Coordination in plants - class-X

Phototropic curvature is the result of uneven distribution of auxin. Darwin and Darwin observed that the coleoptiles of canary grass responded w unilateral illumination by growing towards the light source (phototropism). After a series of experiments, It was concluded that the tip of coleoptile contains auxin that caused the bending of the entire coleoptile in relation to the direction of light.

Auxins induce phototropism in plants, that growth of a plant part towards light (shoot) or away from light (root). 

The pollen tube paves its way through the solid part of the stigma and style by secreting pectinases and hydrolytic enzymes. Pollen tube travels inter-cellularly and chemotropically along the concentration gradient of calcium-boron-Inositol sugar complex.

Positive geotropism is the movement towards earth. In the case of roots, they grow towards the earth and are thus, called as positively geotropic. Whereas shoots are negatively geotropic.

Irritability, reactivity and sensitivity are excitatory response shown by plants to respond to changes in their environment. The most common response shown by plants is movement in response to environment change. For example, closing of leaves of Mimosa pudica on touching or closing of traps on a Venus fly trap.

The area of the plant which receives a stimulus is called as perceptive region. Tip or apex of the shoot is the perceptive region for the light. It is the site which receives the phototropic stimulus and shows corresponding response. 

The movement of plant part in response to contact with a solid touch is called as thigmotropism. The movement of plant part in response to light is called as phototropism. The movement of plant part in response to force of gravity is called as geotropism. The movement of plant part in response to external chemical stimulus is called as chemotropism.

The movement of plant part in response to force of gravity is called as geotropism. The movement of plant part towards the gravity is called as positive geotropism. Roots show positive geotropic movement. The movement of plant part away from the gravity is called as negative geotropism. Stems show negative geotropic movement. 

Wilting of leaves is the loss of rigidity and caused when turgor pressure is lignified and reach zero it happens in the inadequate water supply and is caused by the hormone abscisic acid to prevent water loss.

The area of the plant which perceives a stimulus is called as perceptive region. Tip of the stem is the perceptive region for the light. The area of the plant which shows the response is called as responsive region. 

Hydrotropism is the response of the plant towards the water stimulus. It was first demonstrated by Johnson in 1829. During the course of his experiments, he found that when the air into the roots of seedlings penetrated, the roots continued to grow downwards. Hydrotropism can be positive as in case of growth of roots towards the water and also negative which is shown by shoot growing away from the water source. 

Geotropism is the plant response to the stimulus of gravity. Plant growth away from the gravity is called as negative geotropism. Stem shows negative geotropism. Plant growth towards the gravity is called as positive geotropism. Root shows positive geotropism.

Auxin is the hormone that stimulates cell elongation and growth. In the shoot when light falls on it the hormone gets activated and also promote the movement of shoot towards the light.

Thigmotropism is the growth or movement of a plant in response to touch. The telegraph plant (Codariocalyx motorius) exhibits rapid leaf movement in response to touch/vibration.

Phototropism of shoot and geotropism of root are due to several hormonal action. The hormones responsible include auxin plant hormone. Auxin is responsible for the growth of shoot positively phototrophic. Auxin also induces apical dominance in shoots.

Pnuematophores are called as breathing roots. These are found in mangrove trees. These are the modifications in root which grows in the same direction as that of shoot. Thus, they are negatively geotropic as well as positively phototrophic.

Haptotropism or thigmotropism is known as the movement of parts of a plant in response to a touch stimulus. Chemotropism is the growth of organisms such as bacteria and plants, navigated by chemical stimulus from outside of the organism or organisms part. The response of the organism or organism part is termed 'positive' if the growth is towards the stimulus or 'negative' if the growth is away from the stimulus. Geotropism or gravitropism is a turning or growth movement by a plant in response to gravity. Phototropism is the movement of plants in response to light.

'The power of movement of plants' is a book by Charles Darwin on phototropism and other types of movement in plants. This book contains his works in producing evidence for his theory of natural selection. The power of movement of plants was published on 6th November 1880, and 1500 copies were quickly sold by publisher John Murray. This book stands at the culmination of a long line of study in plants and is immediately preceded by 'The different forms of flowers on Plants of the same species' (1877).

