اثر محلول‏پاشی پتاسیم و روی بر شاخص‏های فیزیولوژیک رشد، پارامترهای فلئورسانس کلروفیل و عملکرد دو رقم گندم نان تحت تاریخ کاشت تاخیری

به‏منظور بررسی اثر محلول‏پاشی پتاسیم و روی بر شاخص‏های فیزیولوژیک رشد، پارامترهای فلئورسانس کلروفیل و عملکرد دو رقم گندم نان تحت تاریخ کاشت تاخیری، آزمایشی به‏صورت کرت‏های دو بار خرد شده در قالب طرح پایه بلوک‏های کامل تصادفی با سه تکرار در شهرستان رامهرمز اجرا گردید. عامل‏های آزمایشی شامل تاریخ کاشت در دو سطح مناسب (30 آبان) و تاخیری (15 دی) به‏عنوان عامل اصلی، محلول‏پاشی در چهار سطح با آب (شاهد)، پتاسیم، روی و پتاسیم + روی به‏عنوان عامل فرعی و دو رقم گندم نان پیشتاز و چمران 2 به‏عنوان عامل فرعی فرعی بودند. نتایج نشان داد که تاریخ کاشت تاخیری به‏دلیل تنش گرمای انتهایی شاخص سطح برگ (lai) (25.96درصد)، دوام سطح برگ (lad) (48.44 درصد)، سرعت رشد محصول (cgr) (21.76درصد)، سرعت رشد نسبی (rgr) (13.72 درصد)، سرعت جذب خالص (nar) (22.43درصد)، حداکثر عملکرد کوانتومی فتوسیستم ii در شرایط سازگار شده با تاریکی (fv/fm) (3.25 درصد)، عملکرد کوانتومی موثر فتوسیستم ii(φpsii) (4.37 درصد)، حداکثر عملکرد کوانتومی فتوسیستم iiدر شرایط سازگار شده با روشنایی (fv /fm ) (3.24 درصد) و عملکرد دانه (27.02 درصد) ارقام گندم نان را به‏طور معنی‏داری کاهش داد، اما موجب افزایش معنی‏دار خاموشی غیرفتوشیمیایی (npq) (22.73 درصد) گردید. محلول‏پاشی پتاسیم و روی غیر از npq صفات lai (17.50درصد)، lad (17.62درصد)، cgr (33.49درصد)، rgr (12.00درصد)، nar (37.62درصد)، fv/fm (3.12درصد)، φpsii (7.37درصد)،fv /fm (6.65 درصد) و عملکرد دانه (17.30 درصد) ارقام گندم نان را تحت تاریخ کاشت تاخیری به‏طور معنی‏داری بهبود بخشید. به‏طور کلی، استفاده از محلول‏پاشی روی و روی + پتاسیم در رقم چمران 2 به‏عنوان بهترین ترکیبات تیماری در بهبود صفات فیزیولوژیک و عملکرد دانه در هر دو تاریخ کاشت مناسب و تاخیری توصیه می‏شود.

Effect of Potassium and Zinc Foliar Application on Growth Physiological Indices, Chlorophyll Fluorescence Parameters and Yield of Two Bread Wheat Cultivars under Late Planting Date

