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Study on the Mechanism of Nitric Oxide Promoted Maize Seed Germination and Seedling Growth under Salt Stress

Author: TangJing
Tutor: LiuXin;LiuHongQing;ZhaoFangGui;Liu(?)Yao
School: Qingdao Agricultural University
Course: Biochemistry and Molecular Biology
Keywords: nitric oxide salt stress maize seed maize seedling hormone signal
CLC: S513
Type: Master's thesis
Year: 2008
Downloads: 329
Quote: 2
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Abstract


Maize (Zea mays L.) was used to study the mechanism of maize seed germination and seedling growth promoted by NO under salt stress. The results showed that the inhibition of seed germination by 150 mmol/L NaCl could be obviously relieved by 0.001-1.0 mmol/L sodium nitroprusside (SNP) and optimum SNP concentration was 0.1 mmol/L. 0.1 mmol/L SNP could significantly increase seed germination rate, promote growth of embryo and radicle, form fibrous root and enhance radicle vigour under salt stress. 0.1 mmol/L SNP could enhance amylases activity (α-amylase,β-amylase and amylase) under salt stress. This may be one of the reasons for SNP promoted seed germination and influenced seedling growth in the late. Using extracellular dissociation Ca2+ chelant EGTA, in combination with blocker of plasma membrane Ca2+ channels LaCl3 and inhibitor of vacuole Ca2+ release ruthenium red to studied if Ca2+ was involved in the signal transduction pathway of SNP promoted maize seed germination under salt stress. The result showed extracellular Ca2+, inward flow of extracellular Ca2+ and intracellular Ca2+ release were involved in the regulation of SNP promoted maize seed germination under salt stress.The maize seedlings at the stage of three mature leaves and one new leaf were treated with 150 mmol/L NaCl. The results showed that SNP could promote seedling growth, root elongation and fibrous root formation and increase the content of IAA and GA in leaves and root tips of maize seedling under salt stress. NO synthesis inhibitor L-NAME and NaN3 and NO scavenger cPTIO can weaken the increase of IAA and GA concent induced by SNP treatment. It indicated that NO participated in regulating the accumulation of IAA and GA under salt stress. Furthermore, it exhibited negative interaction between the indoleacetic acid oxidase (IOD) and peroxidase (POD) activities and the IAA content. IOD and POD are important factors that involved in the regulation of IAA content in plants. SNP could indirectly control the IAA level by regulating the activities of IOD and POD. In the early period of salt stress, the iPA content was decreased in response to salt stress, but when treated with SNP, the iPA content was increased. When treated with NO production inhibitors L-NAME and NaN3 and NO scavenger cPTIO, the iPA accumulation were lowered. But this result showed that a long-term salt stress could induce iPA accumulation. It was presumed that NO was involved in the regulation of growth related hormone accumulation in maize seedling to improve the salt resistance.In order to prove the mechanism of NO accumulation and signal transduction pathway in plants under salt stress, this article studied the content of endogenesis NO, the activities of NR and NOS, effects of L-NAME and NaN3 on the content of endogenesis NO in maize seedling under salt stress. The NO distribution and content in root of maize seedling was detected by Confocal. The effect of salt stress on the activity of NO receptor ACO was detected too. The results indicated that the content of endogenesis NO in maize seedling leaves and root tips were increased in response to salt stress, so was the activity of NOS, but was not that of NR. The effect of L-NAME on the NO content was more significant than that of NaN3, so NOS-dependent NO production is associated with salt tolerance in maize seedling. NO was distributed mainly in the root epidermis and hairs. The content of NO in maize seedlings treated with L-NAME decreased more significantly than those treated with NaN3. From these results, it was deduced that the production of endogenesis NO in root of maize seedling was mainly due to the improvement of NOS activity. The activity of ACO decreased rapidly in a very short time, this result showed that ACO could play a role as receptor in response to the change of the NO content.

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CLC: > Agricultural Sciences > Crop > Cereal crops > Corn ( maize )
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