Charles Darwin studied phototropism by covering different parts of oat coleoptiles and subjecting them to light from one direction. When he covered or removed coleoptile tip, phototropic response did not occur and concluded that phototropic bending in the zone of elongation was controlled by the tip. The movements which allow organs of plants to move in or the other directions is called movements of curvature. His demonstration that the site of photoreception at the shoot tip and the location of curvature are separable. From his observations, Darwin was able to propose that a transmissible substance produced in the tip is responsible for inducing curvature in lower regions of the plant. This insightful discovery eventually lead to the discovery of first plant hormone - auxin.

A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. Tropisms are typically associated with plants (although not necessarily restricted to them). Where an organism is capable of directed physical movement (motility), movement or activity in response to a specific stimulus is more likely to be regarded by behaviorists as a taxis (directional response) or a kinesis (non-directional response).
Therefore, the correct answer is option A.

Phototropism was first studied by Charles Darwin in 1880 in Canary Grass and oat coleoptiles. Later on F.W. Went in 1923, suggested the involvement of auxins in this phenomenon. Experimental approach to demonstrate positive phototropism in shoot tips is a darkened black box. The black box is having a small window at one side. A well-watered potted plant is placed inside the box. The is referred to as a phototropic chamber or heliotropic chamber. The window is kept closed for about 24 hours and the plant shows normal growth. If the window is kept opened, it is found after two days, that the shoot tip bends and grows towards light proving that it is positively phototropic.

The movement of plants in response to light is referred to as phototropism and to gravity is called geotropism. Arachis hypogea or peanut or groundnut belonging to the family Fabaceae or Leguminoseae, this is a herbaceous plant with yellowish organ flowers borne on auxillary clusters with ovary positioned at the base of the floral cup. The stigma is supported on a long style and before fertilization this shows positive phototropism.

Most vines and other climbing plants have tendrils that coil rapidly around supports. These grasping organs usually grow straight until they touch something; the contact stimulates a coiling response caused by differential growth of cells on opposite sides of the tendrils, the directional growth in response to touch is called thigmotropism, and it allows the vine to take advantage of whatever mechanical supports it comes across as it climbs upward toward a forest canopy.

Pneumatophores are negatively geotropic roots found in mangroves. They have pores for gaseous exchange. These pores are important because the soil is waterlogged and there is deficiency of air in the soil.

The Cholodny-Went model, proposed in 1927, is an early model describing tropism in emerging shoots of monocotyledons, including the tendencies for the shoot to grow towards light (phototropism) and the roots to grow downward (gravitropism). In terms of phototropism, the Cholodny-Went theory proposes that:

Plants of Family Cucurbitaceae have weak stems supported by tendrils. Tendrils are sensitive to touch and show thigmotropism, i.e., growth movement in response to touch. Haptotropism is a related term and essentially has same meaning, i.e., the movement of parts of a plant in response to a touch stimulus. In case of family Cucurbitaceae, these terms are used to describe growth of tendrils which support weak stem of the plants of this family.

Thigmotropism- In this type of tropic movement stimulus is touch or contact. This type of movement helps weak stem of vines and climbers to coil around the support with the help of tendrils.

A tropism is a plants growth response to an external stimulus. If resulting plant growth is toward the stimulus, it is called as a positive tropism. If the resulting plant growth is away from the stimulus, it is called as a negative tropism. There are several different types of tropisms, including phototropism, gravitropism, and thigmotropism. 

A tropism can be positive or negative.
Positive: the growth response is in the direction of the stimulus.
Negative: the growth response is away from the stimulus.
Light intensity, day length, gravity and temperature are major factors that influence plant growth. Phototropism is the growth response of a plant in response to light direction. Positive phototropism and negative geotropism of stems. The stems will grow towards the light and up away from gravity.

Gravitropism (also known as geotropism) is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms.Therefore, the correct answer is option B.

