Nutrition of Multicellular Plants - 257 



STORAGE PROBLEMS AMONG THE 

 PLANTS 



The storage of reserve organic products is 

 largely a matter of self-preservation for the 

 individual plant, although if plants had not 

 developed this capacity, much of the food 

 that supports the animal kingdom — includ- 

 ing mankind — would not be produced. The 

 individual plant accumulates organic re- 

 serves to tide it over periods when photo- 

 synthesis cannot be carried on. Among seed 

 plants, for example, the embryo cannot grow 

 independently until the seed has sprouted 

 and the new sporophyte has developed a 

 functional root, stem, and leaf system. Ac- 

 cordingly the parent plant deposits a reserve 

 of organic substances in the seed and fre- 

 quently in the surrounding fruit structures 

 as well. Deciduous plants, which shed their 

 leaves each season, also depend upon organic 

 reserves laid down during the previous year 

 in the stems or roots or both. In the spring, 

 deciduous plants use these organic reserves 

 for the matter and energy without which a 

 growth of the new foliage could not occur. 



The most abundant organic reserve in the 

 plant kingdom is starch, and the starch grains 

 of different plants display many characteristic 

 variations of size and form (Fig. 4-9). Given 

 starch — or glucose derived from starch — 

 plants can synthesize all their growth re- 

 quirements, provided inorganic salts and 

 oxygen are also available. In addition to 

 starch, some seeds contain fat globules and 

 crystals of reserve proteins in the cells of the 

 cotyledons. Reserve proteins permit the em- 

 bryo to grow more extensively prior to the 

 time when the roots develop a capacity to 

 absorb an adequate quantity of nitrates and 

 other inorganic salts. In perennial plants, 

 reserve starch is deposited mainly in the 

 colorless parenchyma: more or less equally 

 in the stem and root; or predominantly in 

 the stem, or root, depending on the species. 



ECONOMIC IMPORTANCE OF PLANT 

 PRODUCTS 



The importance of plant products, as di- 

 rect sources of man's food, and in the suste- 

 nance of animals which in turn become 

 man's food, is altogether inestimable. Plant 

 seeds (corn, wheat, oats, barley, rye, rice, and 

 a wide variety of nuts) and fruits (apples, 

 oranges, eggplant, squash, pumpkin, etc.) 

 have a world-wide cultivation and give tre- 

 mendous yields. Roots (beets, carrots, par- 

 snips, radishes, turnips, sweet potato, tapioca, 

 etc.) and stems (sugar cane, sugar maple, 

 white potato, onion, etc.), and finally leaves 

 (lettuce, spinach, artichoke, cabbage, etc.) 

 also provide a considerable quantity of man's 

 needs. Moreover, leaves, especially of the 

 grasses, provide the staple food of all man's 

 grazing livestock. 



Many other economic values of plant prod- 

 ucts can also be enumerated: (1) lumber, for 

 construction and other purposes; (2) drugs, 

 such as aconite, asafetida, and valerian (from 

 roots); quinine, cascara, and ephedrine (from 

 stems); belladonna, cocaine, and digitalis 

 (from leaves); and castor and chalmoogra 

 oils (from seeds); (3) spices and flavors, such 

 as horse-radish, sarsaparilla, and sassafras 

 (from roots); garlic and ginger (from stems); 

 sage, wintergreen, and thyme (from leaves); 

 and anise, nutmeg, and mustard (from seeds); 

 and (4) miscellaneous other products, such as 

 latex for rubber; oils, gums, resins, and tur- 

 pentine for paints, varnishes, and soaps; 

 cork for stoppers; fibers for ropes and fabrics; 

 and many other items. Man has been very 

 prodigal in his expenditure of wild plant 

 resources, especially in the ravaging of forests. 

 Only in the cultivation of many selected 

 plant species has man given a fair degree of 

 reciprocity. Under cultivation a plant is 

 assured of perpetuation, and man takes 

 only the excess of the synthesized prod- 

 ucts. 



