分类： 生物学 >> 生态学 提交时间： 2023-02-07 合作期刊: 《干旱区科学》
摘要：Stipagrostis ciliata (Desf.) De Winter is a pastoral C4 grass grown in arid regions. This research work focused on assessing the growth of S. ciliata accessions derived from two different climate regions (a wet arid region in the Bou Hedma National Park in the central and southern part of Tunisia (coded as WA), and a dry arid region from the Matmata Mountain in the south of Tunisia (coded as DA)) under water stress conditions. Specifically, the study aimed to investigate the phenological and physiological responses of potted S. ciliata seedlings under different water treatments: T1 (200 mm/a), T2 (150 mm/a), T3 (100 mm/a) and T4 (50 mm/a). Growth phenology, net photosynthesis (Pn), stomatal conductance (gs), midday leaf water potential (Ψmd), predawn leaf water potential (Ψpd), soil water content (SWC) and soil water potential (Ψs) were observed during the water stress cycle (from December 2016 to November 2017). The obtained results showed that the highest growth potential of the two accessions (WA and DA) was recorded under treatment T1. The two accessions responded differently and significantly to water stress. Photosynthetic parameters, such as Pn and gs, decreased sharply under treatments T2, T3 and T4 compared to treatment T1. The higher water stress increased the R/S ratio (the ratio of root dry biomass to shoot dry biomass), with values of 1.29 and 2.74 under treatment T4 for accessions WA and DA, respectively. Principal component analysis (PCA) was applied, and the separation of S. ciliata accessions on the first two axes of PCA (PC1 and PC2) suggested that accession DA was detected in the negative extremity of PC1 and PC2 under treatments T1 and T2. This accession was characterized by a high number of spikes. For treatments T3 and T4, both accessions were detected in the negative extremity of PC1 and PC2. They were characterized by a high root dry biomass. Therefore, S. ciliata accessions responded to water stress by displaying significant changes in their behaviours. Accession WA from the Bou Hedma National Park (wet arid region) showed higher drought tolerance than accession DA from the Matmata Mountain (dry arid region). S. ciliata exhibits a significant adaptation capacity for water limitation and may be an important species for ecosystem restoration.
分类： 生物学 >> 植物学 提交时间： 2018-01-29 合作期刊: 《干旱区科学》
摘要：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 (PEG6000) 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 PEG6000 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 PEG6000 solutions, with R2 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.
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