A Cytokinin Analog Thidiazuron Suppresses Shoot Growth in Potted Rose Plants via the Gibberellic Acid Pathway.

Fisun G Çelikel,Yanlong Zhang,Qingchun Zhang,Michael S Reid,Cai-Zhong Jiang

doi:10.3389/fpls.2021.639717

Abstract

Application of thidiazuron (N-phenyl-N′-1,2,3-thiadiazol-5-ylurea, TDZ), a cytokinin analog, to inhibit the leaf yellowing that occurs after pinching potted rose plants, resulted in compact plants with shorter shoots and thicker internodes. Two weeks after treatment with 100 μM of TDZ, new shoots were half as long as those in control plants, and stem diameters were about 40% greater. This effect of TDZ is associated with changes in cell architecture. Although TDZ treatment stimulated ethylene production by the plants, inhibitors of ethylene biosynthesis (2-aminoethoxyvinyl glycine) or action (silver thiosulfate) did not affect the response of plants to TDZ. We found that TDZ treatment significantly suppressed the expression of bioactive gibberellic acid (GA) biosynthesis genes encoding GA3 and GA20 oxidases and slightly increased the expression of GA catabolism genes encoding GA2 oxidase. Application of GA3 and TDZ together resulted in normal elongation growth, although stem diameters were still somewhat thicker. Our results suggest that TDZ regulates shoot elongation and stem enlargement in potted rose plants through the modulation of bioactive GA biosynthesis.

Highlights

Potted miniature roses (Rosa hybrida L.) are popular year-round potted plants, with an increase in production for special days such as Mother’s Day and Easter in the United States
The results showed a significant negative linear relationship between the length of the primary shoot and TDZ treatment concentration (Figure 1)
The substantial improvement in compactness in plants treated with 100 μM TDZ, whose height was essentially unchanged after 2 weeks (Figure 2), was not accompanied by any negative effects on the plants

Summary

INTRODUCTION

Potted miniature roses (Rosa hybrida L.) are popular year-round potted plants, with an increase in production for special days such as Mother’s Day and Easter in the United States. TDZ Regulates GA-Mediated Shoot Growth extending the life of potted plants (Jiang et al, 2009) and preventing leaf yellowing after pinching potted miniature roses (Çelikel et al, 2019). In addition to effective prevention of leaf yellowing, we found that concentrations of TDZ higher than 80 μM inhibited shoot growth, resulting in plants with shorter and thicker stems. 2-Aminoethoxyvinyl Glycine One day before treatment with 100 μM TDZ, potted roses were sprayed with a 0.5 mM solution of 2-aminoethoxyvinyl glycine (AVG; Sigma) to inhibit ethylene production (Saltveit, 2005). Potted rose plants were sprayed with 0.2 mM STS to inhibit ethylene action (Serek and Reid, 1993) and allowed to dry for 8 h before being sprayed with 100 μM TDZ. Cell sizes (i.e., length and width) were determined from images photographed using a binocular microscope

MATERIALS AND METHODS

RESULTS

DISCUSSION

DATA AVAILABILITY STATEMENT