Cytokinin content

Figure 6. Contents of cytokinins in C. roseus. crown gall cells. Open circle yield of cells open column cytokinin content in the cells.

Fig. 5. Seasonal change of cytokinin content in the shoot and root of rice. MR milky ripening stage, DR dough ripening stage...

Tissues were extracted in Bieleski s medium [6]. Techniques to collect exudates and to analyze cytokinins using HPLC methodology and bioassays are described elsewhere [15]. These analyses clearly indicated that the cytokinin content in leaves of induced plants increased above the control level, starting at 16 h. This increase was most marked at 16 h, and was observed mainly in the fraction having the same Rt as Z (Lejeune, unpublished). 

The growth retardant CCC increases cytokinins in the bleeding sap of grape (Skene 1970). Skene has interpreted this as an indication that CCC acts directly on the root meristem to increase cytokinin production. However, since the effect of CCC is counteracted by GA, it is possible that the enhancement of cytokinin production by CCC is mediated by a CCC-induced reduction in GA. This indicates that GA may act to suppress cytokinin production in roots (Woolley and Wareing 1972 a), a possibility supported by Teltscherova (1970) who noted that CCC causes an increase in the cytokinin content of apical buds of Chenopodium rubrum and that GA can overcome this effect. lAA also reduces cytokinins in buds of Chenopodium, indicating that both GA and lAA may be involved in the regulation of cytokinin production in this material. 

Sinee eytokinins enhance GA levels and since GA appears to suppress cytokinin levels, the possibility of GA-mediated feedback inhibition of cytokinin production must be recognized. Also, the evidence that lAA can increase GA levels in apical buds of Chenopodium rubrum (Teltscherova 1970) indicates that the suppressing effect of lAA on cytokinin content may be a secondary effect mediated by GA. 

Low temperature strongly retards apparent cytokinin biosynthesis in corn roots (Atkin et al. 1973). Temperature affects the cytokinin content of the root exudate of Thompson Seedless grape vines in both a qualitative and quantitative manner. So-called Fraction 2 cytokinins are present in exudate of vines grown at 20° C but not in vines grown at 30° C (Skene and Kerridge 1967). 

Kohler K-H, Dorfler M, Goring H (1980) The influence of light on the cytokinin content of Amaranthus seedlings. Biol Plant 22 128-134 Kondo K, Watanable A, Imaseki H (1975) Relationships in actions of indoleacetic acid, benzyladenine and abscisic acid in ethylene production. Plant Cell Physiol 16 1001-1007... 

Burrows WJ, Carr DJ (1969) Effects of flooding the root system of sunflower plants on the cytokinin content in the xylem sap. Physiol Plant 22 1105-1112 Cande WZ, Ray PM (1976) Nature of cell-to-cell transfer of auxin in polar transport. Planta 129 43-52... 

Yoshida R, Oritani T (1974) Effects of nitrogen topdressing on cytokinin content in the root exudate of rice plant. Proc Crop Sci Soc Jpn 43 47-51... 

Burg SP, Burg EA (1966) The interaction between auxins and ethylene and its role in plant growth. Proc Natl Acad Sci USA 55 262-269 Burrows WJ, Carr DJ (1970) Cytokinin content of pea seeds during their growth and development. Physiol Plant 23 1064-1070... 

Fig. 3.31. Change in cytokinin content during grain development in Triticum aestivum cv. Kloka. Horizontal bar indicates the period of anthesis. After Wheeler, 1972 [197]...

Since cytokinins are exported from the roots it has been suggested that these organs supply the developing seeds. There is evidence in wheat in favour of this hypothesis since here the maximum cytokinin levels transported through the stem precede the peak of cytokinin concentration in the developing kernels by just a few days [197], On the other hand, P. sativum seeds, developing in the pod under in vitro culture, show approximately a 30-fold increase in cytokinin content over 18 days, thus establishing that the seeds themselves are capable of hormone synthesis [73]. 

Kado, C. I. The Prokaryotes. Springer-Verlag New-York, 1992, V. 2, p. 352. Arkhipova, T. N., Melent ev, A. L, Martynenko, E. V, Kudoyarova, G. R., Veselov, S.Yu. Comparison of effects of bacterial strains differing in their ability to synthesize cytokinins on growth and cytokinin content in wheat plants. Russian Journal of Plant Physiology. 2006, T. 53. JT 4. C. 507-513. 

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