بررسي اثر هورمون‌هاي سيتوكينين و اكسين و الگوي كاشت بر عملكرد و اجزاء عملكرد ذرت دانه‌اي (Zea mays L.) در شرايط شور

Study of Cytokinin and Auxin Hormones and Planting Pattern Effects on Yield and Yield Components of Grain Maize (Zea mays L.) under Saline Conditions

جهت بررسی اثر زمان محلول‌پاشی هورمون‌های سیتوكینین (عدم مصرف، مصرف در مرحله V5-V6 و V8-V10) و اكسین (عدم مصرف، زمان ظهور ابریشم و دو هفته پس از آن) و الگوی كاشت (یك ردیفه، دو ردیفه و كف فارو) بر عملكرد و اجزاء عملكرد ذرت دانه‌‌ای (Zea mays L.) در شرایط شور آزمایشی در سال 1392 در مركز تحقیقات كشاورزی و منابع طبیعی بوشهر به‌صورت اسپلیت فاكتوریل در قالب طرح بلوك‌‌های كامل تصادفی با سه تكرار اجرا گردید .الگوی كاشت به‌عنوان فاكتور اصلی و مصرف یا عدم مصرف هورمون‌‌‌‌‌‌‌‌‌‌های اكسین و سیتوكینین به‌صورت فاكتوریل در كرت‌های فرعی بررسی گردید. اثر الگوی كاشت بر ارتفاع بوته، طول و قطر بلال، تعداد ردیف دانه، تعداد دانه در ردیف، وزن هزار دانه، عملكرد بیولوژیك، عملكرد دانه و شاخص برداشت معنی‌دار بود. بیشترین عملكرد دانه با كشت كف فارو با 55/7 و كمترین آن با كشت معمول با 09/4 تن در هكتار بود. از نظر ارتفاع بوته و تعداد ردیف دانه برتری با زمان مصرف 8 تا 10 برگی بود ولی وزن هزار دانه و شاخص برداشت در زمان مصرف 5 تا 6 برگی حداكثر بود. بیشترین تعداد دانه در ردیف بدون مصرف سیتوكینین به‌دست آمد. اثر اكسین روی وزن هزار دانه، عملكرد بیولوژیك، عملكرد دانه و شاخص برداشت در سطح 1% معنی‌دار گردید و بیشترین عملكرد دانه با زمان مصرف ظهور ابریشم به‌دست آمد. به‌طور كلی با كاشت كف فارو و مصرف سیتوكینین در مرحله 8 تا 10 برگی و مصرف اكسین در زمان ظهور ابریشم به‌ترتیب با غلظت 50 و 10 گرم در لیتر اثرات شوری بر گیاه كاهش یافته و عملكرد دانه افزایش یافت.

<strong >Introduction </strong > Maize (Zea mays L.) which belongs to the Poaceae family is the third important cereal crop of the world after wheat and rice. Salinity is one of the major environmental factors limiting plant growth and productivity. Maize is sensitive to salinity. Planting method is a crucial factor for improving crop yield. Planting methods in saline and non-saline conditions are different. Kinetin is one of the cytokinins known to significantly improve the growth of crop plants grown under salinity. Indole acetic acid (IAA) is also known to play a significant role in plant tolerance to salt stress. However, little information appears to be available on the relationship between salinity tolerance and auxin or cytokinins levels in plants. In this respect, the objective of this study was to study the effects of foliar applications of cytokinin and auxin hormones on yield and yield components of grain maize under different planting patterns in saline conditions. <strong >Materials and Methods </strong > The experiment was carried out at Bushehr Agricultural and Natural Resources Research Center, Dashtestan station with 29° 16´ E latitude and 51° 31´ N, longitude and 70 m above the see surface during the 2013 growing season. Dashtestan region is a warm-arid region with 250 mm precipitation per year. The field plowed by April 2013 and then prepared and sowed by August 2013. There were five rows with 75 cm distance. The experiment was conducted as a split-plot factorial design based on complete randomized blocks with three replications. Planting pattern (ridge planting, double rows of planting on a ridge in zigzag form and furrow planting) as the main factor and time of cytokinin (0 as a control, V5- V6 stage and V8- V10 stage) and auxin (0 as a control, silking stage, two weeks after silking stage) foliar-applied was considered in a factorial. Cytokinin (Benzyl Adenine, Merck) and Auxin (Indole-3-Butiric Acid, Merck) were sprayed on the entire plant in the evening with concentration of 50 and 10 g. l-1, respectively. All morphological and yield component traits measured on 10 randomly selected plants of each plot. Yield was measured in 9 m2 for each treatment. Data analyzed using the SAS (Ver.9.1) and comparing of the means was conducted using Duncan’s multiple range test. <strong >Results and Discussion </strong > Results showed that the planting pattern had a significant effect on plant height, ear (cob) length, ear diameter, kernel row number, per ear, kernel number per row, 1000- kernel weight, biological yield, grain yield and harvest index. The highest and the lowest yield obtained through furrow planting and conventional planting, respectively. Applying furrow planting, resulted in water use improvement and reducing side effects of saline soils Cytokinin application in V8- V10 stage produced the highest plant height and row number per ear and the highest 1000- kernel weight and harvest index was belong to the application of cytokinin in V8- V10 stage. The maximum kernel number per row was obtained without cytokinin. Auxin effect on 1000- kernel weight, biological yield, grain yield and harvest index were significant (p≤0.01). The highest grain yield by a mean of 6.57 tons.ha-1 produced by time of auxin foliar-applied in the silking stage. It has been found that both auxin and cytokinin may have a role in mediating cell division in the endosperm during the grain-filling stage. Therefore, these hormones might regulate the grain capacity (sink size) for the accumulation of carbohydrates. It has been found that IAA actively participated in the mobilization and accumulation of carbohydrates in seeds. Auxin and cytokinins hormones are also thought to be involved in regulating the sink strength either by mediating the division and enlargement of endosperm cells or by controlling the import of assimilates to the sink. <strong >Conclusions </strong > The results indicated that the foliar application of cytokinine and auxin hormones counteracted some of the salt induced adverse effects and improved the maize yield .Due to its effect on diminishing salt aggregation in relation to ridge planting, furrow planting, prepare semi saline and saline areas for growing crops. It is concluded that furrow planting with CK application in V8- V10 stage (50 g. l-1) and IBA in silking stage (10 g. l-1) reduced the effects of salinity on plant and produced the highest grain yield.