Abstract
Leaves cut from cucumber seedlings (0.7 leaf-stage) grown in the greenhouse, at 2:00PM on a fine day (Feb. 1987), contained fructose (3.38mM), glucose (3.25mM) and sucrose (10.19mM). When these seedlings were placed in a dark room for 24hr, no carbohydrates were detected (carbohydrate free) in their leaves. Leaves of carbohydrate free cucumber seedlings, which were soaked in 2% sucrose solution for a subsequent 24hr in the dark, contained 1.6mM sucrose. Sucrose (4.5mM), fructose (17.6mM) and glucose (15.0mM) were detected in them 48hr after soaking. For cucumber leaves placed in the greenhouse, Sphaerotheca fuliginea (Schlecht.) Pollacci elongate hyphae 1592.9μm in length (48hr), formed 64.8 haustoria (96hr), and 74.3 conidiophores per mm2 (7 days) after inoculation, respectively. For leaves of carbohydrate free cucumber, S. fuliginea elongated the hyphae to 71.4μm in length, and formed the first haustorium under the germ tube 24hr after inoculation. However, further development of the fungus was arrested completely. On the other hand, the fungus developed further on the carbohydrate free cucumber leaves, which were soaked in 0.5, 1.0, 2.0 and 4.0 sucrose solutions in the dark, and formed 12.8, 21.6, 72.6 and 82.8 conidiophores per mm2 7 days after inoculation, respectively.
