Moran, Jonathan

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    Ion fluxes across the pitcher walls of three Bornean Nepenthes pitcher plant species : flux rates and gland distribution patterns reflect nitrogen sequestration strategies
    (Journal of Experimental Botany, 2010) Moran, Jonathan A.; Hawkins, Barbara J.; Gowen, Brent E.; Robbins, Samantha L.
    Nepenthes pitcher plant species differ in their prey capture strategies, prey capture rates, and pitcher longevity. In this study, it is investigated whether or not interspecific differences in nutrient sequestration strategy are reflected in the physiology and microstructure of the pitchers themselves. Using a non-invasive technique (MIFE), ion fluxes in pitchers of Nepenthes ampullaria Jack, Nepenthes bicalcarata Hook.f., and Nepenthes rafflesiana Jack were measured. Scanning electron microscopy was also used to characterize the distribution of glandular and other structures on the inner pitcher walls. The results demonstrate that nutrient sequestration strategy is indeed mirrored in pitcher physiology and microstructure. Species producing long-lived pitchers with low prey capture rates (N. ampullaria, N. bicalcarata) showed lower rates of NH4 + uptake than N. rafflesiana, a species producing short-lived pitchers with high capture rates. Crucially, species dependent upon aquatic commensals (N. ampullaria, N. bicalcarata) actively manipulated H+ fluxes to maintain less acid pitcher fluid than found in ‘typical’ species; in addition, these species lacked the lunate cells and epicuticular waxes characteristic of ‘typical’ insectivorous congeners. An unexpected finding was that ion fluxes occurred in the wax-covered, non-glandular zones in N. rafflesiana. The only candidates for active transport of aqueous ions in these zones appear to be the epidermal cells lying beneath the lunate cells, as these are the only sites not visibly coated with epicuticular waxes.
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    Foliar reflectance and vector analysis reveal nutrient stress in prey-deprived pitcher plants ( nepenthes rafflesiana )
    (International Journal of Plant Sciences, 1998-11) Moran, Jonathan A.; Moran, Alison J.
    Pitcher plants of the genus Nepenthes trap invertebrate prey in pitchers formed from modified leaf tips. This study investigates the benefits of carnivory to Nepenthes rafflesiana, a common Bornean lowland species. Plants were denied prey capture in their natural habitat for 18 wk and were compared with a control group that was allowed to trap, digest, and assimilate prey as usual over the same period. Resource limitation was demonstrated in prey‐deprived plants, which produced significantly fewer and smaller pitchers than did control plants. Analysis of foliar spectral reflectance showed increased reflectance within part (608–738 nm) of the photosynthetically active wave band in the prey‐deprived plants, signifying a reduction in chlorophyll content. Decreased reflectance at 550 nm in the prey‐deprived plants also indicated increased production of anthocyanins, denoting possible nitrogen or phosphorus limitation. Although no difference was found in tissue concentrations of nitrogen or phosphorus between treatments, vector analysis identified a reduction in content of both elements as a result of reduced biomass production in prey‐deprived plants. Our findings demonstrate the key role carnivory plays in the nutrition of this species in its natural habitat.
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    From carnivore to detritivore? Isotopic evidence for leaf litter utilization by the tropical pitcher plant Nepenthes ampullaria
    (International Journal of Plant Sciences, 2003-07) Moran, Jonathan A.; Clarke, Charles M.; Hawkins, Barbara J.
    Nepenthes pitcher plants trap prey in specialized leaves formed into pitchers. Most lowland species live in open, sunny habitats and capture prey to obtain nutrients, principally nitrogen (N). Nepenthes ampullaria is commonly found under closed canopy forest and possesses morphological traits that indicate adaptation to trap leaf litter as a nutrient source. We tested this hypothesis by comparing foliar stable N isotope abundance (δˆ15N) between plants growing under forest canopy at 20 sites (litterfall present) and those growing in 20 open areas (no litterfall) in Borneo. Foliar δˆ15N values were significantly lower and total N concentrations were higher for the plants with access to litterfall. Using a mixing model, we estimated that N. ampullaria plants growing under forest canopy derived 35.7% ± 0.1% of their foliar N from leaf litter inputs.