Boron

Synonyms: None

Symbol: B

Atomic mass: 10,811 g/mol

Element number 5 in the Periodic Table. Valence number: 3. Electronegativity: 2.0

MP= 2300 ^o C; BP= 2550 ^o C; density: 2340 kg/m³; CAS-number: 7440-42-8;

Boron is necessary for vascular plants and diatoms, in diatoms boron is a part of the cell wall which is mostly composed of silicon compounds. By insufficient boron the plant synthesis of DNA and RNA is inhibited. In vascular plants boron is a part of the cell wall structure in the form of boric acid which create intermolecular ester bonds between the polysaccharides in the cell wall (1,2). Boron is found in minerals as kernite (Na₂B₄O₇ · 4H₂O) and borax (Na₂B₄O₇ · 10H₂O).

(1) Fleischer, A., O'Neill, M.A., Ehwald, R. 1999. The pore size of non-graminaceous plant cell walls is rapidly decreased by borate ester cross-linking of the pectic polysaccharide rhamnogalacturonan II. Plant Physiology, 121:829-838; (2) O'Neill, M.A., Eberhard, S., Albersheim, P., Darvill, A.G. 2001. Requirement of borate cross-linking of cell wall rhamnogalacturonan II for Arabidopsis growth. Science. 294:846-849

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