Transport in Plants

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SÝMPLÅSTÏÇ PÅTHWÅÝ

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It is the system of interconnected protoplasts.

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In this pathway, the water travels through the cytoplasm;

intercellular movement is through the plasmodesmata.

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Neighbouring cells are connected through cytoplasmic

strands that extend through plasmodesmata

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Water has to enter the cells through the cell membrane.

Hence, the movement is relatively slower. Movement is

again down a potential gradient.

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Symplastic movement may be aided by cytoplasmic

streaming. E.g. Cytoplasmic streaming in cells of the Hydrilla

leaf. The movement of chloroplast due to streaming is easily

visible.

Most of the water flow in the roots occurs via the

apoplast since the cortical cells are loosely packed.

So, water can move without resistance. However, the

endodermis is impervious to water because of a band of

suberised matrix called the casparian strip.

Water molecules are unable to penetrate the layer, so they are directed

to wall regions that are not suberised. The water then moves through the

symplast and again crosses a membrane to reach the cells of the xylem.