The Pinus greggii or palo prieto is a conifer of the Pináceas family, native to Mexico and distributed in various areas of the Sierra Madre Oriental. It is a fast-growing, rustic species that grows easily in low-fertility soils.
It adapts to low rainfall conditions and is resistant to attack by various pests in its natural environment. So it is widely used as a commercial crop and in the reforestation of poor and degraded soils.
Pinus greggii. Source: flickr.com
At the regional level, P. greggii is a tree of high economic value for the populations that live in neighboring areas, since it is used to obtain wood for the sawdust industry, and locally to obtain fence posts and fuel wood..
At present, in their place of origin, indiscriminate logging and overexploitation of pine forests has drastically reduced their population. However, due to its resistance and high potential, it has managed to be established in tropical and subtropical areas such as Brazil, India and South Africa.
General characteristics
The black pine is a medium tree 10-25 m high of the evergreen type or with permanent leaves. The bark is smooth in appearance and greyish in color in young plants, becoming rough and dark in adult plants.
Over time the bark of the lower trunk tends to be thick, with deep cracks and long rough scales. At medium-high level and on the branches, the trunk is usually soft, until it acquires a rough texture and a grayish color.
It has acicular leaves 7-14 cm long, with serrated edges, of a bright green color and a rough appearance. The crown is round, not very dense, with elongated and light branches, free to the wind, with a greenish-blue coloration on young branches.
In the winter the plant emits narrow and sharp shoots, pedunculated, with loose scales and a light brown color. The needles are bright green, 10-15 cm long, in groups of three with a small basal sheath.
The ovoid cones are 8-14 cm long and 4 cm in diameter, resinous, with a short and thick peduncle. They look light brown when ripe, closed, long and arched, grouped 5 to 10 on each branch.
Pinus greggii cones. Source: flickr.com
In the cones or cones there are thin and soft scales, with a flattened process, a sunken cusp and a small spine. The 6-8 mm seeds are oval in shape, thick at the base, and have 20 mm long fins, they are dark in color.
In its natural habitat, flowering and subsequent fruiting begins in 4-5 year-old pines. The cones tend to mature between 21-22 months after pollination, during the months of December and January.
Taxonomy
- Kingdom: Plantae
- Division: Pinophyta
- Phylum: Tracheophyta
- Class: Pinopsida (Conifers)
- Order: Pinales
- Family: Pinaceae
- Genus: Pinus
- Subgenus: Pinus
- Section: Trifoliae
- Species: P. greggii Engelm. ex Parl. 1867
- Subspecies: Pinus greggii var. australis, Pinus greggii var. greggii.
- Scientific Name: Pinus greggii Engelm. ex Parl. 1867
- Common names: pine, Chinese pine, squiggle pine, Greggii pine, ocote pine, black pine (Spanish); Gregg's pine (English); pine gregii (ND).
Distribution and habitat
The Pinus greggii is a species adapted to a temperate subhumid climate, located in an altitude range between 1,400 and 3,000 meters above sea level. With average temperatures of -9º to 29º C and annual rainfall of 600 to 1000 mm average.
Pino Prieto Forest. Source: flickr.com
The black pine, as it is also known, adapts to volcanic soils, in areas of broken topography, plateaus and steep slopes. It also develops with less vigor in dry and arid soils, even when the plants are smaller, slow growing and highly branched.
In fact, it is located in areas with heavy or clayey soils, with low content of organic matter, and thin. On the other hand, it adjusts to well-drained soils and with slightly acidic pH conditions.
This species is delimited between 20 ° 13 "and 25 ° 29" north latitude. Its origin is located in the Sierra Madre Oriental de México. Specifically in the states of Coahuila, Hidalgo, Nuevo León, Querétaro, Puebla and San Luis Potosí.
In its natural environment it grows sparsely in association with other plants of the genera Fraxinus, Liquidambar, Platanus and Quercus. It is also associated with other species of the genus Pinus, such as P. arizonica, P. cembroides, P. patula, P. pseudostrobus, P. teocote and P. montezumae.
The species P. greggii var. greggii is located towards the north, and the species P. greggii var. Autralis towards the south zone. Recent experimental crops have made it possible to cultivate the species P. greggii in South Africa, under conditions of low rainfall.
On the other hand, there is a close relationship between P. greggii and P. patula, establishing crosses and production of hybrids under natural conditions. In fact, between the two species the only difference is the presence of longer and drooping needles in P. patula.
Lifecycle
The life cycle of Pinus greggii is characteristic of gymnosperms, the exposed seeds do not develop inside a fruit. In pines the seeds are located within a structure called pineapple, strobilus or cone.
This species, like all conifers, is monoecious; male and female flowers are found individually in the same tree. Male flowers (1-2 cm) are characterized by the presence of various spiral-shaped stamens on an axis.
The female cone-shaped structures are composed of a group of alternate bracts within an inflorescence called the strobilus. At the insertion of each bract, the female flower is located where the ovuliferous scale that receives the pollen is located.
In the case of conifers, cross pollination occurs, pollen is carried by the wind from one plant to another. In fact, the female cones are located on the upper branches and the male inflorescences on the lower branches.
Pollination begins in the spring, the pollen freely penetrates the strobili until it comes into direct contact with the fertile ovules. Subsequently the bracts or ovuliferous scales are closed in order to protect the embryo.
Within this structure, the maturation of the pollen grain or male gametophytes and the ovocell or female gametophyte occurs. This process lasts for one year, so fertilization occurs in the spring of the following year.
Male gametes join the egg cell, initiating the formation of the respective embryo, which later develops a radicle and several cotyledons. The cycle is completed at approximately two years, when the seeds are detached from the cones.
Ripe pineapple from Pinus greggii. Source: flickr.com
The seeds provided with a wing-shaped integument are carried by the wind. The cycle concludes in the fall of the second year after pollination occurred.
References
- Farjon, A. (2013) Pinus greggii. The IUCN Red List of Threatened Species. Recovered at: iucnredlist.org
- Morphology of Vascular Plants (2012) Morphological Botany. Faculty of Agricultural Sciences. Recovered at: biologia.edu.ar
- Black pine (Pinus greggii) (2018) EncicloVida. CONABIO. Recovered in: EncicloVida.mx
- Ramírez-Herrera, C., Vargas-Hernández, JJ, & López-Upton, J. (2005) Distribution and conservation of natural populations of Pinus greggii. Acta botánica mexicana, (72), 1-16.
- Pinus greggii Engelm. ex Parl. (2018) ITIS Report. Recovered at: itis.gov
- Pinus greggii (2018). Wikipedia, The Free Encyclopedia. Recovered at: wikipedia.org.