DOI: 10.5061/dryad.c866t1gc0
title: Host age affects the performance of the root hemiparasitic plant Rhinanthus alectorolophus

description: Interactions between root hemiparasitic plants and their hosts are
 strongly affected by host identity but may also depend on the condition of
 the host. An important determinant of host quality could be host age, as
 it may influence host size, allocation patterns, responses to infection,
 and the strength of competition for light between parasite and host. We
 investigated the effects of host species identity, host age and
 above-ground separation of hemiparasite and host on the interactions
 between the hemiparasite Rhinanthus alectorolophus and five host species
 in a factorial experiment. The host species were planted at six different
 times, from ten weeks before the parasite was planted to four weeks after.
 Host age strongly influenced the performance of the parasite, but these
 effects also varied among host species. Parasites grew largest with hosts
 planted at the same time or two weeks earlier, but their performance
 strongly declined both with increasing host age and with the time they
 grew autotrophically. A large part of the variation due to host age but
 not of that due to host species identity could be related to the negative
 influence of host size at the likely time of parasite attachment. The low
 quality of older hosts was not due to light competition, suggesting that
 effective exploitation of these hosts was prevented by other factors like
 harder roots, stronger defence against parasite attack or competition for
 resources taken up by the host roots. Suppression of host growth by the
 parasites declined with increasing host age. The results indicate that the
 choice of host age may influence the results of studies on hemiparasites.
 They also highlight the importance for annual root hemiparasites of
 attachment in early spring, i.e. at a time when their mostly perennial
 hosts produce fresh roots but are still poorly developed above ground.
description: The dataset is a collection of
 plant traits from plants grown in a pot experiment in 2 growth chambers.
 We grew the root hemiparasitic plant <em>Rhinanthus</em>
 <em>alectorolophus</em> with several host plants. We used five
 host species and six different host ages (hosts were planted 10 weeks
 before the parasite, 4 weeks before the parasite, 2 weeks before the
 parasite, at the same time as the parasite, 2 weeks after the parasite or
 4 weeks after the parasite). In half of the
 pots, above-ground competition between hemiparasite and hosts
 was prevented by separating hemiparasite and hosts by an aluminium
 foil. We also grew hosts
 without parasites with all possible combinations of host species and age
 and we also grew parasites without hosts. Several traits of hosts and
 parasites were measured at the end of the experiment (9 weeks after
 parasite planting).  To study potential influences of host traits at
 the time of parasite attachment, we also grew hosts without parasites and
 measured them at a time when the parasites had grown for two weeks in the
 other pots. Analyses were carried out with R version
 4.2.1. 
description: Microsoft Excel (version 2007 and newer) is the recommended
 program to open and work with the data (format .xlsx), but WPS Office
 Spreadsheets, OpenOffice Calc, LibreOffice Calc and Apple Numbers could
 also be used to open the file.