Effects Of Shading Treatment On The Physiological Indexes And Photosynthetic Characteristics Of Four Hydrangea Varieties

Hydrangea macrophylla(Thunb)Ser.has rich flowers and colors and is an important garden plant.Its vigorous growth period is from April to August.At this time,it is summer in southern my country,and the sunlight is strong,and its leaves are easily burned,causing the whole plant to wilt.Even death,seriously affecting its ornamental value.In this experiment,four different varieties of hydrangea were shading treatment,setting CK(60% shading rate),T1(20% shading rate),T2(40%shading rate)and T3(80% shading rate)to simulate different treatments.The light environment conditions of different species were measured,the changes of morphological indicators,photosynthetic characteristics and physiological indicators were measured,and related indicators were analyzed multiple times,to explore the adaptability of different varieties of hydrangea to light,and to seek the most suitable light environment for the growth of hydrangea.The cultivation and garden application provide theoretical guidance.The main conclusions are as follows:(1)From the perspective of morphological indicators,the growth state of’Sinai Fairy’ is the best at a shading rate of 40% and above;the best shading rate of’Jiacheng’is 40%;the best shading rate of’lapis lazuli’ and’blue mother’ The best shading rate is60%.When the shading rate reached 60% and 80%,the plant height and crown growth of the four hydrangeas were the largest;but shading did not affect the relative water content of the leaves of the hydrangeas.(2)Shading treatment reduces the stress damage of strong light to the four varieties of Hydrangea,and adapts to different light environments through osmotic adjustment.Among them,the physiological index change law of "Jiacheng" is different from that of the other three varieties.The MDA content reached the highest at 130 days of shading,while the other varieties reached the highest at 110 days of shading.From the comprehensive analysis of four physiological indicators,’Jiacheng’plants are damaged when the shading rate is 20% and 80%;’Sinai Fairy’ can reduce the damage of strong light to plants when the shading rate is higher than 20%;’ Lapis Lazuli and Blue Mama need a shading rate of 60% for the best plant growth.(3)The daily variation trends of Pn,Tr,and Gs of the four varieties under shading treatment are consistent,showing a bimodal curve,while the daily variation trend of Ci is opposite,showing a "W" shape;photosynthesis occurs in all four varieties under the influence of stomatal factors "Lunch break phenomenon." The shading treatment reduces the transpiration rate and stomatal conductance of the hydrangea,and improves the water utilization ability of the hydrangea.The photosynthetic ability of’Sinai Fairy’ at the shading rate of 40%-60% is stronger than other treatments;’Jiacheng’ has the strongest photosynthesis rate at the shading rate of40%,and it has better water utilization ability;’lapis lazuli’ is not resistant to strong light,The best shading rate is 60%-80%.The best shading rate for ‘Blue Mom’ is60%.The four varieties all had the highest intercellular carbon dioxide concentration under the shading rate of 80%.(4)According to the results of principal component analysis,the main component of morphological characteristics is crown width,the main components of physiological indicators are MDA,POD and SSC,and the main components of photosynthetic characteristics are Pn,Tr and Gs.In garden applications,according to the characteristics of the four varieties of hydrangea,it is believed that’Sinai Fairy’ has a wide range of light exposure and can be applied under environmental conditions with a shading rate of more than20%;’Jiacheng’ has moderate negative resistance and suitable shading The rate is40%-60%;’lapis lazuli’ likes a weak light environment,the best planting at a shading rate of 60% and above,’blue mother’ likes half shade,suitable for planting in a light environment with a shading rate of 60%.