The Role of Ectomycorrhizal Symbiosis in the Resistance of Forests to Water Stress

2000 ◽  
Vol 29 (1) ◽  
pp. 63-69 ◽  
Author(s):  
Jean Garbaye
Keyword(s):  
Water Stress ◽  
Sustainable Management ◽  
Fine Roots ◽  
Forest Ecosystems ◽  
Water Status ◽  
Forest Trees ◽  
Direct Effects ◽  
Ectomycorrhizal Symbiosis ◽  
Protection Mechanisms

Forest trees live in enforced symbiosis with specialized fungi that form composite organs (ectomycorrhizas) with fine roots. This paper examines how this association contributes to the water status of trees and how it plays a major role in the protection mechanisms by which trees and forest stands resist drought-induced water stress. It shows how ectomycorrhizal symbiosis has both direct effects (at the uptake level) and indirect effects (at the regulation level) on the water status of trees. The facts presented are discussed in terms of forest adaptation to changing environmental conditions and the practical consequences for the sustainable management of forest ecosystems.

scholarly journals Contribution of fine tree roots to the silicon cycle in a temperate forest ecosystem developed on three soil types

2018 ◽  
Vol 15 (7) ◽  
pp. 2231-2249 ◽  
Author(s):  
Marie-Pierre Turpault ◽  
Christophe Calvaruso ◽  
Gil Kirchen ◽  
Paul-Olivier Redon ◽  
Carine Cochet
Keyword(s):  
Seasonal Dynamics ◽  
Forest Floor ◽  
Fine Roots ◽  
Temperate Forest ◽  
Forest Ecosystems ◽  
Soil Layer ◽  
Soil Types ◽  
Root Decomposition ◽  
Soil Layers

Abstract. The role of forest vegetation in the silicon (Si) cycle has been widely examined. However, to date, little is known about the specific role of fine roots. The main objective of our study was to assess the influence of fine roots on the Si cycle in a temperate forest in north-eastern France. Silicon pools and fluxes in vegetal solid and solution phases were quantified within each ecosystem compartment, i.e. in the atmosphere, above-ground and below-ground tree tissues, forest floor and different soil layers, on three plots, each with different soil types, i.e. Dystric Cambisol (DC), Eutric Cambisol (EC) and Rendzic Leptosol (RL). In this study, we took advantage of a natural soil gradient, from shallow calcic soil to deep moderately acidic soil, with similar climates, atmospheric depositions, species compositions and management. Soil solutions were measured monthly for 4 years to study the seasonal dynamics of Si fluxes. A budget of dissolved Si (DSi) was also determined for the forest floor and soil layers. Our study highlighted the major role of fine roots in the Si cycle in forest ecosystems for all soil types. Due to the abundance of fine roots mainly in the superficial soil layers, their high Si concentration (equivalent to that of leaves and 2 orders higher than that of coarse roots) and their rapid turnover rate (approximately 1 year), the mean annual Si fluxes in fine roots in the three plots were 68 and 110 kgha-1yr-1 for the RL and the DC, respectively. The turnover rates of fine roots and leaves were approximately 71 and 28 % of the total Si taken up by trees each year, demonstrating the importance of biological recycling in the Si cycle in forests. Less than 1 % of the Si taken up by trees each year accumulated in the perennial tissues. This study also demonstrated the influence of soil type on the concentration of Si in the annual tissues and therefore on the Si fluxes in forests. The concentrations of Si in leaves and fine roots were approximately 1.5–2.0 times higher in the Si-rich DC compared to the Si-poor RL. In terms of the DSi budget, DSi production was large in the three plots in the forest floor (9.9 to 12.7 kgha-1yr-1), as well as in the superficial soil layer (5.3 to 14.5 kgha-1yr-1), and decreased with soil depth. An immobilization of DSi was even observed at 90 cm depth in plot DC (−1.7 kgha-1yr-1). The amount of Si leached from the soil profile was relatively low compared to the annual uptake by trees (13 % in plot DC to 29 % in plot RL). The monthly measurements demonstrated that the seasonal dynamics of the DSi budget were mainly linked to biological activity. Notably, the peak of dissolved Si production in the superficial soil layer occurred during winter and probably resulted from fine-root decomposition. Our study reveals that biological processes, particularly those involving fine roots, play a predominant role in the Si cycle in temperate forest ecosystems, while the geochemical processes appear to be limited.

