Poa Nemoralis Research Articles

Importance of ammonium and nitrate to the performance of herb-layer species from deciduous forests in Southern Sweden

Experiments were performed on the effect on growth and uptake of nitrogen given as NH 4 and/or NO 3 in a nutrient solution (pH 4.2) of a composition similar to that of the rhizosphere soil solution of an acidic beech forest but lacking Al. Seven treatments (0.2 and 0.4 mM NH 4 and NO 3, respectively, and 0.1 + 0.1, 0.2 + 0.2, 0.4 + 0.4 mM of NH 4 + NO 3) were used in a flowing solution culture without recirculation. The seven species tested have ecological distributions which range from very acid soils with low nutrient levels and nitrogen mainly present as NH 4, to less acidic and nitrifying soils. In the solution experiment, species occurring in very acidic soils had small preferences for nitrogen form or combination ( Deschampsia flexuosa, Carex pilulifera, Milium effusum), while Aegopodium podagraria of less acidic soils preferred NO 3. The other three species, Poa nemoralis, Bromus benekenii and Carex sylvatica, grew best in a mixed solution. Results of a short-term (2–24 hr) exposure experiment showed that all species had a higher nitrogen uptake from NH 4 in the solo and mixed solutions. Total N uptake was, however, similar for the solo NH 4 and mixed solutions for all species except D. flexuosa and C. pilulifera, which had the highest N uptake with solo NH 4. It was concluded that none of the species studied grew best when NH 4 was supplied as the sole N source. This may restrict the distribution of species in very acid soils, where nitrification may be lacking.

Experimental evidence for the relative sensitivity of deciduous forest plants to high soil acidity

Thirteen species of deciduous forest vascular plants were established from seeds: Brachypodium sylvaticum, Carex sylvatica, Circaea lutetiana, Deschampsia flexuosa, Galium odoratum, Lamium galeobdolon, Lathyrus vernus, Luzula pilosa, Milium effusum, Poa nemoralis, Sanicula europaea, Stellaria holostea and Stellaria nemorum. An acid beech forest soil was variously treated with carbonates (CaCO 3 + MgCO 3 or SrCO 3) to obtain a soil solution pH of 3.3–5.2. The experimental results were compared with the field distribution of the same species in 230 south Swedish deciduous forests with regard to soil pH. In general, the species reacted to increasing soil pH in accordance with their field distribution. Addition of SrCO 3 was almost equally effective as CaCO 3 + MgCO 3 (both at pH 4.2 in the soil solution) in promoting establishment and growth, whereas most species failed in the untreated soil (pH 3.3). There were no indications that the Ca or Mg concentrations of the soil solution were below minimum or even suboptimal for plant growth in the untreated soil. Within the pH range (pH ⩽ 3.5–4.3) which proved critical to establishment and growth in most of the species, the reactive Al 3+ concentration of the soil solution did not vary significantly. It is suggested that the high acidity of the rhizosphere solution, possibly aggravated by Al 3+, obstructed the uptake or retention of mineral nutrients by the roots in the untreated acid beech forest soil.

Soil chemical properties excluding field-layer species from beech forest mor

Experiments were made to elucidate why many field-layer plants in beech forests do not grow in mor (raw humus), a layer of organic matter in various stages of decay containing little or no mineral soil particles. Three possibilities were considered directly or indirectly: (i) tree root competition and litter shading, (ii) phytotoxic and nutrient complexing organic compounds in the soil solution, and (iii) high H-ion concentration in the solution. Rhizomes of eight species (Allium ursinum, Carex sylvatica, Convallaria majalis, Deschampsia flexuosa, Galium odoratum, Poa nemoralis, Stellaria holostea, Stellaria nemorum) were collected in late winter and used in a soil experiment to test reestablishment and growth in untreated mor (soil solution pH 3.6) and after pH was raised to 4.3 by addition of SrCO3. A flowing solution experiment was used with five of the species mentioned. The solution was composed according to the soil solution of the untreated mor but lacking organic compounds. pH was adjusted to and maintained at 3.6 and 4.3. The experiments showed that even when root competition, litter shading and organic compounds were excluded as limiting factors, only Deschampsia flexuosa, and partly Convallaria majalis, could produce new roots in the untreated mor or in the pH 3.6 solution treatment. Some shoot biomass developed in all species except in Galium odoratum, though significantly less than at pH 4.3. It was concluded that high H-ion concentration of the soil solution precludes establishment and growth of many forest plants in beech forests developed on mor podzols.

