Submitted to: Journal of Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/10/2012
Publication Date: 2/1/2012
Citation: Sicher Jr, R.C., Timlin, D.J., Bailey, B.A. 2012. Responses of growth and primary metabolism of water-stressed barley roots to rehydration. Journal of Plant Physiology. 169:686-695. DOI:10.1016/J.JPLPH.2012.01.002. Interpretive Summary: Industry and changes of land use have added chemicals to the atmosphere. These chemicals have altered the climate and increased episodes of drought in many crop growing areas of the world. This is important because water stress is already one of the most important factors limiting crop productivity worldwide. This study investigated how re-wetting plants after a period of water stress affected shoot and root growth. Shoot growth stopped after four days of drought but root growth continued for five additional days. This root growth ceased immediately when drought treated plants were watered and no root growth was observed for an additional three days. Chemical changes that occurred in roots after re-wetting indicated that roots were recovering from drought and that renewed shoot growth was favored over root growth during the recovery period. These findings should be of interest to investigators studying plant stress and climate change. Government policymakers and crop modeling specialists should also benefit from these findings.
Technical Abstract: Barley seedlings [Hordeum vulgare L. Brant] were grown in pots in controlled environment chambers and drought treatments were imposed 11 days after sowing. Soil water content decreased from 92% to 10% after an additional 14 days of water stress. Shoot and root growth ceased after 4 and 9 days of water stress, respectively. Thirty barley root metabolites were monitored and 85% were significantly altered by drought. Sucrose, raffinose, glucose, fructose, maltose, malate, asparagine and proline increased and myo-inositol, glycerate, alanine, serine, glycine and glutamate decreased during drought. Root growth ceased immediately when plants given 8 days of water stress were rehydrated and dry matter accumulation was not observed for 3 days. Rates of photosynthesis and stomatal conductance recovered in 2 days and shoot growth commenced the 3rd day after rehydration. Malate and proline recovered in 1 day but serine was only partially reversed 6 days after rehydration. Malate and raffinose decreased below well-watered, control levels and aspartate, which was unresponsive to drought, decreased by half 1 day after rehydration. The above results suggested that primary metabolism was involved in various crucial processes during water stress including, osmotic adjustment, nitrogen sequestration, ammonia detoxification and an inhibition of glycolysis and gluconeogenesis. Changes in metabolite levels due to drought reversed after rehydration but the extent and time necessary for full recovery varied. The above results indicated that roots were highly metabolically active during the lag phase in growth following rehydration.