Study On Cutting Propagation Technology Of Three Species Of Buddleja L.and Its Response To Pb、Cd Stress

Buddleja L.is a monotypic genus of Buddlejaceae,with about 100 species in the world and 29 species in China.Most of the plants of this genus are shrubs,which have high ornamental value,ecological value and medicinal value,and have good absorption capacity for heavy metals such as Pb and Cd.It is a kind of plant with great ecological restoration potential.At present,only a few species of this genus are cultivated as garden plants,and most of them are still in the wild state and need to be developed and utilized.There are three common species of Buddleja L.in Chongqing,namely Buddleja davidii,Buddleja oficinalis and Buddleja asiatica.In order to provide a large number of high-quality seedlings in a short time and explore the feasibility of their popularization and application in heavy metal polluted areas,this experiment carried out the research on the cutting propagation technology of Buddleja davidii and Buddleja asiatica from the aspects of cutting matrix,cutting diameter,hormone species,concentration and treatment time,and discussed the physiological response of Buddleja davidii,Buddleja oficinalis and Buddleja asiatica to Pb and Cd stress.The main results are as follows:1.Research results of cutting propagation technology of drunken Buddleja davidii and Buddleja asiatica:（1）From the cutting matrix,the effect of perlite:vermiculite=1:1 is the best.（2）In terms of cuttage thickness,the cutting effect of thin branches（3～5mm）of Buddleja davidii and Buddleja asiatica is better than that of thick branches（5～7mm）.（3）In terms of hormone type,concentration and treatment time,the cuttings of Buddleja davidii treated with NAA 800 mg/L for 15s had the best effect,the rooting rate reached 98.89%,and the rooting effect index was 2.59;The cuttings of Buddleja asiatica treated with IBA 800 mg/L for 15s had the best effect,the rooting rate reached100.00%,and the rooting effect index was 4.14.2.Research results of response to Pb、Cd stress of Buddleja davidii,Buddleja oficinalis and Buddleja asiatica:（1）Effects of Pb、Cd stress on plant growth.Cd²⁺promoted and inhibited the growth of Buddleja davidii and Buddleja oficinalis at low concentration,and inhibited the growth of Buddleja asiatica;Pb²⁺showed the effect of"low promotion and high inhibition"on the growth of three plants.From the change of morphological indexes,the resistance of the three plants to Cd and Pb was Buddleja oficinalis>Buddleja davidii>Buddleja asiatica.（2）Effects of Pb、Cd stress on photosynthetic pigment content in plant leaves.With the increase of Cd²⁺concentration,the contents of chlorophyll a,chlorophyll b,chlorophyll a+b and carotenoids in the leaves of Buddleja davidii and Buddleja oficinalis first increased and then decreased,and the contents of photosynthetic pigments in the leaves of Buddleja asiatica gradually decreased;With the increase of Pb²⁺concentration,the content of photosynthetic pigments in the leaves of the three plants increased first and then decreased.（3）Effects of Pb、Cd stress on relative water content of plant leaves.With the increase of Pb²⁺and Cd²⁺concentrations,the relative water content of leaves of three species of Buddleja davidii increased first and then decreased.（4）Effects of Pb、Cd stress on relative conductivity of plant leaves.With the increase of Cd²⁺concentration,the relative conductivity of leaves of Buddleja davidii and Buddleja asiatica first decreased and then increased,and the relative conductivity of leaves of Buddleja oficinalis gradually increased;With the increase of Pb²⁺concentration,the relative conductivity of the leaves of the three plants first decreased and then increased.（5）Effects of Pb、Cd stress on antioxidant enzyme activity in plant leaves.With the increase of Pb²⁺and Cd²⁺concentrations,the activities of antioxidant enzymes in the leaves of the three plants increased first and then decreased;However,the activities of SOD in the leaves of Buddleja davidii under Cd²⁺stress and CAT in the leaves of Buddleja asiatica under Pb²⁺and Cd²⁺stress decreased gradually.（6）content of osmoregulatory substances in plant leaves.With the increase of Pb²⁺and Cd²⁺concentrations,the contents of soluble protein and proline in the leaves of Buddleja davidii and Buddleja oficinalis basically increased gradually,while the contents of two substances in Buddleja asiatica leaves increased first and then decreased.Under the stress of Pb²⁺and Cd²⁺,the content of soluble sugar in the leaves of three species of Buddleja davidii was not high,which was basically lower than CK.（7）Through the comprehensive analysis of each index by membership function method,it was found that under the stress of Pb²⁺and Cd²⁺,the resistance of the three plants was Buddleja oficinalis>Buddleja davidii>Buddleja asiatica.The performance of each index of the three plants under Pb²⁺stress is better than that under Cd²⁺stress,indicating that Cd²⁺has a greater toxic effect on the plants Buddleja L.