نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه علوم باغبانی، دانشکده کشاورزی، دانشگاه بوعلی سینا، همدان، ایران.
2 گروه زیست شناسی، دانشکده علوم پایه، دانشگاه بوعلی سینا، همدان، ایران.
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
The off-season cultivation of strawberry is often restricted under greenhouse conditions because of low light intensity, short-length day, and casting shade of plants on each other. This study aimed to investigate the effect of supplemental light quality (during the day) on morphological and photosynthetic characteristics of strawberry cv. 'Camarosa' under greenhouse conditions. In this context, the treatments included different supplemental lightings as follows: 100% red light (100% RL), 100% blue light (100% BL), 83% red light + 17% blue light (83% RL+67% RL), 67% red light + 33% blue light (67% RL+33% BL), 50% red light + 50% blue light (50% RL+50% BL), and a daily sunlight with 800 to 1000 μmol/m2/s (DS) as control. Results showed that the highest growth indices were observed in the plants treated with 100% BL as well as 50% RL + 50% BL, while the lowest were obtained in the plants subjected to DS and 100% RL. Furthermore, exposing the strawberry to 100% BL as well as 50% RL+ 50% BL led to production of the highest number of flower per plant. In addition, the highest amount of chlorophyll characteristics including (total chlorophyll, chlorophyll a, and chlorophyll b) and carotenoids was recorded in 100% BL and 50% RL + 50% BL treatments. In contrast, the lowest chlorophyll content was gained using DS and 100% RL. Finally, photosynthetic activity was significantly intensified using 100% BL and a combination of 50% RL and 50% BL, but it was remarkably diminished at DS treatment. In conclusion, the results of this study could substantiate the role of supplemental lighting not only in activating metabolic pathways associated with production of photosynthetic pigments, but also in enhancing plants’ growth and morphological characteristics of strawberry cv. 'Camarosa' through improving stomatal exchange and photosynthesis rate.
کلیدواژهها [English]
Extended Abstract
Introduction
Strawberry is one of the most valuable crops, widely consumed in the world. Because of its nutritional value and taste, the demand for its production and consumption has extensively been increased; consequently, improving its fruit composition is of great importance. After producing off-season strawberry in the last 20 years, the growers have developed different methods in strawberry production under greenhouse condition. In this regard, a controlled environment can provide an opportunity to produce strawberry in the off-season. It generally requires a long day and a suitable light intensity to gain suitable growth and development. Regarding the existence of low light and short-day length, predominant in a vast majority of the strawberry-producing greenhouses, employing supplemental lighting is crucial on inducing plants’ growth and flowering. Light characteristics (i.e., intensity, quality, and duration) play an important role in regulating strawberry’s growth, development, flowering, and photomorphogenesis. As a main source of energy for photosynthesis in plants, light usually stimulates some changes in gene expression, physiological, morphological, and metabolic characteristics through photoreceptors. Strawberry cv. 'Camarosa' is a short-day plant in which vegetative growth is influenced by day length and temperature. The present study aimed to evaluate the effect of the quality of supplemental light on the morphological and photosynthetic characteristics of strawberry cv. 'Camarosa' under greenhouse condition.
Materials and Methods
This research was carried out in the research greenhouses of the Department of Horticultural Sciences, Bu-Ali Sina University in the autumn and winter seasons. The plants of strawberry cv. 'Camarosa' were initially transferred to the greenhouse and cultivated in a hydroponic bed containing cocopeat and perlite (70:30 ratio). Afterwards, they were fed three days interval using Hoagland nutrient solution. During the experiment, the environmental condition inside the greenhouse was adjusted as follows: temperature (25°C day/15°C night), relative humidity (70%), and the period of natural lighting 11 h per day/13 h per night on average. The experiment was conducted as a completely randomized design with three replications. A total of six treatments of this experiment included 100% red light (660 nm) (100% RL), 100% blue light (440 nm) (100% BL), 83% red light +17% blue light (83% RL + 17% BL), 67% red light + 33% blue light (67% RL + 33% BL), 50% red light + 50% blue light (50% RL + 50% BL), and daily sunlight (DS) as control. Lighting with an approximately intensity of 250 μmol/m2/s was supplied with light emitting diodes (LED) and sunlight (800 to 1000 μmol/m2/s) for 14 hours from 5 am to 7 pm. Finally, some morphological characteristics and photosynthetic parameters of strawberry were measured after about one month of supplemental lighting.
Results and Discussion
Results of this study revealed that our treatments were effective on the morphological characteristics including petiole length, leaf area, flower number, flower petiole length, runner number, runner length, crown diameter, and leaf number. The highest leaf number, petiole length, leaf surface, flower number, runner number, and crown diameter were observed in the plants subjected to 100% BL and 50% RL + 50% BL, respectively. Except for runner length, both lightings of 100% RL and DS (control) had no significant difference on the growth parameters. Overall, supplemental lighting was found to have a significant impact on the content of chlorophyll a, b, total, and total carotenoids. As such, the highest increase in chlorophyll content was belonged to the 100% BL, followed by 50% BL as well as 50% RL, as compared with DS. Moreover, no significant difference was found between 67% RL+33% BL and 84% RL +16% BL in terms of photosynthetic pigments. Although exposing the plants to the 100% RL increased both chlorophyll and carotenoid content in comparison with the control, no significant difference was recorded between them. In addition, lighting 100% BL significantly amplified photosynthetic activity, stomatal conductance, sub-stomatal CO2, and water use efficiency (WUE), while the 100% RL and the control reduced the above-mentioned physiological characteristics.
Conclusion
The results of this study provide evidence on the efficiency of supplemental lighting using LEDs for improving growth parameters and morphological characteristics of strawberry cv. 'Camarosa'. In this context, supplemental lighting could activate the metabolic pathways related to the production of photosynthetic pigments, improve stomatal exchange, and increase the rate of photosynthetic activity.
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