با همکاری انجمن علمی منظر ایران
نوع مقاله : مقالات پژوهشی
نویسندگان
گروه علوم باغبانی و مهندسی فضای سبز، دانشکده کشاورزی، دانشگاه فردوسی مشهد، مشهد، ایران
کلیدواژهها
عنوان مقاله English
نویسندگان English
Introduction
With respect to the expansion of arid areas and the escalating severity of water scarcity in various parts of the country, it is necessary to identify drought-tolerant groundcover species to replace grass in urban green spaces. This study aimed to research the morphological and physiological reactions of three groundcover species; tall fescue (Festuca arundinacea), Phyla nodiflora, and Sedum acre under various levels of drought stress (20, 40, 60, and 80 % of field capacity). The results demonstrated that as drought stress intensity intensified, root length, fresh and dry weight, relative leaf water content, and chlorophyll a and b levels decreased significantly, whereas electrolyte leakage increased substantially. The highest shoot length in Festuca was observed at 80% of field capacity (13.5 cm), But in Phyla, the highest growth was achieved at a moisture level of 60% (17 cm), which had a significant difference at the 5% probability level with the 80% level (14 cm). The Phyla species was superior in most physiological and functional traits, the highest amount of chlorophyll a and chlorophyll b was observed for this species at a moisture level of 20%. While for the other two species, the highest value was observed at a moisture level of 60%. Sedum spp. showed the most stress symptoms under conditions of increased irrigation period, considering its root structure and function. Overall, the results of this study showed that Phylla nodiflora can be a suitable alternative to grass in urban green space design in dry areas as a resistant species with low water requirements.
Materials and Methods
The experiment was performed under greenhouse conditions at the Ferdowsi University of Mashhad (36°20′N, 59°39′) to assess drought stress responses among groundcover species that were chosen for this study. Seeds of F. arundinacea were planted in a pot, while Phyla nodiflora and Sedum acre were propagated from cuttings with uniform root systems. A completely randomized design was utilized, involving four irrigation levels (20%, 40%, 60%, and 80% of field capacity) and three replications for each species. Treatment for the drought commenced once the area was fully established and persisted for 75 days. Characteristics such as shoot height, root length, and fresh and dry biomass, along with physiological properties like relative water content and electrolyte leakage, and biochemical markers including chlorophyll a and chlorophyll b, were evaluated at the experiment's conclusion. Measurements of relative water content (RWC) and electrolyte leakage (EL) were carried out using established procedures (Yang et al., 2021; Samieiani, 2012), while pigment contents were determined via spectrophotometry (Lichtenthaler, 1987). The daily water usage was calculated through weighing, followed by ANOVA and LSD test analysis conducted at a 5% significance level within Minitab 22, with the graphs produced using Excel software.
Results and Discussion
Analysis of variance revealed that drought stress significantly affected all morphological traits of Festuca and Sedum at the 1% probability level, and most traits of Phyla at either 1% or 5%. The greatest shoot length in Festuca was recorded under 80% field capacity (FC), not significantly different from 60% FC, while Phyla showed its maximum shoot length at 60% FC, with a significant decline under both milder and more severe stress. In all species, minimum shoot length occurred at 20% FC. Root length followed a similar trend, decreasing with increasing drought intensity. Festuca showed the highest root length under 80% FC, whereas Sedum and Phyla exhibited variable responses among stress levels. Root fresh weight was highest at 80% FC in all species and declined significantly under increased drought stress. Compared with control conditions, reductions in root fresh weight at 60% FC were 7% for Festuca, 9.5% for Sedum, and an increase of 72.5% for Phyla, indicating differential tolerance. Similarly, shoot fresh weight decreased with increasing stress in Festuca and Sedum, while Phyla reached its maximum value at 60% FC. Relative water content (RWC) declined with higher stress intensity, with the greatest reductions observed under 20% FC (reductions of 51.72%, 62.12%, and 49.6% for Festuca, Sedum, and Phyla, respectively). Electrolyte leakage increased significantly with stress severity, reaching maximum values of 44%, 62%, and 57% in Festuca, Sedum, and Phyla under 20% FC. Chlorophyll a and b contents showed variable patterns across species. In Festuca and Sedum, maximum chlorophyll a and b occurred at 60% FC, while in Phyla, the highest values were observed under severe drought stress (20% FC). These differences suggest species-specific physiological adjustment mechanisms under water deficit conditions.
Conclusion
The groundcover species examined in this study responded differently to drought stress. Phyla nodiflora performed better in most physiological and morphological parameters with notable tolerance to water deficit stress. On the other hand, Sedum acre was the most sensitive plant to drought. As drought severity increased, key parameters such as root length, fresh biomass, relative water content of leaves, and chlorophyll content decreased, whereas electrolyte leakage increased. These findings reinforce the importance of utilizing drought-tolerant species like Phyla nodiflora for future sustainable urban landscape design. Replacement of high-water-demand lawns with such robust groundcovers can help significantly in the preservation of water resources. However, more studies need to be carried out to find out the long-term adaptation and adaptability of these species under diverse weather and irrigation regimes.
Acknowledgment
We would like to express my appreciation for the financial support provided by Ferdowsi University of Mashhad for conducting this research.
کلیدواژهها English
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