EFFECTS OF LIGHT INTENSITY, PHOTOPERIOD AND NITROGEN ON THE GROWTH OF SEEDLINGS OF AGROPYRON REPENS (L.) BEAUV. AND AGROSTIS GIGANTEA ROTH

Abstract

Seedlings of Agropyron repens (L.) Beauv. and Agrostis gigantea Roth were grown in two light intensities with two photoperiods and with two amounts of nitrogen. On two occasions plants were also transferred between photoperiods.The early growtJi of the seedlings was increased most by increasing the light intensity, but later nitrogen had the greatest effect. In short photoperiods, plants of both species were decumbent and had many more shoots than in long photoperiods. At the end of the experiment, plants of both species responded more to nitrogen in bright than in dim light, and the dry weight o£ Agropyron was increased more than that o[ Agrostis by increased photoperiod and nitrogen.Agropyron initiated rhizomes sooner than Agroslis; it had fewer rhizomes but they were longer and thicker and weighed more. Brighter light, longer photoperiod and nitrogen all increased rhizome weight. Photoperiod did this mainly by producing more rhizomes, light by increasing thickness or density, and nitrogen by both. The effects of photoperiod and nitrogen on the rhizome dry weight of Agropyron, but not ot Agroslis, were additive.Transferring plants from short to long photoperiods or from long to short, respectively increased or decreased total growth, but had an opposite effect on the rhizomes. de I'intensiU lumineuse, de la phoiopiriode et de I'azote sur ta croissance de plantules d'Agropyron repens (L.) Beauv. et (/'Agrostis gigantea Roth . Des plantules 6'Agropyron repens (L.) Beauv. et d'Agrostis gigantea RotJi ont 6t6 Der Einjluss von Lichtintensitat, Pftoto/ieriode und Stickstoff auf das Wachstum der Sdmlinge von Agropyroa repens (L.) Beauv. und Agrostis gigantea Roth Zusammenfassung. Samlinge von Agropyron repens (L.) Beauv. und Agrostis gigantea Roth wurden bei zw^ci Lichtintensitaten mit zwei Photoperioden und zwei verschiedenen Stickstoffaufwandmengen wachsen gelassen. In zwei Fallen wurden die Pflanzen zwischen den Photoperioden verpflanzt. Das Jugcndwachstum der Samlinge wurde am meisten durch die zunehmende Lichtintensitat gcfbrdert, spater hatte der Stickstoff den grossten Eflekt. In langen Photoperioden waren die Pflanzen beider Arten niederliegend und hatten viel mehr Sprosse als in kurzen 159 160 E. D. Williams

Elymus repensbiomass allocation and acquisition as affected by light and nutrient supply and companion crop competition

“…Our results, similarly to Williams (1971), indicate that light has a relatively strong and early effect on E. repens biomass acquisition, allocation and morphological traits such as tillering, while the effect of reduced nutrient supply on E. repens biomass acquisition appears later and is most pronounced when light is not limited. Although single resource studies cannot be used for direct comparisons between limitations of different resources, this pattern is seemingly confirmed by studies on the effect of either nutrient supply (McIntyre, 1965;Turner, 1966) or light supply (Williams, 1970;Skuterud, 1984) on E. repens biomass allocation and acquisition.…”

“…The primary mode of resource competition may also be important in determining how efficiently E. repens is suppressed in systems with under-sown companion crops. A number of studies have investigated the effects of resource limitation on E. repens and, at least in regards to limited nutrient and light, the rhizome biomass allocation appears to follow the same pattern as the root biomass (McIntyre, 1965;Williams, 1970Williams, , 1971Skuterud, 1984). Thus, crops that compete heavily for light should have an especially high suppression rate as they would not only lower biomass acquisition, but also change the E. repens allocation away from rhizome production.…”

Harvest time and N fertilization effects on forage yield and quality of quackgrass (Elytrigia repens L.) in northeastern Saskatchewan

“…The mean DMY across the 3 yr increased by 64, 95 and 105% at the corresponding N rates. Fertilizer N has been observed to increase the number of tillers and buds for quackgrass and its biomass (Tardif and Leroux 1992) and also increased the ratio of aboveground to underground biomass (McIntyre 1971;Williams 1971). In a large field study, application of N has increased shoot dry weight and decreased rhizome dry weight of quackgrass (Bandeen and Buchholtz 1967).…”

Studies on the Biology of Wild Oats. Ii. Growth.

“…Beauv. ) and Williams (1971) (Sharma et al 1976 In our experiments, the growth of wild oats was adversely affected by soil acidity (pH below 7.5). However, the ability of wild oats to withstand more acid soil conditions than wheat or barley has been reported (Thurston 196l …”