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Australian Journal of Botany Australian Journal of Botany Society
Southern hemisphere botanical ecosystems
RESEARCH ARTICLE

Calcium : magnesium ratio affects environmental stress sensitivity in the serpentine-endemic Alyssum inflatum (Brassicaceae)

Rasoul Ghasemi A F , Zohreh Zare Chavoshi B , Robert S. Boyd C and Nishanta Rajakaruna D E
+ Author Affiliations
- Author Affiliations

A Department of Biology, Payame Noor University, 19395-4697, Tehran, I.R. of Iran.

B Department of Biology, Payame Noor University, 81395-671 Isfahan, I.R. of Iran.

C Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA.

D College of the Atlantic, Bar Harbor, ME 04609, USA.

E Unit for Environmental Sciences and Management, North-West University, Potchefstroom, 2520, South Africa.

F Corresponding author. Email: rasoul.ghasemi@es.isfpnu.ac.ir

Australian Journal of Botany 63(2) 39-46 https://doi.org/10.1071/BT14235
Submitted: 8 September 2014  Accepted: 22 December 2014   Published: 8 April 2015

Abstract

Plants endemic to serpentine soils are adapted to harsh environmental conditions typical of those soils, particularly, low (<1) calcium (Ca) : magnesium (Mg) ratios. We compared survival of two perennial Alyssum species native to Iran under experimental manipulations of Ca : Mg ratio, including when Ca : Mg ratio was varied under conditions of high ammonium concentration and heat stress. Alyssum inflatum is a serpentine endemic capable of nickel (Ni) hyperaccumulation, whereas A. lanceolatum is found on non-serpentine soils and is not known to hyperaccumulate Ni. We grew plants of both species under four Ca : Mg ratios (0.4, 2, 20, 40) and tested survival when plants were exposed to elevated ammonium levels (0, 1 and 4 mM) and heat stress (control conditions vs a 5-h 36°C treatment daily for 5 days). Alyssum lanceolatum was more tolerant of Ca : Mg ratio variation (100% survival in all treatments), whereas A. inflatum survival was maximum at Ca : Mg = 2, reduced at Ca : Mg = 0.4, and very low for Ca : Mg ratios of 20 and 40. Alyssum lanceolatum also tolerated ammonium and heat stress, whereas survival of A. inflatum declined at higher Ca : Mg ratios when subjected to both stresses. We conclude that at higher Ca : Mg ratios, the serpentine endemic has reduced tolerance for these environmental stresses and may be more susceptible to human-driven climate change-associated stressors than the non-serpentine species.

Additional keywords: global climate change, heat stress, local adaptation, nitrogen deposition, serpentine endemism.


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