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Ciri-ciri Daun
#11
Leaf
From Wikipedia, the free encyclopedia
For other uses, see Leaf (disambiguation).

This article may be expanded with text translated from the corresponding article in German. (February 2017) Click [show] for important translation instructions.
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Leaf of Tilia tomentosa (Silver lime tree)

A leaf is an organ of a vascular plant and is the principal lateral appendage of the stem.[1] The leaves and stem together form the shoot.[2] Leaves are collectively referred to as foliage, as in "autumn foliage".[3][4]
Diagram of a simple leaf.

Apex Midvein (Primary vein) Secondary vein. Lamina. Leaf margin Petiole Bud Stem

Although leaves can be seen in many different shapes, sizes and textures, typically a leaf is a thin, dorsiventrally flattened organ, borne above ground and specialized for photosynthesis. In most leaves, the primary photosynthetic tissue, the palisade mesophyll, is located on the upper side of the blade or lamina of the leaf[1] but in some species, including the mature foliage of Eucalyptus,[5] palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves have distinctive upper surface (adaxial) and lower surface (abaxial) that differ in colour, hairiness, the number of stomata (pores that intake and output gases), epicuticular wax amount and structure and other features.

Broad, flat leaves with complex venation are known as megaphylls and the species that bear them, the majority, as broad-leaved or megaphyllous plants. In others, such as the clubmosses, with different evolutionary origins, the leaves are simple, with only a single vein and are known as microphylls.[6]

Some leaves, such as bulb scales are not above ground, and in many aquatic species the leaves are submerged in water. Succulent plants often have thick juicy leaves, but some leaves are without major photosynthetic function and may be dead at maturity, as in some cataphylls and spines. Furthermore, several kinds of leaf-like structures found in vascular plants are not totally homologous with them. Examples include flattened plant stems called phylloclades and cladodes, and flattened leaf stems called phyllodes which differ from leaves both in their structure and origin.[4][7] Many structures of non-vascular plants, such as the phyllids of mosses and liverworts and even of some foliose lichens, which are not plants at all (in the sense of being members of the kingdom Plantae), look and function much like leaves.

Contents

1 General characteristics
2 Morphology (large-scale features)
2.1 Basic leaf types
2.2 Arrangement on the stem
2.3 Divisions of the blade
2.4 Characteristics of the petiole
2.5 Veins
2.6 Morphology changes within a single plant
3 Anatomy (medium and small scale)
3.1 Medium-scale features
3.2 Small-scale features
3.3 Major leaf tissues
3.3.1 Epidermis
3.3.2 Mesophyll
3.3.3 Vascular tissue
4 Leaf development
5 Ecology
5.1 Biomechanics
5.2 Interactions with other organisms
5.3 Seasonal leaf loss
6 Evolutionary adaptation
7 Terminology
7.1 Shape
7.2 Edge (margin)
7.3 Apex (tip)
7.4 Base
7.5 Surface
7.6 Hairiness
7.7 Timing
7.8 Venation
7.8.1 Classification
7.8.1.1 Hickey system
7.8.1.2 Other systems
7.8.2 Other descriptive terms
7.9 Size
8 See also
9 References
10 Bibliography
10.1 Books and chapters
10.2 Articles and theses
10.3 Websites
11 External links

General characteristics
File:3D rendering of a micro CT scan of a piece of dried leaf..ogvPlay media
3D rendering of a computed tomography scan of a leaf

Leaves are the most important organs of most vascular plants.[8] Since plants are autotrophic, they do not require food from other living things to survive but instead use carbon dioxide, water and light energy, to create their own organic matter by photosynthesis of simple sugars, such as glucose and sucrose. These are then further processed by chemical synthesis into more complex organic molecules such as cellulose, the basic structural material in plant cell walls. The plant must therefore bring these three ingredients together in the leaf for photosynthesis to take place. The leaves draw water from the ground in the transpiration stream through a vascular conducting system known as xylem and obtain carbon dioxide from the atmosphere by diffusion through openings called stomata in the outer covering layer of the leaf (epidermis), while leaves are orientated to maximise their exposure to sunlight. Once sugar has been synthesized, it needs to be transported to areas of active growth such as the plant shoots and roots. Vascular plants transport sucrose in a special tissue called the phloem. The phloem and xylem are parallel to each other but the transport of materials is usually in opposite directions. Within the leaf these vascular systems branch (ramify) to form veins which supply as much as the leaf as possible, ensuring that cells carrying out photosynthesis are close to the transportation system.[9]

