1.How Plants grow and move July 31, 2009 fri.ppt

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Slide 1 : Dr. Aman Biswas How plants grow and move

Circadian Clocks : Circadian Clocks Endogenous timekeepers Keep plant responses synchronized with the environment. Characteristics Must continue to run in absence of external inputs Must be about 24 hours in duration Can be reset or entrained (to determine or modify the phase or period of ) Can compensate for temperature differences

Slide 4 : Exhibited by living cells Exhibited by dead plant parts Xerochasy Hygrochasy

AUTONOMIC Movements (Spontaneous) : AUTONOMIC Movements (Spontaneous)

Movements of locomotion PARATONIC or TACTIC : Movements of locomotion PARATONIC or TACTIC

Movements of Curvature(Bending in some plant parts) : Movements of Curvature(Bending in some plant parts) AUTONOMIC Variation Movement (Temporary bending) Growth Movement (Permanent bending)

Variation Movement (Temporary bending) : Variation Movement (Temporary bending) Eg. Telegraph Plant (Desmodium gyrans) Telegraph Plant, perennial tick clover, member of the legume family, native to tropical Asia.

Telegraph Plant : Telegraph Plant The plant grows to a height of 1.2 m (4 ft) and produces pealike violet flowers. The telegraph plant is also called the semaphone plant. It is sometimes grown as a curiosity because of the movements of the small lateral leaflets of its trifoliate leaves. In daylight, when the air is moist and warmer than 22°C (72°F), every few minutes the leaflets jerk up and down (360o angle) like the arms of a semaphone (device for signaling using one or more movable arms). At night they droop down.

Slide 11 : Desmodium gyrans

Autonomic Growth Movements : Autonomic Growth Movements 1. HYPONASTIC Growth is more on the lower side of petals or sepals The pictures projected on this free session belong to the beholder on the internet. We thank them

2. EPINASTIC : 2. EPINASTIC Growth more on upper side of petals or sepals

3.NUTATION : 3.NUTATION Growth rapid on one side of stem and then passes on the opposite side so that becomes ZIGZAG Eg. Trailers and Creepers

4.CIRCUMNUTATION : 4.CIRCUMNUTATION Growth in Spiral form making structure coiled TENDRIL and TWINERS

Paratonic Growth Movements : Paratonic Growth Movements Two kinds

PLANTS RESPOND TO ENVIRONMENTAL STIMULI : PLANTS RESPOND TO ENVIRONMENTAL STIMULI Tropisms Plant growth toward or away from a stimulus such as light or gravity.  Nastic Movements Response to environmental stimuli that are independent of the direction of the stimulus. Pre-determined response.

What are Tropic Responses ? : What are Tropic Responses ? Directional movements by growth in response to a directional stimulus Geotropic Phototropic Thigmotropic or Haptotropic Hydrotropic Chemotropic Thermotropic

Plant tropisms : Plant tropisms Growth in a particular direction in response to an external stimulus Response to gravity is called Gravitropism To light is Phototropism To touch is Thigmotropism

Geotropic = Gravitropism : Geotropic = Gravitropism Oligotropic In response to gravity stimulus When it grows at right angle to gravitational force E.g.Rhizome

Plageogeotropic : Plageogeotropic When it grows at an oblique angle to gravitational force E.g. Lateral roots and shoots

Plants Respond to Gravity : Plants Respond to Gravity Gravitropism Response to the earth’s gravitational field. Present at germination Auxins play primary role ABA secondary role

Slide 23 : Four steps Gravity perceived by cell Signal formed that perceives gravity Signal transduced intra- and intercellularly Differential cell elongation

Slide 24 : Gravitropism = Geotropism The pictures projected on this free session belong to the beholder on the internet. We thank them

Positive plageotropism : Positive plageotropism

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