J. Rozema
VU University Amsterdam
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Featured researches published by J. Rozema.
Trends in Ecology and Evolution | 1997
J. Rozema; Jos van de Staaij; Lars Olof Björn; Martyn M. Caldwell
Recent studies indicate that increasing solar UV-B is not merely an environmental stress for plants. Solar UV-B can cause plant morphogenetic effects, which can, in turn, modify the architecture of plants and the structure of a vegetation, In addition, UV-B radiation affect the production of various secondary metabolites (such as flavonoids, tannins and lignin) with important physiological and ecological consequences.
Plant Ecology | 1997
J. Rozema; Marcel Tosserams; H. J. M. Nelissen; L. M. Van Heerwaarden; Rob Broekman; N. Flierman
This study reports changes in the plant’s chemical composition and the decomposition of this plant material under enhanced solar UV-B radiation. Calamagrostis epigeios, a dominant grass species in the dune grassland in The Netherlands, was grown outdoor on an experimental field under ambient and enhanced solar UV-B (5 and 7.5 kJ m-2 day-1 UV-BBE, respectively), corresponding to about 15% stratospheric ozone depletion. After one growing season aerial plant parts were harvested. The decomposition of this harvested leaf material was studied in a dune grassland and on the above mentioned experimental field under ambient (5 kJ m-2 day-1 UV-BBE) and enhanced (7.5 kJ m-2 day-1 UV-BBE) radiation, using litter bags. The chemical quality of the leaves grown under enhanced solar UV-B changed. There was an increase in the leaf content of lignin, while no significant changes occurred for the content of α-cellulose, hemicellulose and tannins under enhanced UV-B. In the field, the rate of decomposition of leaf material grown under enhanced UV-B (with an increased content of lignin) was reduced. The content of lignin of the decomposing leaf material increased, but less under exposure to enhanced UV-B. The latter may be explained by photodegradation of the lignin. The consequences of enhanced UV-B radiation for carbon fluxes in the dune grassland ecosystem are discussed.
Journal of Photochemistry and Photobiology B-biology | 2001
J. Rozema; Rob Broekman; Peter Blokker; B.B. Meijkamp; N. Bakker; Jos van de Staaij; Adri van Beem; Freek Ariese; S. Kars
UV-B absorbance and UV-B absorbing compounds (UACs) of the pollen of Vicia faba, Betula pendula, Helleborus foetidus and Pinus sylvestris were studied. Sequential extraction demonstrated considerable UV-B absorbance both in the soluble (acid methanol) and insoluble sporopollenin (acetolysis resistant residue) fractions of UACs, while the wall-bound fraction of UACs was small. The UV-B absorbance of the soluble and sporopollenin fraction of pollen of Vicia faba plants exposed to enhanced UV-B (10 kJ m(-2) day(-1) UV-B(BE)) was higher than that of plants that received 0 kJ m(-2) day(-1) UV-B(BB). Pyrolysis gas chromatography-mass spectrometry (py-GC-MS) analysis of pollen demonstrated that p-coumaric acid and ferulic acid formed part of the sporopollenin fraction of the pollen. The amount of these aromatic monomers in the sporopollenin of Vicia faba appeared to increase in response to enhanced UV-B (10 kJ m(-2) day(-1) UV-B(BE)). The detection limit of pyGC-MS was sufficiently low to quantify these phenolic acids in ten pollen grains of Betula and Pinus. The experimental data presented provide evidence for the possibility that polyphenolic compounds in pollen of plants are indicators of solar UV-B and may be applied as a new proxy for the reconstruction of historic variation in solar UV-B levels.
