CRASSULACEAE: CHARACTERISTICS, SPECIES, CARE, DISEASES - BIOLOGY - 2025

The crassulacean make up a family of plants more or less uniform species of angiosperms, besides 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 together succulent plants that have pinnate or entire 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.

Crassulaceae. Source: pixabay.com

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 succulents is their photosynthetic metabolism, which is called the acid metabolism of crassulaceae.

Said metabolism allows these plants to grow under conditions of humidity restriction, and to capture carbon dioxide at night to avoid losses of water from the plant during the day, when the ambient temperature is high.

Flower of Echeveria sp. Source: pixabay.com

Succulents are plants with great economic and commercial value due to the beauty of their morphology, which makes them ornamental species worthy of being collected.

characteristics

Plant

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 at ground level.

Graptopetalum sp. Source: pixabay.com

Leaves

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 can be cartilaginous, hairy, or papillous.

The leaves are thick, small and greyish-green in color, and with the peculiarity of storing a lot of water.

flowers

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. On the other hand, 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.

Flower of a succulent plant. Source: pixabay.com

Fruit

The fruits of the crassulaceae are shaped like free follicles and can have one or many seeds.

Reproduction

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.

Morphological adaptations

Crassulaceae have morphological adaptations that make it possible for them to inhabit places with environmental conditions of temporary or permanent drought.

Spiral rosette of a crassulaceous. Source: pixabay.com

Consequently, these adaptations may 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.

Physiological aspects

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 CO ₂ during the night, 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, carbon dioxide is assimilated into the chloroplasts through the Calvin cycle.

CAM plant species, especially the more succulent crassulaceae that store a large amount of water, maintain the maximum rate of photosynthetic assimilation (CO ₂) for a longer time, as well as maintain a favorable carbon balance even after 30 days of drought..

Many CAM photosynthetic species grow and thrive best in microenvironments where they get more water and light at optimal levels.

Habitat

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 south-central 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 thickets, tropical evergreen forest. Therefore, in the underwater habit, this family has very little presence.

Typical crassulaceous. Source: pixabay.com

Frequently, among the vegetation with which succulent plants are associated, we can find the Quercus forest, Quercus-Pinus forest, xerophilous scrub, grasslands, tropical deciduous forest or tropical evergreen forest, among others.

Taxonomy

Crassulaceae taxonomy is generally problematic. This is because 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 and Crassuloideae.

The Crassulaceae family has about 35 genera, of which approximately 1500 species have been determined.

Representative species

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 species easily recognizable as succulents are: Echeveria gibbiflora, Echeveria elegans, Villadia diffusa, Kalanchoe pinnata, Sedum morganianum, Tillaea saginoides, and Villadia guatemalensis.

Echeveria sp. Source: pixabay.com

Care

The importance of succulent plants lies in their use as ornamental species. This is due to the showy flowers they have, as well as the vegetative growth forms they present.

That is why fans of the cultivation of crassulaceae take special care to maintain their plants.

Within these cares, special care can be found in the frequency of irrigation, as 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, being 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 between 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.

Preventive Maintenance

Another growing practice for greenhouse or collection conditions is to quarantine newly acquired succulent plants, keeping them isolated from other plants in the collection for several weeks.

This is a way to prevent the eggs of potential pests 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 to kill larvae, eggs and adult individuals of pest insects.

Crassulaceae in collection. Source: pixabay.com

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.

Diseases

Some of the most common diseases are:

Aloe oxide: it 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 the 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 whiteflies, 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.

Pests

Although succulents 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

References

1. Andrade, JL Barrera, E., Reyes, C., Ricalde, MF, Vargas, G., Cervera, JC 2007. The acid metabolism of crassulaceae: diversity, environmental physiology and productivity. Bulletin of the Botanical Society of Mexico 81: 37-50.
2. Pérez.Calix, E., Martínez, F. 2004. Crassulaceae. In: AJ García-Mendoza, MJ Ordoñez, M. Briones-Salas (eds.) Biodiversity of Oaxaca. Institute of Biology, UNAM-Oaxacan Fund for Nature Conservation-World Wildlife Fund. Mexico. pp 209-217.
3. Caballero, A., Jiménez, MS1978. Contribution to the foliar anatomical study of the Canary crassulaceae. Vieraea 7 (2): 115-132.
4. The Taxonomicon. (2004-2019). Family Crassulaceae J. St.-Hil. (1805) - stonecrop family. Taken from: taxonomicon.taxonomy.nl
5. Tropics. 2019. Crassulaceae J. St.-Hil. Taken from: tropicos.org
6. Garden plants. 2019. Diseases and pests of cacti and succulents complete guide. Taken from Plantasdejardin.com