Showing papers on "Polygonum published in 1984"

Alpine Annual Plants: Phenology, Germination, Photosynthesis, and Growth of Three Rocky Mountain Species

Abstract: Field microenvironments of three annual alpine species, Koenigia islandica, Polygonum confertiflorum, and P. douglasii, were characterized over two growing seasons. Germination, photosynthesis, and growth of all three species were investigated in field and laboratory experiments. The Polygonum species occurred in warm, dry alpine sites which melted out early in the growing season but also dried out early; plants died by mid—August. Koenigia grew in sites which melted out later, but plants remained alive later in the season since their sites did not dry out. Polygonum plants experienced higher soil surface, air, and leaf temperatures than did Kogotus plants. Seeds of the Polygonum species required stratification before they germinated, and light increased germination. Koenigia seeds germinated equally well in light and dark, and stratification was not necessary, although it increased germination percentages. Photosynthetic responses to light were similar in all three species. Koenigia's photosynthetic temp...

Comparison of the Photosynthetic Capacity between Intact Leaves of Triazine-Resistant and -Susceptible Biotypes of Six Weed Species

Abstract: The rate of photosynthesis in intact leaves of a triazine-resistant biotype of Amaranthus retroflexus was about 15% lower than that of a triazine-susceptible biotype. Differences in photosynthesis between resistant and susceptible biotypes of Polygonum lapathifolium, Poa annua and Solanum nigrum were not significant, and absent in Chenopodium album and Stellaria media. The results are brought in relation to the appearance of resistant biotypes in the field.

Phytophagous insect fauna of Polygonum perfoliatum, an Asiatic weed recently introduced to Pennsylvania.

Abstract: Insect surveys of a recent Asiatic adventive, Polygonum perfoliatum L. (Polygonaceae), were conducted in southcentral Pennsylvania during 1981 through 1983. The associated insects are listed, and the phenology and known host range of selected common species are discussed. The fauna, consisting of 34 species (5 orders, 15 families) that develop on the weed and 12 species that feed on Polygonum only as adults, is dominated by polyphagous, ectophagous sap- and foliage-feeding insects; only two oligophagous species associated with other polygonaceous plants were collected. Herbivory generally was casual, and several niches on P. perfoliatum remain unfilled. The fauna is compared with that of crownvetch ( Coronilla varia L.), an introduced legume of similar growth habit that occupies similar habitats in Pennsylvania.

Alpine annual plants: phenology, germination, photosynthesis, and growth of three

Abstract: Field microenvironments of three annual alpine species, Koenigia islandica, Polygonum confertiflorum, and P. douglasii, were characterized over two growing seasons. Germination, photo- synthesis, and growth of all three species were investigated in field and laboratory experiments. The Polygonum species occurred in warm, dry alpine sites which melted out early in the growing season but also dried out early; plants died by mid-August. Koenigia grew in sites which melted out later, but plants remained alive later in the season since their sites did not dry out. Polygonum plants experienced higher soil surface, air, and leaf temperatures than did Koenigia plants. Seeds of the Polygonum species required stratification before they germinated, and light increased germination. Koenigia seeds germinated equally well in light and dark, and stratification was not necessary, although it increased germination percentages. Photosynthetic responses to light were similar in all three species. Koenigia's photosynthetic tem- perature optimum was lower than those of the Polygonum species (27° vs. 32°C). Maximum net photosynthetic rates (CO2 uptake of whole plants) of each species ranged from 12 to 17 Mmol m-2. s- Koenigia plants grew significantly larger and produced more seeds at daytime temperatures of 15° rather than 25° in growth experiments. The reverse was true for the Polygonum species. A single extra week of growth often doubled seed production in these rapidly developing species. Differences in habitat and physiological response probably reflect the evolutionary origins of these species. Koenigia colonized the Rocky Mountains from the Arctic, and it inhabits the coolest, wettest, alpine bogs. The Polygonum species appear to have originated at lower elevations in the temperate zone and to have colonized the warmest and driest alpine habitats. The species' photosynthetic, reproductive, and growth responses reflect the conditions in their respective habitats.