Types and functions of stems.
Introduction
Like roots, stems are modified to perform various specialized functions. When a permanent change occurs in the structure of tribes to perform new functions suited to the environment, this is known as "tribe modification". According to their nature, there are three types of root modifications, namely:
- Arrangement Mods
- sub-air modifications
- Underground Tribe Mods
aerial haste mods
1. Tendrils:Some plants with weak stems produce thin, coiled, delicate organs called tendrils. Vines are useful for climbing. When the tendrils come into contact with the support, they wrap around the support and help the plant climb. Tendrils may develop from axillary or terminal buds.
In Passiflora, the axillary bud develops into tendrils, while in Cissus quadrangularis and Vitis vinifera the terminal buds develop into tendrils.
2. Thorns: Thorns are hard, woody, pointed structures intended for protection. They are supplied with vascular tissue. They can develop from axillary or terminal buds.
In Bougainvillea, Punica granatum and Duranta, the axillary buds develop into spines and aid in climbing, while in Carissa carundus the terminal bud produces a pair of spines to aid in protection. In Duranta, the thorns give leaves and flowers. In Punica granatum, the thorns carry leaves and branches.
3. Hook: They are delicate, curved woody structures that develop from axillary or terminal buds. In Hugonia, axillary buds on opposite leaves develop into hooks. In Artabotrys, the apical bud develops into an inflorescence and the stem into a hook that aids in climbing.
4. phylloclade:It is a special rod modification. In general, plants growing in arid and desert regions have many adaptations to control the rate of transpiration. In these plants, the leaves are modified into scaly or prickly leaves. In these plants, the main stem or branches are modified into green leaf-like structures to carry out the function of photosynthesis. These leaf-like stems are called "phylloclates".
Specimens: Opuntia, Cocoloba, Casuarina etc.
In Opuntia, all leaves from the axillary bud turn into a cluster of thorns. Some thorns are small and appear like hairs. They are called peaks. The group of barbed spines present at each node is called an areola.
Types and functions of stems.
Important point !
Cladophyll or Cladodion: On some plants, one or more short, cylindrical or sometimes flattened, green, limited-growing branches develop from the stem or branch node in the axil of a scale leaf. Such a branch is known as cladophyllum. It is a variation of the phylloclate.
Example: asparagus, ruscus
In asparagus, cladophylls are green and cylindrical and occur in the leaf axils of the scales. Here the cladodes have an internode length.
In Ruscus, the flat green leaf-shaped organs are the cladophylls. They bear male or female flowers from a midpoint along their surface in the axil of another scale leaf. Here the cladodes are two internodes in length.
5. Bulbous stems: Above-ground stems that store food and become bulbous are called bulbous stems.
Example: Brassica oleracea gangyloides (cabbage), Bulbophyllum
Onbulbophile, an epiphyte, usually an internode (or sometimes the stem), stores food and water and becomes bulbous. It appears as a bulbous structure and is called a pseudobulb. This adaptation allows the plant to survive in unfavorable conditions.
In Knol-khol, the entire stem turns into a green tuberous stem.
6. Bulbs: In some plant species, the vegetative and flower buds are modified into condensed branches. They store groceries. These modified buds are called "bulbils". At maturity, the tubers develop into new plants, forming adventitious roots when separated from the plant. In this way, they participate in vegetative propagation.
OnDioscorea bulbiferaBulbils develop from the leaf axils. at theagave americanayGlobba bulbiferaThey develop in the axils of the inflorescence bracts. In some species of oxalis, a cluster of bulbils emerges from the soil at the tip of the bulbous root.
Types and functions of stems.
Subaerial beam mods
In some plants with weak stems, the stem remains partly above ground and partly underground. These stems are called subaerial stems. These specialize in vegetative propagation. There are four types of subaerial rods, namely runners, stolons, suckers and offsets. Let's study each of them
1. Corridor:In some plants with weak stems, the stems drag along the ground and root at the node. When the internodes break, the nodes lead independent lives. These weak-stemmed plants are called suckers. They help in vegetative propagation.
Example:Hydricotyle vulgaris, Lippia nodifloraand some species of oxalis.
2. Stolons: In some plants, long thin branches slant downward from the base of the stem. When these branches touch the ground, they form adventitious roots. These branches are called "spurs". When these corridors separate from the plant, they live as independent plants. The method of vegetative cultivation of layered plants mainly depends on the stolon principle.
Example:nerium, jasmineyPink. Mammal
3. Sucker:Plants like chrysanthemums and mint have part of the stem in the ground. Subterranean branches grow obliquely upward from the axillary buds of subterranean nodes. These branches produce many rope-like roots from their undersurface. These underground branches are called "suckers". When these corridors separate, they will develop into new plants.
4. Compensation: They are found in free-swimming aquatic plants such as pistia and eichhomia. In these plants, the stem is reduced to a disc-shaped structure. Many leaves develop in a rosette shape from this stem. The axillary shoots of these leaves develop into short, slender branches, usually an internode in length, and grow horizontally above the water. These branches are called "offsets". The apex of each unconformity has a cluster of leaves at the top and cord roots at the bottom. When these stumps are broken off, they develop into new plants. Offsets are rarely found in land plants like Agave americana.