Thigmotropism' also known as 'Haptotropism' term arises from; Thigm+ tropism. 'Thigm' means a touch. 'Tropism' means an orienting response of an organism to the stimulus. 'Thigmotropism' is the directional growth movement which occurs as a mechanosensory response to a touch stimulus. The response exhibited by the organism to the stimulus is mostly involuntary, which means it can go either away or towards from the stimulus of the source as in taxis. The directional response is generally caused by the induction of some pattern of differential growth. The best example is climbing tendrils of the sweet pea when feel the solid object like tree trunk, causes the tendrils to actually attain curvature with that object. Thigmotropism can be positive or negative

Thigmotropism is the directed tropical growth movement of plant in response to touch. Tendrils are the modified leaves that grow straight until it touch the support. Contact with any support stimulates the cell to grow at different rates at opposite sides of tendrils and causes their curling around the support. Thus, option A is correct. 

The directional growth movements in which direction of growth is determined by the direction of stimulus are known as tropic movements. Tropic movement of plants/plant parts in response to moisture or water is called as hydrotropism. This makes options A and B incorrect as the question is about the movement of plants in response to light stimulus. Growth movement of plants in response to light is known as phototropism. Growth movement of plants towards the stimulus is known as positive tropism while movement of plant/plant parts away from the stimulus is known as negative tropism. This makes option C incorrect and option D correct as the movement of root away from light is known as negative phototropism. The correct answer is D.

Thigmotropism is response of plants to touch or contact with a solid object. Tendrils feel the solid object resulting in the coiling response. This type of movement helps weak stem of vines and climbers to grow. Thus the correct answer is option C.

Phototropism is the growth of organisms in response to a light stimulus. It is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light have a chemical called auxin that reacts when phototropism occurs. This causes the plant to have elongated cells on the farthest side from the light. Phototropism is one of the many plant tropisms or movements which respond to external stimuli. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism. Thus, option D is correct and other options are wrong.

Geotropism is a turning or growth movement by a plant or fungus in response to gravity. It is a general feature of all higher and many lower plants as well as other organisms. Phototropism is the orientation of a plant or other organism in response to light, either toward the source of light (positive phototropism) or away from it (negative phototropism). Thermotropism or Thermotropic movement is the movement of a plant or part of a plant in response to a change in temperature. A common example is the curling of Rhododendron leaves in response to cold temperatures. Mimosa Pudica also show thermotropism by the collapsing of leaf petioles leading to the folding of leaflets, when temperature drops. 

• Plant cells change their shape by changing the amount of water in them, resulting in swelling or shrinking. 

• Hydrotropism is a plant's growth response to water concentrations. The response can be positive (towards the water) or negative (away from the water). Roots, for instance, are positively hydrotropic. 
• That means they grow towards moist soils to avoid drought stress. Once a root cap has sensed water, it bends and then the root grows towards it. 

The greater growth of roots in moist soil zones than in dry soil zones is not usually a result of hydrotropism. Hydrotropism requires a root to bend from a drier to a wetter soil zone. Roots require water to grow so roots that happen to be in moist soil will grow and branch much more than those in dry soil. 
Roots cannot sense water inside intact pipes via hydrotropism and break the pipes to obtain the water. 
Roots cannot sense water several feet away via hydrotropism and grow toward it. At best hydrotropism probably operates over distances of a couple millimeters.

• An example of chemotropic movement can be seen during the growth of the pollen tube, where growth is towards the ovules.
•  Fertilization of flowers by pollen is achieved because the ovary releases chemicals that produce a positive chemotropic response from the developing pollen tube. 
• An example of positive and negative chemotropism is shown by plant roots. 
• The roots grow towards useful minerals displaying positive chemotropism and grow away from harmful acids displaying negative chemotropism. 

Tropic moments are shown according to the direction of stimuli. They do not diffuse and show unidirectional moments.

• The stem of the plants like cucumber and bitter gourd are very thin and slender. The stem shows the property of thigmotropism. 
• This is the phenomenon in which there is a movement like the bending or the curling of the stem. 
• Whenever there is stimulus received in the form of touch, there is curling of the stem and the tendrils of the plant. 
• This provides support to the plant in climbing against the surfaces.
• Thus, the correct answer is option B. 

