Ayoub Molaahmad Nalousi

Turfgrasses are integral to landscape design. Unfortunately, in arid and semi-arid regions, salinity stress, alongside drought stress, poses a significant environmental challenge to grass growth. Therefore, employing environmentally friendly and sustainable development methods is essential. This study was conducted as a factorial experiment based on a completely randomized design, featuring 12 treatments and 6 replications (pots). The first factor examined was salinity stress at three levels (no salinity, 50 mM, and 100 mM sodium chloride), while the second factor involved foliar application with four levels: fulvic acid alone (2 g L-1), silicon nanoparticles alone (100 mg L-1), a combination of fulvic acid and silicon nanoparticles, and distilled water as a control. Seeds of red fescue grass (Festuca rubra cv. Carousel) were sown in pots containing a soil mixture. After establishment, the plants were mowed, and the respective foliar treatments were applied. One week later, salinity treatments were introduced via drenching. Foliar sprays of fulvic acid and silicon nanoparticles were repeated weekly. Foliar spraying of fulvic acid and silicon nanoparticles was conducted once a week, while the salinity treatment was applied every three days. After 6 foliar sprayings and 12 salinity treatments, we measured the morpho-physiological and biochemical characteristics of the turfgrasses. The results showed that salinity stress significantly reduced shoot fresh and dry weight, but increased root fresh and dry weight, with the greatest increase in root fresh and dry weight at 50 mM salinity. Silicon nanoparticles alone significantly increased root fresh and dry weight at both salinity levels. The root to shoot dry weight ratio also increased under salinity, and silicon nanoparticles alone significantly increased this ratio in both salt-free and 100 mM salinity conditions. Salinity stress reduced leaf relative water content and changed the cell membrane stability index. Fulvic acid alone or in combination with silicon nanoparticles significantly increased the cell membrane stability index at 50 mM salinity. Also, salinity stress reduced the maximum quantum efficiency of photosystem II, which fulvic acid increased this index, especially at 50 mM salinity. In biochemical characteristics, salinity increased chlorophyll b, total chlorophyll, carbohydrates, proteins, proline, hydrogen peroxide, malondialdehyde (MDA), and the activities of peroxidase and superoxide dismutase enzymes. Chlorophyll a decreased at 50 mM salinity and significantly increased at 100 mM. Fulvic acid and silicon nanoparticles reduced chlorophyll a and b and total chlorophyll at all three salinity levels. These compounds also reduced hydrogen peroxide and MDA, indicating a decrease in oxidative stress. The greatest reduction in hydrogen peroxide was observed at 50 mM salinity with combined application and at 100 mM salinity with fulvic acid alone. Peroxidase enzyme activity increased in salinity, but fulvic acid and silicon nanoparticles alone or in combination reduced this activity. Superoxide dismutase activity also increased under the influence of salinity; in non-salinity conditions, silicon nanoparticles alone or in combination with fulvic acid reduced this activity, but in 100 mM salinity, these compounds significantly increased enzyme activity. Overall, fulvic acid and silicon nanoparticles as biostimulants played an important role in modulating the morphological, physiological, and biochemical responses of red fescue grass under salt stress, and their combined application could be an effective strategy for improving the resistance of this grass to salinity by increasing root growth, antioxidant defense, and reducing oxidative.

Orchids, belonging to one of the most diverse plant families, exhibit remarkable ecological and morphological diversity, making them a fascinating subject for scientific studies. This research focused on 15 species of terrestrial orchids collected from diverse habitats in Iran, aiming to assess the morphological diversity of their seeds and its implications for phylogenetic relationships and conservation. The study employed scanning electron microscopy (SEM) to evaluate 16 morphological traits, including seed length (SL), cell length (CL), cell width (CW), and embryo volume (EV), among others. These traits were analyzed using statistical approaches such as correlation analysis, clustering, and principal component analysis (PCA). The results highlighted significant variability among the species, with seed length ranging from 260 µm to 680 µm and embryo volume varying from 0.02 mm³ to 0.08 mm³. Strong positive correlations were observed between seed and embryo dimensions, particularly between seed volume (SV) and embryo volume (EV), with a correlation coefficient (r) of 0.92. Clustering analysis grouped the studied species into distinct clusters, with species from the genus Ophrys forming a separate group due to their unique seed characteristics, such as high embryo-to-seed volume ratios. The PCA revealed that the first three components explained 73.6% of the total variance, with seed length, cell length, and embryo dimensions being the most influential traits. Notably, the Ophrys species demonstrated substantial interspecies morphological diversity, reflecting their unique evolutionary adaptations. Furthermore, the morphological variation observed among other species, such as Orchis anatolica and Gymnadenia conopsea, highlighted both phylogenetic relationships and ecological influences on seed morphology. This study underscores the importance of seed morphological traits as reliable markers for distinguishing closely related species and understanding their phylogenetic relationships. Although morphological analysis has limitations due to environmental influences, the integration of advanced statistical methods such as PCA and clustering provided a comprehensive framework for analyzing genetic diversity. These findings not only enhance our understanding of terrestrial orchid diversity but also contribute to their conservation by providing critical insights into species differentiation and genetic management strategies. Future studies should incorporate genomic tools alongside morphological analyses to develop a more robust understanding of orchid evolution and adaptation.