Differential effects of water stress on respiration in the light in woody plants from wet and dry habitats

1976 ◽  
Vol 54 (21) ◽  
pp. 2457-2464 ◽  
Author(s):  
James A. Bunce ◽  
Lee N. Miller
Keyword(s):  
Water Stress ◽  
Woody Plants ◽  
Dark Respiration ◽  
Water Status ◽  
Net Photosynthesis ◽  
Protective Role ◽  
Leaf Water Status ◽  
Analogue Model ◽  
Free Air

Respiration in the light, dark respiration, and leaf water status were monitored once a day in leaves of woody plants as seedlings dried during 7- to 10-day periods. Light respiration was estimated from an electrical analogue model of the response of net photosynthesis to ambient CO2 concentration and also by the rate of CO2 evolution into CO2-free air. Respiration in the light was found to increase with water stress in four dry-habitat species and to decrease with stress in four wet-habitat species. Dark respiration changes could not account for the different trends observed. When light respiration in dry-habitat plants under water stress was temporarily inhibited, net photosynthesis during recovery from water stress was reduced compared with controls for at least a week. This may indicate a protective role of light respiration in these plants when under water stress.

scholarly journals Sugar Accumulation Enhanced by Osmoregulation in Satsuma Mandarin Fruit

1996 ◽  
Vol 121 (3) ◽  
pp. 466-472 ◽  
Author(s):  
Hiroshi Yakushiji ◽  
Hiroshi Nonami ◽  
Toshio Fukuyama ◽  
Sukeyuki Ono ◽  
Nobuo Takagi ◽  
...  
Keyword(s):  
Water Stress ◽  
Water Potential ◽  
Osmotic Potential ◽  
Fine Roots ◽  
Water Status ◽  
Sugar Content ◽  
Stress Conditions ◽  
Sugar Accumulation ◽  
Satsuma Mandarin ◽  
Response To Water

The effect of water stress induced to enhance sugar accumulation in Satsuma mandarin (Citrus unshiu Marc.) fruit was investigated. Satsuma mandarin trees were subjected to water stress using mulch cultivation from late August to early December. In mulch treatment, soil was covered with double-layered plastic sheets that prevented rainfall from permeating the soil, but allowed water from soil to evaporate. The water status of soil, fine roots, pericarps, and juice vesicles was determined using the isopiestic psychrometer. As the severity of water stress increased, both water potential and osmotic potential of fine roots and pericarps significantly decreased in plants grown under mulch cultivation compared to well-watered trees. Although water potential and osmotic potential decreased, turgor of both roots and pericarps of the water stressed trees did not decrease under water stress conditions. Because turgor was maintained, osmoregulation occurred in Satsuma mandarin trees in response to water stress. The osmotic potential of juice vesicles in water-stressed fruit gradually decreased, and sugars accumulated in vesicle cells. Concentrations of sucrose, fructose, and glucose increased in fruit sap under water stress, and the acidity in the fruit juice increased. Furthermore, the total sugar content per fruit of water stressed trees was significantly higher than in fruit of well-watered trees. These results suggest that sugar accumulation in Satsuma mandarin fruit was not caused by dehydration under water stress but rather that sugars were accumulated by active osmoregulation in response to water stress. When sugar components in osmoregulated fruit were analyzed, it was found that monosaccharides, i.e., glucose and fructose, were largely responsible for active osmoregulation in fruit under water stress conditions.

scholarly journals Silicon cycle in a temperate forest ecosystem: role of fine roots and litterfall recycling and influence of soil types

