The tuna (Opuntia ficus-indica) is a species of cactus with shrub or arboreal growth that belongs to the Cactaceae family. It is commonly known as tuna, nopal, fig of the Indies, etc; and it is a plant native to Mexico, where it has been domesticated. This plant is widely distributed in the tropical regions of the world.
It is a plant that is characterized by presenting a lignified primary stem with an average height of 2.5 meters. In turn, this plant develops cladodes, which are modified stems from which the prickly pear spines and flowers arise..
It is known that the tuna is a cactus native to Mexico, with a natural distribution in almost all of Latin America. However, in Mexico this plant has undergone an intense domestication process, therefore, few varieties are found in their natural state..
It is a species that grows in xerophytic environments, with a worldwide distribution in these landscapes; in Europe it is widely cultivated in the Mediterranean region. This is the most important cactus species from the economic point of view, since it is cultivated to harvest the fruits; and cladodes, for their part, are used as fodder.
The reproduction of this species of cactus is closely related to the floral morphology and the shape of the pollinators. In this case, bees play key roles in the pollination process, and therefore a process of coevolution of this plant and the other members of the genus is suggested. Opuntia with the bees.
On the other hand, the shape of the fruits is closely related to dispersal by animals, especially birds. However, vegetative reproduction seems to be the key to the evolutionary success of this species of cactus..
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Opuntia ficus-indica It is a slow-growing perennial shrub that can grow to between 3 and 5 meters in height. This cactus develops lignified primary stem that varies in color from light green to dark brown. In addition, this stem is cylindrical about 50 cm long and 20 cm wide..
Cladodes are modified stems that serve as leaves or branches. On O. ficus-indica cladodes are elliptical in shape, varying to obovate, circular, oblong, etc. 2 to 3 year old cladodes are 27 to 63 cm long, 18 to 25 cm wide, and 1.8 to 2.3 cm thick.
In addition, they are pale green in color and have 8 to 11 series of areoles, spiral shaped, with a distance between them of 2 to 5 cm..
On the other hand, the young cladodes have conspicuous pruning and develop conical leaves approximately 6 mm long. In turn, each areola has a needle-shaped spine and two spines with hairs.
Meanwhile, mature cladodes may contain 50 to 70 areoles per surface, elliptical or obovate in shape, and rarely circular. Flowers and new cladodes emerge from each cladode. The latter are known as nopalitos.
Spines are generally absent in Opuntia ficus-indica. However, a few cladodes develop a white sunken needle-like spine 3 to 10 mm long..
Anthesis occurs during the day and up to ten flowers can appear per cladode. Usually, flowering occurs in the apical part of each cladode. The flowers are hermaphroditic, crown-shaped and have cylindrical or conical carpels 4 to 8 cm long and 2 to 3 cm in diameter..
The flowers arise from oblanceolate areoles, 1 to 4 cm long and 2 to 3 mm wide. The outer segments of the perianth vary from green to yellow-green in color, with transparent edges..
Meanwhile, the internal segments of the perianth are yellow with a bright appearance. These segments are spatulate in shape and are truncated at the base. Each internal segment measures an average of 2.3 cm long and 1.6 cm wide.
The stamen are numerous and straight, and the filaments are white or yellow, 0.5 to 1.2 cm long. On the other hand, the anthers are yellow 1.4 to 2.1 cm long.
The fruit of Opuntia ficus-indica It is shaped like a top, which can vary from cylindrical to elliptical. Usually the fruits are yellow with a shiny appearance, however, they can be red, depending on the variety..
Each fruit has a length range of 7 to 9 cm and a width of 5 to 6 cm. Likewise, the fruit usually weighs an average of 116 grams. The pulp can be the same color as the skin and is fleshy, juicy, and very sweet..
Prickly pear seeds are lens-shaped or ellipsoidal, 4 to 5 mm long by 3 to 4 mm wide, and a thickness that varies from 1 to 2 mm. Each fruit can contain an average of 266 seeds, of which 35 or 40% are aborted..
- Kingdom: Plantae.
- Subkingdom: Viridiplantae.
- Under realm: Streptophyte.
- Super division: Embryophyte.
- Division: Tracheophyte.
