| Ananascomosus var.bracteatus has green,white and red leaf mosaic,which is a kind of color-leafed plant with great ornamental value.The color of its leaves,especially red,is closely related to the growth and development of the plant and environmental factors.Light and temperature are important environmental factors that affect the appearance of its leaf color.In this study,the ornamental value of the plants was evaluated synthetically from three aspects: leaf color,stripe definition,burn or wilt degree of the leaves under different shading and temperature conditions,so as to select the suitable shading and temperature conditions,which can provide guidance for the cultivation and application of Ananascomosus var.bracteatus in the garden.The study on the composition,content proportion,distribution area of pigment and the metabolism characteristics of anthocyanin in leaves under different shading and temperature conditions provided a theoretical basis for revealing the mechanism of color rendering in color-leafed plants.The main results are as follows:1.Effect of shading in summer on the leaf color appearance of Ananascomosus var.bracteatus.(1)With the increase of the shading degree,the green tissues and white tissues of Ananascomosus var.bracteatus leaves become lighter in red,and the white tissues on the edge of the blade appear green spots.Under full light condition(CK),the stripes of leaves are clear,and the red characters of green tissues and white tissues maintain the best,but the leaves have burn spots,which affects the ornamental quality of plants.Under 75% shade condition(T2),the plants grow normally without dry burn,but the red color of green tissues and white tissues of leaves almost disappears,only the serrations of leaf edges show red,and the white tissues of leaf edges show large green spots.Under 50% shading(T1),the plant still maintained a high Vornamental value at 45 days.At 60 days,the green tissues and white tissues of leaves became light red,the white tissues on the edge appeared light green spots,the stripes of leaves were fuzzy,and the ornamental value decreased slightly.Therefore,in general,Ananascomosus var.bracteatus can show better growth state and ornamental effect under 50% shade in summer.(2)The content of chlorophyll and carotenoid in green tissues and white tissues of Ananascomosus var.bracteatus increased with the increase of shading degree,while the content of anthocyanin decreased with the increase of shading degree.75%shading conditions(T2)has the most significant effect on leaf pigment content.(3)With the increase of shading degree,the L* and b* values of the white tissue on the edge of the leaves of Ananascomosus var.bracteatus increased,the a*value decreased,the red and light of the white tissue on the edge of the leaves became lighter,and when the green spots appeared on the white tissue on the edge,the L*values,b* and a* decreased;with the increase of shading degree,the L* values of the green tissue in the center of the leaves did not change significantly,the b* value increased,the a* value decreased,and the center green The color structure changed from red green to green.(4)As the shading degree increases,the number of red cells per unit area in the leaf epidermal tissue of Ananascomosus var.bracteatus decreases,and the number of green cells per unit area in the mesophyll tissue increases;as the shading degree decreases,the leaf green,The mesophyll parenchyma cells in the white tissue contracted,and the cells were irregular in shape and loosely arranged.2.Effect of low temperature in winter on the leaf color appearance of Ananascomosus var.bracteatus.(1)Under the indoor 16℃ constant temperature environment(CK),the growth of Ananascomosus var.bracteatus was normal,and the white tissue on the edge of the leaf was red,the green tissue in the center was green,and there was no significant change in the experimental period.Under the outdoor natural low temperature environment(T1),the leaves of Ananascomosus var.bracteatus suffered severe cold damage and withered,the red color of the white tissue on the edge of the leaf faded,and lost the ornamental value.Greenhouse environment(T2)although the lower Ananascomosus var.bracteatus can grow normally,the tip of the leaf withers,and the red color of the white tissue on the edge of the leaf disappears in January and recovers slightly in March.Therefore,Ananascomosus var.bracteatus is suitable for indoor growth at 16℃ in winter.(2)Temperature has a significant effect on the change of pigment content.The content of chlorophyll,carotenoid and anthocyanin in the leaves of outdoor natural environment(T1)and greenhouse environment(T2)decreased with the decrease of temperature in December in winter,and the content of chlorophyll,carotenoid and anthocyanin in the leaves of T1 group was larger than that of T2 group,and the content of pigment in T2 group increased slightly when the temperature rose in March next year.The pigment content of the leaves under constant temperature at 16℃ in the room(CK)was greater than that of the other two groups during the whole test period.(3)With the decrease of temperature,the values of L* and b* of the white tissue on the edge of the leaves of Ananascomosus var.bracteatus increased,the values of a* decreased,the red of the white tissue on the edge became lighter,and the tissue became brighter;the values of L*,a* and b* of the green tissue in the center of the leaves had no significant change,and the green tissue was always green.(4)In the greenhouse environment(T2),the number of red cells per unit area in the green and white tissue epidermis of Ananascomosus var.bracteatus leaves decreased,and the mesophyll parenchyma cells of the leaves were oval or irregular.The volume of the mesophyll parenchyma cells and the diameter of the vascular bundle increased significantly compared with the indoor 16℃ constant temperature environment(CK).When the temperature exceeds the range that Ananascomosus var.bracteatus can bear,the number of cells containing chlorophyll and anthocyanin in the leaves is significantly reduced,and the shape of mesophyll parenchyma cells was irregular.3.Metabolic characteristics of anthocyanins in Ananascomosus var.bracteatus leaves under low temperature.(1)The soluble sugar content in the green tissues and white tissues of leaves increased sharply when the temperature dropped suddenly in December in winter.From January to March in the next year,the soluble sugar content in the green tissues and white tissues of leaves decreased.According to correlation analysis,there was no significant correlation between soluble sugar and anthocyanin content in the green and white tissues of Ananascomosus var.bracteatus.(2)In the process of leaf color change in winter,the PAL activity and anthocyanin content in green tissues and white tissues of leaves showed a significant positive correlation only in outdoor natural low temperature environment(T1).When the PAL activity of green tissues and white tissues decreased rapidly in this temperature environment,the anthocyanin content also showed a downward trend.The CHI activity of green tissues and white tissues in Ananascomosus var.bracteatus leaves under three different temperature environments is indoor 16℃ constant temperature environment(CK)> outdoor natural low temperature environment(T1)>greenhouse environment(T2).According to correlation analysis,except for the edge white tissue in CK environment,the CHI activity and anthocyanin content of green and white tissue in leaves under other temperature environments are significant or extremely significant Positive correlation.It is suggested that CHI activity in the leaves of Ananascomosus var.bracteatus may play a role in anthocyanin synthesis,which may be the key enzyme in anthocyanin synthesis.(3)Under the low temperature in winter,the stress reaction was produced in the Ananascomosus var.bracteatus,the PPO and POD activity in the leaves increased,which alleviated the low temperature stress to a certain extent and maintained the normal growth of the plants.According to correlation analysis,there was no significant correlation between PPO and POD activity and anthocyanin content in green tissues and white tissues of Ananascomosus var.bracteatus leaves under different temperatures.The mechanism of PPO and POD activity and anthocyanin degradation needs further study. |
