تاثیر پیش‌تیمار سالیسیلیک اسید بر جوانه‌زنی بذر، رشد و شاخص‌های بیوشیمیایی گیاهچه‌های کینوا (chenopodium quinoa willd.) تحت تاثیر تنش کادمیوم

برای بررسی تاثیر سالیسیلیک اسید بر شاخص های جوانه زنی بذر و رشد گیاهچه‌های کینوا تحت تاثیر تنش کادمیوم، آزمایشی به‌صورت فاکتوریل در قالب طرح پایه ی کامل تصادفی در چهار تکرار در دانشگاه محقق اردبیلی انجام شد. تیمارها شامل تنش کادمیوم در پنج سطح (صفر، 50، 100، 150 و 200 میلی گرم در لیتر)، سالیسیلیک اسید در پنج سطح (صفر، 1، 1.5، 2 و 2.5 میلی مولار) بودند. نتایج نشان داد با افزایش شدت تنش، میانگین درصد و سرعت جوانه زنی، وزن خشک و طول گیاهچه‌های کینوا کاهش یافته بود. در شرایط بدون تنش، درصد و سرعت جوانه زنی و وزن خشک گیاهچه های حاصل از بذرهای پیش‌تیمارشده با سالیسیلیک اسید به طور معنی داری بیشتر از بذرهای شاهد بود. همچنین پیش تیمار بذر تحت سالیسیلیک اسید منجر به افزایش معنی دار صفات درصد جوانه زنی، سرعت جوانه زنی، میانگین درصد جوانه زنی، طول و وزن خشک گیاهچه، فعالیت آنزیم های کاتالاز، پراکسیداز و پلی فنل اکسیداز شد، اما میانگین مدّت جوانه زنی، زمان تا 90 درصد جوانه زنی، را کاهش داد. کاربرد 2.5 میلی مولار سالیسیلیک اسید به‌صورت پیش تیمار در شرایط بدون تنش و تنش کادمیوم منجر به افزایش طول گیاهچه بین 46.48 و 73.83 درصد شده بود. با کاربرد غلظت 2.5 میلی مولار سالیسیلیک اسید فعالیت آنزیم‌های کاتالاز، پراکسیداز و آنزیم پلی فنل اکسیداز به ترتیب 45.30 تا 93.89، 22.51 تا 51.6 و 25.4 تا 45.17 درصد افزایش داد .در مجموع، پیش تیمار بذر با 2.5 میلی مولار، در سطوح مختلف تنش کادمیوم از راه افزایش توان بذر و گیاهچه و افزایش فعالیت آنزیم های آنتی اکسیدانی بیشترین اثر مثبت را بر جوانه زنی و رشد گیاهچه های کینوا داشت.

effect of seed pretreatment with salicylic acid on seed germination, growth and biochemical indices of quinoa seedlings (chenopodium quinoa willd.) under cadmium stress