A flexible hinge located at the base of the stalk of the leaf is called as the pulvinus and a sudden loss of turgor pressure in the motor cells of the pulvinus is called as a thigmonastic movement which is seen in Mimosa pudica.

The process of hydrotropism is started by the root cap sensing water and sending a signal to the elongating part of the root. Coconut roots usually grow to a depth of close to 0.80 m with 60-90% found in the top 0.5 m of the soil. In 10-year old dwarf coconut grown under rainfed conditions, the effective root zone of absorption was at 1.4 m from the trunk. Coconut has no root hairs but it produces plenty of roots with a large number of rootlets. Coconut tree roots growth is determined by a stimulus or gradient in water concentration. 

Roots grow mostly positively geotropic. That is, they grow towards the earth. Whereas, shoots are negatively geotropic.

Protoplasmic streaming: Rapid movement of cytoplasm inside the cell. It is an autonomic movement of locomotion. Autonomic movements are the movements which occur due to factors are inherent in plant body.

Phototropism in stem and root are due to differential phytohormonal effect. Stem grows positively phototropic. Roots grow negatively geotropic. Auxin is responsible for apical dominance and positive phototropism by stem.

Tropic movement is growth movement shown by plant in response to a unidirectional external stimulus. It is specific for direction and depends on the direction of stimulus. Movement towards the direction of stimuli is called as positive tropism while movement away from stimuli is called as negative tropism. It results in positioning of the plant part in the direction of the stimulus.

Turgor movement is a reversible change in position of a plant part due to a change in turgidity of cells. It is mostly caused by contact. In plants, turgor changes occur in thin walled cells of pulvinus present on lower side and pulvinnules present on upper side. Both side has different concentration of potassium and calcium ions. Upon touching, potassium ion concentration changes in the cells which results in turgor movement.

Thigmotropism is the directional response of a plant part to touch with a solid object. It is best seen in tendrils. Upon contact with the stimulus, it shows curving up towards the stimulus. Tendrils grow toward the touch stimulus, and wrap around the object.

The movement of parts of a plant in response to a touch stimulus is called as haptotropism. The movement of parts of a plant in response to external chemical stimulus is called as chemotropism. An example is growth of the pollen tube towards the ovules. The movement of parts of a plant in response to air current is called as anemotropism. The movement of parts of a plant in response to sunlight is called as heliotropism. 

Tropic movement is growth movement shown by plant in response to a unidirectional external stimulus. It is specific for direction and depends on the direction of stimulus. Movement towards the direction of stimuli is called as positive tropism while movement away from stimuli is called as negative tropism. Plant part shows tropic response in terms of cell elongation. For example, in phototropism, faster cell elongation is seen on the shaded side than on the illuminated side. 

Thigmotropism is a directional growth movement in response to a touch stimulus. It is found in twining plants and tendrils. Grape vine tendril entwines around a support due to thigmotropic movement. Nutation is the bending movement shown by plant during its development. Growth movement in response to gravity is called as gravitropism. Nastic movement in response to external stimulus is called as chemonasty. 

Auxin is a plant hormone that plays important role in phototropism, growth movement in response to light. It promotes cell elongation. It is unequally distributed in the plant cells. It is transported towards the shady side and thus present in higher concentration. However, less auxin is transported towards the side exposed to light. Due to this, the plant grows more on the shaded side and bend in the direction of the light source. It shows positive phototropism where faster cell elongation is seen on the shaded side and less on the illuminated side. 

Auxin is a plant hormone that plays important role in phototropism, growth movement in response to light. It promotes cell elongation. It is unequally distributed in the plant cells. It is transported towards the shady side and thus present in higher concentration. However, less auxin is transported towards the illuminated side. Auxin synthesis is inhibited on illuminated side. It moves from the illuminated side to shaded side. Due to this, the plant to grow more on the shaded side and bend in the direction of the light source. It shows phototropic response where faster cell elongation is seen on the shaded side than on the illuminated side. 

Auxin is a plant hormone that plays important role in the growth of stem and roots to gravity. Geotropism is the plant response to the gravity. Root shows positive geotropism and shoot shows negative geotropism. In stems, auxin accumulates towards the lower side. It results in increase in cell expansion and results in the shoot growing upright. In roots, auxin accumulates towards the lower side. However, it inhibits cell expansion and roots grow downwards.

