Tag: tropic and nastic movements in plants

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.