what does cytokinin do in plants

Cytokinin Functions

• Stimulates cell division.
• Stimulates morphogenesis (shoot initiation/bud formation) in tissue culture.
• Stimulates the growth of lateral buds-release of apical dominance.
• Stimulates leaf expansion resulting from cell enlargement.
• May enhance stomatal opening in some species.
• Promotes the conversion of etioplasts into chloroplasts via stimulation of chlorophyll synthesis.

Full Answer

What are cytokinins?

Cytokinins are a group of hormones that promote cell division in plant roots and shoots and the growth of buds.

What is cytokinin action in vascular plants?

While cytokinin action in vascular plants is described as pleiotropic, this class of plant hormones specifically induces the transition from apical growth to growth via a three-faced apical cell in moss protonema.

How does cytokinin promote shoot growth?

This promotes shoot growth, and restricts lateral branching. Cytokinin moves from the roots into the shoots, eventually signaling lateral bud growth. Simple experiments support this theory. When the apical bud is removed, the axillary buds are uninhibited, lateral growth increases, and plants become bushier.

How do you control cytokinin degradation in plant cells?

Most of the control mechanisms depend directly on the concentration and/or compartmentation of the cytokinins in the cell. Cytokinin degradation in plant cells is significantly enhanced in vivo after their exposure to exogenous cytokinins [ 156,157 ].

What is the role of cytokinin in plants?

Cytokinins promote cell division and increase cell expansion during the proliferation and expansion stages of leaf cell development, respectively. During leaf senescence, cytokinins reduce sugar accumulation, increase chlorophyll synthesis, and prolong the leaf photosynthetic period.

What is the main effect of cytokinin?

Cytokinins induce cell division and promote the growth of developing shoot buds, root apices, young fruits, etc. It promotes the development of lateral shoot and thereby helps in overcoming apical dominance. Cytokinins delay leaf senescence by promoting nutrient mobilisation.

What are the two functions of cytokinin?

Cytokinins are synthesized in the root apex of plants. The two functions of cytokinins include an increase in cell division and delay of senescence.

Does cytokinins affect plant growth?

Cytokinins are N6 substituted adenine derivatives that affect many aspects of plant growth and development, including cell division, shoot initiation and growth, leaf senescence, apical dominance, sink/source relationships, nutrient uptake, phyllotaxis, and vascular, gametophyte, and embryonic development, as well as ...

What is the function of auxin and cytokinin?

The hormones auxin and cytokinin are key regulators of plant growth and development. As they are active at minute concentrations and regulate dynamic processes, cell and tissue levels of the hormones are finely controlled developmentally, diurnally, and in response to environmental variables.

What is the mode of action of cytokinin?

At the cell level, cytokinins act by controlling the expression of many genes [49], the development of chloroplasts [36] and by stimulating the synthesis of secondary metabolites like betacyanins [3] or indolic alkaloids [32].

What is cytokinin short answer?

cytokinin, any of a number of plant hormones that influence growth and the stimulation of cell division. Cytokinins are synthesized in the roots and are usually derived from adenine.

Where is cytokinins produced in plants?

Where are cytokinins produced in plants? Cytokinins are more abundant in developing tissues and organs, such as root tip, shoot apex, cambium, and immature organs, and initially it was thought that cytokinins are synthesized in these limited tissues and organs.

What is the role of cytokinin in seed germination?

Cytokinins were applied to stimulate subsequent regeneration in seedlings. However, an unexpected effect was noted with respect to seed germination. All cytokinins used were able to accelerate the germination rate and increase the final germination percentage.

Does cytokinin promote root growth?

Cytokinin (CK), synthesized in the root cap, promotes cytokinesis, vascular cambium sensitivity, vascular differentiation and root apical dominance. Auxin (indole-3-acetic acid, IAA), produced in young shoot organs, promotes root development and induces vascular differentiation.

Is cytokinin a stress hormone?

Recently, it has been established that cytokinin plays an important role in stress responses, but does not act alone. Indeed, the hormonal control of plant development and stress adaptation is the outcome of a complex network of multiple synergistic and antagonistic interactions between various hormones.

What hormone makes leaves change color?

Ethylene (plant hormone responsible for ripening and senescence), Abscisic acid -ABA (stress hormone), and Auxin (growth hormone) all play a symphony and cause 'Abscission- falling/separation of leaf tissue' from the plant.

What is the main function performed by cytokinin class 11?

cell divisionThe main function of cytokinin is to promote cytokinesis or cell division.

