Phytoremediation through microstructural and functional alterations in alkali weed (Cressa cretica L.) in the hyperarid saline desert

Abstract

Salt excretory halophytes are the major sources of phytoremediation of salt-affected soils. Cressa cretica is a widely distributed halophyte in hypersaline lands in the Cholistan Desert. Therefore, identification of key physio-anatomical traits related to phytoremediation in differently adapted C. cretica populations was focused on. Four naturally adapted ecotypes of non-succulent halophyte Cressa cretica L. form hyper-arid and saline desert Cholistan. The selected ecotypes were: Derawar Fort (DWF, ECe 20.8 dS m⁻¹) from least saline site, Traway Wala Toba (TWT, ECe 33.2 dS m⁻¹) and Bailah Wala Dahar (BWD, ECe 45.4 dS m⁻¹) ecotypes were from moderately saline sites, and Pati Sir (PAS, ECe 52.4 dS m⁻¹) was collected from the highly saline site. The natural population of this species was collected and carefully brought to the laboratory for different structural and functional traits. As a result of high salinity, Na⁺, Cl^–, K⁺, and Ca²⁺ content significantly increased at root and shoot level. At root level, some distinctive modifications such as increased sclerification in vascular bundles, enlarged vascular bundles, metaxylem vessels, phloem region, and storage parenchyma (cortex) are pivotal for water storage under extreme arid and osmotic condition. At the stem level, enhanced sclerification in outer cortex and vascular bundles, stem cellular area, cortical proportion, metaxylem and phloem area, and at the leaf level, very prominent structural adaptations were thicker and smaller leaves with increased density of salt glands and trichomes at surface, few and large stomata, reduced cortical and mesophyll parenchyma, and narrow xylem vessels and phloem area represent their non-succulent nature. The ecotype collected from hypersaline environments was better adapted regarding growth traits, ion uptake and excretion, succulence, and phytoremediation traits. More importantly, structural and functional traits such as root length and biomass, accumulation of toxic ions along with K⁺ in root and shoot, accumulation of Ca²⁺ in shoot and Mg²⁺ in root, excretion of toxic ions were the highest in this ecotype. In conclusion, all these alterations strongly favor water conservation, which certainly contributes to ecotypes survival under salt-induced physiological drought.

Novelty statement

Naturally adapted salt tolerant plants provide exceptional material for exploring adaptive mechanisms they use to confront high salt concentrations. Cressa cretica is a hypersaline hyperarid desert colonizer, which was previously underexplored. In the present study, we focused on the new insight on relationship among anatomical modifications, salt accumulation and excretion and phytoremediation potential of this rare species.

Keywords:

• Functional adaptation
• ion exclusion
• non-succulent
• physiological drought
• salt glands
• structural adaptation

Acknowledgments

The project is not funded by any organization.

Author contributions

Nargis Naz collected plant material and performed the experiment. Mansoor Hameed and Muhammad Ashraf supervised the experiment and proofread the manuscript. Ansa Asghar, Sana Basharat, Sana Fatima, and Syed Mohsan Raza Shah helped in material collection, experimentation, and manuscript writing. Muhammad Sajid Aqeel Ahmad analyzed the data and structuring the whole manuscript.

Ethical approval

The study does not include any animal or human subjects and no specific ethical approval is needed. Other necessary guidelines set by University of Agriculture, Faisalabad for handling of plant material during conduction of laboratory work were followed. All samplings were done with the least possible disturbances to plant communities and environment. After completion of study, all experimental materials were properly discarded/incinerated in a controlled environment to avoid bio-contamination.

Consent form

The contribution of all participants/parties involved in this study has been appreciated either in authorship OR acknowledged in the acknowledgement section. All contributors listed in this manuscript have substantially participated in this study and preparation of the manuscript.

Disclosure statement

All authors declare that there is no conflict of interest with any individual, and educational, industrial or commercial institution.

Data availability statement

The voucher specimens used for plant identification are deposited to the herbarium facility of the Department of Botany, University of Agriculture, Faisalabad, and are available for verification on request. Anatomical slides, photographs, and raw data calculated from these photographs are available with the primary author and can be requested if needed.

Additional information

Funding

This research work is a result of independent studies and there is no involvement of any individual or institutional funding agency.