It may noted that Osmosis is responsible for the ability of plant roots to draw water from the soil this is very clearly described in the Mahabharata. 

SHANTI PARVA 184.16 "As one draws water up with the mouth (by suction) through a lotus stalk, the plant, endowed with air (pressure) drinks with its feet"    

The knowledge of Osmosis in Mahabharata was later discovered by Kramer - 1969 AD which states 
"Due to rapid evaaporation of water from leaves during transpiration, a tense is created and transmited to the xylem of the roots, causing the water to cross cell wall and rise upwards".

Mahabharata throws more light on the awareness of plants and there responsiveness. In the Mahabharata it is explained that plants can SHANTI PARVA 184.13-14 "The creeper moves above the trunks, covering it all around. There is no path for the one without sight. Hence trees can see. The heat rays of the sun discolours the barks, leaves and flowers of trees. Since they also fade and perish because of heat, trees have the sense of touch. When covered with incense and smoke the trees become disease-free and flower a plenty. Hence they repond to gases".

"By the sound of wind, fire and lightening, the fruit and flower perish. Sound is perceived by the ear, hence the trees hear".