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\hypersetup{pdftitle={Modelling Concepts for Sodium and Potassium Uptake in Rice Plants as a Function of Transpiration},pdfauthor={Uday Sankar Das},pdfsubject={Tropentag 2010: Abstract},pdfkeywords={Genotype, modelling, transpiration},pdfpagemode=None,colorlinks=true}
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\parbox[b]{13.4cm}{\centering \large{\textbf{Tropentag, September 14-16, 2010, Zurich}}\\[1ex] \Large{``World Food System  ---\\A Contribution from Europe''\\[2ex]}}
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\Large{\textbf{Modelling Concepts for Sodium and Potassium Uptake in Rice Plants as a Function of Transpiration\footnote{\textbf{Contact Address:} Uday Sankar Das, Urban Development Directorate, Department of Urban Development, 82. Segunbagicha, 1000~Dhaka, Bangladesh, \mbox{e-mail}: \email{uday2104@yahoo.com}}\\[0.8ex]}}
\normalsize{\textsc{Uday Sankar Das}}
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\item[]{\small{\textit{Urban Development Directorate, Department of Urban Development, Bangladesh}}}
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\index[author]{Das, Uday Sankar}
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\textbf{Abstract}
\begin{abstract}
\normalsize{
Models can be used to study and understand plant physiological processes. In order to understand the traits enabling resistance to salt models are needed to simulate sodium uptake and distribution in the rice plant. Sodium uptake in rice is transpiration driven, therefore this model must be able to simulate the transpirational behaviour of the plant. Transpiration occurs on the leaf blades, therefore the model must be able to predict the number and sizes of leaves, particularly leaf blades. Any changes in this, due to a stress the model should reflect in order to predict the actual amount of sodium that can be taken up to the plant. This study was conducted to develop: \textbf{(1)}~a mathematical description of leaf appearance in irrigated rice as affected by salinity \textbf{(2)}~a concept to describe leaf development and leaf senescence level for different leaves \textbf{(3)}~calculate water loss from individual leaves \textbf{(4)}~a mathematical description of the physiological activity level of different leaves during their entire life span \textbf{(5)}~concept for sodium and potassium uptake and distribution as related to the transpiration of the particular leaf. Leaf appearance pattern was hastened under salt stress compared to control conditions but in the same environment genotypes did not differ. Leaf development stages were defined, ranging from -1 (leaf initiation) over 0 (full extension) to +1 (\mbox{100\,\%} senescence). Under salinity leaf development covered from control conditions and among genotypes. The concept of leaf senescence as a driving force for leaf appearance seemed to be present independent of treatment and genotypic. Sodium uptake was linearly related to water loss. The tolerant genotype accumulated less sodium per unit of water that was lost from the sensitive genotype. Tissue level tolerance to and the distribution of sodium in the plant seemed to be depending on the respective potassium concentration of the tissue. Leaf sheaths retained more sodium when more potassium was present and leaf senescence rate was less when potassium concentrations in the leaf blades were high. A concept of transpiration driven sodium and active potassium uptake and distribution is included in the model structure. 







}

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\noindent \textbf{Keywords:} Genotype, modelling, transpiration
\index[key]{Genotype}
\index[key]{Modelling}
\index[key]{Transpiration}
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