Response Of Introduced Acer Rubrum ‘Red Champions’ Growth And Coloration To Water-Fertilizer Coupling

Excellent color leaf plants are of great significance to beautify the city and improve the quality of urban landscape.Colorful leaf plants are favored by more and more people,and colorful leaf tour has become a new favorite to stimulate the local tourism economy,such as Xiangshan Red Leaf,Three Gorges Red Leaf,Ginkgo Village,etc.In recent years,a large number of colorful plants such as Acer rubrum have been introduced into Chongqing,and colorful leaf tour and red leaf tour have been carried out.However,most of the results are not good.The main problems,such as dim leaf color and short viewing time,have brought considerable economic losses to the introduced units,enterprises or individuals.It was found that most of Chongqing belonged to the suitable area of Acer rubrum,and reasonable coupling measures of water and fertilizer were helpful to its growth and development,but growth and coloration were two completely different physiological processes.In order to investigate the adaptability and ornamental value of Acer rubrum introduced in Chongqing,the annual cuttings of Acer rubrum’Red Champions’,a variety of Acer rubrum introduced in Chongqing,were used as experimental materials.On the basis of previous investigation,a total of 18 treatments（T）were set by water and fertilizer tests.Among them,9 treatments were planted under rain cover,9 treatments were planted under no rain cover,and the natural growth treatment was used as the control.Acer rubrum’Red Champions’growth（including plant height,ground diameter,biomass,and root development characteristics）,leaf traits（including leaf length,leaf width,leaf area,leaf water content,stomatal density,stomatal length,stomatal width,stomatal index（SPI）,leaf thickness,specific leaf area,and leaf tissue density）,leaf photosynthesis,leaf water potential,and leaf color indexes（including Lab ginseng）were measured Number,anthocyanin（Ant）content,chlorophyll（Chls）content,carotenoid（Car）content,soluble protein（SP）,soluble sugar（SS）,phenylalanine ammonia lyase activity（PAL）,leaf p H value and ornamental period length),by analyzing the correlation between growth and physiological changes of Acer rubrum‘Red Champions’,A linear regression model was established to analyze the effects of coupling effects of water and fertilizer on the growth and color of Acer rubrum’Red Champions’,to determine the physiological response of Acer rubrum’Red Champions’,under different coupling conditions of water and fertilizer,and to screen the suitable treatment for Acer rubrum’Red Champions’,growth and good color quality,so as to provide reference for the introduction of Acer rubrum in Chongqing.The main research results are as follows:（1）Under each treatment condition,the increase of plant height ranged from 7.00±2.27 cm to 22.4±5.49cm;The increment of ground diameter ranged from 2.33±1.41 mm to 7.38±3.90 mm.The root dry weight ranged from 12.12±2.60g to 91.25±1.88g.Stem weight ranged from 14.50±1.15g to 70.50±6.64g.The total dry weight ranged from 26.50±3.75g to 156.52±6.06g.The root-shoot ratio ranged from 0.69±0.06 to 1.91±0.01.Seedling quality index（Q_I）ranged from 3.00±0.54 to 23.21±0.55.The plant height,ground diameter,biomass and root development of Acer rubrum‘Red Champions’were significantly lower than those of control（P<0.05）when the soil water content was 40%to 45%of the maximum field water capacity（H₃）.Under the same soil water content,there were no significant differences in plant height,ground diameter,root growth and biomass among different fertilizer treatments（P>0.05）.The increment of ground diameter of T7-T9 and T11 was significantly higher than that of the control（P<0.05）,and the increment of ground diameter of T8 was the highest.The plant height of T6-T9,T11-T12 and T13 was significantly higher than that of the control（P<0.05）,and the cumulative plant height of T11 was the largest.The total dry weight increment of T5-T6,T8-T9 and T12 was significantly higher than that of the control（P<0.05）,and the increment of T9 was the largest.The Q_I of T4,T8-T9 and T11-T12 was significantly higher than that of the control（P<0.05）,and the Q_Iof T9 was the highest.According to the results of linear regression equation,within the scope of this experiment,no matter the level of fertilization,soil water content kept at 80%～85%of the maximum field water capacity（H₁）had the largest contribution rate to growth indicators such as plant height,ground diameter,root growth and biomass,that is,the contribution rate of water to growth>nutrient,and water was the main influencing factor for the growth of Acer rubrum’Red Champions’.（2）Under each treatment condition,leaf length growth ranged from 120.93±4.85 mm to 40.83±7.60 mm.Leaf width growth ranged from 29.91±1.62 mm to 90.30±3.98 mm.The increase of leaf area ranged from709.78±125.78mm² to 6287.00±139.71mm².Blade thickness varies from 0.09±0.01mm to 0.28±0.01mm.Acer rubrum’Red Champions’had strong leaf morphological plasticity.Under different water-fertilizer coupling treatments,leaf morphology was significantly different.Leaf width,leaf length,leaf area,leaf thickness,leaf water content,leaf tissue density and stomatal parameters were significantly different under different soil water content treatments（P<0.05）.However,there were no significant differences among the treatments with the same soil water content and different fertilizer amounts（P>0.05）.Analysis of the linear regression model showed that the contribution of soil water content to leaf morphology was higher than that of nutrients.Under the condition of rain cover（E₂）,when soil water content was H1 and fertilization N:P:K=3:1:2,22.5g/plant（F₂）（T8）,the coupling effect of water and fertilizer was the best,and the leaves were the largest and thickest.