2017 ◽  
Author(s):  
Marie-Pierre Turpault ◽  
Christophe Calvaruso ◽  
Gil Kirchen ◽  
Paul-Olivier Redon ◽  
Carine Cochet
Keyword(s):  
Seasonal Dynamics ◽  
Forest Floor ◽  
Fine Roots ◽  
Temperate Forest ◽  
Forest Ecosystems ◽  
Soil Types ◽  
Soil Horizon ◽  
Root Decomposition ◽  
Soil Horizons

Abstract. The role of forest vegetation in the silicon (Si) cycle has been widely examined. However, to date, no study has investigated the specific role of fine roots. The main objectives of our study were to assess the influence of fine roots as well as the impact of soil properties on the Si cycle in a temperate forest in northeastern France. Silicon pools and fluxes in solid and solution phases were quantified within each ecosystem compartment, i.e., the atmosphere, aboveground and belowground tree tissues, forest floor, and different soil horizons, on three plots, each with different soil types, i.e., Dystric Cambisol (plot S1), Eutric Cambisol (plot S2), and Rendzic Leptosol (plot S3). In this study, we took advantage of a natural soil gradient, from shallow calcic soil to deep moderately acidic soil, with similar climates, atmospheric depositions, species composition and management. Soil solutions were measured monthly for four years to study the seasonal dynamics of Si fluxes. A budget of dissolved Si was also determined for the forest floor and soil layers. Our study highlighted the major role of fine roots in the Si cycle in forest ecosystems for all soil types. Because of the abundance of fine roots mainly in the superficial soil horizons, their high Si concentration (equivalent to that of leaves and two orders higher than that of coarse roots) and their rapid turnover rate (approximately one year), the mean annual Si fluxes in fine roots in the three plots ranged from 68 to 110 kg ha−1 y−1 for the Rendzic Leptosol and the Dystric Cambisol, respectively. The turnover of fine roots and leaves was approximately 71 % and 28 % of the total Si taken up by trees each year, respectively, demonstrating the importance of biological recycling in the Si cycle in forests. Less than 1 % of the Si taken up by trees each year accumulated in the perennial tissues. This study also demonstrated the influence of soil type on the concentration of Si in the annual tissues and therefore on the Si fluxes in forests. The concentrations of Si in leaves and fine roots were approximately 1.5–2.0 times higher in the Si-rich Dystric Cambisol compared to the Si poor Rendzic Leptosol. In terms of the dissolved Si budget, there were large amounts of dissolved Si in the three plots on the forest floor (9.9 to 12.7 kg ha−1 y−1) and in the superficial soil horizon (5.3 to 14.5 kg ha−1 y−1), and Si decreased with depth in plot S1 (1.7 kg ha−1 y−1). The amount of Si leached from the soil profile was relatively low compared to the annual uptake by trees (13 % in plot S1 to 29 % in plot S3). The monthly measurements demonstrated that the seasonal dynamics of the dissolved Si budget were mainly linked to biological activity. Notably, the peak of dissolved Si production in the superficial soil horizon was during the winter and probably resulted from fine root decomposition. Our study reveals that biological processes, particularly those of fine roots, play a predominant role in the Si cycle in temperate forest ecosystems, while the geochemical processes appear to be limited.

When will firms conduct joint R&D? : The role of organizational innovation and protection mechanisms

2019 ◽  
Vol 42 (4) ◽  
pp. 3-27
Author(s):  
Do Bum Chung ◽  
Hye Jeong Jang ◽  
Byung il Kim
Keyword(s):  
Organizational Innovation ◽  
Protection Mechanisms

Monitoring Crop Water Status and Irrigation Needs Using Multispectral Airborne Sensors

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 905D-905
Author(s):  
Thomas R. Clarke ◽  
M. Susan Moran
Keyword(s):  
Water Stress ◽  
Near Infrared ◽  
Water Status ◽  
Canopy Cover ◽  
Stress Index ◽  
Crop Water ◽  
Vegetative Cover ◽  
Crop Water Stress Index ◽  
Water Stress Index ◽  
Subsurface Drip