Types and functions of stems.
Underground Tribe Mods
Formally, the stems are airy. But in some plants they grow underground. These types of stems are called "underground stems". They store food and become fleshy and bulky. They also act as vegetative and perennial reproductive organs. Since these stems grow underground, they are protected from herbivorous animals. Because they perform all these functions, underground plug modifications are also known as multipurpose plug modifications. These stems contain nodes, internodes, scales, leaves, axillary and terminal buds. Based on the growth pattern and the parts where the food material is stored, these stems are divided into four types, namely rhizome, corm, stem tuber and bulb. Let's study each of them
1. Rhizome: It is an underground stem that grows horizontally underground. Contains nodes and internodes. It differentiates dorsoventrally and produces aerial branches as well as "reproductive organs" on the dorsal side and adventitious roots on the ventral side. Fallen leaves are present at the nodes. The branches developed from the axillary buds not only store food, but also maintain the horizontal growth of the rhizome. The terminal bud develops and produces aerial branches. The underground rhizome remains alive even during drought.
Example: Zingiber officinalis, Curcuma longa, Musa paradisiaca and Carina indica
2. Tubers: This underground trunk grows vertically into the ground to a certain depth. It stores food materials that are synthesized in the aerial branches and become bulbous. It has nodes and internodes. The leaves are reduced to sheets of scales. The axillary buds of these scale leaves produce daughter tubercles. The apical bud is large and produces shoots above the ground. Cord roots usually develop from the base, but sometimes from the sides.
For example: Amorphophallus from Colocasia
Some plants, such as the corm Amorphophallus, are held down to a certain depth in the soil by a few specialized adventitious roots called "contractile roots" or "traction roots".
3. Stem tuber:In some plants, the branches that develop from the base of the stem to the ground. The tips of these underground branches store food and become bulbous. These are called "stem tubers"
Examples: Solanum tuberosum (batata), Helianthus tuberosus, Stachys tubifera.
The tuber is covered with a brown coating. It has many "eye"-like structures that represent the nodes. Each "eye" has a crescent-shaped leaf scar and an axillary bud in its armpit. The scar represents the position of the scale blade. These bulbous stem eyes aid in the vegetative propagation of the plant. Stem tubers have no roots. The root tuber stores starch in the potato. The stem tuber of Helianthus tuberosus stores "inulin", that of Stachys tubifera "stachyose".
4. Lamp:It's a special kind of clandestine tribe. The stem is reduced to a disc-shaped biconvex structure. Does not store food. The disk has many random roots at the bottom. Many leaves develop on top of the disc and grow above the ground. The bases of the leaves (leaf scales) store food and water and become fleshy. Axillary buds produce daughter bulbs. The terminal bud present in the center of the bulb develops into an aerial bud that produces inflorescences. The daughter bulbs help with vegetative propagation. The bulb is considered the only underground stem that does not store food.
Depending on the arrangement of the scale leaves, there are two types of onion.
Fireplace: In this species, the fleshy leaf bases, or scales, overlap in concentric circles. The entire bulb is covered with dry, scaly, membranous leaves called "tunica".
Example: Allium cepa (onion). 
Schuppenknolle:It is also known as "scaly tuber" or "naked tuber". In this, the scale leaves are fleshy and loose. The whole onion is not covered by the tunic.
Example: Lilium candidum, Allium sativum (garlic). In Allium sativum, a row of fleshy scaly leaves called cloves are arranged as scaly bulbs, and a bunch of these cloves is surrounded by a thin, whitish tunic.
Types and functions of stems.
Difference between rhizome and tuber.
| Rhizome | Government |
|---|---|
| It is an underground stem that grows horizontally. | It is an underground stem that grows vertically. |
| It is dorsiventral with adventitious roots on the ventral side. | There are dorsiventral cord roots that normally develop from the base. |
| The apical bud is small. | The apical bud is large. |
| Contractile (or tension) roots are absent | Contractile roots (or traction roots) are present |
| Example:ginger, saffron | Example:amorphous |
Difference between tuber stem and stem tuber.
| tuberous trunk | stem tuber |
|---|---|
| The tuberous stem is an aerial stem that stores food material. | It's a swollen end of an underground branch |
| has roots | has no roots |
| It's usually green | It is brown in color |
| goodbyes are missing | the eyes are present |
| Example:knol-kohl | Example:papaya |
The difference between Bulb and Bulbil
| pera | Bulbul |
|---|---|
| It is a small reduced underground trunk | It is a modified vegetative or floral button. |
| Does not store food. The food is stored on the underside of the leaves or on the scale leaves. | Store food stuff. |
| The daughter bulbs that develop from the axillary buds become new plants. | Bulbs separated from the parent plant become solitary plants. |
| It has adventitious roots at the bottom. | It has no adventitious roots until germination. |
| Example:a lily | Example:Dioscorea, Agave, Globba |
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