Control and Coordination Test 29

• The movement of animals towards or away from the stimulus is called as the taxis. The taxis may be negative or positive. 
• The movement away from a stimulus is called negative taxis and the movement towards the stimulus is called positive taxis.

In the course of research on auxin biology, many compounds with noticeable auxin activity were synthesized. Many of them had been found to have the economical potential for man-controlled growth and development of plants in agronomy. Auxins are toxic to plants in large concentrations. They are most toxic to dicots and less so to monocots. Because of this property, synthetic auxin herbicides, including 2,4-D and 2,4,5-T, have been developed and used for weed control. However, synthetic auxins, especially 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants or for different agricultural purposes such as the prevention of fruit drop in orchards. Used in high doses, auxin stimulates the production of ethylene. Excess ethylene (also native plant hormone) can inhibit elongation growth, cause leaves to fall (abscission), and even kill the plant. 

The phenomenon of geotropism explains the movement of the plant towards the ground. This is due to the gravitational pull which allows the plant to move. There is a gravitational force acting on all the sides. The clinostat is the device which was used to remove the effects of the gravitational force on the plants. The device rotates to cancel the amount of force which is acting on all the sides and then study the movement of the plant cells when externally force is provided.

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 somatic reflex arc affects the muscles and the receptor organ is skin whereas, the effector organ is skeletal muscles. The visceral reflex arc affects the internal organs and the receptor organ is epithelial lining of the gut whereas, the effector organ is smooth muscles. 

• Amygdala is a part of the telencephalon, located in the temporal lobe, involved in memory, emotion, and fear. 
• The amygdala is both large and just beneath the surface of the front, the medial part of the temporal lobe where it causes the bulge on the surface called the uncus. 
• This is a component of the limbic system. 
• The hippocampus plays a major role in learning and memory.
• Thalamus is responsible for sensory and motor signals, as well as regulation of consciousness and alertness

• Abscisic acid is one of the most important plant growth regulators. This class of PGR is composed of one chemical compound normally produced in the leaves of plants, originating from chloroplasts, especially when plants are under stress. In general, it acts as an inhibitory chemical compound that affects bud growth, and seed and bud dormancy. 
• It mediates changes within the apical meristem, causing bud dormancy and the alteration of the last set of leaves into protective bud covers. 
  

Abscisic acid is an inhibitory plant hormone which gives a response to the abiotic stress conditions. It induces dormancy in seeds by blocking germination and promoting the synthesis of storage proteins. It reduces the stomatal aperture in less water availability and causes the closing of stomata to reduce transpiration in winters. Another effect of ABA is to promote the development of winter buds; it mediates the conversion of the apical meristem into a dormant bud.