Which of the following is the main effect of cytokinins in the tissue culture system?

promote shoot formationWhich of the following is the main effect of cytokines in the tissue culture system? Explanation: Cytokines promote shoot formation while it inhibits the formation of roots. It also promotes cell division and callus formation. 9.

What effect do cytokinins have on cell division?

Cytokinin influences cell division activity in embryos and mature plants through altering the size and activity of meristems as seen when cytokinin levels are altered, by transgenes such as IPT or CKX (Medford et al., 1989; Werner et al., 2001), and by mutations such as amp1 (Chaudhury et al., 1993).

What is the main origin of cytokinin?

Cytokinins are synthesized in the roots and are usually derived from adenine. They move upward in the xylem (woody tissue) and pass into the leaves and fruits, where they are required for normal growth and cell differentiation.

1. Why it is called cytokinin?

The biochemical substance that promotes cytokinesis or cell division is called cytokinin. It is a plant hormone produced by the roots in complex sp...

2. What is the function of a hormone?

Hormones are steroidal biochemical substances produced naturally in a living organism to promote different functions. For instance, auxin is a plan...

3. What is the prime role of cytokinin in plant growth and development?

This hormone promotes protein synthesis in plant cells. It helps a plant cell to increase in size and to attain the foundation stage to conduct mit...

Why are cytokinins used in plants?

Uses. Because cytokinins promote plant cell division and growth, they have been studied since the 1970s as potential agrochemicals, however they have yet to be widely adopted, probably due to the complex nature of their effects.

How does cytokinin signaling work in plants?

Cytokinin signaling in plants is mediated by a two-component phosphorelay. This pathway is initiated by cytokinin binding to a histidine kinase receptor in the endoplasmic reticulum membrane. This results in the autophosphorylation of the receptor, with the phosphate then being transferred to a phosphotransfer protein.

What is the relationship between cytokinin and auxin?

A higher ratio of cytokinin induces growth of shoot buds, while a higher ratio of auxin auxin induces root formation. Cytokinins have been shown to slow aging of plant organs by preventing protein breakdown, activating protein synthesis, and assembling nutrients from nearby tissues.

How does cytokinin affect plant growth?

Cytokinins are involved in many plant processes, including cell division and shoot and root morphogenesis. They are known to regulate axillary bud growth and apical dominance. According to the "direct inhibition hypothesis", these effects result from the ratio of cytokinin to auxin. This theory states that auxin from apical buds travels down shoots to inhibit axillary bud growth. This promotes shoot growth, and restricts lateral branching. Cytokinin moves from the roots into the shoots, eventually signaling lateral bud growth. Simple experiments support this theory. When the apical bud is removed, the axillary buds are uninhibited, lateral growth increases, and plants become bushier. Applying auxin to the cut stem again inhibits lateral dominance. Moreover, it has been shown that cytokinin alone has no effect on parenchyma cells. When cultured with auxin but no cytokinin, they grow large but do not divide. When cytokinin and auxin are both added together, the cells expand and differentiate. When cytokinin and auxin are present in equal levels, the parenchyma cells form an undifferentiated callus. A higher ratio of cytokinin induces growth of shoot buds, while a higher ratio of auxin auxin induces root formation.

What is the name of the hormone that promotes cell division in plants?

The cytokinin zeatin is named after the genus of corn, Zea. Cytokinins ( CK) are a class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth, and leaf senescence.

How much does cytokinin increase yield?

One study found that applying cytokinin to cotton seedlings led to a 5–10% increase in yield under drought conditions. Some cytokinins are utilized in tissue culture of plants and can also be used to promote the germination of seeds.

What is the role of cytokinin in tobacco?

Cytokinins have recently been found to play a role in plant pathogenesis.

What is a cytokinin?

Read More on This Topic. hormone: Cytokinins. Cytokinin s are compounds derived from a nitrogen-containing compound (adenine). One cytokinin is 6-furfurylaminopurine... Cytokinins such as 6-furfurylaminopurine ( kinetin) are used commercially in the storage of green vegetables to reduce yellowing.

Where do cytokinins come from?

Cytokinins are synthesized in the roots and are usually derived from adenine. They move upward in the xylem (woody tissue) and pass into the leaves and fruits, where they are required for normal growth and cell differentiation.

What hormones are involved in senescence?

