Marianne Popp

Bio: Marianne Popp is an academic researcher from University of Vienna. The author has contributed to research in topics: Pinitol & Crassulacean acid metabolism. The author has an hindex of 37, co-authored 82 publications receiving 3725 citations. Previous affiliations of Marianne Popp include University of Münster & Australian National University.

MANGROVE ISOTOPIC (δ15N AND δ13C) FRACTIONATION ACROSS A NITROGEN VS. PHOSPHORUS LIMITATION GRADIENT

Abstract: Mangrove islands in Belize are characterized by a unique switching from nitrogen (N) to phosphorus (P) limitation to tree growth from shoreline to interior. Fertilization has previously shown that Rhizophora mangle (red mangrove) fringe trees (5–6 m tall) growing along the shoreline are N limited; dwarf trees (≤1.5 m tall) in the forest interior are P limited; and transition trees (2–4 m tall) are co-limited by both N and P. Growth patterns paralleled a landward decrease in soil flushing by tides and an increase in bioavailable N, but P availability remained consistently low across the gradient. Stable isotopic composition was measured in R. mangle leaves to aid in explaining this nutrient switching pattern and growth variation. Along control transects, leaf δ15N decreased from +0.10‰ (fringe) to −5.38‰ (dwarf). The δ15N of N-fertilized trees also varied spatially, but the values were consistently more negative (by ∼3‰) compared to control trees. Spatial variation in δ15N values disappeared when the trees were fertilized with P, and values averaged +0.12‰, similar to that in control fringe trees. Neither variation in source inputs nor microbial fractionation could fully account for the observed patterns in δ15N. The results instead suggest that the lower δ15N values in transition and dwarf control trees were due to plant fractionation as a consequence of slower growth and lower N demand. P fertilization increased N demand and decreased fractionation. Although leaf δ13C was unaffected by fertilization, values increased from fringe (−28.6‰) to transition (−27.9‰) to dwarf (−26.4‰) zones, indicating spatial variation in environmental stresses affecting stomatal conductance or carboxylation. The results thus suggest an interaction of external supply, internal demand, and plant ability to acquire nutrients under different hydro-edaphic conditions that vary across this tree-height gradient. The findings not only aid in understanding mangrove discrimination of nitrogen and carbon isotopes, but also have implications for identifying nutrient loading and other stress conditions in coastal systems dominated by mangroves.

The role of solute accumulation, osmotic adjustment and changes in cell wall elasticity in drought tolerance in Ziziphus mauritiana (Lamk.)

Abstract: bulk tissue elastic modulus (wall rigidity) which resulted in turgor loss at the same h in both stressed Ber (Ziziphus mauritiana Lamk.) is a major fruit tree and unstressed leaves. The possible ecological signicrop of the north-west Indian arid zone. In a study of ficance of maintenance of turgor potential and cell the physiological basis of drought tolerance in this volume at low water potentials for drought tolerance species, two glasshouse experiments were conducted in Ziziphus is discussed. in which trees were droughted during single stresscycles. In the first experiment, during a 13 d drying Key words: Ziziphus mauritiana, drought, solute accumulacycle, pre-dawn leaf water (Y leaf ) and osmotic (Y p ) tion, osmotic adjustment, proline. potentials in droughted trees declined from ’0.5 and ’1.4 MPa to ’1.7 and ’2.2 MPa, respectively, for a decrease in relative water content (h) of 14%. During Introduction drought stress, changes in sugar metabolism were associated with significant increases in concentra- Drought is probably the most important factor limiting tions of hexose sugars (3.8-fold), cyclitol (scyllo- crop productivity world-wide (Jones and Corlett, 1992). inositol; 1.5-fold), and proline (35-fold; expressed per In semi-arid regions, where the amounts and patterns of unit dry weight), suggesting that altered solute parti- seasonal rainfall are often erratic and unpredictable, deeptioning may be an important factor in drought toler- rooting perennial species may exploit deep soil water ance of Ziziphus. On rewatering, pre-dawn Y leaf and h reserves. This facilitates production of yields in situations recovered fully, but Y p remained depressed by 0.4 MPa of high light coupled with drought, where shallow-rooted relative to control values, indicating that solute con- annual crops would normally fail. The use of perennials centration per unit water content had changed during may help buVer farmers’ production against year-to-year the drought cycle. fluctuations in yields from annual crop species. Under Evidence for osmotic adjustment was provided from such conditions, an ability to maintain cell water status a second study during which a gradual drought (e.g. through osmotic adjustment and/or leaf area adjustwas imposed. Pressure‐volume analysis revealed a ment) and cell integrity (by protecting cells against photo0.7 MPa reduction in osmotic potential at full turgor, and chemical oxidation) may be an advantage. There are with Y leaf at turgor loss depressed by ~1 MPa in many cases where plants growing in hostile environments drought-stressed leaves. Coupled with osmotic adjust- exhibit increased oxy-stress enzyme activities to combat lipid peroxidation by free radicals, hydrogen peroxide

Physiological and morphological adaptations of the fruit tree Ziziphus rotundifolia in response to progressive drought stress