- Subdivision: Euphylophytin.
- Infra division: Lignofita.
- Class: Spermatophyte.
- Subclass: Magnoliofita.
- Superorder: Caryophyllanae.
- Order: Caryophyllales.
- Family: Cactaceae.
- Subfamily: Opuntioideae.
- Gender: Opuntia.
- Species: Opuntia ficus-indica (Linnaeus) P. Mill- Indian fig.
The prickly pear is common in xerophytic areas, with severe drought conditions. It is established in poor soils and in areas where the average annual rainfall is 326 mm or less. It is a shrub that tolerates eroded soils, but not salinity and low temperatures.
Although paleobotanical data suggest that the ancestor of Opuntia ficus-indica was distributed in Mexico, this plant is widely spread throughout the dry regions of the world.
In Europe, the prickly pear is naturalized in the Mediterranean region and is a plant that was moved from the New World in colonial times. Due to its easy adaptation to dry and harsh conditions, the prickly pear has been able to colonize the arid areas of Africa, Asia, and Australia. In Southamerica O. ficus-indica was introduced in colonial times.
In all arid tropical areas, the prickly pear that was cultivated or naturalized, was subjected to genetic variations and therefore to morphological modifications. Thus, in countries such as Argentina and Bolivia, varieties of this species were initially classified as new species..
The prickly pear grows in any type of soil. However, it frequently colonizes soils limited by hard layers approximately 25 cm thick. As mentioned earlier, Opuntia ficus-indica It does not grow in soils with high salt content, nor in flooded soils, due to the fact that the roots are sensitive to oxygen deficiency.
Prickly pear plants begin to produce fruit after 2 to 3 years of establishment, and they produce at a peak of 6 to 8 years. Fruit production is maintained for 20 to 30 years, however this depends on the variety and management.
Meanwhile, flowering depends substantially on the age of the cladodes. Thus, 1-year-old cladodes produce more flowers than 2-year-old cladodes. This is reflected in the number of fruits. Furthermore, 2-year-old cladodes are mostly responsible for vegetative reproduction.
The flowering period is during spring, depending largely on environmental conditions such as light and temperature. Each flower bud develops rapidly, a process generally conditioned by the physiology of gibberellin and auxin..
Flower development requires 21 to 47 days and this period is conditioned by the latitude where the crop is located. Pollination is carried out by different species of bees. However, apomixis is very common in this species and depends substantially on the levels of gibberellic acid..
The fruits mature from 80 to 100 days after flowering, with rapid growth in the first 20 to 30 days, which then slows down from 59 to 90 days after anthesis. The fruits are consumed by various species of birds, which spread the seeds to new territories.
The germination rate of the seeds is high and the seeds can remain viable for up to 12 years. However, the seeds require scarification processes to break dormancy.
Although sexual reproduction plays an important role in the reproduction of the prickly pear, this species of cactus also propagates vegetatively. According to some experts this is due to the demands of the seeds and then the seedlings to establish themselves. The vegetative dispersal mode corresponds to the fallen cladodes with adventitious roots.
Opuntia ficus-indica It is the most important cactus species from the ecological point of view, since it is cultivated to obtain its fruits, and the cladodes are used as forage. Mexico is the country with the largest extension of land cultivated with this species.
It is a kind of cactus used in cooking, especially in Mexican culture. It also has various ethnobotanical uses, mostly by rural populations.
The most intense use that has been given to it is forage, since it is applied as livestock feed in several countries in South America. From an environmental point of view, the prickly pear has received attention for its ability to regenerate soils highly degraded by erosion.
Opuntia ficus-indica it tolerates high temperatures, being considered a promising plant as a source of forage in times of climate change. However, this plant is extremely sensitive to low temperatures, especially those that drop below -5 ⁰C.
In general, this plant tolerates water deficiency, although irrigation is recommended when rainfall averages less than 300 mm per year. The abundant rain is not ideal for the cultivation of the prickly pear, since its roots are sensitive to waterlogging.
The prickly pear prefers sandy soils with a pH between 6.5 to 7.5, and low in salinity. Fertilization should be applied after a thorough analysis of the soil. It is recommended that the magnesium level is not higher than the calcium level.
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