Seed storage compound

Tab. 3.1 M ain seed storage compounds (percentages) of different crop species...

Morrison WR. In Shewry PR, Stobart AK, eds. Seed Storage Compounds Biosynthesis, Interactions and Manipulation. Oxford, UK Oxford University Press 1993. 

Shewry, PR. Biological and evolutionary aspects of cereal seed storage proteins. In Shewry, PR. and Stobart, K. (Eds.), Seed Storage Compounds Biosynthesis, Interactions, and Manipulations, Clarendon Press, Oxford, U.K., 1993. 

Many organisms can store orthophosphate or polyphosphates. In plants, inositol hexaphos-phate (IHP) can form a major storage compound for phosphorus, particularly in seeds. Although relatively low in concentration, diesters may contribute to short-term bioavail-able pool more than monoesters. Compared to monoesters, diesters are more accessible to microbial attack. This fraction was shown to be rapidly made available to plants. 

If the thousands of glucose units are linked by alpha 1-4 bonds, that molecule is called starch. Plants use starch as their primary storage compound, and all of our common food seeds—corn, wheat, barley, oats, etc.—are really just packages of starch. A smaller version of this glucose polymer also occurs in animals as the energy-storage molecule called glycogen. 

Phytic acid, myo-inositol hexakis (dIhydrogen phosphate), as-l,2,3,S-tnns-4,6-cyclohexanehexol-hexaphosphate a major phosphate storage compound in plants, which is especially abundant in oil seeds, legumes and cereal grains. It is the hexaphosphate of A/yo-inositol (see), in which each OH-group of myoinositol is esterified with phosphoric acid. Calcium and magnesium salts of P.a. are known as phytin. The commercial preparation of myo-inositol involves extraction of P. a. from com (maize) steep liquor, hydrolysis of the P.a. to myo-inositol and inorganic phosphate, and crystallization of the myo-inositol from water. 

Very recently, a distinct but similar class of oleosin-like proteins also containing the characteristic central hydrophobic domain has been found in the pollen of rapeseed and corresponding genes have been isolated from both rapeseed and Arabidopsis [1]. Like seeds, pollen cells are propagules which carry their own storage compounds which are required to support their metabolism after germination. In the case of rapeseed and Arabidopsis, Ae seeds and pollen each contain oil bodies and are desiccation tolerant [Ij. This established a correlation between desiccation tolerance and the presence of oil body proteins in both gametophytic and sporophytic plant tissues. 

Polysaccharides have various functions. In plants they serve both as structural support (example cellulose, the polysaccharide present in the greatest amount by far) and as storage compounds in seeds and tubers (starch). In animals they rarely serve as structural substances (cellulose is found only in tunicates chitin occurs in insects and crabs). Glycogen is accumulated by animals as a storage substance. 

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