Effects Of Different Light Intensity And Substrate On The Growth And Related Physiological Indexes Of Bretschneidera Sinensis

Bretschneidera sinensis is a perennial tall deciduous tree,relict species of tertiary tropical flora,in our country the distribution range is very narrow,the number is very rare,was listed in the List of Key State Protected Wild Plants of China(First Batch).And the plant has high ornamental value and great potential for development and utilization in landscaping.In this paper,by setting different light and water treatment,we studied the morphological and physiological changes of Bretschneidera sinensis under different conditions,searched for suitable growth conditions,and provided theoretical reference for the protection and promotion of this species.The results as follows:(1)In order to provide seedling reserve for protention of wild resources and population restoration of B.sinensis,with four different natural sunlight treatments(100%,50%,30%and 20%)in open field during the whole growing season were used to compare and analyze growth and morphological indexes,chlorophyll content and other physiological indexes of seedlings explore the suitable light conditions for the growth of B.sinensis seedlings,we found that light had a significant effect on the growth of B.sinensis,which showed as follows:the increases in height and caliper,biomass of seedlings under the three low-light intensity treatments(50%,30%and 20%)were all higher than 100%light intensity treatment,the plants grew well under 30%light intensity treatment seedlings grew poorly in full light environment,with few leaves,stunted plants and more deaths.The thickness of the leaves of different treatments continued to increase,but at the end of the test there was no significant difference.The specific leaf weight of 30%light intensity treatment was the lowest.The chlorophyll content changed significantly.At the beginning of the experiment,the chlorophyll content gradually increased with the decrease of light intensity;at the later stage,the solar light decreased and the sunshine time shortened.With the decrease of light intensity,the chlorophyll content gradually decreased.Under 100%light treatment,the content of soluble sugar was the highest,while the content of MDA continued to rise,causing harmful effects on plant growth.SOD enzyme activity was high while POD enzyme activity was low.The growth of the two enzymes was not coordinated,and the regulatory function of plant system was damaged,and the imbalance between the production and elimination of reactive oxygen in plants was unbalanced.The three groups of shading treatment had different levels,but the changes of total content were the same,and they grew well under shading condition.High or low light intensity will lead to lower photosynthetic rate(Pn);The transpiration rate(Tr)is related to light exposure,the Tr of the 100%light intensity treatment was highest,but the water use efficiency(WUE)was lowest.The Tr decreased with the decrease of light intensity.The transpiration affected the body temperature of plants and indirectly affected the P and stomatal conductance(Gs).Therefore,B.sinensis seedlings were not resistant to strong light,should to be properly shaded in summer with 30%light intensity as the best,and it is not suitable to shading for a long time,shading net should be removed when the light intensity is reduced and the light time is shortened.(2)In order to provide seedling reserve for protention of wild resources and population restoration of B.sinensis,with five different substrate processing(120%、110%、100%、90%and 80%)during the whole growing season were used to compare and analyze growth and morphological indexes,chlorophyll content and other physiological indexes of seedlings explore the suitable light conditions for the growth of B.sinensis seedlings,we found that soil with higher water content had a certain effect on the growth of B.sinensis seedlings:in the seedling growth period,the plant height diameter of each treatment was higher with 80%water content,and the number of pinnately compound leaves increased with 90%water content,but the overall growth trend was the same,and the change of height to diameter ratio was also the same,and the effect of higher water content on the plant growth was not obvious.The biomass accumulation was higher at 80%and 90%water content,but lower at root and cap;The leaf thickness of each treatment increased uniformly,and the difference of specific leaf weight was not significant in the later stage.The content of chlorophyll a changed slightly,and chlorophyll b increased first and then decreased.The chlorophyll content of 120%and 110%higher water content in the later period was significantly lower than that of the other three groups,showing slight flooding stress.100%water content processing the soluble protein content of the four group were first increased then decreased,suggests that plant gradually adapt to the conditions of hydrated,handling 100%water content of soluble sugar and soluble protein increased,due to poor soil permeability,root respiration is abate,the more serious stress.MDA,SOD and POD showed an increasing trend in all treatments.The increase of MDA content in 80%and 90%water content groups was small.SOD and POD cooperate in scavenging ROS and free radicals in plants,and the simultaneous increase of ROS content is beneficial for plants to adapt to higher water conditions.Therefore,the growth of B.sinensis seedlings needs a higher water condition.Under the condition of maintaining a higher water condition,sand soil should be added appropriately to keep the ventilation of the soil,and the water content of the soil should be about 80%.