Abstract: The physiological basis of drought resistance in Ziziphus rotundifolia Lamk., which is an important, multipurpose fruit tree of the northwest Indian arid zone, was investigated in a greenhouse experiment. Three irrigation regimes were imposed over a 34-day period: an irrigation treatment, a gradual drought stress treatment (50% of water supplied in the irrigation treatment) and a rapid drought stress treatment (no irrigation). Changes in gas exchange, water relations, carbon isotope composition and solute concentrations of leaves, stems and roots were determined. The differential rate of stress development in the two drought treatments did not result in markedly different physiological responses, but merely affected the time at which they were expressed. The initial response to decreasing soil water content was reduced stomatal conductance, effectively maintaining predawn leaf water potential (Psi(leaf)), controlling water loss and increasing intrinsic water-use efficiency, while optimizing carbon gain during drought. Carbon isotope composition (delta13C) of leaf tissue sap provided a more sensitive indicator of changes in short-term water-use efficiency than delta13C of bulk leaf tissue. As drought developed, osmotic potential at full turgor decreased and total solute concentrations increased in leaves, indicating osmotic adjustment. Decreases in leaf starch concentrations and concomitant increases in hexose sugars and sucrose suggested a shift in carbon partitioning in favor of soluble carbohydrates. In severely drought-stressed leaves, high leaf nitrate reductase activities were paralleled by increases in proline concentration, suggesting an osmoprotective role for proline. As water deficit increased, carbon was remobilized from leaves and preferentially redistributed to stems and roots, and leaves were shed, resulting in reduced whole-plant transpiration and enforced dormancy. Thus, Z. rotundifolia showed a range of responses to different drought intensities indicating a high degree of plasticity in response to water deficits.

Sample preservation for determination of organic compounds: microwave versus freeze-drying

Abstract: In search of a reliable drying method, which might be used even under field conditions, microwave drying was compared to freeze-drying of plant material. Leaves of Ananas comosus and Avicennia germinans as well as buds and phloem of Acer pseudoplatanus were used and checked for one or more of the following substances: sugars, sugar alcohols, organic and amino acids, total nitrogen, and glycinebetaine. With most samples good agreement was achieved between the two drying methods. Only in the case of the Ananas comosus leaves, which exhibited low pH and high water content, did appreciable differences occur in organic and amino acids. Besides that, sucrose was the compound most susceptible to alterations, which was especially evident when leaves of Sambucus nigra were dried in the two different compartments (condenser compartment, drying bell jar) of the freeze-dryer in use. For Ananas comosus leaf samples it was shown that microwaving can also be used prior to extraction of tissue sap.

Chemical composition of halophytes from the Neusiedler Lake region in Austria

Abstract: The ionic relations in halophytes from the region east of Neusiedler Lake in Austria have been investigated. The study encompasses the following compounds: Na, K, Mg, Ca; Cl, SO4, phosphate, nitrate, and organic acids.

Carbon Isotope Discrimination and Photosynthesis

Abstract: We discuss the physical and enzymatic bases of carbone isotope discrimination during photosynthesis, noting how knowledge of discrimination can be used to provide additional insight into photosynthetic metabolism and the environmental influences on that process

Plant cellular and molecular responses to high salinity.

Abstract: ▪ Abstract Plant responses to salinity stress are reviewed with emphasis on molecular mechanisms of signal transduction and on the physiological consequences of altered gene expression that affect biochemical reactions downstream of stress sensing. We make extensive use of comparisons with model organisms, halophytic plants, and yeast, which provide a paradigm for many responses to salinity exhibited by stress-sensitive plants. Among biochemical responses, we emphasize osmolyte biosynthesis and function, water flux control, and membrane transport of ions for maintenance and re-establishment of homeostasis. The advances in understanding the effectiveness of stress responses, and distinctions between pathology and adaptive advantage, are increasingly based on transgenic plant and mutant analyses, in particular the analysis of Arabidopsis mutants defective in elements of stress signal transduction pathways. We summarize evidence for plant stress signaling systems, some of which have components analogous to t...

Water relations, drought and vesicular-arbuscular mycorrhizal symbiosis

Abstract: Vesicular-arbuscular mycorrhizal fungi can affect the water balance of both amply watered and droughted host plants. This review summarizes these effects and possible causal mechanisms. Also discussed are host drought resistance and the influence of soil drying on the fungi.

Biomass allocation to leaves, stems and roots: meta-analyses of interspecific variation and environmental control

Abstract: Contents Summary 30 I. Allocation in perspective 31 II. Topics of this review 32 III. Methodology 32 IV. Environmental effects 33 V. Ontogeny 36 VI. Differences between species 40 VII. Physiology and molecular regulation 41 VIII. Ecological aspects 42 IX. Perspectives 45 Acknowledgements 45 References 45 Appendices A1–A4 49 Summary We quantified the biomass allocation patterns to leaves, stems and roots in vegetative plants, and how this is influenced by the growth environment, plant size, evolutionary history and competition. Dose–response curves of allocation were constructed by means of a meta-analysis from a wide array of experimental data. They show that the fraction of whole-plant mass represented by leaves (LMF) increases most strongly with nutrients and decreases most strongly with light. Correction for size-induced allocation patterns diminishes the LMF-response to light, but makes the effect of temperature on LMF more apparent. There is a clear phylogenetic effect on allocation, as eudicots invest relatively more than monocots in leaves, as do gymnosperms compared with woody angiosperms. Plants grown at high densities show a clear increase in the stem fraction. However, in most comparisons across species groups or environmental factors, the variation in LMF is smaller than the variation in one of the other components of the growth analysis equation: the leaf area : leaf mass ratio (SLA). In competitive situations, the stem mass fraction increases to a smaller extent than the specific stem length (stem length : stem mass). Thus, we conclude that plants generally are less able to adjust allocation than to alter organ morphology.