Introduction ;Wheat (Triticum aestivum L.) is one of the most important sources of plant food for human among the main crops globally. High temperature resulting from delay in planting is one major environmental factor limiting growth and production of wheat, especially in tropical regions. Most of the Iranian soils have high pH and calcareous nature, so absorption of nutrients is limited in these soils. Mineral nutrition of plants plays a critical role in increasing plant resistance to environmental stresses. Among the mineral nutrients, potassium plays a crucial role in the survival of crop plants under environmental stress conditions. Potassium is essential for many physiological processes, such as photosynthesis, maintenance of turgidity and activation of enzymes under stress conditions. Zinc is a ubiquitous micronutrient. It is required as a structural and functional component of many enzymes and proteins.;Materials and Methods ;To study the effect of potassium and zinc foliar application on growth physiological indices, chlorophyll fluorescence parameters and yield of two bread wheat cultivars under late planting date, an experiment was conducted as splitsplit plot based on randomized complete blocks design with 16 treatments and three replications in Ramhormoz city during 20152016. The experimental factors were included planting date in two levels optimum (November 21) and late (January 5) as the main factor, nutrients foliar application in four levels (water as a control, potassium, zinc and combination potassium + zinc (each 3 l.ha1)) as the sub factor and two cultivars of bread wheat Pishtaz and Chamran 2 as the subsub factor. Solutions for foliar application were prepared by using potassium (21%) and zincchelate (7.5%). Traits measured were included leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), relative growth rate (RGR), net assimilation ratio (NAR), maximal quantum yield of PSII in the darkadapted state (Fv/Fm), effective quantum yield of PSII photochemistry (ΦPSII), maximal quantum yield of PSII in the lightadapted state (Fv /Fm ), nonphotochemical quenching (NPQ) and grain yield. To determine LAI, LAD, CGR, RGR, NAR, Fv/Fm, ΦPSII, Fv /Fm and NPQ were used from equations 19, respectively.; LAI= Pla×den /10000; LAD= 1/2 (LA2+LA1) (T2T1) ; CGR= [(W2 – W1)/(T2 – T1)] × (1/GA) × 100; RGR= [(lnW2 – lnW1)/( T2 – T1)] × 100; NAR= CGR/LAI; Fv/Fm= (Fm – F0)/Fm; ΦPSII= (Fm – Ft)/Fm ; Fv /Fm = (Fm –F0 )/Fm ; NPQ= (Fm – Fm )/Fm ;where, Pla is average leaf area per plant (cm2); den is real density (plant m2); LA1 is primary leaf area (cm2); LA2 is secondary leaf area (cm2); T1 is first sampling time (day); T2 is second sampling time (day); W1 is primary dry weight (g); W2 is secondary dry weight (g); GA is ground area (m2); lnW2 – lnW1 is natural logarithm difference of dry weight; Fm is maximal fluorescence yield of the darkadapted state; F0 is minimal fluorescence yield of the darkadapted state; Fv is variable fluorescence (dark) (FmF0); Ft is fluorescence emitted by the leaves adapted to lighting; Fm is maximal fluorescence yield of the lightadapted state; F0 is minimal fluorescence yield of the lightadapted state, and Fv is variable fluorescence (light) (Fm F0 ). The grain yield was determined at maturity stage and through the harvest of all spikes from the level of 1 m2 per plot and after removing 0.5 m from the beginning and end respective planting rows (rows 5 and 6).Analysis of variance was performed using general linear model (GLM) procedure of statistical analysis system (SAS version: 9.3). The means were analyzed using the least significant difference (LSD) method at P=0.05 (LSD 0.05).;Results and Discussion ;The results showed that late planting date due to terminal heat stress significantly decreased LAI (30.0%), LAD (48.4%), CGR (21.8%), RGR (13.7%), NAR (22.4%), Fv/Fm (3.2%), ΦPSII (4.4%), Fv /Fm (3.2%) and grain yield (27.0%) of two cultivars of bread wheat Pishtaz and Chamran 2, but increased significantly the NPQ (22.7%). Potassium and zinc foliar application improved significantly traits the LAI (17.5%), LAD (17.62%), CGR (33.5%), RGR (12.0%), NAR (37.6%), Fv/Fm (3.1%), ΦPSII (7.4%), Fv /Fm (6.6%) and grain yield (17.30%) of two cultivars of bread wheat Pishtaz and Chamran 2 under late planting date except for the NPQ. Among the interactions of nutrients foliar application and bread wheat cultivars, the response of Pishtaz and Chamran 2 cultivars were more suitable to potassium foliar application, and zinc and zinc + potassium foliar application, respectively. As well as, among wheat cultivars cultivated under the conditions of nonapplication of potassium and zinc (control), Chamran 2 cultivar had a comparative advantage in all measured traits under both optimum and late planting dates compared to Pishtaz cultivar.;Conclusions;In general, it can be used from timely planting date, potassium and zinc foliar application and suitable wheat cultivar such as Chamran 2 as three management strategies to reduce the harmful effects of terminal heat stress caused by late planting date in Ramhormoz city.