|MadSci Network: Botany|
Seeds typically contain large amounts of reserve molecules, and in particular proteins, starches, and lipids. These reserve molecules are broken down (hydrolyzed) to simpler molecules (e.g. amino acids, glucose, fatty acids) during germination and early seedling growth. These molecules supply the seedling with the materials needed for growth until it becomes and established photosynthesizing plant. The same is true for other molecules of chemical groups needed for growth. In the case of phosphorus (needed for nucleic acids, nucleotides, and phospholipids), the reserve molecule is generally phytic acid - a hexaphosphate of myo-inositol. The phytic acid is hydrolyzed by phosphatase (yes, I finally got to your question!) to give myoinositol (which is useful for a number of things, and phosphate ion. One possibility for why you find different amounts of phosphatase activity in different species of seeds because they may have different requirements, either in terms of how rapidly they must break down the phytate, or how much phytate is in the seed. Do you find any correlation between the level of phosphatse activity, and how rapidly the seed germinates or the seedling grows? Another possibility is that the difference is artifactual. The phosphatase from different species may have different pH or buffer composition optima. If you only use one standardized system, you may not detect the maximal level of activity in each seed species.
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