ارزيابي اثرات پيش‌تيمار بذر و نوع بستر كاشت بر خصوصيات نشاء توليدي ذرت‌‌ شيرين (Zea mays L.)

Evaluation of the Effect of Seed Priming and Seedbed on Characteristic of Transplant Sweet Corn (Zea Mays L.)

به‌منظور بررسی تأثیر پیش‌تیمار بذر و نوع بستر كاشت بر ویژگی‌های نشاء تولیدی ذرت‌‌ شیرین آزمایشی به‌صورت فاكتوریل در قالب طرح كاملاً تصادفی با سه‌تكرار در گلخانه‌ی تحقیقاتی دانشگاه فردوسی مشهد انجام‌شد. فاكتورهای آزمایش شامل پیش‌تیمار بذور در سه‌سطح: بدون‌پرایمینگ(p1)، هیدروپرایمینگ (p2) و بیوپرایمینگ (p3) و نوع بستر در هفت‌سطح: ورمی‌كمپوست (b1)، پرلیت (b2)، كوكوپیت (b3)، ورمی‌كمپوست+پرلیت(b4)، ورمی‌كمپوست+‌كوكوپیت(b5)، پرلیت+كوكوپیت (b6) و ورمی‌كمپوست+كوكوپیت+پرلیت (b7) بودند. نتایج این آزمایش نشان‌داد كه پیش‌تیمار بذر و نوع بستر بر خصوصیات نشاء ذرت‌‌ شیرین تأثیر معنی‌داری داشت. بذور پیش‌تیمار‌‌شده (P2, P3) از لحاظ ویژگی‌های نشاء نسبت به تیمارهای پپیش‌تیمار‌‌نشده (P1) برتر بودند. تیمار بستر ورمی‌كمپوست بیش‌ترین طول اندام‌هوایی، سطح برگ در بوته، وزن اندام‌هوایی و وزن ریشه را در بین بسترهای مختلف نشان‌دادند. بیش‌ترین سطح برگ در بوته و وزن خشك اندام‌هوایی به‌ترتیب با میانگین 111‌سانتی‌متر مربع و 798‌میلی‌گرم در تیمار هیدروپرایمینگ با بستر ورمی‌كمپوست (P2b1) مشاهده‌شد. نتایج این تحقیق نشان‌داد بستر ورمی‌كمپوست بهترین بستر برای نشاء ذرت‌‌ شیرین است و هم‌چنین تیمارهای هیدروپرایمینگ و بیوپرایمینگ نیز باعث بهبود خصوصیات نشاء می‌شوند.

<strong > Introduction </strong > Corn (Zea mays L.) is one of the main cereals in the tropical and temperate regions of the world. Sweet corn obtained from a genetic mutation on chromosome 4 locus SU conventional maize resulting accumulation of sugars and polysaccharides which are soluble in seed endosperm. Unlike other types of corn, sweet corn endosperm contains a lot of sugar to starch, which is called Amylodextrin and it is soluble in water. Producing healthy and uniform plants is one of the requirements of modern agriculture. Considering the unsuitable climatic condition in Iran (arid and semiarid) transplantation is one of the requirements for sustainable agriculture particularly in sweet corn production with high water requirement where transplantation is able to save at least 2-3 times of irrigations. Therefore, producing high quality transplants is an important practice for successful seedling establishment. Hence, the objective of this study was to evaluate the effects of seed priming and substrate types on the characteristics of sweet corn transplants. <strong > Materials and Methods </strong > This experiment was conducted as factorial based on a completely randomized design with three replications. Treatments were three levels of seeds pretreatment: no priming (p1), hydropriming (p2) and biopriming (p3), and another factor was seedbeds types in seven levels including: vermicompost (b1), perlite (b2), cocopeat(b3), vermicompost+perlite(b4), vermicompost+ cocopeat (b5), perlite+ cocopeat (b6) and vermicompost+ cocopeat +perlite (b7). Biopriming using bioaminopalis biological fertilizer applied on the seeds for 24hours in a solution containing micro-organisms such azotobacter and Pseudomonas. Then the non-primed and the primed seeds were sown in the plastic pots and grown in a greenhouse with average temperature of 22-25° C. Samples were taken three weeks after planting. <strong > Results and Discussion </strong > Mean emergence time Emergence is shoot elongation and growth leading the shoots out of the soil. Shorter mean emergence time indicates the plants emergence more quickly as a desirable characteristic. Results from analysis of variance showed that the mean emergence time was significantly influenced by seed priming treatments (P≤0.01). The type of seedbed and interaction of two factors, seedbed and priming had no significant effect on mean emergence time (Table 1). Non treated seeds (P1) had the longest mean emergence time of 3.06 days compared with treated seeds (P2, P3) (Table 2). Shoot length The results showed that the type of the seedbed and seed priming pretreatment had a significant effect on the shoot length on the sweet corn transplants. The interaction between these two factors on shoot length was also significant (Table 1). Bioprimed seeds produced transplants with 17.86 cm shoot length superior to the non-primed seeds, while it did not show statistically significant difference with the hydroprimed seeds. Sweet corn seeds inoculation with bacteria resulted a significant increase in the seedling shoot length. Sayed-Sharifi and Khavazi (2011) also found similar results. Seed bed also had a significant effect on sweet corn seedling shoot length. As the vermicompost + cocopeat and vermicompost seedbeds produced seedlings with shoot length of 21 and 20.68 cm respectively, while perlite+coco peat and perlite showed the lowest shoot length of 10.98 and 11.08 respectively (table 2). Nicknam et al. (2012) also investigated the influence of different substrates on the growth of two cultivars of lily (Lilium ledebourii) and found that seedbeds containing vremikvlayt and perlite produced transplants with a shorter shoot length. P3b5 treatment where the seeds primed with microorganisms such as pseudomonas and the seedlings grown in the vermicompost resulted in the highest (24 cm) shoot length possibly due to more availability of the nutrients while P1b2 treatments produced the shortest (9.9 cm) shoot length seedlings (Figure 1) Leaf area The seeds pretreatment (P≤0.05), the kind of seedbed and the interactions between these factors (P≤0.01) have significant effect on the sweet corn leaf area (Table 1). The seedlings of the bioprimed seeds produced a higher leaf area of 60.65 cm2 compared with the control and hydropriming treatments possibly due to more availability of the nutrients. Seed pretreatment with biological fertilizer of bioaminopalis that contained bacteria, azotobacter and pseudomonas had direct and indirect effects on plant growth leading to expansion of the leaf area. The direct effects of these bacteria could be used in producing chemical components needed for plant growth, facilitating nutrients uptake, atmospheric nitrogen fixation and plant hormones production such as auxin and gibberellins, enhancing plant growth in various stages of development, or construction of enzymes involved in the plant growth. <strong > Conclusions </strong > Seed priming and vermicompost seedbed improved the quality of the produced transplants. This system was recommended for sweet corn production in Iran using transplants in order to save at least 2-3 times of the irrigation per year where the country is suffering from serious water crises.