A role for nickel in osmotic adjustment in drought-stressed plants of the nickel hyperaccumulator Stackhousia tryonii Bailey

Our plain-English summary of A role for nickel in osmotic adjustment in drought-stressed plants of the nickel hyperaccumulator Stackhousia tryonii Bailey, by N.P. Bhatia, A.J. Baker, K.B. Walsh, et al (Planta, 2005).

The study

• Authors: N.P. Bhatia, A.J. Baker, K.B. Walsh, D.J. Midmore
• Journal: Planta
• Published: 2005;223(1):134-9
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The hypothesis that hyperaccumulation of certain metals in plants may play a role in osmotic adjustment under water stress (drought) was tested in the context of nickel hyperaccumulator Stackhousia tryonii. Field-collected mature plants of S. tryonii, grown in native ultramafic soil, were pruned to soil level and the re-growth exposed to five levels of water stress (20, 40, 60, 80 and 100% field capacity; FC) for 20 weeks. Water stress had significant (P<0.05) influence on growth (biomass), water potential and shoot Ni concentrations, with progressively more impact as water stress was increased from 80 to 40% FC. Shoot Ni concentration increased significantly from 3,400 microg g(-1) dry weight (at 100% FC) to 9,400 microg g(-1) dry weight (at 20% FC). Assuming that Ni is uniformly distributed through the shoot tissue, the Ni concentration could account for 100% at the 80 and 60% FC conditions, and 50% at the 40 and 20% FC conditions of plant osmotic regulation. The results are consistent with a role of Ni in osmotic adjustment and protection of S. tryonii plants against drought.

In plain English

This article does not concern asbestos. It is a glasshouse experiment on Stackhousia tryonii, a central Queensland plant that builds up very high nickel levels from ultramafic (serpentine) soils. The authors dug up mature plants from one wild population, cut them to soil level, and kept the regrowth at five soil-water levels (20, 40, 60, 80 and 100% of field capacity) for 20 weeks, five plants per level. Shoot nickel rose from 3,400 micrograms per gram dry weight at 100% to 9,400 at 20%. Plants at 20% survived but produced very little growth. Plants at 80% had almost ten times the shoot dry weight of plants at 20% (11.77 g versus 1.24 g). Sap rising from the roots showed no change in dissolved-substance level. The authors assumed nickel was evenly spread and fully dissolved into ions. On that basis they calculated it accounted for 41 to 125% of the change in plant water status, noting these estimates may be high. The authors concluded nickel may aid drought adjustment but presumably plays an 'accidental' role, not a direct adaptive strategy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Glasshouse experiment on field-collected plants exposed to five water-stress (drought) treatments
• Who was studied: Mature Stackhousia tryonii plants (a nickel hyperaccumulator) dug up from a single population on alluvial ultramafic soil near the Eden Bann turnoff on the Bruce Highway, central Queensland, Australia; five replicate plants per treatment
• Exposure: Soil water held at 20, 40, 60, 80 or 100% of field capacity for 20 weeks, in native ultramafic soil containing 60 ppm available (DTPA-extractable) nickel. No asbestos or fibers were studied.
• Main results:
  • Shoot nickel concentration rose as water was reduced, from 3,400 micrograms per gram dry weight at 100% field capacity to 9,400 micrograms per gram dry weight at 20% field capacity
  • Plants at 20% field capacity survived but produced very little biomass. Plants at 80% field capacity showed an almost tenfold increase in shoot dry weight compared with plants at 20% (Table 1: 11.77 g at 80% versus 1.24 g at 20%; 7.27 g at 100%).
  • Growth was also reduced at 100% field capacity compared with 80%. The authors presumed this was related to root anaerobiosis (lack of oxygen around the roots).
  • Xylem sap osmolality did not change with water stress
  • Total plant water potential fell to about -1.5 MPa under the low soil-moisture treatment
  • Calculated nickel solute potential accounted for between 41 and 125% of the observed change in plant water status (Table 1: 41% at 20%, 53% at 40%, 125% at 60% and 100% at 80% field capacity, each relative to 100%)
  • Total shoot nickel per plant was 11.7, 26.1, 52.8, 68.2 and 24.5 mg at 20, 40, 60, 80 and 100% field capacity respectively. From this the authors judged that increased nickel transport was not expected with changed water status.
• The authors' conclusion: The authors concluded that nickel may function in osmotic adjustment in S. tryonii but is relatively inflexible as an osmoticum. They presumed nickel plays an 'accidental' role in plant water relations rather than being a direct adaptive strategy against drought.
• Limitations the authors state:
  • The solute-potential estimates may be too high, because nickel was assumed to be present as a totally dissociated salt
  • The calculation assumed nickel was evenly distributed throughout the shoot tissue
  • Nickel concentrations varied widely within each treatment

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

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