The nopal (Opuntia) is a genus of cactus whose species have been used for more than 100 years by the inhabitants of Mexico, the United States-Mexico border, and the United States. These cacti are also known as prickly pears, and they are plants for ornamental use..
Opuntia it is the most diverse and widely distributed genus in America. In the world, about 1600 species are known. This genus is strongly associated with pollination by bees and coevolved with at least two genera of these insects..
Spectacular examples of associations formed by these cacti known as nopaleras can be seen in nature. The nopaleras consist of the grouping in nature of cacti of various genera. Within these groupings there may be around 144 variants of the genus Opuntia.
The flowers and fruits of the Nopal are closely associated with pollination and seed dispersal by animals. Sexual reproduction and vegetative multiplication by fragmentation is common and explains the reproductive success of the genus. Opuntia.
This cactus has been studied for its hypoglycemic properties, and its potential use for the treatment of type 2 diabetes..
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Mexico is the most important center of diversity with 669 species and 244 sub species of Opuntia. In fact, the Nopal is part of the figures that appear on its flag.
Specifically, the genre Opuntia It is native to central Mexico, and from there it has been dispersed into North America, Central America, and the Caribbean, and possibly South America in pre-Columbian times. From there, tourists have transported the Nopal from Mexico or nearby countries to Europe and the rest of the world..
Cacti roots generally receive little attention. They develop when the areolas make contact with the ground. These types of roots differ from other plants because they develop xeromorphic characteristics that allow the plant to survive in drought conditions. These roots can contribute to drought tolerance in different ways:
The cladodes are the modified stems with leaf function. These stems have small shoots known as areolas that have hairs and thorns. Cladodes are succulent stems with green bark and photosynthetic function. They are oblong, spatula-oblong, about 30 to 40 cm long, sometimes up to 80 cm, and 18-25 cm wide..
The areolas present in the cladodes produce, in addition to spines, small short spines like hairs called glochids. The stomata are abundant and are present on the entire surface of the stems and are evenly distributed.
The epidermis of the cladodes has several functions such as regulating the movement of carbon dioxide into the plant such as oxygen out of the plant, retaining water within the plant body, and protecting the plant from fungi, insects and light. intense solar.
Cactaceae have CAM metabolism (crassulaceae acid metabolism), and are generally considered drought resistant because they store large amounts of water in their stems..
Consequently, the presence of thorns is a particular characteristic of cacti. The spines grow from the areoles and two types of spines can be distinguished (spines and hairs, the latter better known as glochids).
The spines are leaves modified to avoid the loss of water and serve as a defense against predators. They have great importance as a morphological character with taxonomic potential.
Unlike other cacti, in the nopal, the new cladodes (nopalitos) and flower buds grow from the areolar meristems. These can already produce a flower or a cactus. Once produced, the meristem does not carry out this process again.
Also, it has been studied that the phytohormone gibberellic acid promotes the development of flower buds and the indole-butyric acid stimulates the vegetative growth of the buds. In this way, a high floral production reduces the production of nopalitos, and vice versa. The production of flowers and nopalitos can vary from one year to another throughout the life of the nopal..
In subtropical regions, flower buds of Opuntia they begin when the monthly average temperature exceeds 16 ° C. This is in March-April in the Northern Hemisphere, and September-October in the Southern Hemisphere. The floral period fluctuates between 3 and 5 weeks in some species such as O. ficus-indica, and up to 25 weeks in O. joconostle.
The floral axis shows from its base upwards, a pedicel that joins the flower with the cladode, as well as the pericarp that surrounds the lower ovary and the receptacle that contains the perianth, androecium and gynoecium. Some species have 24 tepals (O. polyacantha), and others have 19 (O. phaeacantha)
Opuntia flowers are generally yellow, but are also found in orange, pink, purple, red, white, or mottled. Hermaphroditic flowers are the most common. Also, they possess numerous stamens, for example, 265 in O. polyacantha, 358 in O. phaeacantha, 450 in O. viridirubra and 598 in O. brunneogemmia. These stamens are normally yellow or green with a circle or spiral in the style.
Pollen grains are spherical, cubic, or dodecahedral, 65-130 μm in diameter, and pointed or cross-linked.
Some species have nectaries at the base of the style. The style is simple, hollow, usually green or yellow, although sometimes it is pink, red, or orange. The stigma appears above the anthers and in the center of the flower. Each seminal primordium consists of the nucela, embryo sac, integuments, and micropil.
The fruits of Opuntia they are unilocular and polyspermic. There are three types of fruits: fleshy (they contain seeds with pulp around it and a thin shell), dried fruits (seeds with almost no pulp and a thin shell), and xoconostle fruits (seeds with little pulp and a thick, acid shell)..
In fleshy fruits, when they ripen, the skin thickens, the tubers become imperceptible due to the turgor of the tissue, and the surface becomes colored. 90% of the pulp is made up of parenchymal cells originating in the dorsal part of the epidermis of the funicular covering, and the remaining 10% is funicular tissue.
