Differential accumulation of nutrient elements in some New Zealand mistletoes and their hosts

Abstract

It has been generally assumed that differential accumulation of mineral nutrients, leading to greater accumulation of elements in mistletoe tissues, is associated with greater transpiration in the mistletoe than in the host. Only a few investigations have measured both tissue element concentrations and transpiration, or transpiration-related parameters such as carbon isotope ratios (δ13C). Seasonal means for foliar concentrations of Ca, Mg, K, Na, P, N, transpiration and δ13C were obtained from ten mistletoe–host pairs, nine involving the mistletoe Ileostylus micranthus and one with Tupeia antarctica. Annual means of transpiration and δ13C were similar in mistletoes and hosts, but hosts showed greater variation in both transpiration and δ13C than mistletoes. Foliar concentrations of Ca and Mg in mistletoes were similar to those of their hosts, N concentrations were less, and foliar concentrations of K, Na and P were greater in mistletoes than in their hosts. Ratios of foliar concentrations of Ca, Mg and P in mistletoes to those in their hosts (M/H) were greatest when host transpiration was low, when host δ13C was least negative, and when the difference between mistletoe and host δ13C was most negative. The lack of a phloem connection between host and mistletoe, combined with circulation of elements in the host phloem and their transfer into the host xylem, provides a mechanism that explains the accumulation of phloem-mobile elements in the mistletoe.

A comparative study of aluminium and nutrient concentrations in mistletoes on aluminium‐accumulating and non‐accumulating hosts

“…It is usually accepted that mistletoes have higher leaf N concentrations than the host plants (Glatzel 1983;Lamont 1983;Ehleringer et al 1985;El Sharkawy et al 1986;Panvini & Eickmeier 1993). However, in this study we found no differences between hosts and mistletoes in N leaf concentration, and a number of other studies have reported leaf N concentrations of parasitic plants that were similar or even lower than their respective host (Lamont & Southall 1982;K€ uppers et al 1992;Bannister et al 2002;Bowie & Ward 2004;Burns et al 2011). Higher leaf N concentrations than the host might make mistletoe leaves more attractive to herbivores (Marvier 1995;Kyto et al 1996) and lead to a decrease in their fitness. Mistletoes could therefore benefit from down-regulating the amount of N in their leaves to avoid higher rates of herbivory.…”

African mistletoes (loranthaceae); ethnopharmacology, chemistry and medicinal values: An update

“…The relationships between Loranthaceae and their hosts have been a subject for study in the past and will continue to be for the lesser-known African mistletoes particularly. The sucker ensures the continuity of the major elements, Na + , K + , Ca² + , Mg² + etc., of the two plants and enables the diversion of water and nutritive substances from the plant to the parasite (Bannister et al, 2002). Apart from minerals, organic acids and pigments, how much of the host plant constituents may be transported to the mistletoe and vice versa?…”

Influx of double labelled glutamine into mistletoes (Viscum album) from the xylem sap of its host (Abies alba)

“…This upload may either be interpreted as a flux of organic compounds from the host stem, in particular the phloem, or from the haustorium, or a mixture of both. Phloem-xylem interchange has been reported in herbaceous plants and conifers [7,21] and is considered part of the mechanism responsible for accumulating elements in mistletoes [2]. Back-flow of solutes from haustoria into host xylem was observed in other parasites [15,16] despite high transpiration rates driving solutes into haustoria.…”