Study Of The Physiological Mechanism Of Bougainvillea Flower Bud Differentiation Induced By Different Duration Of Water Control Treatments

Bougainvillea（Bougainvillea spectabilis Willd.）is a woody flower of the genus Bougainvillea in the family Nyctaginaceae,which has high ornamental value and commercial value.The flower bud differentiation of bougainvillea is closely related to the water supply of the plant.In the production of bougainvillea,the flowering period of bougainvillea is often advanced by controlling water to a certain extent.However,the study of water control on bougainvillea mainly focuses on morphological observation,and the study of physiological indicators is less.In this experiment,the potted‘Chaozhouhong’（Bougainvillea’San Diego Red’）bougainvillea was used as the material.Stop watering until 2/3 of the leaves of the entire plant wither and droop,and start water control for potted bougainvillea plants.The water control treatment lasts for 7,14,and 21 days,and the water was restored after 7 days,14 days,and 21days of water control,respectively.The changes of nutrient content and amylase activity,endogenous hormone content and enzyme activity related to endogenous hormone metabolism,polyamine content and enzyme activity related to polyamine synthesis of bougainvillea leave during the water control treatments and after 7 and 14 days of rehydration were measured and the growth and flowering of bougainvillea after rehydration were recorded.The study explored the physiological and biochemical changes in the leaves of bougainvillea during water control and after rehydration and provided a reference for studying the mechanism of water control induced flower bud differentiation in bougainvillea.The main results were as follows:1.Effects of different water control treatments and rehydration on flower bud differentiation and leaf nutrients of bougainvillea.The normal watered bougainvillea plants were used as the control,and water control treatments were performed on bougainvillea for 7,14,and 21 days,and rehydration was performed after the water control treatment.The relationship between water control induced flower bud differentiation of bougainvillea and leaf soluble protein,soluble sugar,starch content,and amylase activity was explored.The results showed that compared with plants that were normally watered,the three duration water control treatments could all cause early flowering of bougainvillea,and the flowering of bougainvillea was better after 14 days of water control.The study found that compared with the control,the soluble sugar and starch content of bougainvillea leaves increased under water control treatment,while the amylase activity and soluble protein content decreased.After rehydration,the soluble sugar and starch content of bougainvillea decreased,while the amylase activity and soluble protein content increased under three different water control treatments.Water control increased the accumulation of carbohydrates in the leaves of bougainvillea,and it’s profit for flower bud differentiation,while water control stress inhibited the synthesis of soluble proteins in bougainvillea leaves.After rehydration,bougainvillea undergoes a compensatory effect,consuming carbohydrate energy to restore growth and promote flowering.After rehydration,the soluble protein content increases to promote growth recovery.2.Effects of different water control treatments and rehydration on endogenous hormone and metabolism-related enzyme activities in leaves of bougainvillea leaf.Using normal watering as the control,this study investigated the changes in ABA,IAA,and GA₃contents,ABA/IAA,ABA/GA₃,and IAA/GA₃ratios,as well as the activities of IAAO and ABA metabolism related enzymes（ZEP,NCED,AAO）in the leaves of bougainvillea after different duration water control treatments and rehydration.The results showed that compared with the control,the content of ABA and GA₃in the leaves of bougainvillea increased from 7 days to 14 days of water control,while the content of IAA decreased,resulting in an increase in the ratio of ABA/IAA to ABA/GA₃,which is beneficial for the fonmation of flower bud.After 21 days of water control,the controlled water stress in the bougainvillea plant affected the imbalance of endogenous hormone levels,resulting in a decrease in ABA content,an increase in IAA content,and a decrease in the ratio of ABA/IAA to ABA/GA₃,which had adverse effects on the formation of flower buds.After rehydration,the levels of endogenous hormones in the leaves of bougainvillea under three long-term water control treatments gradually recovered,and the ABA content,ABA/IAA to ABA/GA₃ratio decreased,while the IAA to GA₃content increased.During the treatment period,the IAA/GA₃ratio of bougainvillea leaves remained at a relatively low level,indicating that a low level of IAA/GA₃ratio was beneficial for the induction of flower formation in bougainvillea.Under water control treatment,the IAAO activity of bougainvillea leaves showed an upward trend,but decreased after rehydration,which was opposite to the change trend of IAA content.Under water control treatment,the activities of ZEP,NCED,and AAO in bougainvillea showed an upward trend,which was basically consistent with the trend of ABA content changes.In summary,water control promotes an increase in ABA and GA₃content in the leaves of bougainvillea,while a decrease in IAA content leads to an increase in ABA/IAA and ABA/GA₃ratios,while a decrease in IAA/GA₃ratios,which is beneficial for the early differentiation of bougainvillea flower buds.After 21 days of water control,the controlled water stress in the plant affected the imbalance of endogenous hormone levels.After rehydration,bougainvillea regulates endogenous hormone levels to restore growth.The IAAO activity increased under controlled water treatment,which in turn led to a decrease in IAA content.Water control treatment promotes an increase in the activities of ZEP,NCED,and AAO in bougainvillea,leading to an increase in ABA content.3.Effects of different water control treatments and rehydration on the polyamines and metabolism-related enzymes in the leaves of bougainvillea.Using normal watering as the control,this study investigated the changes in the content of putrescine,spermine,spermidine,total amine,and polyamine metabolism related enzymes（ADC,ODC,SAMDC,SPDS）in the leaves of bougainvillea after different duration water control treatments and rehydration.The results showed that compared with the control,the polyamine content in the leaves of bougainvillea treated with water control significantly increased.With the extension of water control time,the content of putrescine,spermidine,and total amine in bougainvillea leaves decreased,while the spermine content first decreased and then increased.After rehydration,the polyamine content in the 7 days water control treatment remained at a relatively high level compared to the control,while the putrescine,spermidine,and total amine content in the 14 days and 21 days water control treatments increased after rehydration,while the spermine content first decreased and then increased.Water control treatment increased the activities of ADC and SPDS in the leaves of bougainvillea.With the extension of water control time,the activities of ADC,ODC,and SAMDC in the leaves of bougainvillea showed a downward trend,and the activity of SPDS first decreased and then increased.After rehydration,the activities of ADC,ODC,SAMDC,and SPDS in the leaves of bougainvillea increased under three different water control treatments.This indicates that water control treatment promotes an increase in polyamine content in the leaves of bougainvillea,which may have a beneficial effect on the flower bud differentiation.However,with the extension of water control time,the drought resistance of bougainvillea weakens,and the polyamine content decreases accordingly.After rehydration,the polyamine content in the leaves of bougainvillea increased,which may be beneficial for early flowering of bougainvillea.During the water control period and after rehydration,the activity of ADC,ODC,SAMDC,and SPDS in the leaves of bougainvillea showed a consistent trend with the changes in polyamine content,indicating that water control reduced the activity of ADC,ODC,SAMDC,and SPDS in bougainvillea leaves,affecting polyamine synthesis.