High external Pi could reduce the fold of induction of GmSOS1 and GmCNGC by salinity stress, while posses no effect on other gene candidates. The possible effects on the repression of GmSOS1 and GmCNGC by high external Pi were discussed according to the current understandings on their roles in the salt stress responses. / In this study, phenotypical, physiological, cellular and molecular investigations were carried out to delineate the interactive effects of salinity and external Pi in "Pi tolerant" soybeans. The ultimate goals are to provide essential scientific background for practicing soybean cultivation in saline lands and to explore the possibility to improve the salt tolerance together with P-deficiency tolerance of soybeans. / It was found that high external Pi could reduce the salt tolerance capability of 15 "Pi tolerant" soybean germplasms. Such detrimental effect was common among soybeans, regardless of the type (cultivated versus wild), the salt tolerant capability in optimum Pi level, and the sensitivity to Pi level (Pi tolerant versus Pi sensitive). / Salinity is a major abiotic stress significantly reducing crop yield. Moreover, high salinity in soil is usually accompanied with deficiency of available phosphorus (P). Supplementation of inorganic phosphate (Pi) could be an agricultural strategy to enhance crop production on saline lands. However, ionic components in soil often interact to each other to affect the final growth performance of plants. / Soybean is an important crop that is sensitive to both high salinity and P deficiency in soil. Based mainly on the studies using "Pi sensitive" soybean cultivars, physiological investigations concluded that high external Pi could reduce the salt tolerance via excessive accumulation of P and chloride in the foliar tissues. "Pi tolerant" and "Pi sensitive" are relative terms to describe the response of a soybean cultivar to 1.6mM Pi when grown in non-saline nutrient solutions. The "Pi sensitive" cultivars developed a reddish-brown discoloration on their leaves and exhibited retarded growth. By contrast, the "Pi tolerant" cultivars thrived under high Pi supplements. / The physiological mechanism underlining such interaction in "Pi tolerant" soybeans was distinct from that in "Pi sensitive" cultivars. At the in planta level, high level of external Pi external Pi diminished when de-rooted plants were used, suggesting that the root is the primary organ interacting with Pi in the growth medium. Two cell models, including soybean suspension cells and the tobacco Bright-Yellow-2 cell line, were also employed to study the effects of high external Pi at the cellular level. Consistent to the results using the whole plant, high external Pi uplifted cellular sodium ion uptake and reduced cell viability under salinity stress. / To identify the possible molecular targets of high external Pi, the expression of 12 gene candidates in roots of "Pi tolerant" soybean was investigated in response to NaCl stress supplemented with 0.2mM Pi or 2mM Pi. The putative functions of these gene candidates are involved in: (a) Na+ and/or K+ transportation (GmSOS1, GmNHX; GmGLR3, GmCNGC, GmNKCC and GmAKT1); (b) regulation of ion homeostasis (GmSAL1, GmCIPK1 and GmSCA1); and (c) energetic system for the operation of ion transporters (GmAHA1, GmVHA-C and GmVP1). / Phang, Tsui Hung. / "June 2008." / Adviser: Lam Hon Ming. / Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1525. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 132-157). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344176 |
| Date | January 2008 |
| Contributors | Phang, Tsui Hung., Chinese University of Hong Kong Graduate School. Division of Biology. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xx, 175 p. : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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