A cactus is a member of the plant family Cactaceae[a], which has about 127 genera and about 1750 recognized species. Cactaceae belongs to the order Caryophyllales. [4] The Latin word “cactus” is derived from the Ancient Greek word “kktos,” which Theophrastus first used to refer to a spiky plant whose identify is currently unknown. [5] There are many different sizes and shapes of cacti. Most cactus reside in settings that experience at least some drought, despite the fact that some species can tolerate fairly humid situations. Many of them can even be found in the Atacama Desert, one of the driest places on Earth, where they exist in extremely dry circumstances. Cacti have developed a variety of adaptations to conserve water as a result. As an illustration, nearly all cacti are succulents, which means that their swollen, fleshy sections are designed to store water. Unlike many other succulents, most cacti only have a stem where this crucial process occurs. The majority of cacti species no longer have actual leaves; instead, they only have spines, which are heavily modified leaves. Spines help limit water loss by slowing air movement around the cactus and offering some shade, in addition to protecting it from herbivores. Photosynthesis is performed by cacti’s expanded stems in the lack of real leaves. Except for Rhipsalis baccifera, which also grows in Africa and Sri Lanka, all of the Americas, from Patagonia in the south to sections of western Canada in the north, are home to cacti.
Areoles, a type of greatly shortened branch, are specialized structures that create cactus spines. Cacti can be identified by their areoles. Areoles also produce multipetalled, tubular blooms in addition to spines. Because many cacti have extended dormant periods and short growing seasons, they may respond fast to any rainfall. This is made possible by their large but shallow root systems, which swiftly absorb any water that reaches the ground surface. Because cactus stems are frequently ribbed or fluted, they can easily stretch and contract to quickly absorb water after rain and then hold onto it during protracted droughts. The majority of cacti use a unique process called “crassulacean acid metabolism” (CAM) as part of photosynthesis, similar to other succulent plants. Unlike photosynthesis, which occurs during the day, transpiration—during which carbon dioxide enters the plant and water escapes—occurs at night. The plant converts the carbon dioxide it absorbs into malic acid and stores it there until daybreak, when it is solely used for photosynthesis. The cooler, more humid nighttime hours are when transpiration occurs, which greatly reduces water loss.
The globe-shaped stems of many smaller cacti combine the maximum volume of water storage with the smallest surface area of transpiration loss. The largest[b] free-standing cactus is Pachycereus pringlei, which reaches a maximum height of 19.2 m (63 ft)[7], while Blossfeldia liliputiana has the lowest diameter at maturity, measuring just around 1 cm (0.4 in). [8] During a downpour, a mature saguaro (Carnegiea gigantea) is believed to be capable of soaking up 200 US gallons (760 l; 170 imp gal) of water. [9] Only a few species look significantly like the rest of the family. Plants belonging to the genera Leuenbergeria, Rhodocactus, and Pereskia resemble nearby trees and bushes, at least on the surface. They have enduring leaves and, as they age, stems covered with bark. Despite their appearance, they are recognized as cacti by their areoles and have numerous water-saving adaptations. Leuenbergeria is thought to be very closely related to the original species from which all cacti descended. Other cacti develop as forest climbers and epiphytes in tropical areas (plants that grow on trees). Their stems often have fewer or even no spines and are flattened, almost leaf-like in appearance, like the well-known Christmas or Thanksgiving cactus (in the genus Schlumbergera).
Many types of cacti are produced as beautiful plants, while others are raised for fodder or forage, and yet others are utilized as food (particularly their fruit). An bug that lives on some cactus produces cochineal.
Many succulent plants, both in the Old and New Worlds, have spiky stems, including some members of the Euphorbiaceae (euphorbias), which is why they are frequently mistakenly called “cactus.”
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What a cactus looks like and how does it work?
Cacti have numerous adaptations that enable them to survive in arid climates; these adaptations enable the plant to efficiently gather water, store it for a long time, and conserve it (minimizing water loss from evaporation).
Cacti have thick, succulent stems with rigid walls that store water when it rains. The stems are fleshy, green, and photosynthetic. Either the stem’s inside is spongey or hollow (depending on the cactus). The water inside the cactus is prevented from evaporating by a thick, waxy layer.
