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Root System Regulates Whole Plant Growth

By Hank Becker
March 30, 1998

Plants speed up or slow down their growth in response to signals about the soil environment that are sent by the roots to the shoots.

Plant physiologists have uncovered increasing evidence that root tips launch these signals--in the form of hormones and other chemicals--to inform shoots and leaves about the soil's water, nutrient supplies, hardness and temperature, say Agricultural Research Service scientists.

ARS biophysicist Robert M. Aiken and colleagues at ARS' Great Plains Systems Research Unit in Fort Collins, Colo., analyzed growth patterns of corn root systems. He attributed changes in the distribution and architecture of the roots to chemical activity of the tips, the sites of cell division. These changes may increase or decrease the volume of soil accessible to the roots for taking up water and nutrients.

Growing root tips are uniquely positioned to serve many sensory and signaling functions.

Plant physiologists have been uncovering increasing evidence that plant roots chemically signal shoots about soil conditions like hardness and temperature. Signals include nitrate--a plant nutrient--and hormones including cytokinins and abscisic acid, believed to regulate growth and development of shoots and roots.

The shoot responds in two chief ways. Production of enzymes used in photosynthesis slows down or speeds up. Leaf pores enlarge or shrink, also influencing photosynthesis. These responses, in turn, further modify the shoot's nitrogen demand, photosynthesis rate and water use.

Ultimately, researchers hope the information can help farmers better control pests and diseases while reducing the effects of environmental stresses such as drought on crops. The strategy would involve interpreting soil and plant data obtained by precision farming technologies such as remote sensing and yield monitors on combines.

Scientific contact: Robert M. Aiken, Central Great Plains Research, Akron, CO, 80720 phone (970)345-0519, fax (970) 345-2088,

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