Environmental Pollution | 1993
M.L. Otte; M.S. Haarsma; Rob Broekman; J. Rozema
The aim of the research reported here was to investigate the relation between heavy metal concentrations in salt marsh plants, extractability of the metals from soil and some soil characteristics. In April 1987, Spartina anglica and Aster tripolium plants and soil were collected from four salt marshes along the Dutch coast. The redox potential of the soil between the roots of the plants and at bare sites was measured. Soil samples were oven-dried and analyzed for chloride concentration, pH, fraction of soil particles smaller than 63 microm (f < 63 microm), loss on ignition (LOI) and ammonium acetate and hydrochloric acid extractable Cd, Cu and Zn concentrations. The roots and shoots of the plants were analyzed for Cd, Cu and Zn. Because drying of the soil prior to chemical analysis might have changed the chemical speciation of the metals, and therefore the outcome of the ammonium acetate extraction, a second survey was performed in October 1990. In this survey A. tripolium plants and soil were collected from two salt marshes. Fresh and matched oven-dried soil samples were analyzed for water, ammonium acetate and diethylene triaminepentaacetic acid (DTPA) extractable Cd, Cu and Zn concentrations. The soil samples were also analyzed for f < 63 microm, LOI and total (HNO(3)/HCl digestion) metal concentrations. Soil metal concentrations were correlated with LOI. Drying prior to analysis of the soil had a significant effect on the extractability of the metals with water, ammonium acetate or DTPA. Plant metal concentrations significantly correlated only with some extractable metal concentrations determined in dried soil samples. However, these correlations were not consistently better than with total metal concentrations in the soil. It was concluded that extractions of metals from soil with water, ammonium acetate or DTPA are not better predictors for metal concentrations in salt marsh plants than total metal concentrations, and that a major part of the variation in metal concentrations in the plants cannot be explained by variation in soil composition.
Plant Ecology | 1993
J. Rozema
In general, C3 plant species are more responsive to atmospheric carbon dioxide (CO2) enrichment than C4-plants. Increased relative growth rate at elevated CO2 primarily relates to increased Net Assimilation Rate (NAR), and enhancement of net photosynthesis and reduced photorespiration. Transpiration and stomatal conductance decrease with elevated CO2, water use efficiency and shoot water potential increase, particularly in plants grown at high soil salinity. Leaf area per plant and leaf area per leaf may increase in an early growth stage with increased CO2, after a period of time Leaf Area Ratio (LAR) and Specific Leaf Area (SLA) generally decrease. Starch may accumulate with time in leaves grown at elevated CO2. Plants grown under salt stress with increased (dark) respiration as a sink for photosynthates, may not show such acclimation to increased atmospheric CO2 levels. Plant growth may be stimulated by atmospheric carbon dioxide enrichment and reduced by enhanced UV-B radiation but the limited data available on the effect of combined elevated CO2 and ultraviolet B (280–320 nm) (UV-B) radiation allow no general conclusion. CO2-induced increase of growth rate can be markedly modified at elevated UV-B radiation. Plant responses to elevated atmospheric CO2 and other environmental factors such as soil salinity and UV-B tend to be species-specific, because plant species differ in sensitivity to salinity and UV-B radiation, as well as to other environmental stress factors (drought, nutrient deficiency). Therefore, the effects of joint elevated atmospheric CO2 and increased soil salinity or elevated CO2 and enhanced UV-B to plants are physiologically complex.
Environmental Pollution | 1995
M. Tosserams; J. Rozema
Seedlings of Calamagrostis epigeios were exposed to four levels of UV-B radiation (280-320 nm), simulating up to 44% reduction of stratospheric ozone concentration during summertime in The Netherlands, to determine the response of this plant species to UV-B irradiation. After six weeks of UV-B treatment, total biomass of all UV-B treated plants was higher, compared to plants that had received no UV-B radiation. The increase of biomass did not appear to be the result of a stimulation of net photosynthesis. Also, transpiration rate and water use efficiency were not altered by UV-B at any exposure level. Pigment analysis of leaf extracts showed no effect of enhanced UV-B radiation on chlorophyll content and accumulation of UV absorbing pigments. UV-B irradiance, however, did reduce the transmittance of visible light (400-700 nm) of intact attached leaves, suggesting a change in anatomical characteristics of the leaves. Additionally, the importance of including an ambient UV-B treatment in indoor experiments is discussed.
