اثر نوع بستر بر عملکرد فیزیولوژیک و مورفولوژیک زعفران در سیستم کشت بدون خاک

افزایش تدریجی دما، کاهش بارش و کاهش حاصلخیزی خاک در دهه‌های اخیر موجب کاهش شدید عملکرد کلاله زعفران شده است. با توجه به اهمیت اقتصادی و اجتماعی زعفران در ایران، توسعه دانش و فناوری به‌منظور افزایش عملکرد کشت سنتی و توسعه کشت صنعتی آن بسیار ضروری است. بنابراین در این پژوهش گلخانه‌ای، ابتدا ویژگی‌های فیزیکی شش نوع مخلوط مواد اولیه بستر کشت بررسی شد. سپس اثر چهار نوع آن‌ها (شامل سه پرلیت با دانه‌بندی ریز، متوسط و درشت و یک مخلوط پرلیت-کوکوپیت-کوکوچیپس) بر رشد و نمو زعفران در قالب طرح کاملاً تصادفی با پنج تکرار بررسی، و ویژگی‌های فیزیولوژیک و مورفولوژیک برگ (شدت فتوسنتز خالص لحظه‌ای، شدت فتوسنتز کل، وزن، تعداد و سطح)، بنه (وزن، تعداد و درصد بنه‌های درشت) و ریشه (تشکیل ریشه‌های رابط) زعفران ارزیابی شد. اندازه‌گیری ویژگی‌های فیزیکی چهار نوع بستر کشت نشان داد که بستر مخلوط دارای مناسب‌ترین نسبت رطوبت به هوا است. گیاهان کشت‌شده در این تیمار دارای بیش‌ترین وزن برگ، شدت فتوسنتز خالص لحظه‌ای، و وزن (و درصد وزنی) بنه دختری درشت بودند. در بین سه بستر پرلیت خالص، پرلیت با اندازه متوسط ویژگی‌های فیزیکی بهتری داشت و عملکرد گیاهان در این بستر در مجموع بیش‌تر از دو بستر دیگر بود. بنه‌های کشت‌شده در سه بستر پرلیت خالص ریشه رابط تولید کردند. در مجموع یافته‌های این پژوهش نشان داد که هرچند زعفران گیاهی ژئوفیت با نیاز آبی کم معرفی شده است اما تامین کافی آب و عناصر غذایی موجب بهبود معنی‌دار ویژگی‌های فیزیولوژیک و مورفولوژیک، از جمله افزایش ذخیره عناصر غذایی در بنه‌ها می‌شود که برای تکثیر کارآمد آن در نسل‌های بعدی ضروری است.

the impact of substrate type on physiological and morphological performance of saffron in soilless cultivation system