（3）The experiment under different processing conditions,transpiration rate（T_r）changes in the range of0.92±0.06μmol m^-2s^-1～3.17±0.27μmol m^-2s^-1;Instantaneous net photosynthetic rate（P_n）changes in the range of 1.04±0.09μmol m^-2s^-1～9.51±0.17;The intercellular carbon dioxide concentration（C_i）varied from205.31±3.69mmol mol^-1to 338.71±7.78mmol mol^-1.The stomatal conductance（G_s）range of 0.03±0.01 mol m^-2s^-1～0.12±0.01 mol m^-2s^-1;Water use efficiency（WUE）ranged from 0.58±0.01 to 4.59±0.07.Stomatal limit（L_s）ranged from 0.18±0.01 to 0.49±0.01.The dawn water potential of T3,T15 and T18 was significantly lower than that of the control（P<0.05）,while the dawn water potential of T1-T2,T4-T14 and T16-T17 was significantly higher than that of the control（P<0.05）.Afternoon water potential of T1-T6 and T9-T18 was significantly lower than that of the control（P<0.05）,while afternoon water potential of T7 was significantly higher than that of the control（P<0.05）.The difference of water potential in all treatments was significantly higher than that in control（P<0.05）.The water potential difference of T1-T2,T5-T6,T9 and T17 was significantly higher than that of the control（P<0.05）,and the water potential difference of T5 was the largest.The dawn water potential of T2,T5,T7-T9 and T16 was significantly higher than that of the control（P<0.05）,and the dawn water potential of T9was the highest.The afternoon water potential of T1,T3,T6 and T17-T18 was significantly lower than that of the control（P<0.05）,and the afternoon water potential of T6 was the lowest.The WUE of T1 and T6-T10 was significantly higher than that of the control（P<0.05）,and T1 was the highest,followed by T9.Acer rubrum’Red Champions’has a strong ability to adapt to the environment and shows different adaptation strategies under different coupling conditions of water and fertilizer.Under E₂ condition,soil moisture content was H₁,N:P:K=3:1:2 and 45g/plant（F₂）fertilization（T9）had the best water-fertilizer coupling effect.Under the same soil water content,there was no significant difference in P_n and water potential difference of T7-T9 under different fertilization treatments（P>0.05）,while under different soil water content,the photosynthesis,transpiration and water potential differences of T3 and T6 under the same fertilization ratio were significantly lower than that of T9（P<0.05）.It can be seen that the influence of water on leaf photosynthesis and water potential was greater than that of nutrients.（4）The content of chlorophyll A（Chla）varied from 0.01±0.01 mg g^-1to 3.78±0.72 mg g^-1under each treatment condition.Chlorophyll B（Chlb）content ranged from 0.02±0.01 mg g^-1to 2.78±0.57 mg g^-1.The total content of Chls ranged from 0.12±0.05 mg g^-1to 5.22±0.54 mg g^-1.Ant content ranged from 0.57±0.20 U to112.58±38.07 U.Car content ranged from 0.07±0.02 mg g^-1to 3.06±0.16 mg g^-1.Ant/Chls ranged from0.17±0.06 to 3433.71±293.23.At the beginning of color transfer,SS of T2-T4,T7-T8,T10-T12 and T14-T18were significantly higher than those of the control（P<0.05）.Analysis of leaf color parameters（L,a,b,C*）showed that T5,T6,T8,T9,T11 were treated with high color quality,and T9 had the highest leaf color quality.The duration of all treatments was significantly longer than that of the control.The duration of T1,T4-T5,T7-T9,T11-T12,T14-T15 and T18 was longer,and the duration of T8 was the longest,up to 36 days.Most of the leaves were yellow or orange under E₂treatment,while all the leaves were red in the open air environment（E₁）.Sufficient soil moisture was conducive to leaf color,and sufficient nutrients were guaranteed on the basis of water,which could improve the brightness of leaf color and significantly prolong the ornamental period.Analysis of the linear regression equation showed that the contribution rate of nutrients to color and ornamental period was nutrient>water,and appropriate coupling treatment of water and fertilizer could improve leaf color quality.In conclusion,appropriate water and fertilizer coupling treatment can not only promote the growth of Acer rubrum‘Red Champions’,but also improve the color quality of leaves.The contribution rate of water to growth is greater than that of nutrient,and the contribution rate of nutrient to color and ornamental period is greater than that of water.The content of Ant and Chls is the key factor to determine the color quality of leaves,the higher SS content in the early stage of color transformation can promote the Ant synthesis,the content of SP and Ant are the key factors to determine the length of the ornamental period,the treatment of high SP and Ant content（T9）,the ornamental period of leaves is longer（compared with the CK,23 days longer）.In the scope of this experiment,T8,T9 and T11 coupled treatments of water and fertilizer could significantly promote the growth of Acer rubrum‘Red Champions’plants and improve the quality of leaf color,and T9 showed the best performance.