Typically leaves are broad, flat and thin (dorsiventrally flattened), thereby maximising the surface area directly exposed to light and enabling the light to penetrate the tissues and reach the chloroplasts, thus promoting photosynthesis. They are arranged on the plant so as to expose their surfaces to light as efficiently as possible without shading each other, but there are many exceptions and complications. For instance plants adapted to windy conditions may have pendent leaves, such as in many willows and eucalyptss. The flat, or laminar, shape also maximises thermal contact with the surrounding air, promoting cooling. Functionally, in addition to photosynthesis the leaf is the principal site of transpiration and guttation.

Many gymnosperms have thin needle-like or scale-like leaves that can be advantageous in cold climates with frequent snow and frost.[10] These are interpreted as reduced from megaphyllous leaves of their Devonian ancestors.[6] Some leaf forms are adapted to modulate the amount of light they absorb to avoid or mitigate excessive heat, ultraviolet damage, or desiccation, or to sacrifice light-absorption efficiency in favour of protection from herbivory. For xerophytes the major constraint is not light flux or intensity, but drought.[11] Some window plants such as Fenestraria species and some Haworthia species such as Haworthia tesselata and Haworthia truncata are examples of xerophytes.[12] and Bulbine mesembryanthemoides.[13]

Leaves also function to store chemical energy and water (especially in succulents) and may become specialised organs serving other functions, such as tendrils of peas and other legumes, the protective spines of cacti and the insect traps in carnivorous plants such as Nepenthes and Sarracenia.[14] Leaves are the fundamental structural units from which cones are constructed in gymnosperms (each cone scale is a modified megaphyll leaf known as a sporophyll)[6]:408 and from which flowers are constructed in flowering plants.[6]:445
Vein skeleton of a leaf. Veins contain lignin that make them harder to degrade for microorganisms.

The internal organisation of most kinds of leaves has evolved to maximise exposure of the photosynthetic organelles, the chloroplasts, to light and to increase the absorption of carbon dioxide while at the same time controlling water loss. Their surfaces are waterproofed by the plant cuticle and gas exchange between the mesophyll cells and the atmosphere is controlled by minute openings called stomata, about 10 μm which open or close to regulate the rate exchange of carbon dioxide, oxygen, and water vapour into and out of the internal intercellular space system. Stomatal opening is controlled by the turgor pressure in a pair of guard cells that surround the stomatal aperture. In any square centimeter of a plant leaf there may be from 1,000 to 100,000 stomata.[15]


Near the ground these Eucalyptus saplings have juvenile dorsiventral foliage from the previous year, but this season their newly sprouting foliage is isobilateral, like the mature foliage on the adult trees above

The shape and structure of leaves vary considerably from species to species of plant, depending largely on their adaptation to climate and available light, but also to other factors such as grazing animals (such as deer), available nutrients, and ecological competition from other plants. Considerable changes in leaf type occur within species too, for example as a plant matures; as a case in point Eucalyptus species commonly have isobilateral, pendent leaves when mature and dominating their neighbours; however, such trees tend to have erect or horizontal dorsiventral leaves as seedlings, when their growth is limited by the available light.[16] Other factors include the need to balance water loss at high temperature and low humidity against the need to absorb atmospheric carbon dioxide. In most plants leaves also are the primary organs responsible for transpiration and guttation (beads of fluid forming at leaf margins).

Leaves can also store food and water, and are modified accordingly to meet these functions, for example in the leaves of succulent plants and in bulb scales. The concentration of photosynthetic structures in leaves requires that they be richer in protein, minerals, and sugars than, say, woody stem tissues. Accordingly, leaves are prominent in the diet of many animals.
A leaf shed in autumn.

