Adaptive strategies of Parietaria diffusa (M.&K.) to calcareous habitat with limited iron availability*

Abstract

The study of native plants growing in hostile environments is useful to understand how these species respond to stress conditions. Parietaria diffusa (M.&K.) is able to survive in highly calcareous soils and extreme environments, such as house walls, without displaying any chlorotic symptoms. Here, we have investigated the existence of Strategy I complementary/alternative mechanism(s) involved in Fe solubilization and uptake and responsible for Parietaria's extraordinary efficiency. After assessing the specific traits involved in a calcicole-behaviour in the field, we have grown plants in conditions of Fe deficiency, either direct (-Fe) or induced by the presence of bicarbonate (+FeBic). Then, the growth performance, physiological and biochemical responses of the plants were investigated. The study shows that in Parietaria +FeBic, the classical responses of Strategy I plants are activated to a lower extent than in -Fe. In addition, there is a greater production of phenolics and organic acids that are both exuded and accumulated in the roots, which in turn show structures similar to 'proteoid-like roots'. We suggest that in the presence of this constraint, Parietaria undergoes some metabolic rearrangements that involve PEP-consuming reactions and an enhancement of the shikimate pathway.

Metabolome Analysis of Arabidopsis thaliana Roots Identifies a Key Metabolic Pathway for Iron Acquisition

“…It is crucial under alkaline conditions, which represent a major limiting factor for agricultural productivity worldwide. Furthermore, it is interesting to note that the specific adaptations of calcicole plants to calcareous substrates have been hypothesized to be at least in part dependent on a pronounced shift from classic strategy I responses towards phenolics secretion specifically under alkaline conditions [61]. This was observed for Parietaria diffusa , an Fe-efficient plant that can be found on walls and similar substrates in the Mediterranean, when effects elicited by Fe-free medium were compared to those of an alkaline carbonate medium.…”

Efficient acquisition of iron confers greater tolerance to saline-alkaline stress in rice (Oryza sativaL.)

“…In the present study, mixtures of NaCl and Na 2 CO 3 were added into the nutrient solution to mimic the concentrations that occur in saline-alkaline soil with a high Na + concentration and high soil pH. It has been reported that buffering pH to 8.3 leads to substantial precipitation of Fe along with other nutrients in a mural habitat (Donnini et al , 2012). In the current study, we also observed Fe precipitation from the saline-alkaline solution, resulting in a lower available Fe concentration (See Supplementary Table S1 at JXB online).…”

“…Two genes encoding Fe 2+ transporters, IRT1 (Bughio et al , 2002) and IRT2 (Ishimaru et al , 2006), have been isolated in rice plants. The addition of bicarbonate to growth medium has been demonstrated to cause foliar chlorosis in Parietaria diffusa , a Strategy I plant, due to reduction in Fe acquisition (Donnini et al , 2012). Lucena et al (2007) reported that bicarbonate induced foliar chlorosis and inhibited the expression of genes encoding FER-like transcription factors, thus inhibiting the expression of ferric reductase, iron transporter, and H + -ATPase genes in a number of Strategy I plants.…”

Transcriptional Characterization of a Widely-Used Grapevine Rootstock Genotype under Different Iron-Limited Conditions

“…Plants were left into a half-nutritive solution for 10 days, in order to allow them to adapt to the growth conditions. Subsequently, stress treatments were imposed according to Donnini et al (2012). Acclimated plants were transferred into containers containing a modified nutritive standard solution according to the different conditions applied: (i) control (+Fe): 100 μM Fe-EDTA (pH 6 ~ 6.2); (ii) absence of iron (−Fe): 0 μM Fe-EDTA (pH 6 ~ 6.2); (iii) presence of Bicarbonate (FeBic): 100 μM Fe-EDTA, 10 mM NaHCO 3 , and 0.5 g/L CaCO 3 (pH 8.2 ~ 8.3).…”