The crassulaceae make up a more or less uniform family of plants of the angiosperm species, in addition to belonging to the order of the saxifragales. The Crassulaceae family consists of approximately 25 to 38 genera with more than 1500 species.
The Crassulaceae family groups succulent plants that have pinnate or whole leaves, usually fleshy (a distinctive feature of the family), which are agglomerated in a rosette that can be at the base or at the apex of the branches. They can also cluster along the stem in various ways. The flowers are hermaphroditic.
This family of plants is also known as succulent plants, as well as donkey ears, shells, and evergreens. In Mexico, this family has representatives of more than 300 species, which makes it the country with the greatest diversity of succulents..
An important and particular aspect of succulent plants is their photosynthetic metabolism, which is called the acid metabolism of crassulaceae..
This metabolism allows these plants to grow in conditions of humidity restriction, and to capture carbon dioxide during the night to avoid losses of water from the plant during the day, when the environmental temperature is high..
Succulents are plants with great economic and commercial value due to the beauty of their morphology, which makes them ornamental species worth collecting..
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Succulents can present variety in their morphology. Normally, they are small sessile rosettes or with a small peduncle, with herbaceous or sub-shrub bearing. They have short or long stems, many growing flush with the ground.
The leaves of the crassulaceae can be whole or pinnate, peculiarly fleshy and are grouped in a basal rosette or at the end of the branches. They can also be distributed along the stem with opposite, alternate or whorled phyllotaxis. The color of the leaves varies from green to greyish; the edge of the leaves may be cartilaginous, hairy, or papillous.
The leaves are thick, small and greyish-green in color, and with the particularity of storing a lot of water.
Succulent plants have hermaphrodite flowers, with radial symmetry, pentameric and in some cases tetrameric. The colors of the flowers can be very striking from yellow, orange, red, pink, white or present combinations of them.
In addition, the flowers have 1 or 2 whorls that produce stamens. For their part, succulents have a super gynoecium, with free carpels and an equal number of petals and sepals. The receptacle shows a nectariferous scale on each carpel.
The fruits of the crassulaceae are shaped like free follicles and can have one or many seeds..
Asexual reproduction is common in succulent plants. This can be done through rhizomes, stolons, buds or adventitious bulbs, or properly the shoot of a leaf, bract or practically any part that is detached from the plant.
Crassulaceae have morphological adaptations that make it possible for them to inhabit places with environmental conditions of temporary or permanent drought..
Consequently, these adaptations can be the succulence of the different organs, especially the leaves and stems; development of thick and normally pruinous cuticle, pubescent or waxy; rosette-shaped growth, and crowded growth.
Crassulaceae are the plants that gave rise to one of the three types of photosynthesis: the acid metabolism of crassulaceae, CAM in English. This type of photosynthesis is carried out in vascular plants for the assimilation of carbon dioxide from the atmosphere, and is attached to C3 photosynthesis.
Crassulaceous plants, unlike plants that have C3 and C4 metabolism, fix COtwo overnight, and for this they use the enzyme PEPC (phosphoenolpyruvate carboxylase). The products of the reaction (malic acid) are stored in vacuoles, and during the day, under the incidence of light, the carbon dioxide is assimilated in the chloroplasts through the Calvin cycle..
CAM plant species, especially the more succulent crassulaceae that store a large amount of water, manage to maintain the maximum rate of photosynthetic assimilation (COtwo), as well as maintaining a favorable carbon balance even after 30 days of drought.
Many species with CAM photosynthesis grow and develop best in microenvironments where they get more water and light at optimal levels..
The Crassulaceae family is found throughout the world, with the exception of Australia and Polynesia. However, there are some regions where there is a greater diversity of succulent species such as the south-central area of Asia, South Africa and Mexico..
Regarding the conditions of height above sea level, the Crassulaceae family can be found between 150 and 3500 m. Succulent communities prefer dry environments, xerophilous scrub, tropical evergreen forest. Therefore, in the underwater habit, this family has very little presence.
Frequently, among the vegetation with which succulent plants are associated we can find the forest of Quercus, Forest of Quercus-Pinus, xerophilous scrub, grasslands, tropical deciduous forest or tropical evergreen forest, among others.
The taxonomy of crassulaceae is generally problematic. This is due to the fact that the specimens suffer desiccation in the herbaria and because there is great variability in the populations of this family due to the frequency of hybrids. This makes specific determination difficult. The taxonomic description for this family is as follows:
Kingdom: Plantae
Superphylum: Embryophyta
Phylum: Tracheophyta
Class: Spermatopsida
Subclass: Magnoliidae
Order: Saxifragales
Family: Crassulaceae J. St.-Hill (1805)
In addition, three important subfamilies are known for these plants which are: Sedoideae, Kalanchoideae Y Crassuloideae.
The Crassulaceae family has about 35 genera, of which approximately 1500 species have been determined..
The crassulaceae family groups about 1500 species. Of these species, it is possible to find some of the most representative in Mexico, since this country has more than 300 species, being the first country in terms of diversity of succulents..
Some important and easily recognizable species as succulents are: Echeveria gibbiflora, Echeveria elegans, Villadia diffusa, Kalanchoe pinnate, Sedum morganianum, Tillaea saginoides, Y Villadia guatemalensis.
The importance of succulent plants lies in their use as ornamental species. This is due to the showy flowers that they have, as well as the forms of vegetative growth that they present.
That is why fans of the cultivation of crassulaceae take special care for the maintenance of their plants.
Within these cares, special care can be found in the frequency of irrigation, since excessive watering could cause the death of the plant due to root rot, as well as extremely deficient irrigation could cause the plants to wilt..
Therefore, succulent plants require a lot of light daily, and it is advisable to keep them in a place where they receive at least half a day of light..
Likewise, the provision of a substrate composed of a mixture of sand and earth, with good drainage, allows the development of these plants in good conditions. Also, it should be avoided that these plants are in enclosed places to reduce the risk of being attacked by phytopathogenic fungi.
Another growing practice for greenhouse conditions or in collections is to quarantine new succulent plants that are acquired, keeping them isolated from the rest of the plants in the collection for several weeks..
This is a way to prevent the eggs of potential pests contained in the new plants from hatching and infecting other plants. In this way, the pest can be treated locally.
In addition, when transplanting the acquired species, it is important to check the health of the roots to see if there are pests such as mealy bugs, and in this way not to also transport the pest to the rest of the crop.
Good growing practice is to spray systemic insecticide on newly acquired plants before transplanting into the collection. Also, sterilizing the substrate used from time to time helps kill larvae, eggs and adult individuals of pest insects..
The cultivation of crassulaceae is delicate if preventive care is not taken. It is advisable to clean the site used, always removing dead flowers and leaves to avoid the proliferation of pests and diseases..
Some of the most common diseases are:
Aloe oxide: is a fungus that produces round brown or black spots on Aloes and Gasterias leaves. The stain is produced by the oxidation of phenolic substances in the sap of plants right in the infected area.
Black or sooty mold: It is a fungus that is always present in many environments and produces more aesthetic than physiological damage. It is associated with plants that are covered with whitefly, with mealy bugs, or in nectar-producing plants..
Basal stem rot: This disease affects plants both in cold and humid conditions; It occurs at the base at ground level where there is stem-soil contact. It is observed as a rot of black or reddish brown color depending on the microorganism that attacks the plant.
Although succulent plants are infected by fungi, some bacteria and viruses, many of the main problems are caused by pests. The following can be described:
- Mealy bugs
- Snails
- Cypress fly
- Vine weevil
- White fly
- Aphids
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