| Quercus mongolica is characterized by easily germinating lateral branches,which is the main reason for disappear of plant apical dominance and poor plant architecture.Strigolactones(SLs),a group of phytohormones identified recently,the studies on shoot branching regulated by strigolactones have been in-depth in herbaceous model plants now,while the research in the field of Mongolian Oak remain in vacant.In this study,the annual Mongolian Oak seedlings were used as experimental materials.The effects of strigolactones and cytokinin in control the outgrowth of lateral branches in Mongolian Oak were studied.GR24,analogue of strigolactones were supplied in both bud directly and vascular methods,and CTK supplied in vascular method.The conditions of the level and distribution of endogenous phytohormones as well as sucrose response to the stimulation of GR24 were verified by high performance liquid chromatography tandem mass spectrometry and high performance liquid chromatography,aiming to resolve the problems that Mongolian Oak species with overdeveloped lateral buds and poor apical dominance.The main results are as follows:1.GR24 treated in both different methods showed that the growth of axillary buds was inhibited and the apical dominance was promoted.In contrast,the effect of GR24 in vascular supply was more obvious,among which 30mg/LGR24 had the strongest inhibitory effect on lateral branch growth,the number of lateral branches was 51.47% to control 1.24,and the growth of the lateral branch length was only 0.79 cm,38.21% to control 2.09 cm,the growth of lateral branch basal diameter was only 0.32 mm,41.38% lower than that of control 0.55 mm.However,it was extremely unfavorable to the growth of Mongolian oak seedlings in this concentration.3mg/LGR24 had the strongest promoting effect on the height growth of Mongolian oak seedlings,with the increase reaching 2.63 cm,which was 63.29% higher than that of the control group,but the inhibitory effect on lateral branches was not obvious.Although 10mg/LGR24 did not have a strong promoting effect on the height growth of Quercus mongolica seedlings,the effect on the volume of the top bud was up to 5.19mm3,which was 3.82 times to the control group,and its inhibiting effect on the lateral branch growth was only second to that of the 30mg/LGR24 treatment group.2.Both GR24 treatments showed a trend of decrease in biomass of leaves and lateral branches and increase in biomass of apex and root system of Mongolian oak seedlings.The inhibitory effect of 10mg/LGR24 treated by vascular supply on the lateral branch biomass accumulation reached the peak value of 0.063 g,which is only 27.75% of the control,and the promotion effect on the apex and root biomass accumulation was the most obvious,reaching 0.20 g and 7.18 g respectively,which were 2.02 times and 0.65 times higher than control.3.In this study,it was found that endogenous phytohormone IAA and ABA levels were relatively high,while the CTK and GA levels were merely trace in Mongolian Oak seedlings.The absolute contents of IAA distributed in different organs were slightly different with two different treatments of GR24,but the increasing trend of polarity from the stem to the root system was similiar.Moreover,the content of IAA in the axillary branches was significantly increased in response to GR24 in both different methods.In response to GR24 stimulation,the content of ABA in the apex and lateral buds showed a trend of decrease and increase respectively,suggesting that ABA could promote the apical dominance of Quercus mongolica seedlings.4.Sucrose plays an important role in plant apical dominance.Sucrose was accumulated in branches to meet the high demand for sucrose as the axillary buds continue to growth,which increased the competitive intensity of sucrose between the lateral buds and apex.GR24 and CTK regulate the plant architecture by alleviating and intensifying such competition.During the axillary buds growth,the sucrose content in axillary buds was up to 23.53mg·g-1 FW in response to the CTK stimulation,which is 9.92 times higher than apex.However,it was only 0.63 mg·g-1 FW in axillary buds in GR24 treatment group,which was 8.34% of the apex... |
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