Showing papers on "Polygonum published in 1976"

Divergence of Two Co‐Occurring Successional Annuals on a Soil Moisture Gradient

Abstract: Polygonum pensylvanicum and Abutilon theophrasti, components of old—field communities in central Illinois were grown on a controlled soil moisture gradient to determine whether they exhibit different response centers. Germination response of a constant number of seeds per six moisture resource states, height, biomass, and reproductive response of initially constant numbers of plants per state were monitored. States, ranging from saturation down to 13.61 ± 5.53% moisture, are numbered in order of increasing drought. Maximum height of Polygonum occurred in states 4 and 5, and of Abutilon in 4, 5, 6. Vegetative and reproductive biomass maxima of Polygonum and Abutilon occurred in states 5 and 6, respectively. Abutilon reproduced only in states 5 and 6 where it overtopped the Polygonum canopy, while Polygonum reproduced in all states. Polygonum performance declined sharply in state 6. Thus, Polygonum and Abutilon response centers are displaced toward the wetter and drier ranges of the gradient, respectively. On a within—community level, Abutilon reproduces in less mesic resource states where Polygonum canopy height is reduced. In general, Abutilon reproduction may occur throughout the gradient when the Polygonum canopy opens. The performance of these species is strongly influenced by both physical and biotic conditions. Previously investigated adaptations, including drought resistance and rooting patterns in space and time, appear to underlie divergence along the moisture gradient. The response patterns found here are broad and exhibit considerable overlap as expected in fugitive strategies. The patterns of divergence shown on point and gradient scales in this and our previous work reflect a related complex of adaptations and strongly suggest that competitive divergence occurs in early successional communities.

An experimental study of water dispersal in Polygonum spp.

Abstract: The annual smartweeds Polygonum lapathifolium L., P. pensylvanicum L., and P. persicaria L. grow on alluvial river bars during the summer and autumn when their substrate is free of flood waters and...

Submergence experiments on nine species of semi-aquatic polygonum

Abstract: A B S T R A C T Cloning experiments were carried out in growth chambers to determine responses of members of the genus Polygonum (sect. Persicaria) to aquatic submergence. By using both external morphology and anatomical modifications, comparisons were made among 23 populations with respect to their preadaptations after a rise in water level. Varieties of P. amphibium L. responded quite differently to submergence, offering more evidence to the theory that there is a cline of phenotypic plasticity in the species which corresponds roughly with the gradient in morphology. Other than P. amphibium, the species most well adapted to aquatic conditions was P. densiflorum Meisn., a member of the P. punctatum Ell. complex. Populations of P. hydropiperoides Michx. showed a dichotomy of response which appeared to correlate with the habitats in which they were collected. A few species of Polygonum did not survive well after inundation, but most were capable of underwater growth, and were at least half as well adapted to aquatic conditions as was the most plastic variety, P. amphibium var. stipulaceum Colem. MEMBERS of the genus Polygonum exhibit a broad spectrum of morphological and anatomical preadaptation to changes in moisture conditions. Especially within section Persicaria, properties which show variation due to phenotypic modification have often been used inappropriately as diagnostic characters in systematics. With the exception of amphibious Polygonum, little attention has been devoted to the ephemeral nature of certain "key" characteristics of members of the group. The smartweeds also provide an excellent group in which to study evolutionary trends toward the aquatic habit in a family which is primarily terrestrial. This paper reports some of the results of experiments designed to determine the nature and extent of structural modifications which occur in Polygonum tissues when the plants become inundated. Although Gliick (1924) reported on one submergence study with P. hydropiper L., experimentation has been largely restricted to garden

Insects Associated with Polygonum (Polygonaceae) in North Central Florida. I. Introduction and Lepidoptera

Abstract: Interactions of Lepidoptera and semi-aquatic species of Polygonum were investigated in north central Florida. Freshwater shore species of Polygonum are common in Florida and form an important element in such habitats. New host records were obtained for 17 of 43 Lepidoptera species associated with Polygonum in Florida (21 from literature reports and 22 from our rearings). Myriophyllum brasiliense Cambess (Haloragaceae) is an additional new host record for 2 tortricids, Choristoneura parallela (Robinson) and Argyrotaenia ivana (Fernald). An undescribed species of Coleophora and a gelechiid, "Aristotelia" absconditella (Walker), are newly recorded for the Florida fauna. Lepidoptera families involved in this ecological survey include Tortricidae, Coleophoridae, Gelechiidae, Pyralidae, Papilionidae, Lycaenidae, Geometridae, Sphingidae, Arctiidae, and Noctuidae.