عنوان مقاله [English]
Introduction Poinsettia (Euphorbia pulcherrima) from the family Euphorbiaceae is used as potted and cut flower and has great importance in floriculture industry. Appropriate application of nutrients and plant growth regulators has an important role in increasing the quantity and quality of crops. The successful application of various nanoplatforms in medicine under in vitro conditions has generated some interest in agro-nanotechnology. This technology holds the promise of controlled release of agrochemicals and site-specific targeted delivery to improve efficient nutrient utilization and enhanced plant growth. Nanoencapsulation shows the benefit of more efficient use and safer handling of pesticides with less exposure to the environment. Thus, nanofertilizers can be substituted for conventional fertilizers. The role of iron in the activity of some enzymes such as catalase, peroxidase and cytochrome oxidase has been demonstrated. Iron is present as a cofactor in the structure of many enzymes. The results of some studies showed that in the absence of micro-nutrients elements, the activity of some antioxidant enzymes decreased, which resulted in increased sensitivity of plants to environmental stresses. The use of nano-iron fertilizer is an appropriate solution to remove this problem. Some growth retardants such as cycocel, paclobutrazol, bayleton and daminozide reduced the plant growth. Growth reduction in some ornamental plants enhances their overall quality and marketing. Cycocel is one of the most important growth retardants which inhibits gibberellin biosynthesis and activity in plant. Today, a range of artificially made growth-reducing compounds are used in the floriculture industry. The effect of plant growth retardants, depends on the time and method of application, concentration, species and varieties type, type of target organ and environmental and physiological conditions. Plant growth retardants reduce the division and elongation of stem cells. These compounds also reduce stem length and growth by having a negative effect on gibberellin structure. Therefore, the present study investigated the effect of different levels of nano-iron fertilizer and different concentrations of cycocel on growth and development of poinsettia (Euphorbia pulcherrima Willd.).
Materials and Methods These experiments were carried out based on a randomized completely block design in three replications to evaluate the effect of various levels of nano iron chelated fertilizer and cycocel on growth parameters of Euphorbia pulcherrima. Cuttings with a height of 15 to 20 cm, each with 3 nodes, were prepared from the mother plant of poinsettia. Cuttings were placed in water within 24 hours for exudation of latex. Then, cuttings were planted in perlite for rooting. After rooting (60-65 days), cuttings were transferred into substrates including cocopeat, municipal compost and soil in ratio of 1:1:1. Poinsettia cuttings were grown in pots. Treatments include nano-iron fertilizer (0, 0.9, 1.8, 3.6 and 4.5 g l–1) and cycocel (0, 500, 1000, 1500 and 3000 mg l–1). Application of EDTA-based nano-iron chelate as foliar spray was performed on plants at the beginning of the experiment and 30 days later, as well as the use of cycocel 30 days after the start of the experiment as foliar spray. Stem height, internode length, node number, root length, root number, root volume, leaf number, leaf surface, leaf total chlorophyll content, iron content in leaf and the number and longevity of bracts were evaluated.
Results and Discussion Results showed that the least plant height and the most leaf number, root length, root volume, the number and longevity of bracts were obtained in treatments of 1.8 g l–1 nano-iron chelate without or with the concentration of 1000 mg l–1 cycocel. In some traits such as root volume and chlorophyll content, the minimum amount was calculated in the maximum of nano-iron chelate and cycocel concentrations. Suitable root characters were severely reduced through the use of 3000 mg l–1 cycocel. Overall, the most suitable treatment, especially for reduction of stem height and enhancing some vegetative traits (such as leaf number) and flowering (such as bract longevity) was 1.8 g l–1 nano-iron chelate along with 1000 mg l–1 cycocel. Similar results were reported in some species. Studies on some ornamental plants have shown that with increasing concentration of cycocel, plant height was reduced. This study confirms other research studies. The present study shows that cycocel plays an effective role in changing the weight of the aerial and underground parts of plants, as well as leaf iron and chlorophyll. Plant growth retardants increase the content of cytokinin which leads to increased levels of leaf chlorophyll.