اثر نيترات پتاسيم بر رشد و رنگيزه هاي فتوسنتزي ريحان آلوده به Colletotrichum gloeosporioides

Effects of potassium nitrate on growth and photosynthetic pigments of basil infected by Colletotrichum gloeosporioides

اين تحقيق به‌ منظور بررسي اثر غلظت‌هاي مختلف نيترات پتاسيم (0، 4، 8 و 12 ميلي‌مولار) بر رشد و وزن خشك اندام‌هاي گياهي و كلروفيل و فنل كل در ريحان (Ocimum basilicum L.) آلوده به Colletotrichum gloeosporioides انجام گرفت. آزمايش به‌صورت فاكتوريل و در قالب بلوك‌هاي كاملا تصادفي با چهار تكرار در گلخانه اجرا گرديد. در گياهان آلوده به بيمارگر، خصوصيات رشدي، وزن خشك اندام‌هاي هوايي، رنگيزه‌هاي فتوسنتزي و فنل كل كاهش يافتند. كاربرد نيترات پتاسيم به‌ويژه غلظت 12 ميلي‌مولار در شرايط تنش توانست با افزايش مقدار رنگيزه‌هاي فتوسنتزي و فنل كل در گياه ريحان، منجر به كاهش بيماري و افزايش صفات سطح برگ، ارتفاع بوته، وزن خشك اندام هوايي نسبت به گياهان شاهد (غلظت صفر نيترات پتاسيم) شود. كاربرد محلول‌پاشي نيترات پتاسيم تاثير معني‌داري بر وزن خشك ريشه و تعداد برگ در مقايسه با گياهان نداشت. كاربرد نيترات پتاسيم به‌طور معني‌داري ميزان نيترات و فعاليت نيترات ردوكتاز را افزايش مي‌داد.

Introduction: Basil (Ocimum basilicum L.) is an economically important herb crop many other parts of the world. This popular herb is used both as a fresh and as a dried food spice and in traditional medicine. Many diseases such affect the development of basl. Colletotrichum gloeosporioides is one of the common leaf pathogens of basil causing necrotic leaf spots and stem lesions. Intensive research has been done to investigate the effects of foliar application of nutrients on growth and biosynthesis of phytochemicals in medicinal plants (Kazemi, 2014). This study was conducted to investigate the effects of potassium nitrate on growth parameters, total chlorophyll and phenol, nitrate content and nitrate reductase of basil (Ocimum basilicum L.) under C. gloeosporioides infection. Materials and Methods: The seeds were sown in pots in greenhouse and 30 days old plants were sprayed with concentrations of potassium nitrate (0, 4, 8 and 12 mM) early in the morning. Plants were inoculated with C. gloeosporioides 5 days after foliar application of KNO3. Samples were collected 10 days after fungal inoculation and assayed for growth, dry weight, total chlorophyll and phenol, nitrate content and nitrate reductase and disease severity. The experiment was factorial based on a randomized complete block design with four replications. Results and Discussion: Effect of foliar application of KNO3 on vegetative characteristics (dry weight of shoots and roots and photosynthetic pigments) of basil plant under different potassium nitrate levels is presented in Tabel 2. All growth characteristics, dry weight of shoots and roots and photosynthetic pigments of infected plants decreased. Application of potassium nitrate, especially at concentration of 12 mM, could increase the amount and activity of photosynthetic pigments and total phenol in basil which resulted, in reducing the negative effects of C. gloeosporioides infection and an increase on leaf area, dry weight of shoot as compared with those of control (non-application of potassium nitrate). Foliar applications of potassium nitrate not have significant effect on dry weight of roots and leaf number as compared with those of the control. The exogenous application of KNO3 is related to increased nitrate content and nitrate reductase (Fig. 2). The experiments clearly demonstrated the beneficial effects of potassium nitrate application on growth, nutrients concentration and defense reactions of basil plants. These results are in agreement with those obtained by Hegazi et al. (2011) and Jabeen and Ahmad (2011) of olive growth and sunflower and safflower improved by foliar application of KNO3, respectively.