Water application efficiency can be improved by directly monitoring plant water status rather than depending on soil moisture measurements or modeled ET estimates. Plants receiving sufficient water through their roots have cooler leaves than those that are water-stressed, leading to the development of the Crop Water Stress Index based on hand-held infrared thermometry. Substantial error can occur in partial canopies, however, as exposed hot soil contributes to deceptively warm temperature readings. Mathematically comparing red and near-infrared reflectances provides a measure of vegetative cover, and this information was combined with thermal radiance to give a two-dimensional index capable of detecting water stress even with a low percentage of canopy cover. Thermal, red, and near-infrared images acquired over subsurface drip-irrigated cantaloupe fields demonstrated the method's ability to detect areas with clogged emitters, insufficient irrigation rate, and system water leaks.

scholarly journals The Role of Flexibility in the Realization of Inclusive Education

2021 ◽  
Vol 13 (8) ◽  
pp. 4452
Author(s):  
Laura Lübke ◽  
Martin Pinquart ◽  
Malte Schwinger
Keyword(s):  
Social Skills ◽  
Inclusive Education ◽  
Learning Difficulties ◽  
Social Benefits ◽  
Direct Effects ◽  
Behavioral Disturbances ◽  
Teachers Attitudes ◽  
And Behavior ◽  
Mainstream Students

This study focused on associations between teachers’ flexibility and their use of evidence-based strategies in inclusive education in a sample of N = 119 teachers. Flexibility showed direct effects on teachers’ attitudes towards the achievement of mainstream students and students with learning difficulties, attitudes towards social benefits of inclusion for students with emotional and behavioral disturbances, and on teachers’ self-efficacy regarding the support of students’ social skills. Furthermore, indirect effects of flexibility on intentions and behavior regarding the support of social skills were found. The findings emphasize the importance of teachers’ flexibility in the realization of inclusive education.

scholarly journals Cut-and-Mouse and Ghost Control

2021 ◽  
Vol 2 (1) ◽  
pp. 1-23
Author(s):  
Ziya Alper Genç ◽  
Gabriele Lenzini ◽  
Daniele Sgandurra
Keyword(s):  
Winning Strategy ◽  
Denial Of Service ◽  
Behavioral Analysis ◽  
Full Time ◽  
Standard Code ◽  
Additional Protection ◽  
Protection Mechanisms ◽  
Copy And Paste ◽  
Digital Assets

To protect their digital assets from malware attacks, most users and companies rely on antivirus (AV) software. AVs’ protection is a full-time task against malware: This is similar to a game where malware, e.g., through obfuscation and polymorphism, denial of service attacks, and malformed packets and parameters, tries to circumvent AV defences or make them crash. However, AVs react by complementing signature-based detection with anomaly or behavioral analysis, and by using OS protection, standard code, and binary protection techniques. Further, malware counter-acts, for instance, by using adversarial inputs to avoid detection, and so on. In this cat-and-mouse game, a winning strategy is trying to anticipate the move of the adversary by looking into one’s own weaknesses, seeing how the adversary can penetrate them, and building up appropriate defences or attacks. In this article, we play the role of malware developers and anticipate two novel moves for the malware side to demonstrate the weakness in the AVs and to improve the defences in AVs’ side. The first one consists in simulating mouse events to control AVs, namely, to send them mouse “clicks” to deactivate their protection. We prove that many AVs can be disabled in this way, and we call this class of attacks Ghost Control . The second one consists in controlling whitelisted applications, such as Notepad, by sending them keyboard events (such as “copy-and-paste”) to perform malicious operations on behalf of the malware. We prove that the anti-ransomware protection feature of AVs can be bypassed if we use Notepad as a “puppet” to rewrite the content of protected files as a ransomware would do. Playing with the words, and recalling the cat-and-mouse game, we call this class of attacks Cut-and-Mouse . We tested these two attacks on 29 AVs, and the results show that 14 AVs are vulnerable to Ghost Control attack while all 29 AV programs tested are found vulnerable to Cut-and-Mouse . Furthermore, we also show some weaknesses in additional protection mechanisms of AVs, such as sandboxing and CAPTCHA verification. We have engaged with the affected AV companies, and we reported the disclosure communication with them and their responses.

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