UPTAKE AND TRANSLOCATION OF PREY-DERIVED N-15 AND P-32 IN UTRICULARIA-VULGARIS L

The rootless submerged carnivorous hydrophyte Utricularia vulgaris L. is a potentially useful subject for the quantitative study of foliar nutrient uptake and use, because known quantities of nutrients can be supplied precisely to individual leaves. We report here results obtained by hand-feeding prey labelled with N-15 and P-32 to leaves of known age in plants growing in near-natural conditions. Prey-derived N-15 was rapidly taken up and translocated: in plants fed via 3-d-old leaves, about 30% of the prey N-15 appeared in the immature parts of the plant within 2 d. Almost all parts of the plant that were immature at the time of feeding received and retained prey N-15 throughout the 20 d experiment. Some backward translocation of N-15 was observed, but only up to the second day after feeding. P-32 was also taken up and translocated rapidly, but was not retained by young tissues after they had become mature. Backward translocation of P-32 was observed into side-shoot meristems and flowers arising on parts of the plant older than the fed leaves. This is in contrast to N-15 uptake, where side-shoot buds and flowers received labelled nitrogen only if they arose on parts of the plant younger than the fed leaves.