ALBERT

Description: Scientific research concerning growth inhibitors, which has been pursued for several decades already, dealt mainly with the effect of these substances on the germination process. WIESNER (1894) demonstrated the presence of a growth inhibitor in the slime of the mistletoe (Viscum album) which prevented the germination of a great variety of seeds. OPPENHEIMER (1922) supplemented the analysis by placing seeds on the pulp of ripe tomatoes and he observed a strong inhibitive effect as a result of this treatment. In addition, however, he found that the inhibiting substance is thermolabile and insoluble in ether or alcohol. REINHARD (1933) corroborated Oppenheimer’s results for the most part. According to this author, however, the inhibiting agent in tomato juice is thermostabile, and it is not destroyed by boiling, neiher by neutralisation or by diluting the juice 50 times. In other fleshy fruits such as apples, pears and quinces KÖCKEMANN (1934) detected inhibiting substances capable of preventing the germination of Lepidium seeds. These substances were reported to be sensitive to peroxide and to alkali, thermostabile and soluble in water and in ether, but insoluble in petroleum ether. On the other hand, the inhibiting agent extracted by LEHMANN (1937) from the exocarp if buckwheat is thermolabile. In Helianthus annuus and Avena sativa, finally, RUGE (1939) demonstrated the presence of an inhibitor that reduces the speed of germination to a considerable extent. FRÖSCHEL’S investigations on Trifolium and Beta will be dealt with in 4. This survey is not quite exhaustive, but clearly demonstrates that the inhibiting agent should not be regarded as a definite, well-defined chemical substance which is always the same in every individual case, but as a group of substances with analogous activities but most probably with widely divergent physical and chemical properties. Following KÖCKEMANN (1934) we can classify the inhibiting substances into two groups, as follows : 1. inhibiting substances in the testa or in the seed, and 2. inhibiting substances in the mesocarp of pulpy fruits.

Description: Scientific research concerning growth inhibitors, which has been pursued for several decades already, dealt mainly with the effect of these substances on the germination process. WIESNER (1894) demonstrated the presence of a growth inhibitor in the slime of the mistletoe (Viscum album) which prevented the germination of a great variety of seeds. OPPENHEIMER (1922) supplemented the analysis by placing seeds on the pulp of ripe tomatoes and he observed a strong inhibitive effect as a result of this treatment. In addition, however, he found that the inhibiting substance is thermolabile and insoluble in ether or alcohol. REINHARD (1933) corroborated Oppenheimer\xe2\x80\x99s results for the most part. According to this author, however, the inhibiting agent in tomato juice is thermostabile, and it is not destroyed by boiling, neiher by neutralisation or by diluting the juice 50 times. In other fleshy fruits such as apples, pears and quinces K\xc3\x96CKEMANN (1934) detected inhibiting substances capable of preventing the germination of Lepidium seeds. These substances were reported to be sensitive to peroxide and to alkali, thermostabile and soluble in water and in ether, but insoluble in petroleum ether. On the other hand, the inhibiting agent extracted by LEHMANN (1937) from the exocarp if buckwheat is thermolabile. In Helianthus annuus and Avena sativa, finally, RUGE (1939) demonstrated the presence of an inhibitor that reduces the speed of germination to a considerable extent. FR\xc3\x96SCHEL\xe2\x80\x99S investigations on Trifolium and Beta will be dealt with in 4.\nThis survey is not quite exhaustive, but clearly demonstrates that the inhibiting agent should not be regarded as a definite, well-defined chemical substance which is always the same in every individual case, but as a group of substances with analogous activities but most probably with widely divergent physical and chemical properties. Following K\xc3\x96CKEMANN (1934) we can classify the inhibiting substances into two groups, as follows : 1. inhibiting substances in the testa or in the seed, and 2. inhibiting substances in the mesocarp of pulpy fruits.

Description: Whereas scientific research on inhibiting substances has mainly occupied itself with the effect of these substances on the germination process, I was able to demonstrate the presence of a root-inhibiting agent during my studies on root formation in Fuchsia hybrida and Pelargonium zonale (Stolk, 1952). In connection with this previous investigation I tried to find out whether a similar substance is present as well in bulbous plants and, by doing so, as a suitable species for my experiments the Liliaceous Allium Cepa was selected. My principal object was to corroborate and, if possible, extend the results obtained with Fuchsia and Pelargonium. A confirmation appeared highly desirable because the experiments with Fuchsia and Pelargonium could not possibly be very accurate on account of the direct method of measuring and that is why I used in my experiments with Allium a root-auxanometer which will be described in the following section.\nSubstances retarding germination were demonstrated in the slime of Viscum album by WIESNER (1894), in the fruit pulp of ripe tomatoes by OPPENHEIMER (1922), in tomato juice by REINHARD (1933), in other pulpy fruits such as apples, pears, quinces and tomatoes by K\xc3\x96CKEMANN (1934), in the exocarp of buckwheat by LEHMANN (1937), in the fruits of Helianthus annuus and Avena sativa by RUGE (1939) and in Beta by FR\xc3\x96SCHEL (1939, 1940). That not one and the same inhibitor is involved, is evident from the fact that the above-mentioned authors found differences between the inhibiting substances they studied in their behaviour towards high temperatures. The inhibiting substances found by OPPENHEIMER and LEHMANN, for instance, are thermolabile. those discovered by REINHARD, K\xc3\x96CKEMANN and FR\xc3\x96SCHEL thermostabile. Also in their chemical behaviour certain differences can be demonstrated. Whereas the substance studied by K\xc3\x96CKEMANN is soluble in ether, this is not the case with the inhibiting substance found by OPPENHEIMER in tomatoes.

Description: The problem of the retardation of the processes of growth and differentiation is certainly as important as the processes of growth and differentiation themselves. It is striking, therefore, that whereas the analysis of growth has been carried out for a considerable period of time already, the analysis of inhibition was only commenced a few decades ago. It has to be admitted that Wiesner (1894) succeeded in demonstrating the presence of a substance retarding germination in the slime of the mistletoe (Viscum album), but this remained a solitary observation for some time.\nAbout 1920 a series of important publications appeared which deal with inhibiting substances. Oppenheimer (1922) discovered a substance of this kind in the fruit pulp of ripe tomatoes, Reinhard (1933) found one in tomato juice, K\xc3\xb6ckemann (1934) some in other pulpy fruits such as apples, pears, quinces and tomatoes, Lehmann (1937) one in the exocarp of buckwheat, Ruge (1939) some in the fruits of Helianthus annuus and Avena sativa, Fr\xc3\xb6schel (1939, 1940) one in Beta, Stolk (1952, 1953a) some in the roots of Fuchsia hybrida and Pelargonium zonale and in the roots of Allium Cepa.