Genetically modified plant cell, characterised in that it exhibits increased activity in a P-glucan-water-dikinase protein, in comparison to corresponding wild type plant cells that have not been genetically modified, wherein the genetic modification consists of the introduction of at least one foreign nucleic acid molecule into the genome of the plant and wherein the foreign nucleic acid molecule is chosen from the group consisting of: a) Nucleic acid molecules, which code a protein with the amino acid sequence given under SEQ ID NO 2 or SEQ ID NO 4; b) Nucleic acid molecules, which code a protein, which includes the amino acid sequence, which is coded by the insertion in plasmid DSM16264 or the insertion in plasmid DSM16302; c) Nucleic acid molecules, which code a protein, the sequence of which has an identity of at least 60% with the amino acid sequence given under SEQ ID NO 2 or SEQ ID NO 4; d) Nucleic acid molecules, which code a protein, the sequence of which has an identity of at least 60% with the amino acid sequence, which is coded by the coding region of the insertion in plasmid DSM16264 or by the coding region of the insertion in plasmid DSM16302; e) Nucleic acid molecules, which include the nucleotide sequence shown under SEQ ID NO 1 or SEQ ID NO 3 or a complimentary sequence; f) Nucleic acid molecules, which include the nucleotide sequence of the insertion contained in plasmid DSM16264 or plasmid DSM16302; g) Nucleic acid molecules, which have an identity of at least 60% with the nucleic acid sequences described under a), b), e) or f); h) Nucleic acid molecules, which hybridise with at least one strand of the nucleic acid molecules described under a), b), d), e) or f) under stringent conditions; i) Nucleic acid molecules, the nucleotide sequence of which deviates from the sequence of the nucleic acid molecules identified under a), b), e) or f) due to the degeneration of the genetic code; and j) Nucleic acid molecules, which represent fragments, allelic variants and/or derivatives of the nucleic acid molecules identified under a), b), c), d), e), f), g), h) or i). a) Nucleic acid molecules, which code a protein with the amino acid sequence given under SEQ ID NO 2 or SEQ ID NO 4; b) Nucleic acid molecules, which code a protein, which includes the amino acid sequence, which is coded by the insertion in plasmid DSM16264 or the insertion in plasmid DSM16302; c) Nucleic acid molecules, which code a protein, the sequence of which has an identity of at least 60% with the amino acid sequence given under SEQ ID NO 2 or SEQ ID NO 4; d) Nucleic acid molecules, which code a protein, the sequence of which has an identity of at least 60% with the amino acid sequence, which is coded by the coding region of the insertion in plasmid DSM16264 or by the coding region of the insertion in plasmid DSM16302; e) Nucleic acid molecules, which include the nucleotide sequence shown under SEQ ID NO 1 or SEQ ID NO 3 or a complimentary sequence; f) Nucleic acid molecules, which include the nucleotide sequence of the insertion contained in plasmid DSM16264 or plasmid DSM16302; g) Nucleic acid molecules, which have an identity of at least 60% with the nucleic acid sequences described under a), b), e) or f); h) Nucleic acid molecules, which hybridise with at least one strand of the nucleic acid molecules described under a), b), d), e) or f) under stringent conditions; i) Nucleic acid molecules, the nucleotide sequence of which deviates from the sequence of the nucleic acid molecules identified under a), b), e) or f) due to the degeneration of the genetic code; and j) Nucleic acid molecules, which represent fragments, allelic variants and/or derivatives of the nucleic acid molecules identified under a), b), c), d), e), f), g), h) or i).