Correspondingly, leaves represent heavy investment on the part of the plants bearing them, and their retention or disposition are the subject of elaborate strategies for dealing with pest pressures, seasonal conditions, and protective measures such as the growth of thorns and the production of phytoliths, lignins, tannins and poisons.

Deciduous plants in frigid or cold temperate regions typically shed their leaves in autumn, whereas in areas with a severe dry season, some plants may shed their leaves until the dry season ends. In either case the shed leaves may be expected to contribute their retained nutrients to the soil where they fall.

In contrast, many other non-seasonal plants, such as palms and conifers, retain their leaves for long periods; Welwitschia retains its two main leaves throughout a lifetime that may exceed a thousand years.

The leaf-like organs of Bryophytes (e.g., mosses and liverworts), known as phyllids, differ morphologically from the leaves of vascular plants in that they lack vascular tissue, are usually only a single cell thick and have no cuticle stomata or internal system of intercellular spaces.

Simple, vascularised leaves (microphylls) first evolved as enations, extensions of the stem, in clubmosses such as Baragwanathia during the Silurian period. True leaves or euphylls of larger size and with more complex venation did not become widespread in other groups until the Devonian period, by which time the carbon dioxide concentration in the atmosphere had dropped significantly. This occurred independently in several separate lineages of vascular plants, in progymnosperms like Archaeopteris, in Sphenopsida, ferns and later in the gymnosperms and angiosperms. Euphylls are also referred to as macrophylls or megaphylls (large leaves).[6]
Morphology (large-scale features)
See also: Glossary of leaf morphology

A structurally complete leaf of an angiosperm consists of a petiole (leaf stalk), a lamina (leaf blade), and stipules (small structures located to either side of the base of the petiole). Not every species produces leaves with all of these structural components. Stipules may be conspicuous (e.g. beans and roses, soon falling or otherwise not obvious as in Moraceae or absent altogether as in the Magnoliaceae. A petiole may be absent, or the blade may not be laminar (flattened). The tremendous variety shown in leaf structure (anatomy) from species to species is presented in detail below under morphology. The petiole mechanically links the leaf to the plant and provides the route for transfer of water and sugars to and from the leaf. The lamina is typically the location of the majority of photosynthesis. The upper (adaxial) angle between a leaf and a stem is known as the axil of the leaf. It is often the location of a bud. Structures located there are called "axillary".
Translucent glands in Citrus leaves[17]

External leaf characteristics, such as shape, margin, hairs, the petiole, and the presence of stipules and glands, are frequently important for identifying plants to family, genus or species levels, and botanists have developed a rich terminology for describing leaf characteristics. Leaves almost always have determinate growth. They grow to a specific pattern and shape and then stop. Other plant parts like stems or roots have non-determinate growth, and will usually continue to grow as long as they have the resources to do so.

The type of leaf is usually characteristic of a species (monomorphic), although some species produce more than one type of leaf (dimorphic or polymorphic). The longest leaves are those of the Raffia palm, R. regalis which may be up to 25 m (82 ft) long and 3 m (9.8 ft) wide.[18] The terminology associated with the description of leaf morphology is presented, in illustrated form, at Wikibooks.
Prostrate leaves in Crossyne guttata

Where leaves are basal, and lie on the ground, they are referred to as prostrate.
Basic leaf types

Leaves of the White Spruce (Picea glauca) are needle-shaped and their arrangement is spiral

Ferns have fronds
Conifer leaves are typically needle- or awl-shaped or scale-like
Angiosperm (flowering plant) leaves: the standard form includes stipules, a petiole, and a lamina
Lycophytes have microphyll leaves.
Sheath leaves (type found in most grasses and many other monocots)
Other specialized leaves (such as those of Nepenthes, a pitcher plant)

Arrangement on the stem
Main article: Phyllotaxis

Different terms are usually used to describe the arrangement of leaves on the stem (phyllotaxis):
The leaves on this plant are arranged in pairs opposite one another, with successive pairs at right angles to each other (decussate) along the red stem. Note the developing buds in the axils of these leaves.

