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Modifying the cytokinin content in plants is a means of improving plant productivity. Here, we report the development and biological activity of compound TD-K (1-(furan-2-ylmethyl)-3-(1,2,3-thiadiazol-5-yl)urea)which is related to thidiazuron. TD-K—which exhibited extremely high antisenescence activity in the wheat leaf bioassay—and INCYDE (2-chloro-6-(3-methoxyphenyl)aminopurine)—a plant growth regulator reported to inhibit cytokinin oxidase/dehydrogenase (CKX), an enzyme involved in the degradation of the plant hormone cytokinin—were selected for investigation of their effects on the model plant Rapid Cycling <i>Brassica rapa</i> (RCBr). We monitored the expression of <i>BrCKX</i> and isopentenyl transferase (<i>BrIPT</i>), which codes for the key cytokinin biosynthesis enzyme, in developing leaves following INCYDE and TD-K application. Growth room experiments revealed that INCYDE increased RCBr seed yield per plant, but only when applied multiple times and when grown in 5 mM KNO₃. Expression in control leaves showed transient, high levels of expression of <i>BrCKX</i> and <i>BrIPT</i> at true leaf appearance. Following INCYDE application, there was a rapid and strong upregulation of <i>BrCKX3</i>, and a transient downregulation of <i>BrIPT1</i> and <i>BrIPT3</i>. Interestingly, the upregulation of <i>BrCKX3</i> persisted in a milder form throughout the course of the experiment (16 days). TD-K also upregulated <i>BrCKX3.</i> However, in contrast to INCYDE, this effect disappeared after two days. These results suggest that both compounds (CKX inhibitor and cytokinin TD-K) influenced cytokinin homeostasis in RCBr leaves, but with different mechanisms.