Responses Of Lemon Subjected To Different PH Stress And Its Physiological Mechanism

Soil acidification is one of the important factors that affect the growth of plants,soil acidity-alkalinity has different effect on the growth and development of plants,different kinds of plants have different most suitable soil pH value.Lemon has extensive uses,such as edible,medicinal,industry and so on,but the responses of lemon subjected to different pH stress and its physiological mechanism is rarely report.This study adopts potted plant of eureka lemon trees “yunning 1”,studying lemon growth indicators,photosynthetic physiological metabolism,tree nutrient metabolism,the leaf antioxidant enzyme activity and soil nutrient content,those index are measured in the event that pH<3,pH3-4,pH4-5,pH5-6,pH6-7,pH7-8,pH8-9,pH>9 soil pH levels.Finding the most suitable soil pH value of lemon,Provide guidance for the microecological control of lemon orchard soil.The main research results are as follows:(1)Different pH treatment have a great influence on ground diameter,plant height,total slightly on lemon,and all the above indicators showed good growth advantage under the pH6-8 treatment.Strong acid and strong alkali soil will be bad for the growth of lemons.(2)In the case of pH 7-8 in the soil,the levels of chlorophyll a and chlorophyll(a + b)in blade of lemon were higher than other treatments.Chlorophyll b in blade had different variations in the different pH levels of soils and it had the highest contents under pH7-8.Stress levels of carotenoids and chlorophyll b respond to soil pH are basically equal.(3)Under the stress of different pH levels,lemon leaf's intercellular CO2 concentration was the highest in the process of pH7-8 and was the lowest in the process of pH8-9.While the stomatal conductance and transpiration rate are present higher values in pH7-8.Therefore,when cultivating lemons,for the acidic soil,we can consider to adjusting soil pH in the range of neutral environment,which promotes the lemon photosynthetic metabolic reactions and improves the efficiency of photosynthesis.(4)In the different pH levels,the absorption content of the various parts of the lemon tree body to the Ca,Mg,Fe,Mn,Cu,Zn and other nutrients have different levels.The difference in content of different elements is not significant in different pH levels.However,Fe has presented significant differences in different pH levels.This shows that the pH value of the soil influences the absorption of the lemon in Fe.(5)In the different pH levels,lemon leaf enzyme activity shows difference.The activity of SOD,POD and CAT increased with dealing with pH increased and decreased gradually when reaching the maximum.The activity of oxidase was highest in pH6-7 at the very beginning of process.Then it was highest in pH7-8.The differences of three kinds of antioxidant enzyme activity in different processing reached extremely significant level,but the activity of CAT's difference did not reach significant level in different times.(6)The concentration of alkali in nitrogen,instant potassium and rapid phosphorus in soil were the highest under the process of pH6-7.Soil organic matter is highest in ph7-8.Therefore,lemons have the highest amount of active nutrients in the soil pH6-8 range for lemons.In conclusion,the results showed that the soil was more suitable for the lemon to absorb and utilize soil nutrients in the range of pH6-7,and it promoted the physiologi cal metabolism of lemon in the range of pH7-8,which was most suitable for the growt h of lemon.The Comprehensive analysis showed that the range of soil pH6-8 was the dominant soil condition suitable for the cultivation and management of lemon,which is conducive to the promotion of high quality cultivation of lemon orchard.