Alternate
One leaf, branch, or flower part attaches at each point or node on the stem, and leaves alternate direction, to a greater or lesser degree, along the stem.
Basal
Arising from the base of the stem.
Cauline
Arising from the aerial stem.
Opposite
Two leaves, branches, or flower parts attach at each point or node on the stem. Leaf attachments are paired at each node and decussate if, as typical, each successive pair is rotated 90° progressing along the stem.
Whorled, or verticillate
Three or more leaves, branches, or flower parts attach at each point or node on the stem. As with opposite leaves, successive whorls may or may not be decussate, rotated by half the angle between the leaves in the whorl (i.e., successive whorls of three rotated 60°, whorls of four rotated 45°, etc.). Opposite leaves may appear whorled near the tip of the stem. Pseudoverticillate describes an arrangement only appearing whorled, but not actually so.
Rosulate
Leaves form a rosette.
Rows
The term, distichous, literally means two rows. Leaves in this arrangement may be alternate or opposite in their attachment. The term, 2-ranked, is equivalent. The terms, tristichous and tetrastichous, are sometimes encountered. For example, the "leaves" (actually microphylls) of most species of Selaginella are tetrastichous, but not decussate.

As a stem grows, leaves tend to appear arranged around the stem in a way that optimizes yield of light. In essence, leaves form a helix pattern centered around the stem, either clockwise or counterclockwise, with (depending upon the species) the same angle of divergence. There is a regularity in these angles and they follow the numbers in a Fibonacci sequence: 1/2, 2/3, 3/5, 5/8, 8/13, 13/21, 21/34, 34/55, 55/89. This series tends to the golden angle, which is approximately 360° × 34/89 ≈ 137.52° ≈ 137° 30′. In the series, the numerator indicates the number of complete turns or "gyres" until a leaf arrives at the initial position and the denominator indicates the number of leaves in the arrangement. This can be demonstrated by the following:

Alternate leaves have an angle of 180° (or 1/2)
120° (or 1/3): 3 leaves in 1 circle
144° (or 2/5): 5 leaves in 2 gyres
135° (or 3/8): 8 leaves in 3 gyres.

Divisions of the blade

A leaf with laminar structure and pinnate venation

Two basic forms of leaves can be described considering the way the blade (lamina) is divided. A simple leaf has an undivided blade. However, the leaf shape may be formed of lobes, but the gaps between lobes do not reach to the main vein. A compound leaf has a fully subdivided blade, each leaflet of the blade being separated along a main or secondary vein. The leaflets may have petiolules and stipels, the equivalents of the petioles and stipules of leaves. Because each leaflet can appear to be a simple leaf, it is important to recognize where the petiole occurs to identify a compound leaf. Compound leaves are a characteristic of some families of higher plants, such as the Fabaceae. The middle vein of a compound leaf or a frond, when it is present, is called a rachis.

Palmately compound
Leaves have the leaflets radiating from the end of the petiole, like fingers of the palm of a hand; e.g., Cannabis (hemp) and Aesculus (buckeyes).
Pinnately compound
Leaves have the leaflets arranged along the main or mid-vein.

Odd pinnate
With a terminal leaflet; e.g., Fraxinus (ash).
Even pinnate
lacking a terminal leaflet; e.g., Swietenia (mahogany).

Bipinnately compound
Leaves are twice divided: the leaflets are arranged along a secondary vein that is one of several branching off the rachis. Each leaflet is called a "pinnule". The group of pinnules on each secondary vein forms a "pinna"; e.g., Albizia (silk tree).
Trifoliate (or trifoliolate)
A pinnate leaf with just three leaflets; e.g., Trifolium (clover), Laburnum (laburnum).
Pinnatifid
Pinnately dissected to the central vein, but with the leaflets not entirely separate; e.g., Polypodium, some Sorbus (whitebeams). In pinnately veined leaves the central vein in known as the midrib.