Aquatic Botany | 1991
J. Rozema; Frank Dorel; Ruud Janissen; Ger Lenssen; Rob Broekman; Wim Arp; Bert G. Drake
Abstract The C3 grass species Scirpus maritimus L. and Puccinellia maritima (Huds.) Parl., and the C4 grass species Spartina anglica C.E. Hubbard and Spartina patens (Ait.) Muhl. were grown at ambient (340 p.p.m. CO2) and elevated (580 p.p.m. CO2) atmospheric CO2 concentration, at low (10 mM NaCl) and high salinity (250 mM NaCl) under aerated and anaerobic conditions in the culture solution. The relative growth rate of both the C3 grass species was enhanced with atmospheric CO2 enrichment, no such increase was found in the C4 grass species. High salinity reduced growth of the C3 species tested, but this relative growth reduction was not prevented by elevated CO2 concentration. The growth increase at elevated CO2 of Scirpus maritimus and Puccinellia maritima is greater under aerated than under anaerobic solution conditions. Water-use efficiency of all species was increased by elevated CO2. In the case of Scirpus (C3), this increase was caused by increased net photosynthesis, for Spartina patens (C4) photosynthesis was not increased, but transpiration was reduced. The water potential of the shoot was less negative under conditions of CO2 enrichment, in particular at increased salinity (250 mM NaCl).
Archive | 1993
J. Rozema; H. Lambers; S. C. Van de Geijn; M. L. Cambridge
Preface. Methodology. Ecophysiological and Ecosystem Responses: Effects of CO2 Enrichment on Growth and Production. Response to CO2 Enrichment: Interaction with Soil and Atmospheric Conditions. Indirect Responses to CO2 Enrichment: Interactions with Soil Organisms and Soil Processes. CO2 Enrichment: Biosphere-Atmosphere Exchange. Index.
Aquatic Botany | 1991
J. Rozema
Abstract Halophytic angiosperms seem to have secondarily acquired adaptations to saline terrestrial environments, and have lost the requirement for salt of enzymes and membranes as is primarily present in aquatic marine bacteria, algae and fungi. Halophytic monocotyledonae differ in some respects from salt-adapted dicotyledonae: their growth rate is not stimulated by salt and is often lower than in dicotyledonae at increased salinity; they have a markedly lower internal sodium to potassium ratio and a lower water content. In addition, diurnal variation of leaf extension and leaf thickness differs significantly between monocotyledonae and dicotyledonae. This is related to the position of the growth meristem of expanding leaves. Monocotyledonous halophytes seem to be more efficient in the use of water than dicotyledons. The correlation that exists between values of the mean relative growth rate measured under saline conditions and leaf elongation and leaf thickness variation indicates that water stress rather than ion (toxicity) stress is the cause of growth reduction at increased salinity under these circumstances. A qualitative model is presented focusing on the different position and exposition of the growth meristem in monocotyledonae and dicotyledonae, which aims to provide a physiological and morphological explanation of the different growth, water and mineral economy of monocotyledonous and dicotyledonous halophytes.
Agriculture, Ecosystems & Environment | 1990
W.E. van Duin; J. Rozema; W.H.O. Ernst
Abstract Throughout the year roots of 15 halophytes from a Dutch salt marsh were analysed for mycorrhizal colonization. Until April roots of the previous growing season of only few species were infected, with vesicles and internal mycelium present. During the growing season some plant species were mostly heavily infected (newly formed roots became almost immediately infected: especially arbuscles and coiled hyphae were present), others were sometimes infected (including some Chenopodiaceae), and few species were never infected. Most of the non-infected species grow on the lower parts of the salt marsh, that are more frequently flooded with seawater.