VII. High-nutrient conditions
Some CPs may reduce their growth and even die when grown in nutrient enriched soils (see Juniper et al., 1989, p. 134). Dionaea muscipula grew very poorly in a conventional clay-loam garden soil (Roberts and Oosting, 1958). The leathery leaves did not develop traps and flowering was greatly reduced. After 5 months, most plants were dead. Similarly, when grown in a fertilized greenhouse potting soil, roots of Dionaea were atrophied, no new roots formed, and plants died within 70 days. In another experiment, the growth of Dionaea in a sand culture with mineral nutrient solution was poor; plants declined in weight, and died after about 3 months, while the controls watered with distilled water grew much better. The insect- or protein-fed plants showed more vigorous growth than the controls. As follows Dionaea is very susceptible to higher soil nutrient level and its root growth is suppressed in heavier soils (cf. Adamec et al., 1992). Eleuterius and Jones (1969) studied the growth of Sarracenia alata in a southern Mississippi bog and found a growth decrease in fertilized bog soil (seasonal supply of 37.1 g N.m-2 and 5.9 g P.m-2; cf. Stewart and Nilsen, 1992; chapter VI.). Possible negative effects of nutrient-rich soils on the growth of Nepenthes were discussed by Juniper et al. (1989, p. 134).
These findings demonstrate that higher nutrient levels in soils may inhibit growth of some CPs (mainly root growth). Due to shortage of data, it is not clear whether this effect is confined only to some species or whether it is an extreme consequence of the above stated competition between root and leaf nutrient conditions (sensu Chandler and Anderson, 1976a) or of an unsuitable pH (cf. Rychnovská-Soudková, 1953, 1954). However, many CP species including Dionaea may grow vigorously in rather concentrated nutrient solutions (e.g. Small et al., 1977; Simola, 1978; Aldenius et al., 1983) and are generally able to tolerate these conditions. On the other hand, CPs growing in nutrient solutions in vitro lose some features of carnivory. For example, in-vitro grown D. capillaris formed non-functional tentacles, while Dionaea formed immobile leaf lobes (Adamec, unpubl.). Thus, the development of carnivory is partly blocked under high-nutrient conditions.