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Showing papers by "Ernst Detlef Schulze published in 1990"


Journal ArticleDOI
TL;DR: Criteria for defining storage in ecological and eonomic contexts is suggested in order to examine the costs and benefits of storage and the evidence for different types of storage is evaluated.
Abstract: Storage is a characteristic feature of most plants, particularly perennials, and the subject has been thoroughly reviewed according to its chemistry and physiology (9, 40, 59, 80, 133, 139). However, in ecology much of the information on storage is based on observation rather than experimentation, and experiments often fail to confirm common perceptions of the nature and dynamics of stored reserves. For example, clipping studies show that not all carbohydrates are available to the plant, even though they are considered to be stored reserves. In this review we suggest criteria for defining storage in ecological and eonomic contexts in order to examine the costs and benefits of storage. We then evaluate the evidence for, and ecological importance of, different types of storage. We discuss storage in relation to vegetative growth

1,601 citations


Journal ArticleDOI
TL;DR: It is concluded that during the course of a drying cycle the range of maximum leaf conductance seems to be dependent on the concentration of abscisic acid in xylem sap.
Abstract: SUMMARY Individual 1- to 4-year-old almond trees [Prunus dulcis (Miller) D. A. Webb] were grown in lysimeters of different volumes, filled with loess. Once per year, at the beginning of each growing season, the lysimeters were watered to field capacity, and consequently each tree experienced a seasonal drought in relation to the amount of available water depending on soil volume and tree age. Measurements of leaf conductance were performed on youngest fully expanded, sun-exposed leaves in climatized cuvettes. Leaf water potential was measured with a pressure chamber, which was also used for collecting xylem sap. Abscisic acid concentration of the xylem sap was determined with ELISA. There was no consistent diurnal relationship between abscisic acid concentration in xylem sap and leaf conductance. During a drying cycle, however, there was an inverse relationship between maximum leaf conductance and daily average abscisic acid concentration in xylem sap. With soil drying, the concentration of abscisic acid in xylem sap initially increased to a maximum in summer but decreased again towards autumn. Thus, during the first part of the drying cycle the predawn water potential of the leaf was significantly correlated with abscisic acid concentration in xylem sap. As predawn water potential becomes more negative during the first part of the drying cycle, the decline in maximum leaf conductance correlates with an increase in concentration of abscisic acid in xylem sap. With further decrease in predawn water potential towards the end of the drying cycle, the stomata remained closed even though there was a decreasing concentration of abscisic acid in the xylem sap. We conclude that the concentration of abscisic acid in xylem sap is not related to leaf conductance during the course of a day from end of May to September. However, during the course of a drying cycle the range of maximum leaf conductance seems to be dependent on the concentration of abscisic acid in xylem sap.

117 citations


Journal ArticleDOI
TL;DR: The daily courses of xylem water flow were strongly influenced by the orientation of the leaf area to irradiance and its intensity, while leaves of E. polystachya had a constant high stomatal conductance during the day, and S. brachycarpa had a maximum stomatic opening in the morning followed by continuous closure during the rest of the day.
Abstract: A method for determining the mass flow rate of xylem water in thin stems under natural field conditions is presented. Diurnal courses of xylem water flow and stomatal conductance of the vines Entadopsis polystachya, Cyclanthera multifoliolata, and Serjania brachycarpa were examined in a tropical deciduous forest on the west coast of Mexico. E. polystachya (leaf area 23.6 m2) had a maximum water flow rate of 6.50 kg h-1 or 1.44 kg cm-2 stem basal area h-1; daily water use was 2.00 kg m-2 leaf area day-1. S. brachycarpa (leaf area 4.5 m2) and C. multifoliolata (leaf area 3.6 m2) had a maximum water flow rate of 0.72 and 0.19 kg h-1 or 0.63 and 0.92 kg cm-2 stem basal area h-1. Daily water use was 1.26 and 0.39 kg m-2 leaf area day-1, respectively. The daily courses of xylem water flow were strongly influenced by the orientation of the leaf area to irradiance and its intensity. While leaves of E. polystachya had a constant high stomatal conductance during the day, S. brachycarpa had a maximum stomatal opening in the morning followed by continuous closure during the rest of the day. In contrast to the woody species, the herbaceous C. multifoliolata exhibited a strong midday depression of stomatal conductance and wilting of its leaves. The leaf biomass accounted for 8% (Entadopsis), 16% (Serjania), and 23% (Cyclanthera) of above-ground biomass. The relation of sapwood area to leaf area supplied (Huber value) was 0.19 (Entadopsis), 0.18 (Serjania), and 0.06 (Cyclanthera) cm2 m-2

57 citations


Journal ArticleDOI
TL;DR: In this paper, a homogenized loess from the Negev Desert, Israel, was used to fill 48 lysimeters, of which 42 were each planted with a single almond tree.