On O. ficus-indica, unripe green peel has stomatal and photosynthetic activity, contributing 8 to 10% to fruit growth. The areolas of fruits always have glochids and may have thorns or hairs, which may be from the flower stage.
Seed growth and maturation occurs 30 to 70 days after anthesis. The seed of Opuntia it is small and ovoid or lens-shaped. An average seed can be 0.45 cm long, 0.35 wide, and 0.16 cm thick..
The seeds of the nopales present dormancy, which is associated with the impermeability of the integument and the funicular hardening.
The gender Opuntia It was described by Miller in 1754, as follows:
- Kingdom: Plantae.
- Superphylum: Embryophyta.
- Phylum Tracheophyta.
- Class: Spermatopsida.
- Order: Caryophyllales.
- Family: Cactaceae.
- Subfamily: Opuntioideae.
- Gender: Opuntia P. Miller (1754).
The fruit and vegetative parts, such as the spiny cladodes, are closely related to the dispersal of their seeds and the high and efficient vegetative dissemination by animals..
Vegetative multiplication appears to be more efficient than sexual reproduction. However, both reproductions (vegetative and sexual) possibly have contributed to the ecology and evolutionary success of this genus..
The reproductive biology of the species of Opuntia of fleshy fruit, it is related to anthesis. In this sense, flower development requires from 21 to 47 days, and can be extended to 75 days..
In the northern hemisphere, anthesis occurs between May and July, and in the southern hemisphere it occurs between February and August. In nopales, flowering usually lasts between 6 and 12 hours, and if it starts late, it is completed the next day.
In relation to Nopal reproduction, the bee-flower syndrome has been described. From there it is known that the floral structure has facilitated pollination by these insects, thus being the position of the style that protrudes from the stamens, and a large size of the nectary.
In this sense, the stigma lobes and the stigma itself are sticky and also facilitate the adherence of other insects, which serve as dispersers for pollen..
With regard to the flowers, there is no evidence of the fragrance of the Opuntia; However, in fruits of O. ficus-indica more than 17 volatile compounds related to its aroma have been determined.
Visitors to the flowers of Opuntia They are varied, the most abundant group being the Hymenopterans (84 species, and 19 identified only up to the genus), followed by Coleoptera (11 species, 11 genera), two species of Lepidoptera and up to 10 species of birds..
These figures may increase according to the databases of the investigations that have been carried out, in addition to the fact that the pollinators of Opuntia have been determined only for a part of the species of this genus (approximately 19).
For their part, the species of bees that visit Opuntia, vary during the flowering period. For example, in the highlands of San Luis de Potosí and Zacatecas they include continuous and abundant species, continuous and scarce species, rare species present for a short time at the end of the season, and casual species..
In this way, for a visiting insect to become a pollinator of Opuntia it is required that:
Additionally, apomixis occurs frequently in Opuntia. Apomixis is the production of seeds without prior fertilization. In this plant genus, the development of adventitious embryos from the nucellar tissue is very common..
This type of reproduction occurs frequently in Opuntia. In fact, some species reproduce primarily in this way (O. fragilis, O. polyacantha, O. strigil Y O. trichophora).
Some studies have evaluated the importance of reproduction and multiplication in population growth. The high frequency of vegetative multiplication can preserve certain genetic characteristics.
Opuntioid cacti are cultivable species in arid areas, particularly due to their high efficiency in converting water into biomass. For this reason, they are recognized as an ideal crop for arid regimes..
Successfully domesticated crops such as O. ficus-indica they have a fundamental role in the economy. Prickly pears are highly commercialized worldwide. That is why the cultivation of Nopal is as important as the cultivation of agave is for tequila in the agricultural economy of Mexico..
The opuntia cactus achieves high productivity, but only with proper fertilization. Average fertilization is 0.9% N, 0.16% P, 2.58% K and 2.35% Ca, for an annual productivity of 20 tons per hectare per year, considering other macros and micronutrients.
Prickly pears are used as forage food, and as a supplement in animal nutrition.
The Nopal has medicinal properties derived from its fruits and cladodes. These cacti are an important source of bioactive substances and chemical constituents that increase the value of the cactus as a product..
Cacti have high antioxidant activity, they have vitamin C, flavonoids and betalains. In addition, several studies indicate that both the fruits and the cladodes have a high level of nutrients, minerals and vitamins..
Recent studies show the potential of the cactus Opuntia to inhibit carcinogenesis in cell line cultures in vitro and in vivo.
In general, the Nopal has medicinal function in the treatment of ulcers, anti-obesity, anti-inflammatory, healing, antiviral, cholesterol reduction, anti-cancer, neuroprotective, and hypoglycemia.
The most representative species of Opuntia it is O. ficus-indica. In addition to it, there is another that has been quite studied such as: O. basilaris, O. chlorotica, O. fragilis, O. macrocentra, O. stricta, O. polyacantha, O. phaeacantha, O. aciculata, O. azurea Y O. lindheimeri.
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