بررسی تاثیر اسید هیومیک بر شاخص های جوانه زنی و رنگیزه های فتوسنتزی در ژنوتیپ های گندم دیم در مرحله گیاهچه ای در ارتباط با عملکرد دانه

جوانه‌زنی یکی از مراحل حساس در رشد گیاه است و تنوع ژنتیکی قابل ملاحظه ای بین ژنوتیپ های گندم از لحاظ شاخص های مختلف جوانه زنی وجود دارد. این شاخص ها ممکن است تحت تاثیر اسید هیومیک خاک قرار گرفته و با عملکرد دانه مرتبط باشند. در این رابطه، مطالعه حاضر با هدف بررسی تاثیر اسید هیومیک بر ویژگی‌های جوانه‌زنی و رنگدانه‌های فتوسنتزی 12 ژنوتیپ گندم دیم انجام شد. آزمایش به‌صورت فاکتوریل در قالب طرح کاملاً تصادفی شامل دو عامل ژنوتیپ و محیط جوانه‌زنی (آب مقطر به‌عنوان شاهد و محلول اسید هیومیک) طراحی شد. پس از گذشت 8 روز، درصد جوانه‌زنی، طول و وزن خشک ریشه‌چه و ساقه‌چه، ضریب آلومتریک، شاخص بنیه گیاهچه و محتوای رنگدانه‌های فتوسنتزی اندازه‌گیری شد. به منظور ارزیابی رابطه بین شاخص‌های جوانه‌زنی با عملکرد دانه، میزان عملکرد دانه ژنوتیپ‌ها در یک آزمایش چهار ساله تحت شرایط دیم و آبیاری تکمیلی بررسی شد. نتایج نشان داد که اسید هیومیک تاثیر مثبتی بر درصد جوانه‌زنی، میزان رنگدانه‌های فتوسنتزی، طول و وزن تر و خشک ساقه‌چه داشت. با این حال، این تیمار اثر منفی بر طول و وزن تر و خشک ریشه‌چه نشان داد. واکنش ژنوتیپ‌ها به تیمار اسید هیومیک متفاوت بود. ژنوتیپ‌های هشترود و گاودره بهترین گزینه‌ها برای استفاده از اسید هیومیک شناسایی شدند. ژنوتیپ‌هایی با نسبت بالای ریشه‌چه به ساقه‌چه مانند اوحدی در شرایط تنش عملکرد بهتری داشتند. این پژوهش اهمیت انتخاب ژنوتیپ مناسب و شرایط تیماری را برای بهینه‌سازی شاخص‌های حیاتی بذر برجسته کرد و بر تفاوت‌های ژنتیکی در پاسخ به تیمارهای زیستی تاکید نمود، اما رابطه ای بین عملکرد ژنوتیپ های گندم با شاخص های جوانه زنی را نشان نداد.

studying the effect of humic acid on germination indices and photosynthetic pigments in rainfed wheat genotypes at the seedling stage in relation to grain yield

extended abstract: introduction: seed germination is a fundamental physiological process influencing crop establishment and yield potential. environmental stresses such as drought, nutrient deficiency, and biotic factors often inhibit this critical stage. humic substances, particularly humic acid (ha), have garnered significant attention due to their biostimulant properties, including enhancing nutrient uptake, photosynthetic capacity, and root architecture. while their effects have been demonstrated in various crops, there remains a knowledge gap regarding the response of rainfed wheat (triticum aestivum l.) genotypes at the seedling stage to ha treatment. this study aims to explore the physiological and biochemical responses of twelve diverse wheat genotypes to ha application during germination and their potential relationship with field performance.materials and methods: a factorial experiment was conducted using a completely randomized design with two factors: genotype (12 wheat genotypes) and germination environment (distilled water as control and humic acid solution). seeds were surface sterilized and placed in petri dishes under controlled conditions. the ha solution concentration was standardized to ensure uniform exposure. after 8 days, various parameters were measured including germination percentage, root length, shoot length, fresh and dry weight of root and shoot, root-to-shoot ratio, allometric coefficient, seed vigor index, and photosynthetic pigment content (chlorophyll a, b, and total chlorophyll). pigments were extracted in 80% acetone and quantified spectrophotometrically. to correlate laboratory indices with field performance, grain yield data from a four-year field trial under both rainfed and supplementary irrigation conditions were used. this allowed for evaluation of genotype × environment interactions and assessment of genotype stability under variable moisture availability.results and discussion: significant differences were observed among genotypes for all measured parameters, indicating substantial genetic variability. humic acid application significantly increased germination percentage, shoot length, shoot fresh and dry weight, and chlorophyll content, suggesting improved seed vigor and early photosynthetic potential. conversely, ha treatment reduced root length and root biomass in most genotypes, possibly due to altered hormonal balance or osmotic effects at high concentrations. these contrasting effects underscore the importance of genotype-specific responses to biostimulant treatments. among the genotypes tested, ‘hashtrood’ and ‘gavdareh’ consistently exhibited superior performance under ha treatment, demonstrating high shoot vigor and pigment accumulation, and were identified as optimal candidates for humic acid utilization. in contrast, genotypes such as ‘ohadi’ with a high root-to-shoot ratio performed better under stress, suggesting that this trait may contribute to enhanced water acquisition and survival under adverse conditions. analysis of photosynthetic pigments revealed a significant increase in chlorophyll a and b levels following ha treatment, indicating improved light absorption efficiency and potential photosynthetic capacity at the seedling stage. these physiological enhancements are critical for early seedling establishment, particularly in dryland systems where initial vigor determines competitive success. despite observable changes in seedling morphology and physiology, correlation analysis between germination traits and final grain yield revealed no significant relationship. this suggests that while ha improves early-stage indicators, these improvements do not necessarily translate to higher yield under field conditions, likely due to complex genotype × environment interactions and subsequent growth-stage limitations.conclusion: the present study demonstrates that humic acid can positively influence early growth traits and photosynthetic pigment accumulation in rainfed wheat genotypes, though effects are genotype-dependent. the findings underscore the necessity of selecting suitable genotypes when employing ha in seed priming or early-stage treatments. while improvements in seedling vigor were evident, these did not directly correlate with grain yield, indicating that ha’s impact is more pronounced in early physiological processes rather than final yield determination. this research highlights the potential of humic acid as a biostimulant to enhance specific physiological parameters during germination but also emphasizes the need for long-term field studies to validate its efficacy in improving agronomic performance. understanding the genotype-specific responses to ha can inform breeding programs and agronomic practices aimed at improving wheat resilience and productivity under stress-prone environments.