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1

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Experiments on the water balance of individual attached twigs of Picea abies (L .) Karst. in pure and ozone-enriched air (1997)

Maier-Maercker, Uta

Springer

Trees 11 (1997), S. 229-239

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ISSN: 0931-1890

Keywords: Key words Ozone ; Picea abies ; Stomatal control ; Water potential ; Xylem sap flow

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Rates of transpiration and xylem sap flow were continuously measured in individual twigs in the upper crown of an 18-year-old spruce. Two gas exchange chambers were run simultaneously under identical conditions. One of two equivalent twigs was exposed to pure air whereas the other received the ozone-enriched air of the site. A third gas exchange chamber in mid-crown ran independently with normal outside air and was used for basic experiments. At certain times needles were sampled for water potential measurements. Chamber humidity was reduced step by step and the transpiration and xylem sap flow rates were permanently compared. It turned out that sap flow keeps up with transpiration without lagging as long as chamber humidity is high and the twigs outside the chamber are not subject to substantial evaporative demand. However, in warm summer weather and with high flow rates sap flow is no longer sufficient. As the balance quotient (uptake/release) of 0.8 was reached the stomata began to close and water balance improved. The flux quotient increased far above 1.0 without water potential of the needles, which had decreased before, increasing significantly. The balance quotient of the twig in ozone-enriched air fell to relatively low values and only increased again correspondingly slowly due to lagging stomatal closure. Despite increased water uptake after the light phase, the ozone-treated twig ran into a water deficit in the daily balance during the course of an uninterrupted drought period. Water deficit increased from day to day and only disappeared with the next rainfall. For providing insight into the ozone effect shown in this study it was thought necessary to discuss comprehensively the controversial views of the stomatal control mechanism. The results show that the stomata react to small scale changes in water status as expected for an effective negative feedback system. The less sensitive reaction of the stomata under the influence of ozone confirms earlier results. Increased severity and duration of the daily drought stress loads were attributed to a lag in adjustment due to poor stomatal control. The demonstrated function mechanism shows that the detrimental effect of ozone is dependent on weather conditions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/PL00009669

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2

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Image analysis of the stomatal cell walls of Picea abies (L.) Karst. in pure and ozone-enriched air (1998)

Maier-Maercker, Uta

Springer

Trees 12 (1998), S. 181-185

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ISSN: 0931-1890

Keywords: Key words Image analysis ; Ozone ; Picea abies ; Stomata ; UV-absorbance

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The method of image analysis was used to re-investigate previously described structural changes in spruce needles following their exposure to ozone. The changes observed in fumigation experiments were compared with the modifications observed at a site with a similar ozone load. Use was made in each case of needles for which the varying behavioural patterns were known from physiological experiments. In samples with reduced ability to regulate stomatal aperture, the cell walls of the stomatal apparatus showed a reduction in absorptive power at 280 nm. This was interpreted to be a result of delignification of the cell walls in question due to the direct impact of ozone on the surface of the needle.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/PL00009708

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3

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The role of peristomatal transpiration in the mechanism of stomatal movement (1983)

MAIER-MAERCKER, UTA

Oxford, UK : Blackwell Publishing Ltd

Plant, cell & environment 6 (1983), S. 0

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ISSN: 1365-3040

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract. Peristomatal transpiration is defined as the relative high local rate of cuticular water loss from external and internal surfaces around the stomatal pore and its decisive role in the control of stomatal movement is re-emphasized. As the resistance towards changes in air humidity is low in the pore surroundings, the state of turgor is particularly unsteady there. Due to the inherent instability the guard cell ‘senses’ fluctuations in the supply-demand relationship of water and is thus the control unit proper. The environmental variables (supply and demand) are cross-correlated within the subsidiary cell and the information is transmitted to the guard cell through the water potential gradient between the two cells. A conceptual segregation of a ‘humidity response’ by ‘passive’ stomatal movements is rejected.As ions always accumulate at the most distant point of the liquid path and as this point varies with pore width according to the prevailing water potential gradients, it is felt that the water stream is causing the characteristic pattern of ion distribution within the epidermis. Passive import of ions is attributed to local concentration gradients which are steepened by continuous supply and by water uptake into the guard cell in response to starch hydrolysis. A mechanistic model supplements the discussion.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3040.1983.tb01269.x

