Document Type : Research Article
Authors
1 Horticultural Sciences, Faculty of Agriculture, Gilan University, Rasht, Iran
2 professor, Horticulture Department, agriculture College, University of Guilan, Rasht, Iran.
3 Department of Ornamental Plant Biotechnology, Iranian Academic Center for Education, Culture and Research, Branch of Mashhad, Iran
Abstract
Introduction
Light is recognized as a vital factor for plant growth and development. Plants convert light energy into chemical energy through photosynthesis, which is then used for growth and development. Quality, intensity, and photoperiod are among the factors that directly affect plant growth and development processes. In recent years, Light-Emitting Diode (LED) technology has gained significant popularity in agriculture due to its numerous advantages over traditional light sources. These advantages include the ability to produce various light spectra, low energy consumption, long lifespan, and reduced heat emission. These characteristics have made LEDs an ideal light source for cultivating plants in controlled environments such as greenhouses and growth chambers. The primary objective of this study was to investigate the effects of different LED light qualities on the morphological, physiological, and germination traits of marigold (Tagetes erecta) seeds. Given the importance of light in plant growth and the benefits of LED technology, this study can provide valuable insights for improving crop cultivation and production.
Materials and Methods
This experiment was conducted in the Biotechnology Laboratory of Horticultural Plants in the Academic Center for Education, Culture and Research of Khorasan Razavi. F1 hybrid seeds were used in this study. The experimental treatments consisted of five light qualities: white light (100%), blue light (100%), red light (100%), 30% blue light + 70% red light, and 70% blue light + 30% red light. All treatments were subjected to a 16-hour light and 8-hour dark photoperiod using LED grow lights. The photosynthetic photon flux density (PPFD) was maintained at a constant 100 μmol.m⁻².s⁻¹ for all light treatments. Seed germination parameters (Seed Germination percentage, Mean germination Time, Germination rate, Radicle length, Plumule length, lateral roots number, Plumule fresh weight, Radicle fresh weight, Plumule dry weight and Radicle dry) were initially measured in Petri dishes under the growth panels. Subsequently, seeds were sown and grown under the growth panels, and physiological and morphological parameters including plant height, first internode length, stem diameter, node number, leaf area, leaf length, leaf number, lateral shoot number, shoot fresh weight, shoot dry weight, shoot fresh/ dry weight ratio, root fresh weight, root dry weight, root fresh/ dry weight ratio, dry matter, root length, electrolyte leakage, relative leaf water content and chlorophyll content were measured every 15 days for a total of four measurements.
Results and Discussion
Seed germination indices showed that the lowest mean germination time, highest germination rate, longest radicle length, hypocotyl length, number of lateral roots, and fresh weight of radicles were observed under 100% red light treatment, followed by the 70% red + 30% blue light treatment. The application of 100% red light improved germination rate, radicle length, hypocotyl length, number of lateral roots, and fresh weight of radicles by approximately 14%, 29%, 48%, 100%, and 67%, respectively, compared to the control. Plants grown under 100% red light exhibited the greatest plant height at both the beginning and end of the growth period. At the end of the growth stage (75 days after sowing), plants under 100% red light showed increases of approximately 37%, 6%, 33%, and 31% in stem diameter, length of the largest compound leaf, number of leaves, and number of branches, respectively, compared to the white light treatment at the same growth stage. Additionally, the fresh and dry weights of plants increased by approximately 56% and 9%, respectively, compared to the control at the same growth stage. A study of the fresh and dry weights of roots showed that the application of 100% red light increased these two indices by nearly 3 times compared to the control. The lowest fresh and dry root weights were observed under 100% blue light treatment, followed by the 30% red + 70% blue light treatment. Furthermore, plants grown under 100% red light exhibited higher relative water content and lower electrolyte leakage in leaves compared to plants grown under other light treatments.
Conclusions
The research findings indicated that the application of light-emitting diodes (LEDs) with various light qualities enhanced the growth conditions of Tagetes erecta Antigua orange. Comparisons among the light treatments showed that the use of 100% red light resulted in increased germination percentage and rate in marigold seeds. Furthermore, the application of red light under controlled conditions led to an increase in plant growth indices compared to other experimental treatments. Therefore, the use of red light at different growth stages of marigold under controlled conditions is recommended
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