Saprophytism 671 



VIII. SAPROPHYTISM 



A saprophyte (sap'rofite) (Gr. sapros, dead; phyton, plant) Is an 

 organism which secretes enzymes capable of utilizing (absorbing) as foods 

 such dead organic materials as carbohydrates, proteins, etc. Saprophytism 

 differs from other similar phenomena in that two living organisms are 

 not involved but one living organism and a dead substance which may 

 have been part of a living organism originally. The enzymatic actions 

 bring about chemical changes in the dead, organic materials. When the 

 latter involves carbohydrates and is usually associated with the produc- 

 tion of gas, it is called fermentation (L. jermentum, ferment or yeast) ; 

 when it involves proteins and is manifested by the production of foul 

 odors, it is called putrefaction (L. putrere, rotten; facio, to make). 



Plants without chlorophyll cannot photosynthesize foods so must ab- 

 sorb them from outside sources, which involves the presence of a certain 

 amount of necessary moisture. Many bacteria absorb foods from dead, 

 organic substances and are called saprophytic bacteria in contrast with 

 parasitic or pathogenic bacteria. Slime molds may grow on decaying 

 plant materials, rotting woods, and leaf molds; hence, they live sapro- 

 phytically. Certain species of molds (fungi) may live on the dead organic 

 materials of plants or animals or in humus-containing soils. Saprophytic 

 fungi usually live wherever they encounter a suitable supply of organic 

 matter, oxygen, water, and warmth. Rhizopus nigricans (Fig. 36) and 

 similar molds are common saprophytes on moist bread, overripe fruits, 

 foodstuffs, animal dung, etc. Yeasts may live in sugar solutions by utiliz- 

 ing an enzyme, zymase, which they secrete. Alcohol is formed in the 

 process, with the liberation of carbon dioxide. The blue and green molds 

 (Penicillium and Aspergillus) grow on fruits, foodstuffs, tobacco, leather, 

 fabrics, nuts, and other organic materials in damp places. Mushrooms 

 and related fungi live saprophytically^ in soils, on dead leaves, dung, 

 dead wood, and bark and similar organic materials. Shelf fungi (bracket 

 fungi) are common on dead wood, although parasitic species may kill 

 living trees. 



Saprophytism is not as common in higher plants as it is in lower, non- 

 chlorophyll-bearing fungi. The Indian pipe {Monotropa) is a flowering 

 plant that lacks chlorophyll which may obtain food from decaying leaf 

 mold by the aid of fungi which inhabit its underground basal portion. 

 In some instances it may be partially parasitic on the roots of living 

 plants. 



