RESUMENPinus pseudotrobus es una especie con aprovechamiento maderable, distribuida en un amplio gradiente altitudinal, de 1.600 a 3.250 m, lo que sugiere una varianza genética que puede ser aprovechada mediante la selección de árboles que provean semillas que generen plantas con altas tasas de crecimiento relativo. Por lo anterior, se evaluó la sobrevivencia y crecimiento inicial de Pinus pseudostrobus en vivero, con base en la variación de progenies de 38 árboles sobresalientes (procedencias) en rodales naturales de la Sierra Norte de Oaxaca, México. La siembra se realizó en febrero de 2013 en un vivero localizado en Ixtlán de Juárez, cercano a la región de colecta, a 2030 msnm y un clima templado. Además de evaluar la sobrevivencia de 54 a 166 días después de la siembra (dds), se estimaron cinco lecturas de altura de planta, diámetro basal de tallo y cuatro lecturas de número de braquiblastos, y se calculó la tasa de crecimiento relativo para altura de planta. Mediante un análisis de varianza y comparación de medias se determinaron diferencias significativas entre procedencias, en todas las variables. En la evaluación se manifestó un crecimiento exponencial de plantas en vivero, con un promedio de 0,8 a 1,5 mm de altura/día de 54 a 166 dds y un promedio de 1 a 2 braquiblastos en ramillas primarias y secundarias por día en un intervalo de 82 a 166 dds. Del total de procedencias, cuatro de ellas mostraron una alta tasa de crecimiento. PALABRAS CLAVE:Bosque templado, tasa de crecimiento relativo, variación fenotípica. ABSTRACTPinus pseudostrobus is a species with timber harvesting, distributed over a wide altitudinal gradient of 1,600-3,250 m, suggesting a genetic variance, which can be exploited by selecting trees that provide seeds in order to produce plants with high relative growth rates. Therefore, survival and early growth of Pinus pseudostrobus were evaluated under nursery conditions, based on the variation in offsprings of 38 outstanding trees (provenances) in natural stands from Sierra Norte of Oaxaca, Mexico. Seeds were sowing in February 2013 at a nursery located in Ixtlan de Juarez, near the collection site, to 2030 masl and a temperate climate. Survival from 54-166 days after planting (dap) was evaluated, five readings of plant height, basal stem diameter, four readings of number of brachyblasts were recorded, and the relative growth rate for plant height was estimated. Using analysis of variance and mean tests, significant differences among provenances were determined in all variables. In the evaluation, the plants in the nursery showed an exponential growth, an average of 0,8 to 1,5 mm in height/day of 54-166 dap and an average of 1-2 brachyblasts on primary and secondary branches per day in a range of 82-166 dap. From total provenances, four showed high growing rate.

The Agave potatorum Zucc. is a wild species endemic to Oaxaca and Puebla, Mexico. The stem or “head” of the plants of this species contains a large amount of fructans, which, in conjunction with their crassulacean acid metabolism (CAM), helps the agave to survive droughts. The soluble carbohydrates are used to produce mezcal. The objective was to evaluate growth and content of fructans of A. potatorum young plants grown in soil and perlite substrate, fertigated with three nutrient solutions, and subjected to drought. Eight-month-old plants were used and, for 15 months, were fertigated with nutrient solutions: 1) Steiner, 2) Hoagland and Arnon, and 3) Urrestarazu. Irrigation was later suspended to simulate a 5-month drought and induce stress. During fertigation, the vegetative growth was greater in plants irrigated with Hoagland and Arnon and Urrestarazu solutions in perlite and in soil. After the period of water deficit stress, plants in perlite substrate fertigated with the Hoagland and Arnon solution accumulated more fructans in the heads, reaching a maximum of 75%, than plants in soil substrate (42%).

The species Agave angustifolia can be propagated asexually with offshoots from rhizomes, bulbils from inflorescence, and through micropropagation to supply the growing demand for quality plant material for new plantations. In this investigation, Agave angustifolia plants of different initial sizes were evaluated for growth and emission of rhizome shoots, after 14 months under different conditions of substrate, fertigation and application of cytokinins. Bulbils were collected from inflorescences of plants at two sites and classified into two size categories: small (≤ 7 cm) and large (> 7 cm). The bulbils were cultured for 14 months in pots with substrates that were mixtures of sand (A), soil (S), and bovine manure (Bm) (%): 1) A + S (0.3: 0.7); 2) A + S + Bm (0.3: 0.525: 0.175); 3) A + S + Bm (0.3: 0.35: 0.35); 4) A + S + Bm (0.3: 0.175: 0.525). The plants in each substrate were separated into groups for application of different types of irrigation: 1) water; 2) 50% Steiner’s nutritive solution, SNS-50%; 3) SNS-50% + 25 mg L-1 of benzylaminopurine.  The results show that the emission of rhizome offshoots was affected by the substrate, type of irrigation and provenance of the plants. The plants in substrates 3 and 4 formed 2.2 rhizome offshoots, which was more than plants in the other substrates. The plants irrigated with water, SNS-50%, and SNS-50% + benzylaminopurine formed 1.1, 1.6 and 1.9 rhizome offshoots, respectively.