Effects Of Plant Growth Regulator, Light And Temperature Treatments On Florescence And Endogenous Hormones Of Rhododendron Hybridum

Rhododendron hybridum is an important ornamental plant. It was reported that the florescence can be controlled by the application of plant growth regulator and the light or temperature treatment. No conclusion has been reached whether it had certain relationship between the florescence changes caused by these external factors and the endogenous hormones. In this study, the2-year old Rhododendron hybridum which was cultivated in Ningbo city, Zhejiang province, was selected as tested materials. The morphological changes of flower buds were observed and the concentration of endogenous hormones, i.e. zeatin (ZT), gibberellin (GA3),3-indole acetic acid (IAA) and abscisic acid (ABA) in the buds were determined after sprayed different concentrations of gibberellin (GA3), paclobutrazol (PP333), and dami-nozide (B9), or being treated with different light intensity of500,4000,8000,12000or16000Lx, or with low temperature (5℃) for10,17,24,31or38days, respectively.Experiment results showed that GA3promoted the florescence significantly, while PP333and B9delayed the florescence and the blossom was regular after treated with B9. Treatments of various growth regulators had different effects on endogenous hormones of buds. The content of endogenous GA3increased after treated with external GA3, while the concentration of IAA and ABA reduced, the concentration of ZT increased first and then decreased. The concentration of GA3, ZT and IAA decreased, while the concentration of ABA increased after treated with B9or PP333.The florescence of Rhododendron hybridum was promoted significantly along with the increase of light intensity. The florescence was promoted significantly, the blossom was regular and flower quality was good when the light intensity was16000Lx; The florescence was delayed significantly and the flower quality was not so good when the light intensity was4000-8000Lx; There was no flower when the light intensity was500Lx. The content of endogenous hormones in buds changed greatly after treated with different light intensity. When treated with the light intensity of16000Lx, the content of endogenous GA3and IAA increased, ABA decreased, and ZT increased first and then decreased. When treated with the light intensity of4000-8000Lx, the content of endogenous GA3, ZT and IAA decreased, however the content of ABA increased; When treated with the light intensity of500Lx, the content of endogenous GA3and ZT decreased gradually, the content of IAA increased first and then decreased, the content of ABA increased grudually.Different length of low temperature treatment had negative correlation with florescence significantly:the florescence was advanced15d after treated with low temperature for10d;7d advanced after treated for17d;5d advanced after treated for24d;1d advanced after treated for31d; and11d delayed after treated for38d. During the low temperature treatment, the concentration of endogenous GA3, ZT, IAA increased first and then decreased, and the concentration of ABA was decreased first and then increased. The relationship between flowering and endogenous hormones showed that high concentration of ZT and GA3and low concentration of ABA could promot flowering at the stage of flower bud morphological differentiation.