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4

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The effect of air pollution on the mechanism of stomatal control (1992)

Maier-Maercker, Uta ; Koch, Werner

Springer

Trees 7 (1992), S. 12-25

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ISSN: 1432-2285

Keywords: Air pollution ; Drought stress ; Forest decline ; Gas exchange measurements ; Stomatal control

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary A long-term field experiment permanently measuring gas exchange in the top of a 70-year-old spruce, continued for through the 1990 growing season. Two gas exchange chambers were run simultaneously under identical climatic conditions. One of two similar twigs was exposed to ambient air whereas the other received pure air. These experiments aimed to examine the ability of the stomata to control water balance, comparing pure and ambient air. This was done not only in natural climatic conditions but also in experimental, specifically maintained stress situations. Special care was taken to ensure that only steady state values of stomatal responses are related to the environmental stimuli. During a drought period lasting several weeks, overshooting transpiration values were documented for the ambient air. The two twigs do not merely differ in their control capacity, but the behaviour of the stomata in ambient air deviates from the “norm”. The increasingly uncontrolled water losses during the drought period have a negative effect on photosynthetic capacity. The influence of water deficit on stomatal response to other environmental factors (light, CO2) is shown. Due to deficient control quality of the stomata lower stress tolerance in the face of drought is suggested in ambient air as compared with pure air. By tracing dysfunctions to structural changes in the cell walls of the stomatal apparatus, a mechanism is described explaining forest decline under the combined influence of air pollutants and drought stress.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00225227

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5

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Delignification of subsidiary and guard cell walls of Picea abies (L.) Karst. by fumigation with ozone (1989)

Maier-Maercker, Uta

Springer

Trees 3 (1989), S. 57-64

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ISSN: 1432-2285

Keywords: Delignification ; Hydroregulation ; Ozone ; Stomata ; UV absorbance

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary After fumigation with ozone, the exterior periclinal walls of the stomatal apparatus of Picea abies appear to be partially delignified, as in earlier experiments with SO2. This shows up cytophotometrically as reduced UV absorption. Random samples from the stand named Wank in the Bavarian Alps clearly showed a relation between the degree of lignification of the stomatal cells and the grading of the respective trees in their damage classes. The significance of delignification for the regulatory capacity of the stomata is discussed, and a hypothesis is proposed for a specific disturbance of hydroregulation by ozone.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00202401

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6

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Experiments on the water budget of densely and sparsely needled spruces [Picea abies (L.) Karst.] in a declining stand (1991)

Maier-Maercker, Uta ; Koch, Werner

Springer

Trees 5 (1991), S. 164-170

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ISSN: 1432-2285

Keywords: Forest decline ; Osmotic potential ; Picea abies ; Water content ; Water potential

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary The osmotic potentials of needles were compared from numerous trees that had been classified according to needle loss along an altitude profile. With the increasing degree of damage of the trees, the maximum and minimum values deviated more strongly above and below the common mean of all samples. The level of water content of the needles unequivocally reflected the vitality of the trees. Experiments covering a whole vegetation period were performed on a tree pair selected from a natural stand. They were designed to demonstrate differences in water balance between the “healthy” and “damaged” state of the trees. For the “damaged” tree, measurements of the water potentials of single needles showed a greater reduction of potential during the course of the day compared to the “healthy” tree. Recovery in the evenings was slower and often incomplete. The osmotic potentials of “damaged” and “healthy” shoots measured in individual needles also differed both predawn and especially after transpiration stress. Depending on weather and soil desiccation, the differences were more or less pronounced. In the “damaged” tree, the rises in potential after saturation of the twigs fell far short of the “healthy” tree. Reduction of water potential, osmotic potential and relative water content under comparable stress conditions suggest a reduced tolerance of drought by damaged trees. In the context of earlier experiments this result was ascribed to a lack of stomatal control, and long-term pollution effects were thus explained as a specific disturbance of hydroregulation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00204339

