Changes in root characteristics, gas exchange and water use efficiency following water stress and rehydration of Alfalfa and Sorghum

Li, W. and Zhang, S. and Shan, L. and Eneji, A.E. (2011) Changes in root characteristics, gas exchange and water use efficiency following water stress and rehydration of Alfalfa and Sorghum. Australian Journal of Crop Science , 5 (12). pp. 1521-1532.

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Soil water stress has paramount effects on water uptake by roots and its use by shoots. In this study, we determined changes in root hydraulic conductivity (Lpr) and morphology under drought stress and how they regulate shoot gas exchange and water use efficiency in alfalfa and sorghum, two crops with contrasting adaptations to drought, the former exhibiting strong drought avoidance and the later strong drought tolerance. Seedlings of two alfalfa cultivars differing in drought avoidance and one highly drought tolerant sorghum cultivar were subjected to PEG-6000-induced water stress and then rehydrated. The Lpr declined rapidly after the PEG treatment but largely recovered within 48 hours of rehydration; however, inter-specific and cultivar differences were significant. The rapid change in Lpr also led to equally rapid changes in leaf water potential, gas exchange and consequently, the instantaneous water use efficiency (WUEi) in both species. A reasonable correlation was found between Lpr and WUEi. Treatment with Hg2+ indicated that the water stress-induced changes in Lpr were due to the involvement of aquaporins. One year old alfalfa and sorghum cultivars subjected to moderate and severe drought stress at the field level had altered root morphology and reduced biomass production and water dissipation but increased water use efficiency of biomass production (WUEb). These changes were dependent on stress level, species and cultivars. However, not all the root morphological changes contributed to improved water use. For example, the decrease in taproot length negatively affected the WUEb of alfalfa whereas the increase in root surface area was positively related only to the WUEb of sorghum. The difference in drought tolerance between species or cultivars was related to their ability to recover the lost Lpr and CO2 assimilation after rehydration, as well as the ability to effectively regulate root morphological changes to increase WUE.

Item Type: Article
Uncontrolled Keywords: Root hydraulic conductivity, drought tolerance (DT), gas exchange, water use efficiency(WUE), alfalfa(A) and sorghum (S).
Author Affiliation: College of Life Sciences, Institute of Ecological Science and Technology, Henan University, Kaifeng, Henan 475004, China
Subjects: Soil Science and Microbiology
Plant Physiology and Biochemistry > Plant Physiology
Plant Physiology and Biochemistry > Biochemistry
Divisions: Sorghum
Depositing User: Mr B Krishnamurthy
Date Deposited: 09 Feb 2013 13:56
Last Modified: 09 Feb 2013 13:56
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