, and its potential as an ornamental.

Seeds of blue pine, Pinus maximartinezii, have long been used for human consumption. However, no chemical analysis of its nutrient components has been carried out. In this paper, the content of kernel proteins, amino acids and fatty acids is reported and compared with some pinyon pines and other nut species. Proximate analysis showed that blue pine contains about 31% crude protein, 66% defatted protein, 42% crude fat, 2% carbohydrates, 9% crude fibre, 4% ash, and 4% moisture. It contains 18 different amino acids, including all the essential ones, and six different fatty acids; of these about 84% are unsaturated. Nuts of blue pine are of outstanding dietary value and appear to be a promising resource, but the impact of seed harvesting size on the population stability needs to be thoroughly evaluated in order to insure its sustainable use. A conservation strategy for P. maximartinezii, should urgently focus on protecting the specific habitat where this endemic rarity occurs. Las semillas del pino azul, Pinus maximartinezii, han sido usadas desde hace mucho tiempo para consumo humano. Sin embargo, ningún análisis químico de sus componentes nutritivos ha sido llevado a cabo. En este artículo se reporta el contenido de proteína, amino ácidos y ácidos grasos de su nuez y se le compara con algunas especies de pinos piñoneros y otras nueces. El análisis proximal mostró que el pino azul contiene 31% de proteína cruda, 66% de proteína desgrasada, 42% de grasa cruda, 2% de carbohidratos, 9% de fibra cruda, 4% de cenizas y 4% de humedad. Contiene 18 amino ácidos distintos, incluyendo a todos los esenciales, y seis ácidos grasos diferentes, 84% de ellos insaturados. La nuez del pino azul es de valor dietético sobresaliente y parece ser un recurso promisorio. Sin embargo, el impacto de la magnitud de la cosecha de semillas sobre la estabilidad poblacional necesita ser cuidadosamente evaluada para asegurar su uso sostenido. Una estrategia de conservación para P. maximartinezii debe concentrarse en la protección del hábitat donde ésta rareza endémica ocurre. As sementes do pinho azul, Pinus maximartinezii, têm sido usadas desde muito tempo para consumo humano. Porém, não foi feita nenhuma análise química de seus componentes nutritivos. Neste artigo se reporta o conteúdo de proteína, amido ácidos e ácidos grassos de sua castanha e é comparado com algumas espécies de pinhos, pinheiros e outras castanhas. A análise proximal mostrou que o pinho azul contém 31% de proteína crua, 66% de proteína sem gordura, 42% de gordura crua, 2% de carboidratos, 9% de fibra crua, 4% de cinzas e 4% de umidade. Contém 18 amido ácidos distintos, incluindo a todos os essenciais, e seis ácidos grassos diferentes, 84% deles insaturados. A castanha do pinho azul é de valor dietético sobressalente e parece ser um recurso promissório. Porém, o impacto do tamanho da colheita de sementes sobre a estabilidade populacional necessita ser cuidadosamente avaliada para assegurar seu uso sustentado. Uma estratégia de conservação para P. maximartinezii deve concentrar-se na proteção do habitat onde esta rareza endêmica ocorre.

Maxipinon (Pinus maximartinezii Rzedowski), which is confined to a single population of approximately 2000 to 2500 mature trees, covers about 400 ha in southern Zacatecas, Mexico. Genetic diversity measured by expected heterozygosity was 0.122, which is moderate for pines. However, percentage polymorphic loci was low, 30.3%. The fixation index (F) of 0.081 indicated only slight heterozygote deficiency. Mating system analysis indicated a significant but low level of selling; the multilocus outcrossing rate, t,,, was 0.816. The mean of single locus estimates, tS, was smaller (0.761), perhaps suggesting mating among relatives, although the difference between t,.. and ts was not sta- tistically significant. The most striking features of maxipifion's genetic structure were that no polymorphic locus had more than two alleles and most alleles at polymorphic loci were at intermediate frequencies. This is in contrast to other pines, which often have three to five or more alleles at some loci and in which the distribution of allele frequencies is U-shaped, most alleles being present at frequencies less than 10% or greater than 90%. A population with only two alleles per locus and at intermediate frequencies could occur if the population had been reduced to an extreme bottleneck and then expanded rapidly before random drift modified allele frequencies. A novel origin from a hybridization event would also explain the results. Significant gametic disequilibrium was detected at several pairs of loci in both maternal and paternal gametes. The presence of disequilibrium is in agreement with an origin from an extreme bottleneck, perhaps even a single seed. Furthermore, it demands that the event be relatively recent. The number of generations, as calculated from the observed mean disequilibrium, suggested that maxipinion derived from an extreme bottleneck four to five generations ago, which is less than 1000 years in this species.

The response of Pinus maximartinezii Rzedowski to photochemical oxidant air pollution was examined using 100 trees, during a 1 year cycle, at Vivero de Coyoacan, a tree nursery located in the south central part of Mexico City, where exposure to polluted air masses has been continuous. The tree response assessment method was based upon documented symptoms of pollutant injury on the foliage. The results showed a homogeneous pattern of health and vigor and only medium sensitivity (based on foliar injury) to photochemical oxidants, although the trees maintained their needles through a three and not the normal 5 year period as at its geographic location of origin (different habitat or environment). Nevertheless, these data suggest that this species of pine could be proposed as good planting material for reforestation in the urban metropolitan area of Mexico city.

Wood from 92 trees of Pinus culminicola, Pinus nelsonii, Pinus pinceana and Pinus maximartinezii from nine localities and oleoresin from several trees of Pinus nelsonii from one Iocality were analyzed for monoterpenes by gas liquid chromatography. Monoterpenes of Pinus nelsonii were composed mainly of α- and β-pinenes, while the main constituent of the monoterpenes of Pinus pinceana and Pinus maximartinezii was limonene, present in amounts of about 90 percent. The similarity in composition of the monoterpenes of Pinus pinceana and Pinus maximartinezii strongly supports the contention of Rzedowski [12] of the close evolutionary relation of the two pines. Pinus culminicola wood produced monoterpenes composed mainly of α-pinene, sabinene, terpinolene and limonene, with other monoterpenes occurring sporadically in sizeabie amounts. The variability between individual populations was relatively high, probably due to their long-time isolation by the intervening low-elevation barriers. Appreciable differences were found in compositions of monoterpenes from stem and from twigs of Pinus culrninicola.

ResumeLa formation ligneuse a Pin us maximartinezii s'etend de 1800 a 2300 m. Les plus vieux arbres, producteurs de cones, ont de 150 a 200 ans. Le pin se regenere vigoureusement dans les espaces verts.