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    Effects of Melatonin and IAA on Adventitious Root Formation in Rootstock 5BB and cv. Cabernet Sauvignon (Vitis vinifera L.)
    (Kahramanmaras Sutcu Imam Univ Rektorlugu, 2020) Gokbayrak, Zeliha; Engin, Hakan; Kiraz, Hatice
    Both derived from tryptophan, melatonin (MEL) and indole acetic acid (IAA) were tested for their influence on rooting in the cuttings of two Vitis species, the 5BB rootstock and the cultivar Cabernet Sauvignon. The 2-bud cuttings were grown in a growth chamber after the basal ends were dipped in the following treatments; for 5 seconds in IAA solutions at 0 (the control), 5.7, 11.4 and 16.1 mu M concentrations, and for 10 minutes in the melatonin solutions at 0 (the control), 0.1, 0.5 and 1.0 mu M. The results indicated that percentages of rooting, shooting and healthy plants in both species were not statistically significant under the influence of the treatments. However, increasing concentrations of IAA resulted in increasing rooting percentages in 5BB rootstock. On the other hand, 0.1 and 0.5 mu M MEL also induced rooting. In the cuttings of Cabernet Sauvignon, 11.4 mu M IAA provided the highest percentage (100%). Melatonin caused a relative decrease in rooting compared to the IAA. The action of melatonin on rooting seems to be independent of IAA. Hormone treatments caused significant differences in the root number per cutting and fresh root weight in 5BB. Effects of the hormones were important on all the rooting features, including root number, root length, root distribution pattern, and weight of fresh and dry roots in Cabernet Sauvignon. Results indicate that extensive research is needed to extrapolate the influence of melatonin on rooting in grapevine with a possibility in practical use since it is inexpensive and easy to obtain in pure form.
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    Pollen of Arbutus unedo: Effects of plant growth regulators
    (Univ Belgrade, Inst Botany & Botanical Garden, 2020) Gokbayrak, Zeliha; Engin, Hakan; Akcal, Arda; Kiraz, Hatice
    Arbutus unedo is a species mainly used for landscaping purposes and lately for honey production. Its antioxidant characteristics have also been a subject of of research interest. The germination of pollen grains freshly collected from flowers was tested in vitro, and 30% sucrose gave the highest pollen germination. Subsequently, three growth regulators belonging to the categories of gibberellins and brassinosteroids [24-epibrassinolide (Ebl) and 22S,23S-homobrassinolide (Hbl)] were added to the growth medium singly or in double combinations (gibberellin + brassinosteroid), and the petri dishes were kept for 24 hours at 26 +/- 1 degrees C. The results showed that the highest germination rates were obtained from treatments with 0.01 ppm Hbl (45.47%) and 0.001 ppm Hbl (26.74%). They were followed by treatments with 0.001 ppm Ebl, 25 ppm GA(3) and 0.1 ppm Ebl. As the concentration of GA(3) increased, the germination rate declined considerably. Statistical analysis of the combined treatments showed that combinations of growth regulators lowered the germination rates compared to their individual application. Moreover, action of the lowest GA(3) concentration (25 ppm) best matched the effects of brassinosteroids, and increasing the GA(3) concentration in combined treatments did not improve germination. The highest germination was obtained with 0.1 ppm Hbl, followed by all Ebl treatments. Brassinosteroids might be an inducer of pollen germination in plants depending on their type and concentrations. When individually included in the growth medium, the extent of this induction was greater with the homobrassinolide than with the epibrassinolide. Their interactions with gibberellins are shown to be mostly dependent on the concentration of gibberellic acid used. The tested epibrassinolide was more consistent than the homobrassinolide in maintaining higher germination levels. The findings of this study indicate that gathering more information from studies involving other plant species is needed to clarify the role of brassinosteroids in in vitro and in vivo germination.