Phototropism is the growth of plant in response to the light stimuli. Drooping of tamarind leaves after sunset is due to phototropism. Phototaxis is the movement shown by organism in the direction of the external light stimuli. Photonasty is the nastic movement shown by organism in response to the external light stimuli. Chemotaxis is the movement shown by organism in the direction of the external chemical stimuli. 

Geotropism is the response of plant parts to the gravity. Negative geotropism is growth of part of plant against the gravity. Positive geotropism is growth of part of plant in the direction of gravity. Downward growth of roots is example of positive geotropism. Primary stems grows against the gravity in upward direction and thus shows negative geotropism. 

Thigmotropism is a directional growth movement in response to a touch stimulus. It is found in twining plants and tendrils. Grape vine tendril entwines around a support due to thigmotropic movement. 

The movement of plant part in response to contact with a solid touch is called as thigmotropism. The twining movements due to support seen in tendrils and twiners is an example of thigmotropism. Seismonasty is the nastic response of a plant to touch or vibration. Dropping of leaves of Mimosa pudica upon touching is due to seismonasty. Heliotropism is a growth movement or bending of stem in the direction of the light. It is also called as solar tracking. Diageotropism is plant part response to the gravity such that it grows horizontal to the gravity.

The movement or growth of any part of a plant in response to an external stimulus is called tropism or tropic movement because most of the time the root grows underground and stem grows up to the ground and bending of stem towards light are the good examples of negative and positive phototropism.

Chemotropism is the movement of plants in response to a chemical stimulus. A classic example of this type of movement is the growth of the pollen tube towards the ovule, during fertilization, in a flower.

Shoot system shows positive phototropism means it will grow or change its direction in the way where light is present. It is known as the directional movement of plant.

Growth independent movement is a directionless movement of the plant caused due to the variation of the outside environment and plants movement is neither toward nor away from a stimulus. The example is touch me not plant or Mimosa Pudica which fold its leaves due to touching. This movement is not involved in growth hence it is growth independent.

The growth of shoot is the directional movement of the plant that occurs in the direction of stimulus (light) and plant move towards the light and grows in that direction.

Photo means light and tropic means movement so the movement of plants towards light is phototropic movement and is usually shown by the stem of the plant that is why it is known as positively phototropic.

When a plant shows some growth movement in response to a stimulus, it is
known as tropism. Tropism is direction specific and depends on the
direction of stimulus. Plants may either show positive or negative
movement as a response to a stimulus. If the movement is towards the
direction of stimuli, it is known as positive tropism while movement
away from stimuli is known as negative tropism. Answer is true.

Geotropism means growth in response to the gravitational force. Stems grow away from ground (ie in opposite direction in which the gravitational force is exerted), while roots grow toward the ground. Therefore, stems are negatively geotropic, which roots are positively geotropic.

Geotropism is also known as Gravitropism. It is a phenomenon in which growth movement by a plant turns in response to gravity. Roots show positive geotropism as they grow towards the gravity while stems show negative geotropism as they grow upwards. Hence, root shows greater growth on lower side as compared to upper side in positive geotropism.

The work of Charles and Francis Darwin regarding phototropism led to trace back the discovery of Auxin. Tropisms represent the movement in the plant parts which are directed or stimulated by specific stimuli. Plants show phototropism in response to light stimulus. Auxin plays a vital role in exhibiting phototropism in plants.

• Phototropism is the growth of organisms in response to a stimulus. This causes the plant to have elongated cells on the farthest side from the light. Phototropism is one of the many plant tropisms or movements which respond to external stimuli. 
• Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism. Most plant shoots exhibit positive phototropism, and rearrange their chloroplasts in the leaves to maximize photosynthetic energy and promote growth.
  Hence, option A is correct.