52 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss the mechanisms by which air pollution affects forest health and discuss the aetiologies of different syndromes of decline, whereas pathogens seem to be of only secondary importance, whereas exposure to large concentrations of gaseous pollutants appears to have short-term rather than long-lasting effects.
Abstract: Forest decline in Europe is centred around areas where air pollution is heaviest. Although statistical relations are still debatable at the stand level, they are a basis for the discussion of mechanisms by which air pollutants affect forest health. The aetiologies of different syndromes of decline are discussed. Exposure to large concentrations of gaseous pollutants appears to have short-term rather than long-lasting effects, whereas pathogens seem to be of only secondary importance. The deposition of sulphur and nitrogen (nitrate and ammonium) pollutants has significantly modified soil chemistry and plant nutrition. In acidic low-pH soils spruce roots, instead of utilising nitrate, preferentially take up ammonium which interferes with the uptake of other cations, notably magnesium. The nitrate remaining in soil solution, as a result of the preferential uptake of ammonium, is leached together with sulphate to groundwater, accelerating soil acidification and further decreasing the calcium and/or magnesium to aluminium ratios in soil solution. Soil solution chemistry affects root development, and thus water and nutrient uptake. Canopy uptake of nitrogen, especially of ammonium, which is additional to root uptake, may occur and appears to stimulate growth inciting a nitrogen to cation imbalance with the consequential production of decline symptoms.

43 citations


Journal ArticleDOI
TL;DR: Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture, however, increased leaf growth was counterbalanced by leaf abscission which was in turn related to Insect capture and leaf growth.
Abstract: Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture. However, increased leaf growth was counterbalanced by leaf abscission which was in turn related to insect capture and leaf growth. Leaf loss equaled leaf growth in plants having natural rate of insect capture. A large proportion of the nitrogen gain from prey was stored in the hypocotyl; it was estimated from feeding experiments that about 24% to 30% of the nitrogen stored in the hypocotyl after winter originated from insect capture in the previous season. The effect of insect capture is discussed in relation to the life cycle of Drosera.

35 citations


Journal ArticleDOI
TL;DR: It is confirmed that there is no long-term effect of atmospheric pollutants directly on photosynthetic CO2 uptake rates with persistent exposure at the FRG site to high levels of anthropogenic air pollution.
Abstract: Photosynthetic rates and nutrient contents of spruce needles were measured in a region with high levels of air pollution in NE Bavaria, Germany (FRG), and compared to spruce grown under clean air conditions at Craigieburn, in the South Island of New Zealand (NZ). The absolute rates of CO2 uptake, the slope of the CO2 response curve at 240 μl l-1 internal CO2 concentration, and the change of photosynthetic rates with needle age at ambient and saturated CO2 concentrations were virtually identical at both measuring sites. These results confirm an earlier conclusion, that there is no long-term effect of atmospheric pollutants directly on photosynthetic CO2 uptake rates with persistent exposure at the FRG site to high levels of anthropogenic air pollution. Photosynthetic capacity at saturating CO2 concentration was three times higher in the NZ spruce. Needles with high photosynthetic capacity in NZ had lower nitrogen and higher calcium concentrations per unit dry weight but higher concentrations of nitrogen, phosphorus, potassium, magnesium and calcium per unit leaf area, and twice the specific leaf weight.

32 citations


Journal ArticleDOI
TL;DR: In this article, the authors konzentriert sich auf die Situation im Fichtelgebirge, where Wissenschaftler aus sieben bayerischen Universitaten versucht haben, auf den gleichen Versuchsflachen die verschiedenen Hypothesen der Schadensursachen vergleichend zu untersuchen.
Abstract: Charakteristisch fur die “neuartigen Waldschaden” ist, das sie auf groser Flache und an mehreren Baumarten auftreten. Es handelt sich bei ihnen um eine Vielzahl von Symptomen, die im Einzelfall keinesfalls neu zu sein brauchen. Der folgende Beitrag konzentriert sich auf die Situation im Fichtelgebirge, wo Wissenschaftler aus sieben bayerischen Universitaten versucht haben, auf den gleichen Versuchsflachen die verschiedenen Hypothesen der Schadensursachen vergleichend zu untersuchen.

14 citations


Book ChapterDOI
01 Jan 1990
TL;DR: The rate at which plants assimilate CO2 in the field may be quite different from optimal conditions in the test tube or in growth cabinets as mentioned in this paper, depending on the environmental conditions of the habitat which determine to what extent the genetic capability of a plant can actually be used for photosynthesis.
Abstract: Photosynthesis is the process that provides energy to all anabolic and catabolic processes in ecosystems. The rate at which plants assimilate CO2 in the field may be quite different from optimal conditions in the test tube or in growth cabinets. The rate depends on the environmental conditions of the habitat which determine to what extent the genetic capability of a plant can actually be used for photosynthesis. The main factor restricting photosynthesis in the field is the availability of light. But, other factors my become just as rate 1imitating, such as atmospheric carbon dioxide concentration, air humidity and temperature, and water or nutrient supply from the soil. Time is an additional important factor which influences the carbon balance via plant age but also by deterimining the dose of stress.

2 citations