ABSTRACT
This chapter presents a summary of the involvement of cytokinins in seed germination, de novo bud formation, release of buds from apical dominance, leaf expansion, reproductive development, and senescence. The effects of cytokinins on seed germination are not as pronounced; however, numerous studies have shown that cytokinins can influence germination, particularly when conditions are suboptimal for germination. Endogenous cytokinins have been measured in germinating seeds of various species. The level of cytokinin is generally low in dry seeds and initially decreases even further, but then increases during germination. The classic studies by F. Skoog and C. O. Miller demonstrated the dramatic effects of cytokinins on shoot differentiation in tobacco callus. The endogenous cytokinins as well as the metabolism of exogenous cytokinins were determined in relation to adventitious bud regeneration. Cytokinins can inhibit oxidation and prevent the sharp rise in respiration usually occurring during senescence.
