Leiv M. Mortensen

The influence of carbon dioxide or ozone concentration on growth and assimilate partitioning in seedlings of nine conifers

Abstract Seedlings of nine different conifers were exposed to 355 and 730 μmol mol-1 CO2, or low (> 15 nmol mol−1) and elevated 03 concentration (70 nmol mol−1) for 81–116 days. The experiments were conducted in growth chambers placed in a greenhouse. Increased CO2 concentration enhanced the mean relative growth rate (RGR) and total plant dry weight by 4 and 33% in Larix leptolepis, by 4 and 38% in Larix sibirica, by 7 and 47% in Picea glauca and by 3 and 16% in Picea sitchensis, respectively. The growth rates and dry weights of Pimis contorta, Pinus mugo and Pseudotsuga menziesii were not significantly affected. Carbon dioxide enrichment enhanced RGR of two provenances of Picea abies by 4 and 6%, respectively, while a third provenance was unaffected. In Pimis sylvestris, only the RGR of one of three provenances was stimulated by CO2 enrichment (4%). After two growth seasons CO2 enrichment enhanced RGR and total plant dry weight by 11 and 35% in Picea abies and by 12 and 36% in Pinus sylvestris, respectiv...

Effects of Ozone on Growth of Seven Grass and One Clover Species

Abstract Seven species of grass and one of red clover were grown at different ozone (O3) concentrations for about five weeks in growth chambers located in a greenhouse. At an O3 concentration of 55 compared with 10 nmol mol−1 during 7 h day−1 the shoot dry weight decreased by 45% in Phleum pratense, 28% in Dactylis glomerata and Poa pratensis, 23% in Festuca rubra and 16% in Festuca pratensis, while the effects on Agrostis tenuis were not significant. No effect was found at 25 compared with 10 nmol mol−1O3. Visible O3 injury was observed in all six species at 55 nmol mol−1 and this effect was generally well correlated with the effect on the dry weights. In another experiment no effect was found with O3 concentrations of up to 62 nmol mol−1 on Lolium perenne, while the dry weight in Trifolium pratense decreased by 30% at 59 compared with that at 6 nmol mol−1.

Effects of Carbon Dioxide Concentration on Assimilate Partitioning, Photosynthesis and Transpiration of Betula pendula Roth, and Picea abies (L.) Karst. Seedlings at Two Temperatures

Abstract Seedlings of Betula pendula Roth, and Picea abies (L.) Karst. were grown at 350 and 700 μmol mol−1 CO2 for 35 or 45 days at 15 and 20 °C in eight growth chambers. The mean photosynthetic flux was 15–22 mol m−2 day−1. The mean relative growth rate was increased by 7% in Betula and by 10% in Picea at the highest CO2 concentration. This corresponded to an increase in the total plant dry weight of 20 and 19%, respectively. The shoot:root and leafstem ratios were unaffected by the CO2 concentration in both species. High CO2 levels increased the stem diameter and the number of lateral shoots in Betula. Increasing the temperature did not affect the assimilate partitioning between leaf, stem and root in Betula, but the needle:stem ratio decreased in Picea. Elevated CO2 concentration increased the number of lateral shoots in Betula more at 15 than at 20 °C, however, the total weight of the lateral shoots was not affected. With this exception the effect of CO2 was generally the same at both temperatures. M...

The Influence of Elevated CO2 Concentration on Growth of Seven Grasses and One Clover Species in a Cool Maritime Climate

Abstract The effect of elevated CO2 concentration on the growth of eight common species and cultivars in Norwegian meadows—Festuca pratensis “Salten” and “Fure”, Festuca rubra “Koket” and “Leik”, Festuca arundinaceae “Vantage”, Festuca duruiscula “Barfina”, Poa pratensis “Lavang”, Agrostis capillaris “Aros”, Dactylis- glomerata “Apelsvoll”, and Trifolium repens “Grasslands Huia”—was studied during 11 weeks (April 26-early July). The study was performed in ten 9 m2 large field chamber units in a cool (11.3°C) maritime climate under long days (15.1–18.1 h), on the south-west coast of Norway (59°N, 6°E). The different species responded differently to elevated CO2 with respect to tillering, which was enhanced in A. capillaris (81%), D. glomerata (23%) and F. pratensis (36%), but was not significantly affected in the other species. The sward length was significantly decreased by high CO2 concentration, by 20% in P. pratensis, 36% in A. capillaris, 29% in D. glomerata, 26% in F. duruiscula, 36% in F. pratensis ...

The Effect of Elevated CO2 Concentration on Growth of Phleum pratense L. in Different Parts of the Growth Season

Abstract Seedlings of Phleum pratense L. (timothy) of the same age were grown in five sequential four-week periods during one growth season (May 5-September 23) at low (380 μmol mol−1) and high (650 μmol mol−1) CO2 concentration. The experiment was performed in 10 9 m2field plots surrounded by plastic foil walls (“field chambers”) in the relatively cool climate (10-13°C mean temperature) of the west coast of Norway (59°N latitude). Raising the CO2 concentration generally decreased the height of the grass (8-23%), especially at the beginning and end of the growth season The number of shoots was significantly increased (13-42%) by CO2enrichment in all growth periods except the last. Elevated CO2 did not influence the above-ground biomass (dry weight) in the first (May) and last (September) period, but increased it by 14-51% in the intervening periods (June-August). Positive effects of CO2 enrichment on plant biomass were correlated with positive effects on the number of shoots. Elevated CO2 concentrations r...