Effects on beech forest species of experimentally enhanced nitrogen deposition

Three and nine times the current nitrogen deposition in southern Sweden (60 and 180 kg ha -1 year -1 , ammonium nitrate) was applied to two beech stands in Scania, south Sweden, to study effects on cover and biomass of the field-layer vegetation. The study demonstrates that this application had rather small effects on field-layer species in the sites studied. The species composition was unaltered during the 5-year experiment. In one site the vegetation was also in other aspects relatively little changed apart from Impatiens parviflora that increased in cover. In the second site, cover and biomass were reduced for half of the common species ( Anemone nemorosa, Maianthemum bifolium, Oxalis acetosella, Poa nemoralis, Viola rivinianalreichenbachiana ) and no species increased. Species increasing in retrospective studies, probably because of the enhanced nitrogen deposition, have not changed in the present study ( Rubus idaeus, Stellaria nemorum ). Plausible explanations for the negative effects on the vegetation are the acidification of the soil solution due to excess nitrogen in relation to other nutrients, nutrient imbalance in the plants and the decreasing mycorrhizal infection.

Distribution of field layer species in Swedish deciduous forests in 1929-54 and 1979-88 as related to soil pH

Literature data on vascular plant distribution in deciduous forests were compared in 1929-54 and 1979-88. pH in the topsoil was related to the occurrence of 13 common vascular plants. The median of pH (H2O) was 5.2 for the old (n=105) and 4.4 for the new plots (n=132). New plots of pH>5 were scarce and soils of pH<4 were limited to the new plots. Comparison of the pH related frequency curves gave four patterns: (A) a displacement of frequency curves towards lower pHs for the new plots (Stellaria holostea, Milium effusum, Melica uniflora); (B) a widening of the frequency curves into lower pH for the new plots (Viola riviniana/reichenbachiana, Galium odoratum, Lamium galeobdolon, Oxalis acetosella, Maianthemum bifolium); (C) a raised frequency curve for the new plots at all pHs (Stellaria nemorum, Poa nemoralis, Rubus idaeus, Mercurialis perennis); (D) a lowered frequency curve for the new plots at all pHs (Deschampsia flexuosa). It is deduced, that the pH related frequency curves are not stable over long periods as e.g. the studied 40–60 years. The increased amounts of nitrogen and acidifying substances in deposition probably caused an altered soil chemistry and a change in competition among nitrogen favoured and acid tolerant species. As the soil in the new plots was more acidic, the total frequency was higher for many species. However, the frequency of most species decreases with soil pH, and if soil acidification continues without further plant adaptation to low soil pH, there will be a decrease of many species.

AMERICAN CODE AND LATER LECTOTYPIFICATIONS OF LINNAEAN GENERIC NAMES DATING FROM 1753: A CASE STUDY OF DISCREPANCIES

SummaryThe typification of the 112 Linnaean generic names dating to 1753, for which American Code lectotypifications differ from later ones, is reviewed in the light of two proposals to amend the International Code of Botanical Nomenclature at the XIV International Botanical Congress at Berlin in 1987. As part of the review, Dioscorea sativa L. is lectotypified and thus synonymized under D. villosa, and Agrostis alba L. is placed in synonymy under Poa nemoralis L. The two proposals (Proposals 291 and 297) were both included in the report of the Committee on Lectotypification, and are found to have differential effects in 58 of the 112 cases examined. It is shown that adoption of the provision to remove all constraints on the priority of American Code lectotypifications would result in nomenclatural changes in 48 cases as against 10 if the proposal to adopt 1935 as the starting date for priority of lectotypification was adopted. Moreover, with priority of American Code lectotypifications, changes would arise in the names of subdivisions of families in 4 cases and in names very widely accepted at the generic level in 21 cases, whereas no such changes would occur if a 1935 starting date were adopted. The generic names involved include Agrostis, A ndropogon, Apium, Cleome, Cucurbita, Draba, Elymus, Ophrys, Scabiosa, Scirpus and Sisymbrium. At the infrageneric level (including 7 cases in which a few authors recognize segregate genera), changes would be required in 26 cases if Proposal 297 (American Code priority) were adopted on its own, but in only 10 if Proposal 291 (1935 start) were accepted. The authors conclude that stability of nomenclature, at least at the levels of genera and subdivisions of genera of phanerogams, is better served by establishing 1935 as the starting date for priority of lectotypification.

