عنوان مقاله [English]
Introduction Cyclamen with a scientific name known as Cyclamen persicum, is a popular genus of Primulaceae and a winter pot plant that can be marketed within seven months when grown well under suitable conditions. In recent years, the rapid development of light technology has increased the use of several types of LED lamps because of their efficient roles to generate visible light via a wide range of wavelengths. In this regard, GA3 is well known as an environment-friendly growth regulator, which is extensively employed to increase productivity as well as to enhance the phenotypic features of several ornamental products.
Materials and Methods In this experiment, the seeds of the cyclamen large red flower, i.e. the Halios series, were planted in early May, and then kept in a dark and cool greenhouse for one month. After germination and the emergence of cotyledonary leaves, the plants are exposed to two levels of the LED light spectrum for 4 months consisting of the ratios of 70:20:10 and 40:40:20 via white: red: blue with the same intensity 100 µmol/m2/s were subjected to a 16-hour photoperiod. At the end of the third month of growth, GA3 was sprayed on the leaves at four concentrations of 0, 20, 40, and 60 mg/l under three times. Besides, NPK fertilizer with a ratio of 10-52-10 was then applied once a week with a ratio of 20-19-19 until the roots were fully established as well as after the seedlings reached the stage of five full break leaves. Afterwards, the leave area was measured using Digimizer version 5.4.3 software, in which the flowering date was calculated from the time of transferring the plants of each treatment under light and on daily basis. In the following, chlorophyll and carotenoid levels were measured using Lichtenthaler and Wellburn method, leave soluble sugar was measured using the Oregon method, and the chlorophyll fluorescence indices were measured using FluorPen FP 100.
Results and Discussion According to the obtained results, the highest number of cyclamen seedlings in the treatment of 40:40:20 was equal to seven, whereas the highest number of cyclamen seedlings under the light treatment of 70:20:10 was equal to 9.8 cm2. Moreover, the blue LED light affects the differentiation of leave mesophilic cells as well as the development of intercellular spaces, and the red light affects the production of a plant hormone so-called Meta-Topolin, which stimulates cell division and leave expansion. Here, it should be noted that adding white LED light to the composition spectrum increases both growth and photosynthesis because of its deeper penetration into the plant canopy. Furthermore, the maximum root length was achieved at a concentration of 60 mg/l GA3 equal to 5.1 cm. It should be mentioned that GA3 is effective to increase the growth of cells in different parts of the plant (such as roots) by stimulating mitotic division. The closest date to cyclamen flowering was obtained from the interaction of treatment 70:20:10 and the concentration of 0 mg/l GA3 equal to 90 days. Besides, the interaction of GA3 and LED lights are involved in the effect on flowering in those paths that regulate both seed dormancy and germination. Note that the highest amount of chlorophyll b was achieved from the interaction of light treatment 40:40:20 and concentration of 0 mg/l GA3 equal to 0.35 mg/g. Moreover, the ted light is needed for the photosynthesis, whereas the blue light is needed for chlorophyll and chloroplast synthesis, stomatal opening, and photomorphogenesis. The highest amount of soluble sugar of cyclamen seedlings was achieved from the interaction of 40:40:20 and the concentration of 0 mg/l GA3 equal to 0.53 mg / ml. Carbohydrates mostly accumulate in the leaves under blue light, whereas the red light can cause them to accumulate by preventing the transferring the photosynthetic products from the leaves. Among chlorophyll fluorescence indices, the highest VJ index was obtained from 40 mg/l GA3 concentration equal to 0.51. VJ was measured from the first light pulse, in which its increase via increasing the performance of the photosynthetic apparatus reveal the ability of seedlings to make better use of environmental conditions applied to produce more carbohydrates as well as to enhance the growth quality. Meanwhile, the highest values of φ-E0 and Ψ-0 indices in GA3 zero treatment were 0.44 and 0.54, respectively, indicating that increasing them means increasing the performance index of the photosynthetic apparatus. In this way, the external GA3 increases only the amount of chlorophyll and soluble protein content in the leaves of some plants, and interferes with the greater light reflection, chlorophyll fluorescence, and eventually the performance of photosystem II. In this regard, the highest amount of ABS/RC index was resulted in the interaction of 40:40:20 and concentration of 60 mg/l GA3 equal to 2.27, which is equal to increasing the performance index of photosynthetic device. During the plant growth, the use of monochromatic LED light compared to the full visible spectrum or red + blue lights would lead to creating some defects in the electron transport chain.
Conclusions The relationship between the increase in chlorophyll b, leave soluble sugar, and ABS/RC index, all in the 40:40:20 treatment while confirming this correlation, indicate that as the highest light absorption by chlorophyll is in the red and blue light spectrum, so the treatment 40:40:20 is better than 70:20:10 with more red and blue light. It should be mentioned that the effect of LED light at any quality, or GA3 at any concentration on the traits of quality of seedling or plant growth is directly related to the genotype of the plant species, and no specific effects can be determined either on light or hormone quality. Moreover, it should be mentioned that the chlorophyll fluorescence indices are independent of each other in terms of their effect on plant photosynthetic performance. The use of LED light and GA3 hormone (in this paper) can increase the quality of the plant by influencing some traits, but it would be reasonable to use them if it would lead to the production cost reimbursements.