Effects of temperature and water limitation on the germination of Stipagrostis ciliata seeds collected from Sidi Bouzid Governorate in Central Tunisia

Abstract

Most ecological studies in North Africa reveal a process of continuous degradation of rangeland ecosystems as a result of overgrazing. This degradation appears across the decreasing of perennial grass diversity. Indeed, the majority of steppe ecosystems are characterized by a low density of perennial grass species at present. This study evaluated the effects of temperature and water limitation on the seed germination of Stipagrostis ciliata (Desf.) de Winter, a perennial grass species. The seeds were collected from the Bou Hedma Park, Sidi Bouzid Governorate, Central Tunisia. The thermal time and hydrothermal time models were used to describe the seed germination of S. ciliata under different water potentials and temperatures. The germination response of S. ciliata seeds in darkness was evaluated over a range of temperatures (15°C, 20°C, 25°C, 30°C and 35°C) and across a wide range of osmotic potentials (0.0,-0.2,-0.6,-1.2,-1.6 and-2.0 MPa) of the polyethylene glycol (PEG 6000) solutions at each temperature level. Among the tested temperatures, 25°C was found to be the optimal temperature to the germination of S. ciliata seeds. The final germination percentage (75.2%) was obtained with distilled water. The progressive decrease of osmotic potential of the PEG 6000 solutions inhibited the seed germination. However, the number of days to first germination was increased with a reduction of osmotic potential. A significant positive relationship was identified between final germination percentage of S. ciliata seeds and osmotic potential of the PEG 6000 solutions, with R 2 ranging from 0.5678 to 0.8761. Furthermore, a high degree of congruency between predicted and observed germination time course curves was observed. In general, S. ciliata exhibits a significant adaptation capacity for water limitation and high temperature in arid ecosystems.

Do high soil temperatures on Namibian fairy circle discs explain the absence of vegetation?

“…ciliata differs to that reported by Fakhfakh et al [32], who found that the highest germination percentages for this species occurred at 25 °C. This discrepancy could be explained either by Fakhfakh et al [32] using a constant experimental temperature approach, whereas in the current study seeds were exposed to the higher experimental temperatures for six hours each day instead of 24 hours, or by geographical variation in physiology of the species across its range. Both germination rate and growth of S .…”

“…S . ciliata is highly adapted to environments with limited water availability and high temperatures [32]. Within NamibRand Nature Reserve both grass species are associated with the peripheral band of FCs; with S .…”

Modeling the influence of temperature and water potential on seed germination of Allium tenuissimum L.

“…Successful establishment of cultivated plants depends on rapid and uniform seed germination (Fakhfakh, Anjum & Chaieb, 2018;Bidgolya et al, 2018); however, suitable water availability and temperature conditions for seed germination are only available during a short period in most arid and semi-arid regions (Fakhfakh, Anjum & Chaieb, 2018; Belo et al, 2014;Watt & Bloomberg, 2012). Here, we presented a comprehensive study of seed germination responses to different temperatures and water potential levels in A. tenuissimum, an important wild onion species from temperate-desert steppes of north central Asia (He, 2008;Li & Zhang, 2011).…”

“…Consequently, parameters of HTT models can be used to characterize the physiological status of seed populations in response to variable temperature and water potential and have been widely applied to predict germination dynamics in numerous crops such as safflower (Carthamus tinctorius) (Bidgolya et al, 2018;Torabi et al, 2016), sesame (Sesamum indicum) (Bakhshandeh et al, 2017), zucchini (Cucurbita pepo) (Atashi et al, 2015), and watermelon (Citrullus vulgaris cv. 'Crimson sweet') (Bakhshandeh et al, 2015) and other wild species (Abdellaoui et al, 2019;Fakhfakh, Anjum & Chaieb, 2018;Horn, Nettles & Clair, 2015).…”

Germination response of four Arabian desert grasses to low water potential

“…This germination modeling tool has been used to study desert grass species (e.g. Stipagrostis ciliate ; Fakhfakh et al 2018), shrubs (e.g. Retama raetam ; Abdellaoui et al 2019) and plant communities (Huang et al 2016).…”