Regulating Mechanism Of Exogenous Salicylic Acid On Copper Resistance In Nicotiana Tabacum

Now it is very important to find an effective and convenient way to alleviate Cu toxicity and to improve plant tolerance to copper. First of all, Nicotiana tabacum cv. W38 (Cu resistance genotype) and Nicotiana benthamiana (Cu sensitive genotype) were selected as material. We determined the growth characteristic, root activity, membrane permeability and antioxidant system to reveal the tolerance to Cu of the two tobacco cultivars. In addition, A culture experiment was conducted to study the effects of different SA concentrations on carbon metabolism and elements absorption and transportation under copper stress. The second, we selected Nicotiana benthamiana to solve the problem, studying the effects of different SA concentration on ascorbate-glutathione cycle of Nicotiana benthamiana under copper stress. The results were summarized as followings:1. A solution culture experiment was conducted to study the effects of different copper concentration on the growth characteristic, root activity, membrane permeability and antioxidant system of two tobacco cultivars. The result showed that:With increasing concentration of copper processing, root length, plant height, fresh weight, root activity, catalase (CAT), superoxide dismutase (SOD) and catalase (POD) of two tobacco cultivars were first increased and then decreased. The values of membrane permeability were first decreased and then increased. It showed low concentrations of copper stimulated the growth of tobaccos, while high concentrations of copper inhibited tobaccos’growth. With the increase of the concentration of copper processing, the content of proline (Pro) and malondialdehyde (MDA) showed a rising trend.2. To study the effects of different SA concentration on carbon metabolism of two tobacco cultivars under copper stress. The result showed that:The tobacco Seedlings under 4 mg/L Cu Stress for 15 days, the Chi a, Chi b, glucose, fructose, sucrose content and SPS, SS, amylase activity were significantly decreased (p<0.05) of the two tobacco cultivars. The starch content ratio changed in the opposite trend, indicating the differences of the two tobacco cultivars in Cu tolerance. The amylase, AI, NI activity increased. Spraying suitable concentration of SA could improve the content of Chi a, Chi b, glucose, fructose, sucrose and the activity of amylase, AI, NI and reduce the starch content and the activity of AI, NI.300μmol/L was the optimal concentration of exogenous SA to relieve Cu stress of the two tobacco cultivars. SA could alleviate the effect of Cu stress, but it could not eliminate the inhibitory effect of Cu stress on the growth of tobacco, while high concentration of SA might even produce a new stress affection of tobacco.3. To study the effects of different SA concentration on tobacco charaterristics, elements absorption and transportation of different organs of two tobacco cultivars, under copper stress. The result showed that:The tobacco under 4 mg/L Cu Stress for 15 days, the growth of two tobacco were inhibited to some extent, Cu content was increased, and the absorption and transportation of K、Ca、Mg、Fe、Zn、B、Mn were inhibited. The addition of exogenous SA can alleviate copper toxicity to some extent, the inhibition of plant height, root length and fresh weight were alleviated, the Cu content of tobacco decreased and the absorption of nutritional elements K、Ca、Mg、Fe、Mn were promoted, but the influence on Zn、B element was nor obvious.4. The result of exogenous SA on ascorbate-glutathione cycle of Nicotiana benthamiana under copper stress showed that:The Nicotiana benthamiana seedlings under 4 mg/L Cu Stress for 15 days, the malondialdehyde (MDA), super hydrogen (H2O2) content and the ascorbate peroxidase (APX), glutathione reductase (GR) activity were significantly increased (p<0.05). The ascorbate (AsA), glutathione (GSH) content, the dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) activity and the expression of Nicotiana benthamiana monodehy droascorbate reductase (NbDHAR) gene changed in the opposite trend. Meanwhile, adding suitable suitable concentration of SA could promoted the contend of AsA, GSH and the activities of APX, GR, DHAR, MDHAR and the expression of NbDHAR gene. SA could alleviate the effect of Cu stress to Nicotiana benthamiana.