Cytokinin influence

Addition of oligosaccharides to combinations of auxin plus cytokinins also influences the differentiation of shoots and roots in tissue culture. Indeed, many of the pleiotropic effects originally attributed to auxins and other plant hormones may actually be mediated by oligosaccharins. 

Figure 3, Influence of 1AA and cytokinins on ethylene production by postclimacteric avocado tissue slices (16)...

Figure 4. Influence of JAA, GA, cytokinin (IFA), and ABA, alone and in combinations, on ethylene production of pre-climateric, climacteric, and post-climateric apple tissue slices...

Figure 1. Hormonal factors influencing flower initiation in bourse bud of apple. G = gibberel-lins, C = cytokinins, F = florigin P...

Terpenoids, which are also known as isoprenoids, constitute the most abundant and structurally diverse group of plant secondary metabolites, consisting of more than 40,000 different chemical structures. The isoprenoid biosynthetic pathway generates both primary and secondary metabolites that are of great importance to plant growth and survival. Among the primary metabolites produced by this pathway are phytohormones, such as gibberellic acid (GA), abscisic acid (ABA), and cytokinins the carotenoids, such as chlorophylls and plastoquinones involved in photosynthesis the ubiquinones required for respiration and the sterols that influence membrane stmcture (see also Steroid and Triterpene Biosynthesis) (Fig. 1). Monoterpenoids (CIO), sesquiterpenoids (Cl5), diterpenoids (C20), and... 

Out of the array of growth regulators that influence fruit abscission, ones that prevent abscission are fewer in number and seem to fall in the class of auxins (J, 64), gibberellins, or cytokinins 65). Auxin has both indirect (7, 66) and direct (6) effects on abscission, whereas cytokinins... 

Auxins (67), gibberellins (68), cytokinins (69), and abscisic acid (67) can enhance the production of ethylene if added in concentrations that are generally considered stronger than tissue levels. Paradoxically, ethylene was one of the first chemicals identified as a potent defoliant (70), and now it has been shown to be a natural product of plant tissues that seems to regulate abscission (68, 71) as well as an influence on a host of other physiological reactions (7). 

Fig. (17). Effects of cytokinins and influence of light on shoot formation on intemodal segments The segments were cultured on WP solid medium containing cytokinin at 25 °C for 8 weeks whether in 16 hr/day light (80 gEm S" ) or in the dark. Bars represent standard deviation of the means, n=6.

Among the more controversial roles of cytokinins are its involvement in solute mobilization and cell senescence. Early studies by Mothes and coworkers suggested that in leaves, cytokinins can cause cells to become sinks for nutrients, tmd that the influx of nutrients kept the cells from senescing [61]. Since then, the evidence has been mixed, as it has been difficult to decide whether these are direct roles of cytokinins, or only indirect effects. For example, cytokinins might delay senescence by altering stomatal conductance, and influence solute movement by activating cell division, which in turn creates a solute sink [62]... 

Other cytokinin-regulated genes include an invertase and a glucose transporter in Chenopodium rubrum. Cytokinin is known to influence sink-source relations, and cDNAs representing cytokinin induced genes appear to encode activities that may be involved in apoplastic sink-source relations. One is an extracellular isoform of invertase (Cinl), the... 

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