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Shahzad M.A. Basra and Carol J. Lovatt

, cytokinins, gibberellins (GAs), abscisic acid (ABA), and ethylene. Hence, the tools needed by the organic horticulture industry are known, but remain largely unavailable for use in commercial organic crop production. In addition, there are only a few

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Liping Zhang, Chen Shen, Jipeng Wei, and Wenyan Han

and reducing labor cost ( Kender and Carpenter, 1972 ). Cytokinins are plant hormones that regulate cell division and play central roles in shoot branching ( Brenner and Schmülling, 2012 ). Several studies showed that cytokinins synthesized in the stem

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Syuan-You Lin and Shinsuke Agehara

reduction in ‘Natchez’ blackberry, suggesting its potential negative side effects on floral development ( Lin and Agehara, 2020 ). Cytokinins act as an antagonist of GA during floral transition in apple ( Malus × domestica Borkh.) by upregulating the

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Hae-Jeen Bang, Soo-Jung Hwang, Hee Chung, and Jung-Myung Lee

Soybean sprouts are one of the most-favored traditional vegetables around the world. The sprouts are usually consumed 7 to 10 days after sowing depending upon the growing conditions. High-quality sprouts should have less secondary roots, short and well-swollen hypocotyls in pure white color, and small cotyledons in hooked position. Cytokinins were reported to be effective in producing such sprouts by promoting sprout growth while inhibiting the excessive hypocotyl elongation and secondary root growth. Seeds of four soybean cultivars with different characteristics were soaked in water for 4 h and, 2 to 3 h after the imbibition, the seeds were soaked again in solutions of different cytokinins such as benzyladenine (BA), BA-riboside (BAR), BPA, 2iP, 2iP-riboside, 4-CPPU, and kinetin-riboside (KR) for 10 min. After the treatment, the sprouts were grown in a plastic tube (25 cm height × 10.5 cm diameter) a dark culture room with ample watering every 4 h. After 7 days of growth, uniform samples were taken from each treatment and the sprout characteristics were examined. Some cytokinins such as BA, BAR, 4-CPPU were highly effective in promoting the sprout growth (fresh weight) even though the hypocotyl length was markedly reduced. Other cytokinins such as 2iP, 2iPR, and KR had no effect on sprout growth. Hypocotyl diameter was markedly increased by BA and 4-CPPU treatment, thus resulting in short, strong and good quality sprouts. Cultivars responded differently to cytokinin treatment by showing different growth promotion depending upon the sprout parts. Injury-like symptoms, abnormal and twisted heads or cotyledons, appeared in cytokinin-treated sprouts at high concentrations and the symptoms were severe when the sprouts were grown at high temperatures. In all the cultivars tested, BAR appeared to be better than others in terms of sprout quality and growth promoting characteristics.

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Yan Xu and Bingru Huang

both genetically and environmentally regulated senescence are associated with hormonal changes with either upregulating or downregulating effects ( Nooden and Leopoid, 1988 ). Ethylene, abscisic acid (ABA), and cytokinins are three major phytohormones

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Lili Dong, Qi Wang, Feng Xiong, Na Liu, and ShuiMing Zhang

. Vertical bars indicate se . Lowercase letters a and b indicate significant differences. Expression of CmMAX1 was repressed by different phytohormones. To study the regulation of CmMAX1 by strigolactone, auxin, and cytokinin, we detected the expression

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Young Hee Joung, Mark S. Roh, Kathryn Kamo, and Jeoung Seob Song

The main goal of this research was to develop Campanula glaumerata `Acaulis' plants transformed with the isopentenyl transferase (ipt) gene for increased growth of the axillary buds and en-hanced insect resistance. Isopentenyl transferase is a first enzyme in the cytokinin biosynthetic pathway. For Campanula transformation, leaf discs were co-cultivated with Agrobacterium tumefacience LBA4404, which harbored the binary vector pBC34 (A. Smigocki, Beltsville, Md.) that codes for the nos-nptII gene and the ipt gene controlled by the CaMV35S promoter. The transformation frequency was about three times higher when leaf blade explants were infected with LBA4404 containing pBC34 as compared to infection with pGUSINT, which contains the gusint gene instead of the ipt gene. This difference in transformation frequency was attributed to expression of cytokinin from the ipt gene. Transgenic plant lines containing the ipt gene were verified by southern hybridization and divided into three groups by phenotype following culture in vitro on MS medium: 1) yellow/large leaves, no rooting; 2) green/large leaves, no rooting; 3) green/normal leaf size, rooting. These different phenotypes could be due to different levels of cytokinin expression in the transgenic plants.

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Ying Chen, Xinlu Chen, Fei Hu, Hua Yang, Li Yue, Robert N. Trigiano, and Zong-Ming (Max) Cheng

). Micropropagated shoots can be readily rooted either in vitro or ex vitro, and acclimatized to greenhouse conditions. The most important factors in successfully micropropagating A. american were cytokinin and auxin levels. Cytokinin in the medium was reported to

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Robin A. Cohen and Duane W. Greene

Two experiments were conducted to examine the effects of growth regulator application on cytokinin levels in developing apple leaves. In experiment 1, gibberellin GA4/7 (100 mg·liter-1) and benzyladenine (BA, 100 mg·liter-1) were applied alone or in combination as a foliar spray to `Golden Delicious' 7 days after full bloom. In experiment 2, BA was applied at 50 or 100 mg·liter-1 as a foliar spray to `Morespur McIntosh' 18 days after full bloom. Trans-zeatin ribosidelike (t-ZR) levels were determined by immunoassay. In experiment 1, GA1/7 had no effect and BA increased t-ZR-like levels. In experiment 2, BA increased t-ZR levels quadratically with application rate. The increase in endogenous cytokinin levels with BA treatment occured within 2 hours. Initially, t-ZR-like levels were 47 times higher in the BA (100 mg·liter-1) treated leaves as compared to check leaves. Over the next 8 days, t-ZR-like content in treated leaves decreased in a cubic manner.

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William R. Woodson and Amanda S. Brandt

Treatment of cut carnation (Dianthus caryophyllus L. `White Sim') flowers with the synthetic cytokinin benzyladenine (BA) at concentrations >1.0 μm induced premature petal senescence. Flowers treated with 100 μm BA exhibited elevated ethylene production in styles and petals before untreated flowers. The gynoecia of BA-treated flowers accumulated 1-aminocyclopropane-l-carboxyllc acid (ACC) and enlarged before untreated flowers. Removal of the gynoecium (ovary and styles) or styles prevented BA-induced petal senescence and resulted in a substantial delay in petal senescence. In contrast, removal of the gynoecium had no effect on timing of petal senescence in flowers held in water. These results indicate BA stimulates petal senescence by inducing premature ACC accumulation and ethylene production in the gynoecium.