Characteristics of the petiole
The overgrown petioles of rhubarb (Rheum rhabarbarum) are edible.

Petiolated leaves have a petiole (leaf stalk), and are said to be petiolate.

Sessile (epetiolate) leaves have no petiole and the blade attaches directly to the stem. Subpetiolate leaves are nearly petiolate or have an extremely short petiole and may appear to be sessile.

In clasping or decurrent leaves, the blade partially surrounds the stem.

When the leaf base completely surrounds the stem, the leaves are said to be perfoliate, such as in Eupatorium perfoliatum.

In peltate leaves, the petiole attaches to the blade inside the blade margin.

In some Acacia species, such as the koa tree (Acacia koa), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes. There may or may not be normal pinnate leaves at the tip of the phyllode.

A stipule, present on the leaves of many dicotyledons, is an appendage on each side at the base of the petiole, resembling a small leaf. Stipules may be lasting and not be shed (a stipulate leaf, such as in roses and beans), or be shed as the leaf expands, leaving a stipule scar on the twig (an exstipulate leaf). The situation, arrangement, and structure of the stipules is called the "stipulation".

Free, lateral
As in Hibiscus.
Adnate
Fused to the petiole base, as in Rosa.
Ochreate
Provided with ochrea, or sheath-formed stipules, as in Polygonaceae; e.g., rhubarb.
Encircling the petiole base

Interpetiolar
Between the petioles of two opposite leaves, as in Rubiaceae.
Intrapetiolar
Between the petiole and the subtending stem, as in Malpighiaceae.

Veins
See also: § Venation, and § Vascular tissue
Branching veins on underside of taro leaf
The venation within the bract of a lime tree
Micrograph of a leaf skeleton

Veins (sometimes referred to as nerves) constitute one of the more visible leaf traits or characteristics. The veins in a leaf represent the vascular structure of the organ, extending into the leaf via the petiole and provide transportation of water and nutrients between leaf and stem, and play a crucial role in the maintenance of leaf water status and photosynthetic capacity.They also play a role in the mechanical support of the leaf.[19][20] Within the lamina of the leaf, while some vascular plants possess only a single vein, in most this vasculature generally divides (ramifies) according to a variety of patterns (venation) and form cylindrical bundles, usually lying in the median plane of the mesophyll, between the two layers of epidermis.[21] This pattern is often specific to taxa, and of which angiosperms possess two main types, parallel and reticulate (net like). In general, parallel venation is typical of monocots, while reticulate is more typical of eudicots and magnoliids ("dicots"), though there are many exceptions.[22][21][23]

The vein or veins entering the leaf from the petiole are called primary or first order veins. The veins branching from these are secondary or second order veins. These primary and secondary veins are considered major veins or lower order veins, though some authors include third order.[24] Each subsequent branching is sequentially numbered, and these are the higher order veins, each branching being associated with a narrower vein diameter.[25] In parallel veined leaves, the primary veins run parallel and equidistant to each other for most of the length of the leaf and then converge or fuse (anastomose) towards the apex. Usually many smaller minor veins interconnect these primary veins, but may terminate with very fine vein endings in the mesophyll. Minor veins are more typical of angiosperms, which may have as many as four higher orders.[24] In contrast, leaves with reticulate venation there is a single (sometimes more) primary vein in the centre of the leaf, referred to as the midrib or costa and is continuous with the vasculature of the petiole more proximally. The midrib then branches to a number of smaller secondary veins, also known as second order veins, that extend toward the leaf margins. These often terminate in a hydathode, a secretory organ, at the margin. In turn, smaller veins branch from the secondary veins, known as tertiary or third order (or higher order) veins, forming a dense reticulate pattern. The areas or islands of mesophyll lying between the higher order veins, are called areoles. Some of the smallest veins (veinlets) may have their endings in the areoles, a process known as areolation.[25] These minor veins act as the sites of exchange between the mesophyll and the plant's vascular system.[20] Thus minor veins collect the products of photosynthesis (photosynthate) from the cells where it takes place, while major veins are responsible for its transport outside of the leaf. At the same time water is being transported in the opposite direction.[26][22][21]