Long, fibrous roots are common in cactus, and these roots take moisture from the earth. Some cacti, such as ball cacti, have smaller, more compact roots that can capture dew that falls from the cactus.
Most cacti feature scales or spines in place of leaves (which are modified leaves). These scales and spines do not evaporate their water (unlike regular leaves, which lose a lot of water). Predators (animals that would like to consume the cactus to gain food and/or water) are kept at bay by the spines. On a cactus, areoles are a circular collection of spines. An areole is where flowers bud, and it is also where new stems branch.
How Are Cactus Adapted To Survive In A Desert?
Cacti have unique adaptations in their stems, leaves, and roots that allow them to survive in desert conditions. Among these modifications are:
- In order to minimize water loss through transpiration, leaves are reduced to spines.
- Wide and deep roots can collect surface rains and access deep subsurface water.
- To prevent water loss, stomata are recessed.
- Stems with a waxy coating help to retain water and are fleshy and thick to store water and carry out photosynthesis.
What do plants have for specialized structures?
Plants have specific tissues and structures, just like people have organs and tissues. The shoot system and the root system are two major systems made up of tissues and components. The root system is made up of roots, while the shoot system is predominantly made up of leaves, stems, and reproductive components (such as flowers, fruit, seeds, etc.). Each of these structures possesses traits that enable it to fulfill its main purpose.
Leaves
The lamina is the flat portion of a leaf (also known as the leaf blade). The petiole is the portion of a leaf that connects to the stem (also called a leaf stalk). These components are present in most leaves, but not all.
To expose as many of their chloroplasts to sunlight as possible, leaves are typically big and flat.
A leaf’s function is to:
- a space where photosynthesis can take place; and
- be a part of water transpiration.
However, some leaves have unique shapes and colors due to particular purposes. Some may not even be identifiable as leaves! On pine trees and other conifers, the thin needles are actually leaves. These leaves limit water loss thanks to their modest surface area and waxy coating.
Have you ever encountered a poinsettia plant like the one below during the winter holidays?
Bracts are specialized structures that resemble red flowers on plants. The tiny yellow objects between the red bracts are the flowers. Specialized leaves called bracts aid in luring bees and birds—two pollinators—to the flowers. Animals like birds and bees are drawn to many blooms, and they spread pollen—which contains sperm—from one flower to another. These creatures are referred to as pollinators because they aid in the transmission of pollen.
Stems
The center of the shoot system is a structure called the stem. Nodes and internodes are the two components that make up the stem. Nodes are the areas of the stem between the nodes where buds develop into leaves, stalks, or flowers (see Figure 8). Most plants have stems that are found above ground, but others, like potatoes, also have stems that are located below the surface. The edible portion of the potato plant known as the tuber is actually a particular type of subterranean stem that houses the plant’s food reserves.
The stem’s function is to:
- supply the plant with support
- create a space where fruit, flowers, and leaves can flourish;
- keep the leaves face the sun;
- transfer the byproducts of photosynthesis from the leaves down to the roots, and transport water and nutrients up from the roots;
- nutritional reserves.
Plant stems are useful to humans in numerous ways. In order to manufacture maple syrup, we use the sap (a mixture of sugar and water) found in the stems of maple trees and sugar cane, respectively (we call tree stems trunks).
Along with cinnamon and cork, which are both produced from the bark (outer layer) of tree stems, tree stems are also the source of wood and paper.
Roots
The system of buildings that are frequently but not always present underground is known as the root system.
Roots’ function is to:
- firmly fasten the plant to the ground.
- absorb the water and nutrients required for development and growth;
- nutrient and food reserves; and
- provide vegetative (asexual) reproduction as a method of reproduction.
Despite usually being underground, roots still need a little oxygen to survive. Normally, this trace amount of oxygen can be found between soil grains naturally; however, if the soil becomes saturated (full of water), the oxygen is driven out. The plants will begin to generate roots above ground if they don’t have the necessary oxygen underneath. Roots can be short and thick (taproots) (A), thin and hair-like (fibrous roots) (B), or something in between (for example, buttress roots) (C).