Cytokinin application to the shoot apical meristem of Sinapis alba enhances secondary plasmodesmata formation

A single application of cytokinin benzyladenine causes a threefold increase in the frequency of plasmodesmata in the vegetative shoot apical meristem (SAM) of Sinapisalba plants. This increase is observed 20 h after application within all cell layers (L1, L2, L3) as well as at the interfaces between these layers. Evidence is presented indicating that cytokinin promotes mainly the formation of new secondary plasmodesmata. A similar increase in the frequency of secondary plasmodesmata was observed in the Sinapis SAM during the floral transition induced by a single long day, suggesting that this effect of the long day is mediated by cytokinin.