Medulla oblongata: This section of the brain helps transfer messages to the spinal cord and the thalamus in the brain from the body and controls breathing, heart function, blood vessel function, digestion, sneezing, and swallowing. Sensory and motor neurons from the forebrain and midbrain travel through the medulla.The hypothalamus is a section of the brain responsible for hormone production. The hormones produced by this area of the brain govern body temperature, thirst, hunger, sleep, circadian rhythm, moods, sex drive, and the release of other hormones in the body.
The cerebrum or cortex is the largest part of the human brain, associated with higher brain function such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.
The diencephalon is the region of the embryonic vertebrate neural tube that gives rise to posterior forebrain structures including the thalamus, hypothalamus, posterior portion of the pituitary gland, and pineal gland.
Chemo-tropism is the growth of organisms (or parts of an organism, including individual cells) such as bacteria and plants, navigated by chemical stimulus from outside of the organism or organisms part. The response of the organism or organism part is termed positive if the growth is towards the stimulus or negative if the growth is away from the stimulus.
An example of chemo-tropic movement can be seen during the growth of the pollen tube, where growth is always towards the ovules. It can be also written that conversion of flower into fruit is the example of chemo-tropism.

Tendrils are the threadlike organs of plants which are actually specialized stem, leaf or petiole and used for climbing, support or attaching to another for parasitic growth. Most climbing plants such as vines develop tendrils that tend to coil around objects that support it. This feature of the tendrils is due to a phenomenon called thigmotropism - directional growth movement of curvature in response to stimulus or contact.

Auxin is a plant hormone that plays important role in the growth of stem and roots to gravity. Gravitropism is a plant growth response to gravity. Root shows positive gravitropism and shoot shows negative gravitropism. Auxin content is lower on the upper side and more concentration occurs in lower side of the root and stem. This stimulates stem elongation and thus stem grows upwards. In roots, higher growth on upper side occurs due to lower auxin content. This inhibits root elongation and thus root grows downwards showing geotropic response. 

Auxin is a plant hormone that plays important role in the growth of stem and roots to gravity. Gravitropism is a plant growth response to gravity. Root shows positive gravitropism and shoot shows negative gravitropism. When plant is placed horizontally, more concentration occurs in lower side of the root and stem. This stimulates stem elongation and thus stem grows upwards. This inhibits root elongation and thus root grows downwards. 

Turgor movement is a reversible change in position of a plant part due to a change in turgidity of cells. It is mostly caused by contact. Mimosa pudica shows dropping of leaves upon touching. In this sensitive plant, the pulvinus and pulvinnules are responsible for the folding of the leaves. In this, turgor changes occur in thin walled cells of pulvinus present on lower side and pulvinnules present on upper side. This results in folding of pinnules and pinnae comes together causing drooping of the compound leaves.

Nutation is the bending movements shown by some plant parts due to the unequal rate of growth of different parts of plants. Thigmonasty is the nastic response of a plant to touch. The movements of tentacles of Drosera when comes in contact with insect is due to thigmonasty. The movement of plant part in response to contact with a solid touch is called as thigmotropism. The curvature movements due to support seen in tendrils and twiners is an example of thigmotropism. The movement of parts of a plant in response to air current is called as anemotropism. 

Phototaxis is a movement of part of organism in response to the light. This phenomenon is exhibited by zoospores of certain algae like Ulothrix, Chlamydomonas, Volvox, Cladophora. They exhibit positive phototaxic movement in presence of diffused light and negative phototaxic movement in presence of intense light.

Nutation is the bending movements shown by some plant parts like root, stem, leaf due to the unequal rate of growth of different parts of plants. 

Phototropism in plants is primarily mediated by phototropins, which are blue-light receptors. Blue light is significantly more effective at inducing phototropic curvature than red or green light.

Centromere joins the microtubules of 'Chromosomal spindle fibres and helps in the movement of chromosome during cell division. Centromere also plays an important role in the polymerization of tubulin protein used in the formation of microtubules. Hence it is helpful in attaching the chromosome with spindle fibres.

The Foramen of Luschka (lateral apertures) is a paired structure in the brain that allows cerebrospinal fluid to exit the fourth ventricle. The other listed foramina are singular structures.

The hypoglossal nerve (XII) is a cranial nerve present in mammals, including rabbits, but it is absent in amphibians like frogs. In frogs, the tongue muscles are innervated by spinal nerves rather than a dedicated cranial nerve.