Studies On The Physiological Characteristics Of Acer×freemanii ‘Autumn Blaze' And Acer Truncatum During Leaf Color Changing

Acer×freemanii‘Autumn Blaze'and Acer truncatum were used as materials in this study,the physiological characteristics of leaves were studied during leaf color changing in spring and autumn,the physiological changes of leaves in different leaf positions were also studied,and the physiological mechanism of leaf color change was analyzed.Through phloem girdling,branch shading and exogenous sucrose spraying treatments,the artificial control on leaf color of Acer×freemanii‘Autumn Blaze'was discussed in order to provide theoretical support for prolonging the ornamental period and improving the ornamental effect of colorful leaf trees.The results are as follows:1.The juvenile leaves at the top of the branch which were red in spring,would turn green with leaves maturity.In the process,the total chlorophyll increased in both species,the anthocyanin decreased in Acer×freemanii‘Autumn Blaze',the anthocyanin increased in Acer truncatum.But Ant/Chl was 2.5 when leaves turned green.F_v/F_m of these two species increased with leaves maturity in spring.The value of juvenile leaves was between 0.48 and 0.55,the value of mature leaves closed to 0.8 gradually,that proving juvenile leaves were red because they suffered from environment stress probably.2.Leaf color of Acer×freemanii‘Autumn Blaze'and Acer truncatum would change from green to red as the leaves senescence in autumn.The beginning period of color change in the former was earlier than the latter.In the process,the total chlorophyll content of two species decreased,the anthocyanin accumulated gradually.Ant/Chl of two species was 41.8 and 10.1 respectively when the leaves turned red in full.PAL activity and CHI activity in Acer×freemanii‘Autumn Blaze'were both significant increased.The correlation between anthocyanin and these two enzymes was very significant positive correlation?P<0.01?.These two enzymes in Acer truncatum were both not significant increased,PAL activity and anthocyanin content was very significant positive correlation?P<0.01?and CHI activity and anthocyanin content was significant positive correlation?P<0.05?.F_v/F_m of two species was decreased gradually as the leaves senescence.The value was 0.34 and 0.45 respectively when the leaves turned red in full that proving the leaves in autumn also suffered from environment stress.Leaf water content decreased gradually and was significant negative correlation with anthocyanin content.3.The leaves at the top of the branch which were red in summer.The study about different leaf positions found that chlorophyll a and chlorophyll b of two species increased with the leaf position falling,anthocyanin content of Acer×freemanii‘Autumn Blaze'decreased and it increased in Acer truncatum.Ant/Chl decreased with the leaf position falling,the value of Acer×freemanii‘Autumn Blaze'decreased from 0.48 to 0.32 and it decreased from 0.43 to 0.32in Acer truncatum.The change of soluble sugar content of Acer×freemanii‘Autumn Blaze'was not obvious and it didn't not significant correlate with anthocyanin content.Soluble sugar content of Acer truncatum increased and was very significant positive correlation with anthocyanin content?P<0.01?.The study about pigments content percentage showed that the proportion of total chlorophyll of Acer×freemanii‘Autumn Blaze'in leaf position U was 57.9%and it rose to 65.8%in leaf position D.The proportion of anthocyanin of Acer×freemanii‘Autumn Blaze'was 27.5%in leaf position U and it was down to 20.5%in leaf position D.In Acer truncatum,the proportion of total chlorophyll was 57.9%in leaf position U and it rose to67.5%in leaf position D.The proportion of anthocyanin of Acer truncatum was 24.8%in leaf position U and it was down to 21.4%in leaf position D.The leaves were red in leaf position U and they were green in leaf position M1,M2 and D.4.In order to prolong the ornamental period,phloem girdling and sucrose spraying treatments were taken on Acer×freemanii‘Autumn Blaze'.The test found that girdling speeded leaf coloration,sucrose spraying had a little effect on leaf color.Physiological studies showed that a large number of soluble sugar and anthocyanin accumulated in the upper branch where leaves redder than normal leaf after girdling.0.3 mol·L^-1 sucrose spraying had the greatest effect on anthocyanin accumulation.Soluble sugar increased most obviously with 0.5 mol·L^-1 sucrose spraying.The test found that vein cutting also impacted the leaf color.The leaves above cutting point were red and brighter.Girdling and vein cutting stopped the downward transportation of photosynthetic products through the phloem.These two treatments indicated the inducibility of anthocyanin accumulation and also increased the likelihood that sugar accumulation affected this biochemical process.But in a short period of time,the branches and leaves wilted and fell.So girdling and vein cutting were both not conducive to tree health.Sucrose spraying had little impact on the leaf color,but would affect anthocyanin accumulation.The study found that shading inhibited the accumulation of anthocyanin and soluble sugar in leaves and impacted the leaves color.And it was harmful to trees health.Only in the full light conditions,the trees grew healthily and it was better to enjoy leaves.