Title: Evaluation of hydraulic lift in cotton germplasm Authors
Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2009
Publication Date: March 1, 2010
Citation: McMichael, B.L., Lascano, R.J. 2010. Evaluation of hydraulic lift in cotton (Gossypium hirsutum L.) germplasm. Environmental and Experimental Botany. 68(1):26-30. Technical Abstract: Hydraulic lift (HL) in plants is defined as the redistribution of water from wetter to drier soil through the plant roots in response to soil water potential gradients. Water is released from the roots into the dry soil when transpiration is low (night) and reabsorbed by the plant when higher transpiration rates are resumed (daylight). It was hypothesized that since HL is not of sufficient magnitude to meet total transpirational demands, there may be sufficient water transferred to maintain viable roots in the surface soil in anticipation of root water uptake for plant development from rain events before it is lost to water evaporation and/or runoff. Cotton (Gossypium hirsutum L.) plants of diverse genetic backgrounds were grown in a split-root container with roots of one plant divided between the two adjacent soil volumes. The soil in one container was allowed to dry while the adjacent soil container remained wet for the duration of the tests. Cotton transpiration was lowered by covering the plant with black cloth for several hours while changes in soil water content were measured in both containers using calibrated soil water sensors. Results showed that water was transferred from the wet to the dry soil through the root system at low transpiration rates. There was also an indication of genetic diversity in the magnitude of HL that may be due to differences in root resistance to water flow since total root length for a particular genotype was either smaller in the dry soil or similar to total root length in the wet soil. The amount of water transferred was small, but when integrated over a soil depth represented an amount ranging from 11-32% of corresponding daily evapotranspiration rates of 2-6 mm d-1, respectively, which could presumably maintain root viability for additional root water uptake when made available. These results are important in dryland cotton production where additional transpiration represents increased lint yield and plant breeders may consider this trait in their selection of cotton germplasm with drought resistance.