Cytokinins also act in conjunction with auxin ( another plant hormone) to retard senescence, which, at least in its early stages, is an organized phase of metabolism and not just a breakdown of tissue.

How do cytokinins affect plants?

Cytokinins are one of the major plant hormones that regulate numerous aspects of growth and development. Although the role of cytokinins in various developmental processes has been well characterized, our knowledge on their effect on plant stress tolerance is still fragmentary. This is possibly because of complex crosstalk between cytokinin and stress signaling, especially the response related to abiotic stress tolerance ( Zwack and Rashotte, 2015 ). In many developmental processes, cytokinin and gibberellins act antagonistically. Although most studies profoundly suggest a gibberellin-regulated cytokinin action, evidence relating to cytokinin regulating gibberellin activity cannot be ignored. In tomato, cytokinins inhibit gibberellin-dependent hypocotyl elongation as well as leaf serration ( Fleishon et al., 2011 ). One of the most important mechanisms that plants deploy to minimize heat injury is by cooling leaves, the most important organ that performs photosynthesis. Leaf cooling is achieved by increasing transpiration under heat stress. In this response cytokinins play a critical role by stimulating stomatal opening that facilitates transpiration. Cytokinins can induce a number of heat-responsive proteins including small heat shock proteins and glycine-rich proteins under heat stress. Overexpression of cytokinin biosynthetic genes increases endogenous cytokinin levels that eventually enhance heat stress tolerance in grass ( Xing et al., 2009 ). In addition, upregulation of the endogenous cytokinin level by exogenous application of cytokinin can also improve tolerance to heat stress in bent grass ( Xu and Huang, 2009 ). Transgenic tobacco plants overexpressing the cytokinin oxidase/dehydrogenase-1 gene of A. thaliana L. show reduced and delayed stomatal response, but maintain a lower leaf temperature ( Mackova et al., 2013 ).

What controls the levels of cytokinins in plants?

A complex biosynthetic and degradation network controls the levels of the large family of cytokinin molecules found in plants. The mode of action of each cytokinin is determined by a vast spectrum of molecules and interconnecting metabolic pathways. Cytokinins were the second plant hormone (after ethylene) for which receptors were discovered. As was the case for ethylene, the cytokinin receptors were found to be histidine kinase sensors. Interestingly, the two-component signaling system employed by cytokinins in the plant kingdom seems to be absent from the animal kingdom. The diversity of cytokinins and their biological responses, associated with a relatively simple transduction cascade, constitute a paradigm that represents the next challenge for understanding the role of this fundamental plant growth factor.

What are CKs in plants?

Cytokinins (CKs) are the phytohormones involved in cytokinesis and that promote cell division and differentiation. Cytokinin levels were reported to be downregulated during drought stress. This leads to low CK level in roots and leaves (Merewitz et al., 2010 ). Several plants like bentgrass, tobacco, and rice have been proved to be more drought tolerant when either exogenously supplied with CK compounds or overexpressed adenosine phosphate-isopentyl transferase ( IPT) genes ( Peleg et al., 2011 ). It has been suggested that drought mediated signaling hindered the CK production either at CK biosynthesis or at degradation level. Transcript analysis of IPT transgenic plant compared with WT plant was having less upregulated and more downregulated drought-responsive gene ( Rivero et al., 2010 ). It suggested that CK regulates several metabolic processes drought-responsive genes. Interestingly, overexpression of cytokinin degradation enzymes cytokinin oxidase/dehydrogenase1 (CKX1) by the root-specific promoter WRKY6 showed more degradation and low level of CK in root which leads to enlarging the root system required for more water absorption in a water deficit environment ( Macková et al., 2013 ). From these data, it can be hypothesized that in water deficit conditions, low level (WTKY6: CKX1) of cytokinins in roots while high IPT level in shoots (35S: CKX1) have more tolerant effects against drought.

What is the role of cytokinins in shoot regeneration?

