Measuring investment in carnivory: seasonal and individual variation in trap number and biomass in Utricularia vulgaris L.

Abstract

SUMMARYThe partitioning of biomass between traps and leaves is a measure of the investment in carnivory of Utricularia vulgaris and is dependent on the relative values of three attributes: trap size, trap number and leaf size.Marked seasonal and individual variations in trap size, trap number and leaf size occur within a small population of U. vulgaris at Wicken Fen, Cambridgeshire, UK, with some plants consistently having fewer traps per leaf than others, and some smaller leaves than others, throughout the growing season. However, the three attributes vary independently, so that all combinations over the observed ranges of trap size, trap number and leaf size occur simultaneously in the population.In spite of the variation in the three constituent factors, the proportion of biomass invested in traps is close to 50"o in the majority of plants and throughout most of the growing season. The contribution of traps to total biomass cannot be predicted from the number of traps per leaf.Although the proportion of biomass represented by traps is the most useful measure of a plant's investment in carnivory, the precise way in which the biomass is partitioned between a variable number of traps of different sizes may also be an important consideration in cost-benefit analyses.

Field growth characteristics of two aquatic carnivorous plants,Aldrovanda vesiculosa andUtricularia australis

“…Shoot growth (extension) rates recorded in the present paper (Fig. 2) are comparable with other published values for Aldrovanda or Utricularia vulgaris (FRIDAY 1989, 1992, KOMIYA & SHIBATA 1998, ADAMEC 2000. The considerable variation in biomass doubling times between enclosures (Aldrovanda 8.4-21.5 days, Utricularia 9.1-33.2 days; Table 3) could still be partly due to differences between initial plant biomasses.…”

Phagotrophy in phototrophs

“…Here the individual traps on a plant are the functional equivalent of individual cells with their single phagotrophic apparatus in protistan phagotrophic phototrophs. The allocation to traps in the aquatic species of Utricularia can amount to 50% of the biomass, with a considerable variation in volume (25-fold) of individual traps on the same plant (Friday 1991(Friday , 1992. Contradicting initial expectations, Knight and Frost (1991) showed that Utricularia produced more traps when the nutrient concentration in lake water was higher.…”

Uptake and translocation of prey‐derived 15N and 32P in Utricularia vulgaris L.

“…Each axis produces alternate, finely divided, four-lobed leaves (Taylor, 1989) in a linear age sequence. Each leaf bears a cohort of 30-150 suction traps, ranging in size from about 1 mm to more than 5 mm in length (Friday, 1991(Friday, , 1992. The plants studied grow in a clay pond at Wicken Fen, Cambridgeshire, 52° 18' N, 0° 17' E. The pH of the water is 7-8~8-4, the nitrate-N less than 2 mg r^ and orthophosphate-P less than 5-0/igl"t hroughout the year.…”