The number of vein endings is very variable, as is whether second order veins end at the margin, or link back to other veins.[23] There are many elaborate variations on the patterns that the leaf veins form, and these have functional implications. Of these, angiosperms have the greatest diversity.[24] Within these the major veins function as the support and distribution network for leaves and are correlated with leaf shape. For instance the parallel venation found in most monocots correlates with their elongated leaf shape and wide leaf base, while reticulate venation is seen in simple entire leaves, while digitate leaves typically have venation in which three or more primary veins diverge radially from a single point.[27][20][25][28]

In evolutionary terms, early emerging taxa tend to have dichotomous branching with reticulate systems emerging later. Veins appeared in the Permian period (299–252 mya), prior to the appearance of angiosperms in the Triassic (252–201 mya), during which vein hierarchy appeared enabling higher function, larger leaf size and adaption to a wider vaiety of climatic conditions.[24] Although it is the more complex pattern, branching veins appear to be plesiomorphic and in some form were present in ancient seed plants as long as 250 million years ago. A pseudo-reticulate venation that is actually a highly modified penniparallel one is an autapomorphy of some Melanthiaceae, which are monocots; e.g., Paris quadrifolia (True-lover's Knot). In leaves with reticulate venation, veins form a scaffolding matrix imparting mechanical rigidity to leaves.[29]
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#12
Mimosa pudica
From Wikipedia, the free encyclopedia
Mimosa pudica
Mimosa pudica - Kerala 1.jpg
Mimosa pudica showing flower head and leaves
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Fabales
Family: Fabaceae
Subfamily: Mimosoideae
Genus: Mimosa
Species: M. pudica
Binomial name
Mimosa pudica
L.[1]

Mimosa pudica[2] (from Latin: pudica "shy, bashful or shrinking"; also called sensitive plant, sleepy plant, Dormilones, touch-me-not, or shy plant) is a creeping annual or perennial herb of the pea family Fabaceae often grown for its curiosity value: the compound leaves fold inward and droop when touched or shaken, defending themselves from harm, and re-open a few minutes later.[3] The species is native to South America and Central America, but is now a pantropical weed. It can also be found in Asia in countries such as Bangladesh, Thailand, India, Indonesia, Malaysia, Philippines, and Japan. It grows mostly in undisturbed shady areas, under trees or shrubs.

Contents

1 Taxonomy
2 Description
2.1 Plant movement
3 Distribution and habitat
4 Agricultural impacts
4.1 Nitrogen fixation
5 Cultivation
6 Chemical constituents
7 See also
8 References
9 External links

Taxonomy

Mimosa pudica was first formally described by Carl Linnaeus in Species Plantarum in 1753.[4] The species epithet, pudica, is Latin for "bashful" or "shrinking", alluding to its shrinking reaction to contact.

The species is known by numerous common names including sensitive plant, humble plant, shameplant, and touch-me-not.[5]
Description
Mimosa pudica flower from Thrissur, Kerala, India
Flower
Mimosa pudica folding leaflets inward.
Mimosa pudica seeds
Mimosa pudica with mature seed pods on plant
The whole plant of Mimosa pudica includes thorny stem and branches, flower head, dry flowers, seed pods, and folded and unfolded leaflets

The stem is erect in young plants, but becomes creeping or trailing with age. It can hang very low and become floppy. The stem is slender, branching, and sparsely to densely prickly, growing to a length of 1.5 m (5 ft).

