تاثیر محلول‌پاشی زمستانه اوره بر تغییرات پلی‌آمین‌های برگ، گره، عملکرد و خصوصیات زایشی درختان نارنگی ’کینو‘

با توجه به نقش پلی‌آمین‌ها در تشکیل گل و تولید میوه، این تحقیق در سال 95-1394 به منظور بررسی تاثیر اوره بر میزان پلی‌‌آمین‌های آزاد و تولید گل و میزان محصول در درختان 17 ساله نارنگی رقم ’کینو‘ انجام شد. تیمارها شامل سه غلظت اوره (صفر، 0.75 و 1.5 درصد) و سه زمان محلول‌پاشی (1 دی ماه، 15 دی ماه و 30 دی ماه) با سه تکرار قبل از گل‌انگیزی بر روی درختان اعمال شد. پلی‌آمین‌ها در دو اندام برگ و گره مورد تجزیه و تحلیل قرار گرفتند. در این آزمایش از برگ و گره در، 1، 3 و 5 هفته بعد از محلول‌پاشی، نمونه‌برداری و مقدار پلی‌آمین‌های پوتریسین، اسپرمیدین، اسپرمین و نیتروژن اندازه گیری شد. بیشترین مقدار پلی‌آمین‌ها و نیتروژن در برگ‌ها و گره‌ها بعد از محلول‌پاشی 30 دی ماه با غلظت اوره 1.5 درصد به دست آمد. ولی بتدریج با گذشت زمان بعد از محلول‌پاشی مقدار پلی‌آمین‌ها و نیتروژن در برگ و گره کاهش یافت. غلظت پلی‌آمین‌ها در برگ و گره بسته به غلظت اوره و زمان محلول‌پاشی، متفاوت بود. نتایج این تحقیق نشان داد که اسپرمین پلی‌آمین غالب در برگ‌ها و گره‌ها (به‌ترتیب 01/ 44 و 34.41 نانو مول بر گرم بافت تر) بود. همچنین نتایج نشان داد که محلول‌پاشی اوره در زمستان باعث افزایش تعداد گل و عملکرد محصول نارنگی کینو گردید. با توجه به نتایج این پژوهش می‌توان محلول‌پاشی اوره در دی‌ماه، با غلظت 1.5 درصد را به منظور افزایش عملکرد نارنگی رقم ’کینو‘ توصیه کرد.

effect of winter foliar application of urea on changes in leaf and node polyamines, yield and some characteristics of reproductive of kinnow mandarin trees

introduction nitrogen plays an important role in the uniformity and quality of citrus trees. several studies previously reported that a low level of nitrogen in citrus trees is generally caused a reduction in yield and fruit quality (aziz, 1997; khan et al., 2009). in this regard, applying urea is recommended as the most suitable form of nitrogen for foliar application. the polyamines are included; putrescine, spermidine, and spermine which have been considered as plant growth regulators (alcazar et al., 2010; khezri et al., 2010). the role of nitrogen in vegetative and reproductive growth and yield, as well as the correlation between polyamines, flower induction and fruit set in other plants, were proved in previous studies. in this regard, the results of the current study will increase our understanding about the role of polyamines in the morphology of the tree and also the mechanism of regulating the alternate bearing of kinnow mandarin leading to an approach method to address this problem.materials and methodsto conduct this study a 17-year-old uniform of kinnow mandarin (citrus reticulate blanco) grafted onto bitter orange (citrus aurantium) rootstock, which grown in a commercial orchard, located in dezful (khuzestan province in iran). for sampling, the branches which possess leaves and nodes were selected from four sides of each tree, then leaves and nodes were collected at three different time points (one, three, and five weeks post-treatment). samples were immediately frozen in liquid nitrogen after excision and transported to the physiology laboratory of fruit trees within 2h for determining the n fractions and polyamines. the concentration of n in dried leaves and nodes was determined using the colorimetry technique as described by walling et al. (1989). the experiment was set up as a factorial treatment based on a randomized complete block design with three replications to investigate the effect of different concentrations of urea foliar application (0, 0.75%, 1.5%) on nitrogen and polyamines contents at different time points (dec 22, jan 5, jan 20) followed by evaluating flower characteristics and yield in kinnow mandarin plant. data analysis including variance was carried out using mstatc and sas software. to compare the mean of polyamines and nitrogen in leaves and nodes, the cut-out method was used, and also for comparison of pistil dimensions, number of flowers, and yields, duncan’s multiple range test (dmrt) was performed.results and discussion results indicated that polyamines concentration and nitrogen decreased during the period of time and also, in most cases, polyamines concentration was lower in the nodes than the leaves. high levels of polyamines and nitrogen were obtained in leaves and nodes which were treated with the foliar application of 1.5 % urea concentration after jan 20. the polyamines content in leaves and nodes was greatly dependent on the spraying time and urea concentration used. spermine (spm) was the dominant polyamines in leaves and nodes with the highest values of 44.01 nmol/gf.w, 34.41 nmol/gf.w, respectively. regarding the fact that flower density was higher in trees that treated with urea concentration of 1.5 % after jan 5 y than other treatments, however, their yield was lower than the trees that treated on dec 22 with the same urea concentration. this was probably due to the flower abscission as well as the fruit abscission in june. the results of this study showed that the highest yield was obtained with 1.5 % urea concentration after foliar application on dec 22 compared with other treatments. regarding the fact that flower differentiation in mandarin occurs during the late january until late february (in dezful conditions), it can be explained that the foliar application on dec 22 was performed before differentiation and consequently, the trees have received their required nitrogen.