Adaptive Component for salinity tolerance in Cyperus laevigatus L. populations from diverse salt-affected habitats

Abstract

Salinity is a serious concern for agriculture worldwide and it is increasing continuously. Drought-affected lands are severely affected by salinity, and crops production is drastically reduced. Soils of over 100 countries of America, Africa, Australia and Asia are facing serious salinity problem, mainly due to anthropogenic activities like irrigation. Now, salinity has also become a menance for agriculture in Pakistan because it is limiting the production of crops and affecting the country’s economy from nineteenth century. In Pakistan, approximately 6.67 million hactare area is facing the problem of salinity. In Pakistan, salinization is due to natural environmental conditions like ecological fluctuations, inefficient irrigation, high evapo-tanspiration, flooding, usage of low-quality water for irrigation and its poor drainage. This study was conducted to evaluate adaptive components of salt tolerance in Cyperus laevigatus L., which is a hydro-halophytic plant. Six populations of Cyperus laevigatus were collected from Sahianwala, Sargodha, Sangla Hill, Kalar Kahar, Pakka Anna and Domeli and their degree of salinity was assessed by examining their morpho-anatomical and physiological attributes. Cyperus laevigatus populations can be rated as Domeli ˂ Sargodha ˂ Kalar Kahar ˂ Sangla Hill ˂ Sahianwala ˂ Pakka Anna from least tolerant to the most tolerant, based on overall growth and biomass production under high salinities. The most tolerant population from the Pakka Anna relied on increased or maintained photosynthetic rate, high water use efficiency, restriction in Na+ uptake of in root and shoots, high uptake of shoot and root Ca2+ and K+, in addition to high accumulation of organic osmolytes, hence making this population more suitable for salt-affected areas. Structural adaptations like increased root area, thick root endodermal layer and large root metaxylem vessels, large stem area, broad metaxylem vessels, intensive sclerification in stem and leaf, increase in vascular bundle area and large cortical cells in stem, bract and leaves and decreased stomatal area and density all contributed significantly towards its high degree of salinity tolerance. Cyperus laevigatus can easily survive up to 600 mM salt, and differently adapted populations showed differential response towards salt stress tolerance and adopt different mechanisms based on morpho-physiology and anatomy. Therefore, this species can be effectively used to re-vegetate salt-affected areas, as well as for phytoremediation of salt affected lands.