دانشگاه اصفهان علوم زیستی گیاهی 3041-9603 15 4 2024 02 20 Effect of abiotic elicitors and plant growth regulators on Morpho-physiological and biochemical characteristics of Purslane (Portulaca oleracea L.) بررسی تأثیر عوامل غیرزیستی و تنظیم‌کننده‌های رشد گیاهی بر ویژگی‌های مورفوفیزیولوژیکی و بیوشیمیایی گیاه خرفه (Portulaca oleracea L.) 73 96 29040 10.22108/ijpb.2024.141800.1366 FA زهرا ساوری گروه زیست شناسی ، دانشکده علوم ، دانشگاه فردوسی مشهد ، مشهد ، ایران علی گنجعلی گروه زیست شناسی، دانشکده علوم، دانشگاه فردوسی مشهد، مشهد، ایران منیره چنیانی گروه زیست شناسی ، دانشکده علوم ، دانشگاه فردوسی مشهد ، مشهد ، ایران Journal Article 2024 06 11 Purslane (Portulaca oleracea L.) is widespread in various regions around the world. The present study aimed to investigate the effects of different concentrations of salicylic acid, gibberellic acid, and naphthalene acetic acid, as well as the application of mechanical and salinity stresses, on morpho-physiological traits, phenolic compounds, flavonoids, and photosynthetic pigments. Salinity stress at 160 mM NaCl was applied four weeks after seed sowing (seedling stage). Plant growth regulators such as salicylic acid (50 and 100 mg L-1), gibberellic acid (50 and 100 mg L1), and naphthalene acetic acid (130 and 200 mg L-1) and control treatment (distilled water), were sprayed on the leaves during the vegetative stage with two intervals 14 days apart. Wounding treatment was applied eight weeks after sowing (beginning of the reproductive stage) and then all plants were harvested after 24 h. The highest dry weight of the aerial parts and roots was related to the external application of 100 mg L-1 salicylic acid and the control treatment, respectively. Salinity, wounding, and external application of growth regulators significantly increased cell membrane stability and the content of photosynthetic pigments. The highest total phenol and flavonoid content was associated with the 50 mg L-1 gibberellic acid and 160 mM salinity stress, respectively. It seems that the increased activity of enzymes involved in anabolic processes, particularly phenylalanine ammonia-lyase, plays a key role in enhancing phenolic and flavonoid content. Introduction Purslane (Portulaca oleracea L.) belongs to the Portulacaceae family (Rashed et al., 2004(. Due to antimicrobial properties and antioxidant activity, phenolic compounds play an important role in improving resistance to environmental stresses (Oraibi et al., 2017). Growth regulators, including salicylic acid, have various effects on important physiological processes such as flowering, photosynthesis, and antioxidant activity, as well as improving tolerance to biotic and abiotic stresses (Hayat et al., 2008). Studies indicate that the use of gibberellin has various effects on the growth and development of many plants, and often in high concentrations, it has intensified the growth of some plants (Abbasi et al., 2019). Environmental stresses have often improved the content of phenolic compounds, antioxidant capacity, and fatty acid content in various plants including purslane (Choi et al., 2005; Wahid & Ghazanfar, 2006; Boo et al., 2011; Sarker et al., 2018). Anthocyanin, flavonoids, and various phenolic compounds are among the strong antioxidant defense systems of plants that are responsible for removing or inactivating ROS accumulated in stressed plants (Chai et al., 2005). Since very little information is available about the response of purslane to the individual application of growth regulators, as well as wound and salinity stresses, particularly regarding phenolic and flavonoid compounds, the present study was conducted. Materials and Methods The seeds were planted in early March 2022 in plastic pots containing a mixture of soil and sand in a ratio of 2:1. After four weeks of planting (seedling stage), salt stress was applied at 160 mM and the control plants were irrigated based on 90% of the field capacity. In the fourth week (vegetative growth stage), growth regulators were sprayed once every two weeks, including salicylic acid (50 and 100 mg L-1), gibberellic acid (50 and 100 mg L-1), and naphthalene acetic acid (130 and 200 mg L-1), by spraying on the leaves. Wound treatment was applied to the leaves 56 days after sowing (flowering stage). The measurement of the dry weight of the aerial part and the root was done after the plants were removed from the pots for 48 hours in an oven at a temperature of 50 °C. The relative water content and membrane stability index were measured according to the methods of Bian & Jiang (2009) and Sairam & Saxena (2000) respectively. Alcoholic extract was prepared with the method of EI. Kashef et al. )2018). Total phenol and flavonoid content were measured by the method of Velioglu et al. (1998) and Chang et al. (2002) respectively. Photosynthetic pigments were determined by the method of Lichtenthal (1987). Results and Discussion In this study, the highest root dry weight was observed in the control treatment. This can be attributed to negative effects such as osmotic stress, ion toxicity, and reduced nutrient absorption from the soil solution. These factors are among the main reasons for decreased plant growth and development under such conditions (Hassegawa et al., 2000; Munns, 2002). Results showed that the salt stress of 160 mM caused a significant increase in the relative water content of the leaves compared to the control (Figure 3). Wound treatment and external application of growth regulators significantly increased cell membrane stability and photosynthetic pigment content. This suggests that the increase in the content of photosynthetic pigments, including carotenoids, with the increase in the level of applied stress, indicates the defense mechanisms of plants in the face of stress (Kholova et al., 2010; Yidiz & Terzi, 2013). It seems that plant growth regulators, including salicylic acid, play an important role in the processes of plant growth and development by facilitating the absorption of nutrients and influencing the activity of photosynthetic enzymes (Mashayekhi & Atashi, 2012). The results of comparing the average data showed that the highest phenolic content of the total shoot related to the external application of gibberellic acid was 50 mg L-1 (Figure 5). The increase in the content of phenolic compounds can be attributed to the important role of gibberellin in increasing the activity of the enzyme phenylalanine ammonia-lyase, which is one of the most important key enzymes in the biosynthesis of compounds (Al-Ameer & Craker, 2007; Adil et al., 2007‌). Also, in this study, the highest amount of flavonoid content was related to plants that were affected by 160 mM salt stress (Figure 6). The increase of flavonoids under the influence of salinity stress is probably due to the effective role of these compounds in chelating toxic ions. Previous investigations confirm that the increase in phenolic compounds is related to the increase in the activity of enzymes involved in the metabolic processes of phenolic compounds, which is related to the synthesis of new phenols under salt stress (Adil et al., 2007). Conclusion The highest aerial and root dry weight was related to the external application of salicylic acid 100 mg L-1 and the control treatment, respectively. Wound treatment and external application of growth regulators significantly increased cell membrane stability and photosynthetic pigment content. Gibberellic acid (50 mg L-1 ‌) and salinity stress (160 mM) significantly increased the content of total phenol and flavonoid compared to the control. It seems that the main reasons are encouraging the activity of enzymes involved in anabolic processes of phenolic and flavonoid content, especially the phenylalanine ammonia-lyase. خرفه با نام علمی L. Portulaca oleracea در مناطق مختلف دنیا گسترش دارد. پژوهش حاضر با هدف بررسی غلظت‌های مختلف سالیسیلیک اسید، جیبرلیک اسید و نفتالین استیک اسید و نیز تنش‌های مکانیکی و شوری بر صفات مورفوفیزیولوژیکی، محتوی ترکیبات فنلی، فلاونوئیدی و رنگیزه‌های فتوسنتزی انجام شد. چهار هفته پس از کاشت بذور (مرحله گیاهچه‌ای)، تیمارهای آزمایشی شامل تنش شوری به میزان 160 میلی‌مولار‌، سالیسیلیک اسید و جیبرلیک اسید هر یک با غلظت‌های 50 و 100 میلی‌گرم بر لیتر و نفتالین استیک اسید با غلظت‌های 130 و200 میلی‌گرم بر لیتر و تیمار شاهد (آب مقطر) در مرحله رشد رویشی به برگ‌های گیاه در دو مرحله با فاصله 14 روز اسپری شد. تنش مکانیکی (‌زخم)، 8 هفته پس از کاشت (شروع مرحله رشد زایشی) روی برگ گیاهان اعمال شد و پس از 24 ساعت گیاهان در تمامی تیمارهای آزمایشی برداشت شدند. بیشترین وزن خشک بخش هوایی و ریشه به ترتیب به کاربرد خارجی سالیسیلیک اسید 100 میلی‌گرم بر لیتر و تیمار شاهد مربوط بود. تیمار زخم و کاربرد خارجی تنظیم کننده‌های رشد، پایداری غشای سلول و محتوی رنگیزه‌های فتوسنتزی را به طور معنی‌داری افزایش دادند. در این پژوهش بیشترین محتوی فنل کل و فلاونوئید به ترتیب به تیمار جیبرلیک اسید 50 میلی‌گرم بر لیتر و تنش شوری 160 میلی‌مولار مربوط بود. به نظر می‌رسد جیبرلیک اسید و تنش شوری با تقویت فعالیت آنزیم‌های درگیر در فرآیندهای آنابولیستی ترکیبات فنلی و فلاونوئیدی بویژه آنزیم فنیل آلانین آمونیالیاز از جمله دلایل اصلی افزایش محتوی ترکیبات فوق باشد.

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