Washington, Feb 29 : British scientists have shown how roots find their way past obstacles to grow through soil, by finding that plant root hairs have a sense of touch, and "feel" the soil in much the same way as a person would explore his or her way through a hindrance.
According to scientists at the John Innes Centre in Norwich, the discovery explains how plants inhabit poor soils and germinating seedlings burrow down into the earth without dislodging themselves.
The researchers said that roots are covered with a fuzzy coat of hairs, which act as sensitive "fingers."
"The key is in the fuzzy coat of hairs on the roots of plants. We have identified a growth control mechanism that enables these hairs to find their way and to elongate when their path is clear," said Professor Liam Dolan.
The root hairs explore the soil in much the same way as a person trying to navigate in the dark. When they encounter an obstacle, such as a stone, they feel their way around until an opening is discovered through which growing can continue. In the meantime, the plant is held in place as the hairs grip the soil.
This ability is governed by a self-reinforcing cycle, the researchers explained.
A protein at the tip of root hairs called RHD2 produces free radicals that stimulate the uptake of calcium from the soil. Calcium then stimulates the activity of RHD2, producing more free radicals and further uptake of calcium. When an obstacle blocks the hair's path, the cycle is broken and growth starts in another location and direction.
"This remarkable system gives plants the flexibility to explore a complex environment and to colonise even the most unpromising soils", said Professor Dolan.
"It also explains how seedlings are able to grow so quickly once they have established," he added.
In nutrient-poor soils found in parts of Australia and sub-Saharan Africa, plants have adapted by producing extra root hairs.
The researchers said that understanding the processes involved could assist the development of crops able to grow in inhospitable environments.
The study will be published in the forthcoming edition of Science.