LONG DAY CONTROL OF FLOWERING IN POA NEMORALIS IN CONTROLLED AND NATURAL ENVIRONMENTS

SUMMARYFlower initiation and development in a local population of Poa nemoralis L. were studied in controlled and natural environments at As, Norway, 59° 40′ N. At temperatures ranging from 6 to 21 °C flowering occurred in long days (LD) only. At 12 h photoperiod the plants remained vegetative for at least 145 d. The critical photoperiod for floral initiation was about 14 h at IS and 21°C, slightly longer at 9 °C. A minimum of two LD cycles was required for floral induction at 15 °C when flower development took place in 12 h photoperiod, while more than four LD cycles were required for flower development in 8 h photoperiod. Viviparous proliferation of inflorescences resulted from marginal LD induction and subsequent flower development in short days (SD). The observed critical photoperiods agreed well with the time of floral initiation in the field, the critical photoperiod being reached as soon as growth is initiated in the spring. It is concluded that P. nemoralis is an obligatory long day plant with no SD or low temperature vernalization requirement.

THE INDUCTIVE REQUIREMENTS FOR FLOWERING OF SOME TEMPERATE GRASSES

A survey was made of the flowering responses of 47 annual, biennial and perennial grasses, to measure the extent of any winter requirement for floral induction, and to see how far this could be provided by controlled cold or short‐day treatment.The annual species showed little or no inductive requirement, nor did the perennials Arrheuatherum elatius, Ceratochloa unioloides, Phleum pratense and Poa nemoralis. Most perennials possessed a definite inductive requircinent. A few species, such as Lolium perenne, responded to both cold and short‐day given to the young seedling, while others, such as Phleum nodosum, Agrostis alba, A. canina, A. stolonifera and A. tenuis, responded to short‐day induction but not to cold.Many temperate perennials, however, including Cynosurus cn'status, Dactylis glomerata, Festuca pratensis, F. rubra, Poa pratensis and P. trivialis did not respond to seedling induction and possibly have a juvenile stage before they are able to respond to inductive conditions.The sequence of flowering responses in the temperate perennial grasses is evidently more complex than was previously thought, and the perennial habit can be achieved by many different developmental pathways.

Grauballemandens sidste Måltid

Grauballemandens sidste Måltid

Beiträge zur Biologie der Pflanzen

THE third part of Cohn's “Beitrage,” now before us, completes the first volume, and let us express the hope that we may have another volume before very long. Curiously, each of the three parts has been separately paged, an arrangement which renders it necessary to note the part as well as the page when the index is consulted. If we may judge from the size and price, each part has increased in importance, so that the third part has more papers and is nearly double the size of the first. In all the parts there have been papers of great interest and value, and those in the present part are in no way behind their predecessors. Dr. Cohn himself contributes three papers to the present part, Dr. J. Schrœter two, while Drs. L. Just, A. B. Frank, Richard Sadebeck, and Eduard Eidam, each one. The first paper is by Dr. Schrœter on the Development of certain Rust-Fungi. On Carex hirta, one of the Uredineae was observed which Dr. Schrœter believes to be Puccinia caricis of De Candolle; and as he had reason to suspect that AEcidium urticae of Schum was only a stage in the life history of P. caricis, experiments were made to ascertain definitely whether P. caricis was heterœcious, and if so, whether AEcidium urticae was one of the stages. Details of the experiment are given, and Schrœter concludes that AEcidium urtica is a stage of Puccinia caricis. In a note to his paper, Dr Schrœter mentions that Dr. Magnus, of Berlin, has made similar experiments with the same result, an important confirmation of the remarkable habit these curious plants have of changing from one host to another, and at the same time changing the form of their spores, a condition describee by De Bary long ago in the rust of wheat. A second form noticed by our author is a species of rust common on many grasses. It has many names, and Dr. Schrœter calls it Uromyces dactylidis, Ottli, (Uromyces graminis, Cooke). One stage is spent in our common grasses, such as Dactylis glomerata, Poa nemoralis, P. trivialis, P. annna, P. pratensis, c the Muscineae and Vascular Cryptogams having Spermatozoids, while the flowering plants have pollen and pollen-tubes, showing a certain analogy to the pollinodium of some of the Carposporeae. Beitrage zur Biologie der Pflanzen. Herausgegeben von Dr. Ferdinand Cohn. (Breslau, 1875.) Drittes Heft.

Beiträge zur Biologie der Pflanzen

Beiträge zur Biologie der Pflanzen