Cytokinins are a major class of plant hormones that are involved in various aspects of plant development, ranging from organ formation and apical dominance to leaf senescence. Cytokinin and auxin have long been known to interact antagonistically, and more recent studies have shown that cytokinins also interact with other plant hormones to regulate plant development. A growing body of research h...

When tobacco (Nicotiana tabacum L.) cultured cells (line BY-2) at the stationary phase were transferred to culture medium that contained cytokinin (benzyladenine) instead of auxin (2,4-dichlorophenoxyacetic acid), proplastids in the BY-2 cells were converted to amyloplasts within 48 h. The data obtained from in vitro transcription assays using isolated plastid-nucleoids (nuclei) strongly sugges...

The development of avocado fruit (Fuerte in particular) was observed over a number of years as part of a research project investigating the role played by endogenous plant growth regulators in the development of the fruit. Rates of growth of the various fruit tissues were measured and changes in auxin, gibberellin, cytokinin and inhibitor levels were established. Some results of this study have...

The tip of the root is covered by a thimble-shaped root cap that is the site of perception and transduction for many environmental stimuli. Until now, little was known about how the root cap of rice (Oryza sativa) develops and functions to regulate the adaptive behavior of the root. To address this, we examined the formation of the rice root cap during embryogenesis and characterized the anatom...

Auxin produced by an active primary shoot apex is transported down the main stem and inhibits the growth of the axillary buds below it, contributing to apical dominance. Here we use Arabidopsis thaliana cytokinin (CK) biosynthetic and signalling mutants to probe the role of CK in this process. It is well established that bud outgrowth is promoted by CK, and that CK synthesis is inhibited by aux...

MITOSES can be stimulated in mature cells of both plant and animal tissues by a variety of procedures including wounding and hormone treatments. The initial response to these treatments may or may not involve DNA synthesis. Thus, Gelfant [lo] observed that mouse ear epidermis contains populations of cells both in Gl and in G2; the latter cells can be induced to enter mitosis without any precedi...

It has always been clear that different plant hormones affect overlapping processes, such that the output of plant hormone action depends on specific hormone combinations rather than on the independent activities of each. In the last two decades, numerous components of the signal transduction pathways of various plant hormones have been identified, leading to the elucidation of partial or entir...

Leafy gall syndrome is the consequence of modified plant development in response to a mixture of cytokinins secreted by the biotrophic actinomycete Rhodococcus fascians. The similarity of the induced symptoms with the phenotype of plant mutants defective in strigolactone biosynthesis and signalling prompted an evaluation of the involvement of strigolactones in this pathology. All tested strigol...

Hormonal interactions are crucial for plant development. In Arabidopsis, cytokinins inhibit root growth through effects on cell proliferation and cell elongation. Here, we define key mechanistic elements in a regulatory network by which cytokinin inhibits root cell elongation in concert with the hormones auxin and ethylene. The auxin importer AUX1 functions as a positive regulator of cytokinin ...

Sedentary plant parasitic nematodes such as root-knot nematodes and cyst nematodes induce giant cells or syncytia, respectively, in their host plant's roots. These highly specialized structures serve as feeding sites from which exclusively the nematodes withdraw nutrients. While giant cells are symplastically isolated and obtain assimilates by transporter-mediated processes syncytia are massive...