abstractthe gradual rise in temperature, reduced rainfall, and soil fertility decline in recent decades have significantly lowered saffron stigma yield. given saffron’s vital economic and social role in iran, enhancing traditional cultivation methods and advancing industrial cultivation technology are crucial. this study assessed the impact of four non-soil cultivation substrates (three perlite variants - fine, medium, coarse, and a perlite-cocopeat-cocochips mixture) on saffron growth and development. using a completely randomized design with five replications, the physiological and morphological characteristics of leaf (net photosynthesis rate, total photosynthesis rate, weight, number, and area), corm (weight, number, large-sized percentage), and root (contractile root formation) of saffron were evaluated. measuring physical indices revealed that the mixed substrate had the most optimal water-to-air ratio. plants grown in this substrate exhibited the highest leaf weight, net photosynthesis rate, and large-sized cormlet weight (and weight percent). among the three pure perlite substrates, the medium-sized perlite showed superior physical properties and higher plant yield compared to the other two substrates. corms grown in the pure perlite substrates produced contractile roots. overall, the study indicated that despite saffron being a low-water geophyte, adequate water and nutrient supply significantly enhance its physiological and morphological parameters, including nutrient storage in corms, crucial for efficient reproduction in subsequent generations.background and objective: saffron is a sterile plant that reproduces through the growth and development of meristem tissues on the mother corm’s surface (corm) and the production of cormlets (cormlets). the increase in cormlet production is directly related to corm weight. enhancing the quantity and quality of the corm leads to greater production of cormlets, flowers, and stigmas (negbi, 1999). over the past five decades, stigma yield has declined by 35% (ministry of agriculture jihad, 2022), partly due to climate changes and a decrease in irrigation water quantity and quality. cultivating saffron under controlled conditions has been proposed as a viable solution (sabet teimouri et al., 2010). given that the choice of substrate significantly impacts plant growth and crop yield (verdonck et al., 1981), evaluating different substrates is crucial for selecting the most suitable one (olle et al., 2012). this study aims to assess the moisture characteristics of various substrates and determine the optimal saffron cultivation medium based on the plant’s physiological and morphological responses.methods: the physical characteristics of six substrate types were initially assessed, comprising four pure perlites of varying size and two mixed media blends of perlite with cocopeat and cocochips. from which, three pure perlite substrates with particle sizes of > 1, 3–5, and 7–10 mm, along with a mix of 70 %v/v perlite, 15 %v/v cocopeat, and 15 %v/v cocochips, were selected for further analysis in the presence of saffron plants. the aim was to identify the most suitable substrate for saffron cultivation based on the morphological and physiological responses of different plant parts. the experiment followed a randomized complete design with five replications, evaluating characteristics such as net photosynthesis rate, total photosynthesis rate, leaf characteristics (weight, number, and area), corm traits (weight, number, and size distribution), and the formation of contractile roots.results: the m4 substrate (70:15:15 perlite:cocopeat:cocochips mixture), with 78 %v/v total porosity, exhibited the best water-to-air ratio among the substrates. in pure perlites, m2 substrate (1–3 mm granules) showed the most suitable water-to-air ratio. physiological and morphological characteristics were influenced by all substrate types. the m1 (< 1 mm granules) and m3 (3–5 mm granules) substrates showed the least plant part functionality. although the m4 substrate displayed higher leaf weight and net photosynthesis rate compared to m2, no significant difference was noted for the leaf area and total photosynthesis values. however, the m4 substrate had the highest weight of large cormlets and the percentage of large-sized cormlets. the experimental data indicated that saffron leaf thickness is influenced by substrate type and moisture conditions. the thickness is not accounted for in leaf area calculations while it plays a crucial role in total plant photosynthesis rate. notably, saffron plants grown in pure perlite substrates produced contractile roots, which hinders cormlet development. no contractile roots were observed in the perlite:cocopeat:cocochips mixed substrate.conclusions: substrate characteristics are the key factor controlling water and nutrient supply to saffron in hydroponic systems. despite saffron being a geophyte with low water and nutrient requirements, an optimal growing substrate leads to notable enhancements in leaf physiological and morphological characteristics, boosting nutrient storage in corms for efficient reproduction in the next generations.references:1. ministry of agriculture jihad. 2022. agricultural statistics: horticultural and greenhouse products.  available: https://maj.ir/dorsapax/userfiles/sub65/aj3-1401.pdf.2. negbi, m., 1999. saffron cultivation: past, present and future prospects, vol. 154. harwood academic, amsterdam.3. olle, m., ngouajio, m., siomos, a., 2012. vegetable quality and productivity as influenced by growing medium: a review. agriculture 99(4), 399–408.4. sabet teimouri, m., kafi, m., avarseji, z., orooji, k., 2010. effect of drought stress, corm size and corm tunic on morphoecophysiological characteristics of saffron (crocus sativus l.) in greenhouse conditions. j. agroecol. 2(2), 323–334.5. verdonck, o, de vleeschauwer, d., de boodt, m., 1982. the influence of the substrate to plant growth. acta hortic. 126, 251–258. https://doi.org/10.17660/actahortic.1982.126.30.