Robert Sharp, University of Missouri, Root Growth under Water Deficits: Physiological Complexity and Coordination

Root growth is critical for plant adaptation to water deficit conditions, and certain types of roots have the ability to continue growing at water potentials lower than those that inhibit growth of the shoot. This response is shown by the primary root, in which it is important for seedling establishment, and also by the nodal (crown) roots of grasses such as maize. Nodal roots are produced from the stem nodes and form the framework of the mature root system; under drought conditions, these roots have to grow through dry surface soil to reach available water at depth. This seminar will address the complexity and coordination of mechanisms involved in regulating the growth responses of both primary and nodal roots of maize to low soil water potentials. Discussion will focus on: a) the role of ferulate crosslinks as restraints to cell wall extension in water-stressed primary roots; b) the use of a divided chamber model system to impose precise soil water deficits around growing nodal roots, which has revealed the importance of root hydraulic properties in determining the relationship between root growth zone and soil water status; c) initial results from metabolomics analysis of the nodal root growth zone response to drought under field conditions.