Der Einfluß des Bors auf verschiedenaltrige Populationen von Wolffia arrhiza (L.) Wimm, in Chemostat en-Kultur

Abstract

Summary 1. The population of Wolffia arrhiza requires boron for growth. The total absence of boron as well as an excess of boron (autotrophic cultures) result in a rapid decrease of the density of the population (mg dry substance/ml nutrient solution). 2. At lower growth rates the population density is reduced by boron deficiency (autotrophic cultivation conditions) or increased (mixotrophic cultivation conditions). In boron deficiency cultures the dry substance decreases after having exceeded the growth rate of μ = 0.010 h − 1 and the stability of the steady state is cancelled when μ is 0.015 h − 1 . 3. Boron deficiency reduces the amounts of dry substance and protein; on the other hand the amounts of carbohydrate, respiration rates and photosynthesis are increased. With increasing growth rates (transition from relatively old to relatively young populations) the decrease of dry susbtance as well as the enhancement of carbohydrate and respiration are further intensified. The amount of chlorophyll may be reduced. 4. Results of investigations with inhibitors show that with boron deficiency the relation of glycolysis/pentose shunt pathway will be changed in favour of the latter. Furthermore it is supposed that a phenoloxidase system is involved in the respiration of boron deficiency plants and that the capacity of phosphorylation is diminished.