The leaves are bipinnately compound, with one or two pinnae pairs, and 10–26 leaflets per pinna. The petioles are also prickly. Pedunculate (stalked) pale pink or purple flower heads arise from the leaf axils in mid summer with more and more flowers as the plant gets older. The globose to ovoid heads are 8–10 mm in diameter (excluding the stamens). On close examination, it is seen that the floret petals are red in their upper part and the filaments are pink to lavender. The fruit consists of clusters of 2–8 pods from 1–2 cm long each, these being prickly on the margins. The pods break into 2–5 segments and contain pale brown seeds some 2.5 mm long. The flowers are pollinated by the wind and insects.[6] The seeds have hard seed coats which restrict germination.[7]

The roots of Mimosa pudica create carbon disulfide, which prevents certain pathogenic and mycorrhizal fungi from growing within the plant’s rhizosphere.[8] This allows the formation of nodules on the roots of the plant that contain endosymbiotic diazotrophs, which fix atmospheric nitrogen and convert it into a form that is usable by the plant.[9]

Mimosa pudica is a tetraploid (2n = 52).[10]
Plant movement
File:Mimosa pudica in Hainan.ogvPlay media
Video of Mimosa pudica closing when touched in Hainan, China

Mimosa pudica is well known for its rapid plant movement. Like a number of other plant species, it undergoes changes in leaf orientation termed "sleep" or nyctinastic movement. The foliage closes during darkness and reopens in light.[11] This was first studied by the French scientist Jean-Jacques d'Ortous de Mairan.

The leaflets also close when stimulated in other ways, such as touching, warming, blowing, or shaking. These types of movements have been termed seismonastic movements. The stimulus is transmitted as an action potential from a stimulated leaflet, to the leaflet's swollen base (pulvinus), and from there to the pulvini of the other leaflets, which run along the length of the leaf's rachis. The action potential then passes into the petiole, and finally to the large pulvinus at the end of the petiole, where the leaf attaches to the stem. The action potential causes potassium ions to flow out from the vacuoles of cells in the various pulvini. This causes water to flow out from those cells by osmosis through aquaporin channels, making them lose turgor, which is the force that is applied onto the cell wall by water within the cell. Differences in turgidity in different regions of the leaf and stem results in the closing of the leaflets and the collapse of the leaf petiole. [12]

This movement of folding inwards is energetically costly for the plant and also interferes with the process of photosynthesis.[13] This characteristic is quite common within the Mimosoideae subfamily of the legume family, Fabaceae. The stimulus can also be transmitted to neighboring leaves. It is not known exactly why Mimosa pudica evolved this trait, but many scientists think that the plant uses its ability to shrink as a defense from herbivores. Animals may be afraid of a fast moving plant and would rather eat a less active one. Another possible explanation is that the sudden movement dislodges harmful insects.[citation needed]
Distribution and habitat

Mimosa pudica is native to South America, North America and Central America. It has been introduced to many other regions and is regarded as an invasive species in Tanzania, South Asia and South East Asia and many Pacific Islands.[14] It is regarded as invasive in parts of Australia and is a declared weed in the Northern Territory,[15] and Western Australia although not naturalized there.[16] Control is recommended in Queensland.[17] It has also been introduced to Ghana, Nigeria, Seychelles, Mauritius and East Asia but is not regarded as invasive in those places.[14] In the United States of America, it grows in Florida, Hawaii, Tennessee, Virginia, Maryland, Puerto Rico, Texas, Alabama, Mississippi, North Carolina, Georgia, and the Virgin Islands, as well as Cuba and the Dominican Republic.[18]
Agricultural impacts

The species can be a troublesome weed in tropical crops, particularly when fields are hand cultivated. Crops it tends to affect are corn, coconuts, tomatoes, cotton, coffee, bananas, soybeans, papaya, and sugar cane. Dry thickets may become a fire hazard.[6] In some cases it has become a forage plant although the variety in Hawaii is reported to be toxic to livestock.[6][19]

In addition, Mimosa pudica can change the physico-chemical properties of the soil it invades. For example, the total N and K increased in significantly invaded areas.[20]
Nitrogen fixation

Mimosa pudica can form root nodules that are habitable by nitrogen-fixing bacteria.[21] The bacteria are able to convert atmospheric nitrogen, which plants cannot use, into a form that plants can use. This trait is common among plants in the Fabaceae family. Nitrogen is a vital element for both plant growth and reproduction. Nitrogen is also essential for plant photosynthesis because it is a component of chlorophyll. Nitrogen fixation contributes nitrogen to the plant and to the soil surrounding the plant's roots.[22]

