Ramets Of Clones Research Articles

The Effects of Competition on Growth and Form in Glechoma hederacea

Morphological responses to competition were analysed in Glechoma hederacea, a clonal herb with plagiotropic shoots. Ramets of clones were grown either in isolation or in competition with cut or uncut Lolium perenne swards. G. hederacea produced the same above ground biomass, but different morphologies when grown with short and tall grass. Despite considerable reductions in biomass and stolon branching when grown with competition rather than in isolation, the capacity for lateral extension of primary stolons was maintained. All other measured variables were reduced by competition, except for stolon internode length and petiole length and mass. These variables reached their greatest values in the uncut grass treatments. These responses could promote avoidance of competition by escape in both the horizontal and vertical planes; growth through vegetated sites would be rapid, and sites where competitors are absent would be occupied more densely. Reductions in PAR and in the R/FR ratio incident on the plant are both implicated in inducing these morphological changes. Differences in relative humidity, caused by the proximity of neighbours, also appeared to exert a considerable influence upon growth and morphology of G. hederacea. Connected parts of G. hederacea clones grown with and without competition developed different morphologies; each primary stolon behaved as an integrated physiological unit, developing a morphology appropriate for the conditions in which it was growing.

Consistent Interplant Variation in Nectar Characteristics of Mirabilis Multiflora

The volume and sugar content of nectar produced by flowers can affect plant reproductive success by influencing pollinator foraging behavior. Because temporally varying environmental factors can affect nectar characters, the likelihood of pollinator—mediated selection for nectar characters may be reduced. To determine the constancy of interplant variation in floral nectar, I measured the volume and sugar concentration of nectar produced by plants in a population of Mirabilis multiflora within and between seasons. The means and relative ranking of nectar characters varied widely among plants. The means were remarkably constant within a season and across three successive flowering seasons. Variation among plants in sugar produced per flower was significantly correlated with the number of flowers produced (° = 0.29) and sugar concentration of nectar was significantly correlated with the date of peak flowering (° = —0.33). Ramets of clones had similar nectar volumes and total sugar produced, while genetically distinct near neighbors did not, suggesting a genetic component to nectar production. I conclude that plants of M. multiflora vary widely, and consistently through time, in their nectar characters and that this variation could affect pollinator behavior.

Factors Affecting Catches of Male Coneworms, Dioryctria spp. (Lepidoptera: Pyralidae), in Pheromone Traps in Southern Pine Seed Orchards

Four variables affecting pheromone-trap catches of pine coneworms, Dioryctria spp., were studied. These variables were trap design, trap density, trap location within tree crowns, and tree clone. Pherocon lC traps were most effective for capturing male D. amatella (Hulst) moths at low population densities. Traps placed near the tops of loblolly pines, Pinus taeda L., caught twice as many Dioryctria spp. males as traps at midcrown; those at the base of the crowns had very low catches. Also, there were positive correlations between D. amatella and D. disclusa Heinrich catches and trap height, i.e., traps placed in the tops of taller trees caught more moths. Placing traps in ramets of certain clones had some effect on trap catches of D. amatella and D. disclusa . Clonal differences were apparently the result of differences in the height at which traps could be placed in the ramets of each clone. Evidence of competition among traps was found at a trap density of 8 per 0.1 ha but not at 4 per 0.1 ha or lower densities.