Root pressure

Japanese: 根圧 - こんあつ

This is the pressure generated by the roots of a plant, which acts to push water in the xylem upward. It is measured with a root pressure meter attached to the cut surface of the above-ground part or to a hole drilled in the trunk. It reaches its maximum value in early spring before the leaves open, decreases as the leaves open, and can even indicate negative pressure in summer. The maximum value is about 1.5 to 2 atmospheres. Root pressure is thought to occur when the water potential within the plant body becomes lower than the water potential in the soil due to active absorption of salts in the conductive tissue of the roots. The rise of water within the plant body is brought about by the sum of the upward force of root pressure and the upward force of transpiration.

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

植物の根に生ずる圧力で，道管内の水を上方に押し上げるように働く。地上部の切口，あるいは幹にあけた穴に取り付けた根圧計で測定する。春先の開葉前に最大値を示し，開葉とともに低下，夏には負圧を示すこともある。最高値は1.5〜２気圧程度。根圧は，根の通道組織で起こった塩類の能動的吸収によって，植物体内の水ポテンシャルが土壌中の水ポテンシャルよりも低くなるために生じると考えられている。植物体内での水の上昇は，根圧の押し上げる力と蒸散の引き上げる力の和によってもたらされる。

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