Tag: coordination in plants

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.