Effect of Putrescine and Mycorrhiza on Growth, Photosynthesis and Vase Life of Gerbera (Gerbera jamesonii) ‘Dune’ Flowers in Hydroponic Conditions

Gerbera is one of the most important cut flowers in the world and belongs to the Asteraceae family. Due to its diverse and adaptable species for growth with a wide range of climatic conditions, this flower has become a profitable cut flower for growers. Polyamines in plant tissues act as a potent factor in preventing the production of ethylene. Polyamines and ethylene have antagonistic effects (anti-aging and aging effects), so that the balance of these two hormonal groups in plants is very important for plant tissues. The balance between the two opposing regulators leads to a delay or acceleration in the aging process. Mycorrhizal fungi can be useful in hydroponic greenhouse systems, which increase the amount of CO2 in greenhouses by increasing photosynthesis in plants, as well as CO2 emissions in the control environment, which both optimally manage the environment and increase the yield and quality of plant products. Due to the economic importance of cut flowers, it seems necessary to provide treatments (such as the use of putrescine and mycorrhiza) to increase the quality and longevity of this plant. This study was conducted in the research and production greenhouses of Urmia University and the research laboratory of the Department of Horticultural Sciences of the Faculty of Agriculture in 2019-2020. This study was performed as a factorial experiment in a completely randomized design with three replications, each replication consistedd of three pots and each pot contained a plant. The factors of this experiment were Mycorrhizal fungi inoculation (with and without inoculation) during the transplanting process to the culture medium near the roots, and putrescine at four concentrations of 0 (control), 1, 2, and 4 mM, were applied two weeks after transplantation, every 15 day-interval for three months. In order to investigate the effects of putrescine and mycorrhizal fungi on some morphological and physiological characteristics of plants, two weeks after the end of treatments, leaf sampling was performed to measure physiological characteristics. Effects of putrescine and mycorrhizal fungi were assayed in some morphological characteristics including leaf number, leaf length and leaf area, fresh and dry weight of leaves and some physiological parameters including chlorophyll index, chlorophyll content (a, b and total) and soluble sugar as well as vase life and petal’s anthocyanin during postharvest time. The SAS software version 9.1 was used to analyze the variance and compare the mean of the studied traits. Comparison of means was performed using the Tukey’s range test method at a probability level of 1 and 5%. Excel (2016) software was also used to draw the graph. According to the comparison of means, putrescine, along with mycorrhizal fungi, increased the number of leaves, leaf area, and the fresh and dry weight of the leaves as well as chlorophyll index, chlorophyll a, b and total and carotenoid content of leaves. In this study, inoculation with mycorrhiza reduced leaf length but increased leaf area resulted in that mycorrhiza could increase leaf blade because of increasing cytokinin in plant. Putrescine with mycorrhizal fungi, increased leaf growth, photosynthesis of plant and carbohydrates production. In the literatures, it is reported that, the vase life of cut flowers is a very important point in choosing them as great cut flowers. The results showed, putrescine and mycorrhiza had increased the vase life of gerbera flowers, therefore increased the quality of this plant. Putrescine and mycorrhiza also increased the amounts of anthocyanins in the petals, and by the sixth day, the highest levels of anthocyanins were observed in the petals. Probably, the reason for increasing the anthocyanins on the sixth day is the presence of carbohydrates stored in the flower, which due to the reduced respiration and carbohydrate consumption in this process. Based on the results of the present study, it can be concluded that putrescine, with mycorrhizae, improved growth characteristics as well as increasing the postharvest life and the quality of cut flowers of gerbera. It is also observed that among the different concentrations of putrescine, the concentration of 2 mM had the greatest effect on the growth and physiological parameters as well as vase life of gerbera.