Effects of carbon dioxide concentrations on three grass species grown in mixture in two soil types at different ozone concentrations or temperatures

A seed mixture of Phleum pratense L., Lolium perenne L. and Festuca pratensis Huds. was grown in spaghnum peat or sandy soil in six growth chambers placed in a greenhouse compartment. Two different experiments were performed. Increasing the CO2 concentration from 375 to 740 μmol mol−1 increased the total dry weight of the grass mixture by about 30%, while an increase in the O3 concentration from < 10 to 50 nmol mol−1 decreased the dry weight by 18% as a mean in both experiments. The relative dry weights of the three species were not significantly affected by elevated CO2 concentrations at low O3, while Lolium increased its relative dry weight at high O3concentrations at low CO2 on the expenditure of Phleum dry weight. CO2 enrichment counteracted some of this O3 effect. No significant interaction between CO2 concentration and temperature (14 and 19°C mean temperature) was found with respect to the dry weights of the three species. The soil type had generally no influence on the effect of CO2 and O3. Howeve...

Foliar Injuries Caused by Ozone in Betula pubescens Ehrh. and Phleum pratense L. as Influenced by Climatic Conditions Before and During O3 Exposure

Seedlings of Betula pubescens Ehrh. (mountain birch) and Phleum pratense L. (timothy) were grown for 42 days under full light or 50% shade in the field at 12°C, and at comparable photosynthetic active radiation (PAR) levels in a greenhouse at 18°C. Plants from the four pretreatments were exposed to 78 nmol mol-1 (ppb) O3 (8 h day-1) under two temperatures (15 and 25°C), two relative air humidities (50 and 80% RH) or two CO2

Diurnal carbon dioxide exchange rates of greenhouse roses under artificial light as compared with daylight conditions in summer

Abstract Carbon dioxide exchange rates (CER) of greenhouse roses (cut flowers) were measured under daylight conditions in a greenhouse in July, and under artificial light only (300 μmol m−2 s−1 PPFD in 18 h day−1) at two CO2 concentrations (350 and 700 μmol mol−1). The daily CER varied considerably from day to day owing to the large variation in solar radiation. Light saturation of CER seemed not to be reached even on clear days, and a light dose (PAP = number of photosynthetic active photons) produced by variable light over one week in summer gave the same total CER as a similar PAP produced by a constant PPFD. CER at constant PPFD increased rapidly during the first two hours of the photoperiod, followed by a slight increase during the subsequent hours, before CER slightly decreased towards the end of the photoperiod. Raising the CO2 concentration significantly increased CER during the entire photoperiod, and by 32% as a mean for the whole photoperiod. Elevated CO2 decreased the night respiration of the ...

Autumn growth and cold hardening of winter wheat under simulated climate change

Abstract Plant responses to elevated CO2 are governed by temperature, and at low temperatures the beneficial effects of CO2 may be lost. To document the responses of winter cereals grown under cold conditions at northern latitudes, autumn growth of winter wheat exposed to ambient and elevated levels of temperature (+2.5°C), CO2 (+150 µmol mol−1), and shade (−30%) was studied in open-top chambers under low light and at low temperatures. Throughout the experiment, temperature dominated plant responses, while the effects of CO2 were marginal, except for a positive effect on root biomass. Increased temperature resulted in increased leaf area, total biomass, total root biomass, total stem biomass, and number of tillers, but also a lower content of total sugars and a weaker tolerance to frost. The loss of frost tolerance was related to the larger size of plants grown at elevated temperature. The 30% light reduction under shading did not affect the growth, sugar content, or frost tolerance of winter wheat. At the low temperatures found at high latitudes during autumn, the atmospheric CO2 increase is unlikely to enhance autumn growth of winter wheat to any significant extent, while a temperature increase may have important and major effects on its development and growth.

Influence of elevated atmospheric CO2 concentration on common weeds in Scandinavian agriculture

This study investigated the influence of elevated CO2 on three perennial weed species (Achillea millefolium, Leontodon autumnalis and Rumex acetosa) and seven annual species (Chenopodium album, Matricaria matricarioides, Poa annua, Polygoniini persicaria, Senecio vulgaris, Spergula arvensis and Stellaria media). The study was carried out during the period 3 May to 5 August in ten field chamber units of 9 m2 in a cool (12.6°C) maritime climate under long days (15.8–18.1 h day‐1) on the south‐west coast of Norway (59° N, 6° E). Dry weights of the seven annual species were not significantly affected by the CO2 concentration. Of the three perennial species, L. autumnalis increased in dry weight by 27% and A. millefolium by 19% at elevated compared with ambient CO2 concentration. Plant height increased by 8% in L. autumnalis and decreased by 12 and 10% in M. matricarioides and P. annua respectively. Leaf size increased by 32% and specific leaf area decreased by 23% in P. persicaria at elevated CO2, while the o...