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7

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Histological examination of spruce needles from a long-term gas exchange experiment in pure and polluted air in the field (1992)

Maier-Maercker, Uta ; Koch, Werner

Springer

Trees 6 (1992), S. 186-194

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ISSN: 1432-2285

Keywords: Air pollutants ; Bundle sheath ; Picea abies ; Stomata ; UV absorbance

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Summary At the end of a 4-year period of gas exchange measurements in a natural stand in the Lower Bavarian Forest, needles of an adult spruce [Picea abies (L.) Karst.] were harvested from two chambers, one with pure air and the other with ambient air. The needles were examined as to their histological properties in the stomatal apparatus and in the bundle sheath. In needles from the polluted air UV absorbance at 280 nm was decreased in the walls of the stomatal apparatus. Simultaneously, the deposition of compounds with an absorption maximum at 310 nm increased within the encrusted plate-like thickenings of the subsidiary cells. The contents of the lumina of hypodermal cells and of the bundle sheath exhibited a greater degree of autofluorescence in ambient-air material than in pure-air leaf organs. Differences between needles exposed to pure and polluted air are gradual. The “damaged” condition is rare in pure air, common in polluted air. The needles from outside the chambers occupied an intermediate position between pure-air and ambient-air needles. This fact is traced to an unnaturally high pollutant load in the liquid phase of the needle surfaces within the ambient-air chamber because in order to compensate pollutant losses within the system, SO2 and O3 were added even during periods of irrigation. The reduction of absorption capacity at 280 nm in the walls of the stomatal apparatus is attributed to destruction of lignin due to the high reactivity of the pollutants in the liquid phase on the damp needle surface. The importance of delignification with regard to hydroregulation is discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00224334

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8

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Poor stomatal control of water balance and the abscission of green needles from a declining stand of spruce trees [Picea abies (L.) Karst.] from the northern Alps (1995)

Maier-Maercker, Uta ; Koch, Werner

Springer

Trees 10 (1995), S. 63-73

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ISSN: 1432-2285

Keywords: Forest decline ; Osmotic potential ; Picea abies ; Stomatal control ; Water potential

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract On a site on the west slope of the Wank in the northern Alps changes in water potential, osmotic potential and transpiration rate were measured in spruce trees during the dry summer months of 1991. The pattern of decrease in water potential and osmotic potential on days of varying evaporative demand from trees of widely different decline conditions was used to describe the relative ability of the trees to withstand drought stress. Stress diagrams served as a tool for interpreting the state of health of each tree. The criterion is independent of the water situation of the tree and the other external conditions of the respective experiment. These diagrams clearly show that the foliage of spruces with high needle losses reaches the limit of endurance relatively early. For equal evaporative demand much lower turgor levels were observed in spruces with high needle loss compared to undamaged trees. Associated with the occurrence of low turgor values was the shedding of green needles. The abscission zone was shown in sections. The accumulation of highly fluorescent substances in the bundle sheath cells of the same material was described. Incomplete to non-existent stomatal control over water loss was attributed to modifications in the cell walls of the stomata which appear to alter the ability of the guard cells to sense changes in either atmospheric or cellular hydration. Our studies point to the following situation: air pollution directly affects stomatal control, the loss of stomatal control changes the drought avoidance abilities of the foliage and, as a consequence, low turgor levels occur and premature needle abscission is induced. As site water balance decreases, either due to a dry year or to poor moisture holding abilities of the soil, these conditions become apparent.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00192185

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