Cytokinins play pivotal roles in de novo regeneration. Treatment with exogenous cytokinin induces cell proliferation and stimulates shoot induction from calli ( Skoog & Miller, 1957 ). Expression of the Agrobacterium ipt gene to increase endogenous cytokinin levels in the callus can also induce cell division and initiate shoot formation ( Ebinuma, Sugita, Matsunaga, & Yamakado, 1997; Kunkel, Niu, Chan, & Chua, 1999 ). Endogenous cytokinin biosynthesis mediated by AtIPT genes in Arabidopsis are analyzed during shoot regeneration ( Cheng et al., 2013 ). AtIPT3, AtIPT5, and AtIPT7 transcription is upregulated during shoot initiation, suggesting that cytokinin biosynthesis is enhanced during this process. In addition, AtIPT5 exhibits spatiotemporal expression patterns during shoot induction. In mature callus grown on CIM, AtIPT5 expression is detected at low levels around callus edges, while shoot induction on SIM induces strong but restricted AtIPT5 signal distribution at future shoot initiation sites. Patterns of cytokinin biosynthesis appear to be similar to those of cytokinin response, indicating that localized AtIPT -mediated cytokinin biosynthesis contributes to the spatiotemporal distribution of cytokinin response for de novo shoot regeneration.

How are cytokinins degraded?

Cytokinins can be degraded through the activity of a cytokinin oxidase which removes the isopentenyl side chain, yielding the adenine or adenosine from the cytokinin base or nucleoside, respectively.437,581 This reaction requires molecular oxygen. 582 Cytokinin oxidase was purified from wheat, maize kernels, 582 and callus tissues of tobacco 583 and bean, 581 and proved to be a glycoprotein. Synthetic cytokinins with an aromatic substituent at position N6 of the purine ring, such as kinetin and benzyladenine, are resistant to this oxidase. 582 Cytokinin oxidase activity increases 1 h after application of a cytokinin to Phaseolus callus tissues, 581 and this induction is inhibited by a urea derivative, thidiazuron. 584 The activity of this enzyme is also increased as a consequence of elevated cytokinin levels which are caused by the derepression of the tetracycline-dependent ipt gene transcription in tobacco calli and plants transformed with ipt. 585 Auxin enhances the activity of cytokinin oxidase which is purified from tobacco callus tissues transformed with ipt from the T-DNA. 572 This enhancement could contribute to the reduction in cytokinin levels which have been elevated in the transgenic tissues.

What are the cytokinins in the xylem?

The cytokinins present in the xylem exudate are predominantly nucleotides. Once they reach the leaves, they may be converted to the free base or to glucosides. Cytokinin glucosides accumulate to high levels in leaves. Even senescing leaves may have substantial amounts of cytokinin glucosides.

How are cytokinins transported?

Cytokinins are passively transported from roots into the shoot through the xylem. They move through the plant with the transpiration stream along with water and minerals taken up by the roots. The cytokinins present in the xylem exudate are predominantly nucleotides. Once they reach the leaves, they may be converted to the free base or to glucosides. Cytokinin glucosides accumulate to high levels in leaves. Even senescing leaves may have substantial amounts of cytokinin glucosides. Although the glucosides are active as cytokinins in bioassays, they appear to lack hormonal activity after they are formed in leaf cells, possibly because they are compartmentalized in such a way that they are unavailable. This may explain the conflicting observations that, even though cytokinins appear to be readily, although passively, transported by the xylem, when radioactive cytokinins are given to leaves in intact plants, they do not appear to move from the site of application. Glycosylation may be a mechanism for inactivation of cytokinins, along with cytokinin oxidation. Many plant tissues have the enzyme cytokinin oxidase, which will convert zeatin, zeatin riboside, and i6 Ade to adenine or its derivatives. This enzyme inactivates the hormone, possibly as a mechanism for preventing accumulation of toxic levels of the hormone.

Where are cytokinins found in plants?

There are some 200 different types of synthetic and natural cytokinins and most of them are usually developed in the meristem of the roots. It is the name of an area of tissue in the plant that promotes cell division actively. A meristem is a place that grows in the plants like the top of the stem. Cytokinins are usually formed in ...

How do cytokinins help in mitosis?

Cytokinins help in increasing the cell division by maintaining the protein production that is important for mitosis. The term Mitosis refers to a non-sexual division of cells that usually occurs in all the living things by developing additional cells for the growth of the body.

What hormones are involved in plant growth?

Cytokinins. Cytokinins are a group of plant growth regulators which are primarily involved in performing cell division in plant roots, shoot system. This hormone helps in promoting the cell’s growth, development, differentiation, affecting apical dominance and delay in leaf senescence.

What is responsible for growth of plants?

Mitosis is responsible for growth of plants.

How does mitosis work?

Mitosis occurs every day by replacing the damaged cells by allowing them for growth. There are many times when you get hurt and you lost your skin from knee, it’s the same mitosis that helps in the growth of all the cells you lost and gets you the skin. Mitosis is responsible for growth of plants.

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