Plant Responses

Condensed notes on Plant Responses, Geotropisms and Phototropisms and the effects of the plant hormone, Auxin. 

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B6.2 Plant Responses
Plants are Autotrophs ­ meaning they are capable of self-nourishment by
using inorganic materials as a source of nutrients and photosynthesis (this
basically means they make their own food, in a fancy way)
(Heterotrophs require organic compounds for its principal source of food, ie they can't
make their own food and therefore have to eat other things)
Plants are sensitive to three things:
*Gravity(GEOTROPISM)
*Moisture(HYDROTROPISM)
*Light (PHOTOTROPISM)
SHOOTSgrow towards the lightand against the force of gravity
ROOTSgrow towards moistureand in the direction of gravity
Plants produce HORMONES to coordinate and control growth.
AUXINis a HORMONE that controls PHOTOTROPISMand GEOTROPISM.
The responses of plants to these factors are a result of unequal distribution of Auxin,
causing unequal growth rates.
Plant growth hormones are used in agriculture as weed
killers and rooting hormones.

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Auxin and it's effects in more detail:
Auxin is a h
ormone found in plants .
Auxins are mostly made in the tips of the shoots and roots, and
can diffuse to other parts of the shoots or roots.
They change the rate of elongation in plant cells , controlling how
long they become. Shoots and roots respond differently to high
concentrations of auxins:
*cells in shoots grow more
*cells in roots grow less.
PHOTOTROPISMS:
In a shoot, the shaded area has more auxin.…read more

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