Influence of Drought Stress on the Nickel-Hyperaccumulating Shrub Hybanthus floribundus (Lindl.) F.Muell. subsp. floribundus
2011
Kachenko, Anthony George | Bhatia, Naveen | Singh, Balwant
Hyperaccumulation of nickel (Ni) in certain plants may play a role in drought resistance under water stress. This article tests the influence of water stress on the Ni-hyperaccumulating shrub Hybanthus floribundus Lindl. F.Muell. subsp. floribundus. Plants grown in 1000 mg kg-1 Ni-amended Clastic Rudosol were exposed to five levels of soil water potentials (-33 [field capacity], -60, -400, -600, and -1000 kPa) for 12 wk. Water stress did not induce significant changes in growth rate, relative water content, rates of gas exchange, or carbon isotope discrimination. Water use efficiency (WUE) values were approximately threefold lower in plants at water potentials <-400 kPa than they were in those at water potentials of -33 kPa. Low WUE values suggest that this species possesses an efficient water conservation mechanism that enables its survival in competitive water-limited environments. A 38% decline in water potential and a 68% decline in osmotic potential occurred between -1000- and -33-kPa water potentials (), indicating that osmotic adjustment (OA) may have provided turgor maintenance in response to increasing water stress. However, Ni concentration in plants did not significantly increase in response to decreasing water potentials and is therefore unlikely to play a role in OA.
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