Mimosa pudica’s ability to fix nitrogen may have arisen in conjunction with the evolution of nitrogen-fixing bacteria. Nitrogen fixation is an adaptive trait that has transformed the parasitic relationship between the bacteria and plants into a mutualistic relationship. The shifting dynamics of this relationship are demonstrated by the corresponding improvement of various symbiotic characteristics in both Mimosa pudica and bacteria. These traits include enhanced “competitive nodulation, nodule development, intracellular infection, and bacteroid persistence”.[23] As much as 60% of the nitrogen found in Mimosa pudica can be attributed to the fixation of N2 by bacteria. Burkholderia phymatum STM815T and Cupriavidus taiwanensis LMG19424T are beta-rhizobial strains of diazotrophs that are highly effective at fixing nitrogen when coupled with M. pudica. Burkholderia is also shown to be a strong symbiont of Mimosa pudica in nitrogen-poor soils in regions like Cerrado and Caatinga.[9]
Cultivation

In cultivation, this plant is most often grown as an indoor annual, but is also grown for groundcover. Propagation is generally by seed. Mimosa pudica grows most effectively in nutrient poor soil that allows for substantial water drainage. However, this plant is also shown to grow in scalped and eroded subsoils. Typically, disrupted soil is necessary in order for M. pudica to become established in an area. Additionally, the plant is shade intolerant and frost-sensitive, meaning that it does not tolerate low levels of light or cold temperatures. Mimosa pudica does not compete for resources with larger foliage or forest canopy undergrowth.[8]
Chemical constituents

Mimosa pudica contains the toxic alkaloid mimosine, which has been found to also have antiproliferative and apoptotic effects.[24] The extracts of Mimosa pudica immobilize the filariform larvae of Strongyloides stercoralis in less than one hour.[25] Aqueous extracts of the roots of the plant have shown significant neutralizing effects in the lethality of the venom of the monocled cobra (Naja kaouthia). It appears to inhibit the myotoxicity and enzyme activity of cobra venom.[26]

Mimosa pudica demonstrates both antioxidant and antibacterial properties. This plant has also been demonstrated to be non-toxic in brine shrimp lethality tests, which suggests that M. pudica has low levels of toxicity. Chemical analysis has shown that Mimosa pudica contains various compounds, including “alkaloids, flavonoid C-glycosides, sterols, terenoids, tannins, and fatty acids”.[27] The roots of the plant have been shown to contain up to 10% tannin. A substance similar to adrenaline has been found within the plant's leaves. Mimosa pudica's seeds produce mucilage made up of D-glucuronic acid and D-xylose. Additionally, extracts of M. pudica have been shown to contain crocetin-dimethylester, tubulin, and green-yellow fatty oils. A new class of phytohormone turgorines, which are derivatives of gallic acid 4-O-(β-D-glucopyranosyl-6'-sulfate), have been discovered within the plant.[8]

The nitrogen-fixing properties of Mimosa pudica contribute to a high nitrogen content within the plant’s leaves. The leaves of M. pudica also contain a wide range of carbon to mineral content, as well as, a large variation in 13C values. The correlation between these two numbers suggests that significant ecological adaptation has occurred among the varieties of M. pudica in Brazil.[22]

The roots contain sac-like structures that release organic and organosulfur compounds including SO2, methylsulfinic acid, pyruvic acid, lactic acid, ethanesulfinic acid, propane sulfinic acid, 2-mercaptoaniline, S-propyl propane 1-thiosulfinate, and thioformaldehyde, an elusive and highly unstable compound never before reported to be emitted by a plant.[28]
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#13
too much to read..
i didn't get it..
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#14
baca lagi saja dewa supaya kamu mengerti.
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#15
Nanti aku baca deh..
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#16
yang mana yang kamu tidak mengerti dewa?
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#17
menterjemahkannya francesco..
aku jadi pusing..
hehe
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