Studies On Fastness And Quality Physiology Of Nicotiana Labacum L To Copper Stress

In these experiments,7 varieties of tobacco(Nicotiana labacum L.) were tested for their tolerance to Copper toxicity.Using two varieties of tobacco(89112 and Shuang-70) as experiment material.With solution culture,studied the effects of Copper on the physiological characteristic of tobacco,included physiological characteristic of roots, antioxidant enzymes,carbon-nitrogen metabolize,chlorophyll fluorescence and photosyn-thesis. This study investigated the response and endurance of tobacco to Copper stress.The main results were summarized as follows:1.The relative root length of 89112 was 135%which was obviously higher than others and showed the strongest resistance to Cu.In contrast,Shuang-70 was sensitive to Cu with a lower root length of 47%.So 89112 and Shuang-70 were chosen as experiment material for further analysis.2.With the increasing of Cu concentration,free-proline contents and electrical conductivities of tobacco roots first decreased and then increased;With the delay of treatment time,free-proline contents of the two tobacco varieties were all increased;MDA contents and roots activities first increased and then decreased.With the delay of treatment times,each indicator showed an upward trend with the low concentration of Cu treatment and the change scope was higher in Shuang-70 than that in 89112,which probably was caused from the differentia in Cu resistance.The contents of Cu,Fe,Mn were first enhanced and then depressed with the increase of Cu treatment concentrations,but content of Mg was first depressed and then increased.3.As to the two species,O₂^? contents were decreased first and then increased,with the delay of treat time,O₂^? contents were also increased.H₂O₂ contents were increased with the concentration of Cu treatment,but no obvious change was observed with the delay of treat time.Concentration of Cu＜1 mg·L^-1 treatment could promote the activities of SOD, POD,GR and APX to enhance scavenging capacity of free radicals and keeped ROS at a low level so as to avoid the poisoning effect of Cu.However,concentration of Cu＞5 mg·L^-1 treatment restrained activities of antioxidant enzyme and caused ROS accumulation, augmented oxidative stress and lipid peroxidative level,thus the growth of plant were restrained.When treated with Cu,contents of AsA,GSH and MDA were enhanced and then depressed.With the delay of treat time,contents of AsA were increased,while that of GSH and Free-proline were reduced and enhanced respectively under Cu stress.89112 suffered from less oxidative stress than shuang-70 owing to its antioxidant enzyme activity, antioxidant substances content and lower reactive oxygen.4.Cu had obviously effect on carbon-nitrogen metabolism.Contents of NO₃^- -N in two Nicotiana tabacum cultivars were increased firstly and then decreased,and the NO₃^- -N contents in 89112 were higher than in Shuang-70.The negative effect of Cu on the assimilation of NO₃^- -N was increased with increasing treatment time.The activities of GS and GOGAT were increased firstly and then were inhibited by the increased Cu.Then,as the increasing treatment time,the inhibitory effect was increased.In constrast to Shuang-70,the enzyme activities were higher in 89112,implicating that the 89112 was more tolerant to high Cu stress.Compare with the control,activity of glutamate-pyruvate transaminase(GPT) was increased under Cu treatment,but concent of free amino acid was reduced,while the decrease in Shuang-70 was more obviously than in 89112.With the copper treatment concentration increased,starch synthase and sucrose synthase were first increase and then declined.Total soluble sugar and fructoas were increased with the increase of Cu treatment concentration and the duration of treatment.Sugar content was reduced with the increase of Cu concentration in 89112 variety while sugar content was first increased and then decreased with the increase of Cu concentration in Shuang-70. High concentration of Cu inhibited the assimilation and translation of carbon,also accelerated the translation of nitrogen.5.Copper exerted the impact on plants by destroying the integrality of photosynthesis such as electron transfer,destruction of chloroplasts and chlorophyll.In this study,high concentrations of Cu inhibited the synthesis of chlorophyll.Copper treatment affected the chlorophyll fluorescence and photosynthetic indicators,high concentrations of copper inhibited the Fm,Fv/Fm,qP,qN.Tobacco leaf photosynthetic rate,transpiration rate and leaf surface light intensity reduced with high concentration of copper treatment.In conclusion,photosynthetic characteristics with copper treatment was better at 15 d than that at 30 d.