Lipid-Storing Seeds

Development of the reserves in fat-storing seeds has been approached experimentally from two main standpoints (1) to elucidate the pathway of fatty acid biosynthesis and (2) to measure the accumulation of fat and dry matter and analyze it for fatty acid content. 

---

In the early stages of development of soybean seeds the lipid is virtually devoid of triglyceride and the main constituents are phospholipids and glycoli-pids. From the 9th day after flowering triglycerides are rapidly synthesized, coinciding with the onset of deposition of the lipid stores. Phospholipid synthesis continues throughout the period of deposition but at a low rate [144]. 

Plant lipases breakdown of stored lipids in seeds is aided by the formation of a specialized organelle, the glyoxysome... 

Oleosomes — Also called oil bodies, oleosomes are the natural equivalents of liposomes. They are found in plant seeds or fruits, filled with oils, pigments, and vitamins, and serve as specific organelles to store lipid molecules. A protocol to... 

The final extract after evaporation may be partitioned with hexane in a separatory funnel to remove chlorophyll, lipids, carotenoids, and other fat-soluble materials (e.g., in avocado, olives, seeds), if considerable amounts of these compounds are present. However, possible loss of lipophilic polyphenolics should be checked. Performing the liquid-liquid extraction after the evaporation of solvent may reduce the amount of hexane required. The extract should be flushed with nitrogen gas and stored in the... 

Cellulose, the most abundant polysaccharide, is the structural component of plant tissues starch is the energy compound stored predominantly in seeds and tubers glycogen is the animal counterpart of starch, but with shorter, more numerous branches. Cellulose and starch cohabit plant tissues with hemicellulose, protoplasm, lipid, and mineral matter in an organization interrupted by intercellular spaces that can amount to more than 50% of the total volume of some fruits and vegetables. A number of useful polysaccharides and their origins are listed in Table I. 

Lipids occur in cell walls, cellular cytoplasm, and in fat storage cells in animals. In contrast, specialized fat storage cells per se do not exist in plants or seeds. Rather, fatty acids are found in surface waxes that reduce the loss of moisture from leaves, stems, fruits, and seeds of plants in seed cell walls and cytoplasm and as stored triacylglycerols in dispersed spherical organelles in cells of seed embryos (48). 

Many lipids are essential to good human health. Some of them serve as chemical messengers in the body. Others serve as ways to store chemical energy. There is a good reason that babies are born with baby fat. Seeds contain lipids for the storage of energy. People living in Arctic zones seek fatty foods in their diet. 

Researchers were also able to establish the link between declines of other predatory species such as the European sparrowhawk and the use of organo-chlorine pesticides other than DDT. For instance, the cyclodiene insecticides aldrin, dieldrin, and he-ptachlor used as seed treatments caused massive mortality of both seed-eating species and their predators. All of the insecticides had the following points in common they were highly soluble in fats and refractory to metabolism. The impacts on the predatory species typically take place in periods of food stress when fat soluble residues are released from fat stores and returned into general circulation. In a food-stressed individual, the brain remains as the most lipid rich tissue and this is where contaminants move to. Toxicity results when threshold values in brain tissue are exceeded. At sublethal levels, documented effects of cyclodiene insecticides in birds have included changes in their reproductive, social, and avoidance behaviors. 

Plant seeds contain glyoxisomes, small organelles that oxidize stored lipids as a source of carbon and energy for growth. They are similar to peroxisomes and contain many of the same types of enzymes as well as additional ones used to convert fatty acids Into glucose precursors. I... 

---