to investigate the effect of salicylic acid on the indicators of seed germination and growth of quinoa seedlings under cadmium stress, a factorial experiment was conducted in the form of a completely randomized basic design in four replications at mohaghegh ardabili university. the treatments included cadmium stress at five levels (0, 50, 100, 150, and 200 mg/l), and salicylic acid at five levels (0, 1, 1.5, 2, and 2.5 mm). the results showed that with the increase in stress intensity, the average percentage and speed of germination, dry weight, and length of quinoa seedlings decreased. in non-stressed conditions, the percentage and speed of germination and the dry weight of the seedlings obtained from the seeds pretreated with salicylic acid were significantly higher than the control seeds. also, seed pretreatment with salicylic acid significantly increased the characteristics of germination percentage, germination rate, average germination percentage, seedling length, dry weight, activity of catalase, peroxidase, and polyphenol oxidase enzymes, but decreased the average germination time, time to 90% germination. application of 2.5 mm salicylic acid as a pre-treatment in non-stress and cadmium stress conditions increased seedling length by 46.48 and 73.83%. by using 2.5 mm concentration of salicylic acid, the activity of catalase, peroxidase, and polyphenol oxidase enzymes increased by 45.30 to 93.89, 22.51 to 51.6, and 25.4 to 45.17%, respectively. in total, seed pretreatment with 2.5 mm salicylic acid, at different levels of cadmium stress, increased seed and seedling vigor and activity. antioxidant enzymes had the most positive effect on the germination and growth of quinoa seedlings.introductionheavy metal stress is one of the most critical abiotic factors that has attracted a lot of attention in the last 30 years. heavy metal is any element that exhibits a high density and exerts its lethal effects even when present in small amounts. among all the discovered elements, 53 elements have been identified as heavy metals. meanwhile, chromium (cr), lead (pb), cadmium (cd), silver (ag), cobalt (co), platinum (pt), arsenic (as), and nickel (ni) play the most destructive role in plant physiology. (decaroli et al., 2020). quinoa is a multipurpose plant that has recently been used in the human diet as a substitute for animal products as a source of protein. quinoa contains a high amount of protein (12-18%), bioactive compounds, essential amino acids, fatty acids, and minerals. (angeli et al., 2020) quinoa seeds and leaves are used as food. while its biomass is also used in animal feed. in addition, the high contents of saponins and colors make it useful for industrial and medicinal purposes (abd el-moneim et al., 2021). considering the importance of the quinoa plant and the existing problems in the field of germination and growth of its seedlings (due to the sensitive and critical nature of these steps), the use of the seed pretreatment technique in quinoa can be considered as one of the solutions that be effective directly and indirectly on improving the germination and establishment of seedlings under the conditions of heavy metal stress. considering the role of salicylic acid in reducing the effects of heavy metal stress such as cadmium on the germination and growth of seedlings, this study aims to investigate the effect of pretreatment of seeds with salicylic acid on the indicators of seed germination and growth of quinoa seedlings. it was done under cadmium stress. materials and methodsto investigate the effect of salicylic acid on the indicators of seed germination and the growth of quinoa seedlings under cadmium stress, a factorial experiment was carried out in the form of a completely randomized basic design in four replications in the laboratory of seed science and technology of mohaghegh ardabili university in 1400. the test treatments include cadmium concentrations at five levels (zero (control), 50, 100, 150, and 200 mg/liter), and salicylic acid concentrations at five levels (zero (control), 1, 1.5, 2, and 2.5 millimolar). before applying the treatments, the seeds were disinfected with two percent sodium hypochlorite for one minute and then washed with distilled water. to pre-treat the seeds with salicylic acid, after preparing the solutions with concentrations of 1, 1.5, 2, and 2.5 mm, the sterilized seeds were placed in the determined concentrations for 12 hours. then they were kept in an incubator with a temperature of 20 degrees celsius for 12 hours. after the end of the period, the seeds were dried in the laboratory environment until reaching the initial moisture (sheikhzadeh et al., 2021). to perform the germination test, 50 quinoa seeds were randomly placed in petri dishes in 4 replicates using the top-of-paper method, and based on the desired treatments, cadmium solution at concentrations of 50 100, 150, and 200 mg/liter was added to petri dishes (distilled water was used for the control treatment). to measure the biochemical characteristics of seedlings, samples of 10-day-old normal seedlings were randomly selected and these samples were kept in a freezer at -80°c until the biochemical and enzymatic properties were measured. the method of chang & koa (1988) was used to prepare the enzyme extract. the activity of the catalase enzyme was used according to the method of aebi (1984) and the peroxidase enzyme was measured according to the method of chanec maehly & (1955) based on the formation of tetragaiacol from guaiacol in the presence of hydrogen peroxide and guaiacol enzyme. the activity of the polyphenol oxidase enzyme was measured by the method of kar & mishra (1955). statistical analysis of data was done using sas 9.4 statistical software. the normality of data distribution was evaluated using the kolmogorov-smirnov test. the comparison of means was done using duncan’s multiple range test at the 5% probability level. excel software was used to draw graphs. results and discussionin total, the results of this research showed that with the increase in the intensity of cadmium stress, the characteristics of germination percentage, germination speed, average germination percentage, seedling length, and dry weight decreased and the average duration of germination, the time to 90% germination. in women, the activity of catalase, peroxidase, and polyphenol oxidase enzymes increased. cadmium stress causes ionic imbalance, which stimulates the production of reactive oxygen species (ros), which leads to cell membrane disruption, osmotic regulation, and the production of secondary metabolites. considering the negative effect of this stress on the germination and growth of the obtained seedlings, pre-treating quinoa seeds with salicylic acid will shorten the time required for germination, so that in the conditions without stress and the cadmium stress pretreated seeds germinated faster than the control seeds and by reducing the average germination time and the time to 90% germination through increasing the rate of water absorption, repairing and preparing the structure and enzymes of the seed and the weak seed coat. it reduces cadmium damage and protects the germination process against the toxicity of this heavy metal. conclusionwe showed that increasing the activity of antioxidant enzymes during germination, improves the conditions of germination and initial growth, in other words, pre-treating seeds with salicylic acid at a concentration of 2.5 mm and different levels of cadmium stress the way of increasing seed and seedling vigor and increasing the activity of antioxidant enzymes reduces the negative effect of cadmium stress and improves the characteristics of germination and seedling growth.