An investigation on plant-soil interactions in some endemic Centaurea taxa from Hatay, Turkiye

). An investigation on plant-soil interactions in some endemic


Introduction
Endemic plant species are potentially threatened as they are only distributed in limited areas.For this reason, information about the distribution of these species is very important both ecologically as well as in conservation biology and biogeography (Burgman et al., 2007;Murray-Smith et al., 2009;Huang et al., 2011;Memariani et al., 2016).
Globally, Turkiye holds an important position with regard to plant genetic resources and genetic diversity.The country serves as a meeting place for the Near East and Mediterranean diversity centers and gene centers (Demir, 2015).The wide variety of geomorphological, topographical and climatic features of Turkiye are mainly responsible for its wide habitat diversity and plant richness.This situation is also a major reason for the high rate of endemism in the country (Ozturk et al., 2011(Ozturk et al., , 2016)).The rich diversity of endemics is represented by 3035 endemic taxa making up nearly 31.12percent of the total flora of Turkiye (Güner et al., 2012;Ozturk and Altay, 2017).Many studies have been undertaken on the floristic aspect during the last few decades, and a list of its endemic plant taxa of Turkiye has been published (Severoğlu et al., 2011;Ozturk et al., 2011Ozturk et al., , 2012)).Some researchers have evaluated the ecological features of some endemic plants in the country (Ozturk et al., 2011;Eskin et al., 2013;Eroğlu et al., 2014;Altay et al., 2013Altay et al., , 2016aAltay et al., , 2016bAltay et al., , 2017)).
Centaurea is a remarkable genus in Turkiye with high endemism rate including approximately 790 valid species worldwide (Uysal et al., 2022;WFO, 2022).Most of the species belonging to this genus are distributed in the Mediterranean region as well as Near East, and a few are found in Northern Eurasia, North and East Africa, North America, and Australia (Eskin et al., 2013;Eroğlu et al., 2014;Uysal et al., 2022).This genus is represented by 220 taxa in Turkiye, 133 of which are endemic (Uysal et al., 2022).
No detailed studies have been undertaken in the Hatay Province (Türkiye) on the plant-soil interactions of endemic taxa namely: Centaurea arifolia Boiss., C. foliosa Boiss. & Kotschy, C. antiochia Boiss. var. antiochia, C. lycopifolia Boiss. & Kotschy, C. haradjianii Wagenitz, and C. ptosimopappa Hayek.The present study was therefore conducted to fill the gap in knowledge on these taxa, and at the same time it provides insights into the plant-soil interactions of these endemic taxa.

Study area
It is located in the East Mediterranean, between 35°48′ and 37°00′N latitude and 35°46′ and 36°41′ E longitude.The area experiences a typical Mediterranean climate.The annual average temperature is 18.1 °C and average annual rainfall around 1,078 mm, mostly falling during the winter season.The annual precipitation is minimum during spring, but increases in winter.The mean minimum and maximum temperatures lie around 7 o C and 32 °C during January and July, respectively (Altay et al., 2016a). The

Plant and soil analyses
Plant parts (root, stem and leaf) samples of the endemic Centaurea taxa and soil samples from their habitats were collected; oven-dried at 80 °C for 48 h, milled in a micro-hammer cutter and passed through a 1.5-mm sieve.The samples (each 0.5 g) were weighed, transferred into each of Teflon vessels and 8 mL of 65% HNO 3 were added to each vessel.The samples were mineralized in a microwave oven at 145 o C for 5 min., at 165 o C for 5 min.and at 175 o C for 20 min.The samples were filtered using Whatman filters, and the volume was made up to 50 mL with ultrapure water.Standard solutions were prepared by using multi-element stock solutions-1000 mg/L (Merck) (Altay et al., 2017).
Potassium and sodium were measured by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES); nitrogen and phosphorus were appraised by the methods outlined in detail in Ozturk et al. (2016aOzturk et al. ( , 1997)).
Soil samples (each 500 mg) were taken from a depth of 30 cm from all localities.pH was determined by the Hanna 211 pH meter; total soluble salts (TSS) and conductivity values were measured by the Hanna E.C. 211 conductivity meter; soil texture determined with the Bouyoucos Hydrometer; CaCO 3 by the Scheibler calcimeter; N analyzed by the modified Kjeldahl method, and phosphorus was determined by using the Olsen method.All measurements were taken according to the methods outlined in detail in Ozturk et al. (1997).

Results and Discussion
The data for physico-chemical analysis of the soils of endemic Centaurea taxa are presented in Table 1.All endemic Centaurea taxa grow in clayey loam soils.
The data show that these endemic taxa prefer clayey-loamy, non-saline, slightly alkaline soils with high lime content.Potassium is at sufficient levels in the soils.Only Centaurea ptosimopappa grows in nitrogen-poor soils, while other endemic species grow in nitrogen-sufficient-level soils.All endemic species except Centaurea haradjianii prefer phosphorus rich soils (Tüzüner 1990;Ozturk et al. 1997;Altay et al., 2017).
According to Epstein (1999) and Altay et al. (2017), N, P, K and Na standard values are generally reported as 1.5%, 2,000 (mg kg -1 ), 10,000 (mg kg -1 ), and 10 (mg kg -1 ), respectively in plants.In our results, nitrogen and phosphorus were below the standard values in all plant organs and sodium was over the normal value.However, the potassium values varied significantly with different endemic Centaurea taxa.In Centaurea arifolia and C. antiochia var.antiochia, potassium values were over the normal level in all plant parts.In Centaurea lycopifolia and C. ptosimopappa, potassium values were below the normal levels in roots and stems, and over normal in leaves.In Centaurea haradjianii and C. foliosa, potassium was below the normal values in all plant organs.
Endemic plants are an important part of plant diversity which need an immediate intervention in order to ascertain their long-term survival (Ozturk et al., 2011;Altay et al., 2017).The strategies for plant conservation include in situ approaches such as gene sanctuaries, national parks, biosphere reserves and establishment of protected areas.The ex situ approaches include in vitro conservation, field gene banks and seed conservation gene banks.Application of these conservation approaches will help save plant taxa facing multiple threats.These will pave a way for their sustainable use as beneficial resources for humans and at the same time widen our knowledge related to these species (Ozturk et al., 2011;Altay et al., 2017).

Conclusion
The endemic taxa Centaurea arifolia, C. foliosa, C. antiochia var.antiochia, C. lycopifolia, C. haradjianii, and C. ptosimopappa require a high priority.These should be monitored carefully and regularly in order to preserve this genetic diversity.These species are much more vulnerable to extinction than other species.In addition, ecological studies on such endangered endemic taxa should be supported with comprehensive physiological and molecular studies to promote the understanding of endangered endemic plants in general (Ozturk et al., 2011;Eroğlu et al., 2014;Altay et al., 2013;2016a, b, 2017).
Author(s), Editor(s) and Publisher's declarations study material included six endemic Centaurea taxa, viz.C. arifolia, C. foliosa, C. antiochia var.antiochia, C. lycopifolia, C. haradjianii, and C. Ptosimopappa, all collected from different localities in the Hatay Province, Turkiye.The information on the collection sites is given below: