Xylem as the main origin of stem radius changes in Eucalyptus

2014 ◽  
Vol 41 (5) ◽  
pp. 520 ◽  
Author(s):  
Roman Zweifel ◽  
David M. Drew ◽  
Fritz Schweingruber ◽  
Geoffrey M. Downes
Keyword(s):  
Water Relations ◽  
Water Storage ◽  
Passive Layer ◽  
Specific Flow ◽  
Transport Efficiency ◽  
Art Interpretation ◽  
Main Driver ◽  
Additional Water ◽  
Species Specific ◽  
Slow Growing

The state-of-the-art interpretation of stem radius changes (DRTotal) for tree water relations is based on knowledge from mostly slow growing tree species. The ratio between diurnal size fluctuations of the rigid xylem (DRXylem) and the respective fluctuations of the elastic bark (DRBark) is known to be small (<0.4) and is of importance for the localisation of water storage dynamics in stems. In this study, fast growing Eucalyptus globulus Labill. in Tasmania were investigated by point dendrometers in order to investigate tree water relations. Unexpectedly, DRXylem was found to be the main driver of DRTotal with the bark acting as a passive layer on top of the fluctuating xylem under most conditions. Accordingly, the ratio between the diurnal fluctuations of the two tissues was found to be much higher (0.6–1.6) than everything reported before. Based on simulations using a hydraulic plant model, the high tissue-specific elasticity of the Eucalyptus xylem was found to explain this atypical response and not osmotically-driven processes or species-specific flow resistances. The wide zone of secondary thickening xylem in various stages of lignification is proposed to be an important component of the high wood elasticity. The tissue acts as additional water storage like the bark and may positively affect the water transport efficiency.

scholarly journals A One-Day Sensitive Method to Detect and Distinguish Between the Citrus Black Spot Pathogen Guignardia citricarpa and the Endophyte Guignardia mangiferae

Plant Disease ◽  
2006 ◽  
Vol 90 (1) ◽  
pp. 97-101 ◽  
Author(s):  
L. Meyer ◽  
G. M. Sanders ◽  
R. Jacobs ◽  
L. Korsten
Keyword(s):  
South African ◽  
Sequence Data ◽  
Black Spot ◽  
The United States ◽  
Guignardia Citricarpa ◽  
Competitive Edge ◽  
Citrus Black Spot ◽  
Species Specific ◽  
Time Required ◽  
Slow Growing

If South African citrus exporters wish to retain their competitive edge in the European market and access new markets such as the United States of America, it is of quarantine importance to distinguish between the citrus black spot pathogen, Guignardia citricarpa, and the harmless endophyte, G. mangiferae. The endophyte is not a sanitary or phytosanitary concern. This paper describes the design of species-specific primers that are able to detect and distinguish between these two Guignardia species. Application of the primer set CITRIC1 and CAMEL2 in conjunction with the ITS4 primer yielded polymerase chain reaction (PCR) amplicons of approximately 580 bp and 430 bp for G. citricarpa and G. mangiferae, respectively. Results obtained with these primers are in accordance with sequence data, and repeated tests verified accuracy and sensitivity. A BLAST search revealed no matches other than G. citricarpa and G. mangiferae, and no positive PCR results were obtained with Colletotrichum gloeosporioides, which is the most common contaminant in black spot lesions. We are, therefore, able to distinguish G. citricarpa and G. mangiferae unequivocally using a PCR-based method. This method was further improved to directly isolate DNA from fruit lesions by means of the DNeasy Plant Mini Kit (Qiagen). This eliminates the prior need for culturing the slow-growing organism, thereby shortening the time required to one day to test for and verify the presence or absence of the pathogenic G. citricarpa in export consignments.

The effect of fallowing on the yield of wheat. I. The effect on soil water storage and nitrate supply

1978 ◽  
Vol 29 (4) ◽  
pp. 653 ◽  
Author(s):  
RJ French
Keyword(s):  
Water Storage ◽  
South Australia ◽  
Summer Rainfall ◽  
Soil Water Storage ◽  
Wheat Crop ◽  
Two Factors ◽  
Soil Preparation ◽  
Additional Water ◽  
Nitrate Supply ◽  
The Mean

The effect of fallowing before a wheat crop was studied in South Australia in an environment with suboptimal rainfall in the growing season. A 9–10 month pre-sowing fallow increased mean water storage (0–120 cm depth) at sowing by 28 mm, compared with a non-fallow soil preparation (2 month period of cultivation). Variation in additional storage ranged from nil to 125 mm. These amounts depended on soil type and season: in coarse-textured soils, fallowing conserved little additional water, but in fine-textured soils much additional water could be stored. Storage was not related to the summer rainfall (November-March) before sowing but was related to rainfall during July and August in the previous winter—just before or at the start of the fallow period. A combination of these two factors, fine-textured soil and good July–August rainfall, gave considerable storage. Fallowing also increased the nitrate nitrogen content in the surface 60 cm at sowing; the mean additional nitrogen amounted to 19 kg/ha in the coarse-textured soils and 30 kg/ha in the fine-textured soils. The largest increases due to fallowing were recorded in soils following medic leys and with ample rains on the fallow in spring. Comparison is made between these findings and those obtained with fallowing in other parts of Australia.

scholarly journals Plant performance on Mediterranean green roofs: interaction of species-specific hydraulic strategies and substrate water relations

AoB Plants ◽  
2015 ◽  
Vol 7 ◽  
Author(s):  
Fabio Raimondo ◽  
Patrizia Trifilò ◽  
Maria A. Lo Gullo ◽  
Sergio Andri ◽  
Tadeja Savi ◽  
...  
Keyword(s):  
Water Relations ◽  
Green Roofs ◽  
Plant Performance ◽  
Species Specific

scholarly journals Field observations of soil hydrological flow path evolution over 10 millennia

2020 ◽  
Vol 24 (6) ◽  
pp. 3271-3288
Author(s):  
Anne Hartmann ◽  
Ekaterina Semenova ◽  
Markus Weiler ◽  
Theresa Blume
Keyword(s):  
Water Flow ◽  
Preferential Flow ◽  
Water Storage ◽  
Flow Path ◽  
Swiss Alps ◽  
Flow Paths ◽  
Specific Flow ◽  
Water Storage Capacity ◽  
Dye Tracer ◽  
Irrigation Intensity

Abstract. Preferential flow strongly controls water flow and transport in soils. It is ubiquitous but difficult to characterize and predict. This study addresses the occurrence and the evolution of preferential flow during the evolution of landscapes and here specifically during the evolution of hillslopes. We targeted a chronosequence of glacial moraines in the Swiss Alps to investigate how water flow paths evolve along with the soil-forming processes. Dye tracer irrigation experiments with a Brilliant Blue FCF solution (4 g L−1) were conducted on four moraines of different ages (30, 160, 3000, and 10 000 years). At each moraine, three dye tracer experiments were conducted on plots of 1.5 m ×1.0 m. The three plots at each moraine were characterized by different vegetation complexities (low, medium, and high). Each plot was further divided into three equal subplots for the application of three different irrigation amounts (20, 40, and 60 mm) with an average irrigation intensity of 20 mm h−1. The day after the experiment five vertical soil sections were excavated, and the stained flow paths were photographed. Digital image analysis was used to derive average infiltration depths and flow path characteristics such as the volume and surface density of the dye patterns. Based on the volume density, the observed dye patterns were assigned to specific flow type categories. The results show a significant change in the type of preferential flow paths along the chronosequence. The flow types change from a rather homogeneous matrix flow in coarse material with high conductivities and a sparse vegetation cover at the youngest moraine to a heterogeneous infiltration pattern at the medium-age moraines. Heterogeneous matrix and finger flow are dominant at these intermediate age classes. At the oldest moraine only macropore flow via root channels was observed in deeper parts of the soil, in combination with a very high water storage capacity of the organic top layer and low hydraulic conductivity of the deeper soil. In general, we found an increase in water storage with increasing age of the moraines, based on our observations of the reduction in infiltration depth as well as laboratory measurements of porosity. Preferential flow is, however, not only caused by macropores, but especially for the medium-age moraine, it seems to be mainly initiated by soil surface characteristics (vegetation patches and microtopography).

scholarly journals Why are There so Many Bee-Orchid Species? Adaptive Radiation by Intraspecific Competition for Mnemonic Pollinators

2019 ◽  
Author(s):  
Michel Baguette ◽  
Joris Bertrand ◽  
Virginie M. Stevens ◽  
Bertrand Schatz
Keyword(s):  
Adaptive Radiation ◽  
Evolutionary Dynamics ◽  
Evolutionary Relationship ◽  
Ecological Niches ◽  
Local Diversity ◽  
Pollinator Species ◽  
Main Driver ◽  
Adaptive Radiations ◽  
Suitable Habitats ◽  
Species Specific

Adaptive radiations occur mostly in response to environmental variation through the evolution of key eco-morphological innovations that allow emerging species to occupy new ecological niches. However, rapid phenotypic evolution and the evolution of key novelties are likely to also occur when a couple or few species are engaged into narrow ecological interactions. To demonstrate coevolution is a difficult task; only elusive evidences confirm that coevolution is a driver of speciation and diversification. Here we propose that the adaptive radiation of the Mediterranean orchid genus Ophrys, which gave rise to ca. 350 species since the apparition of the genus is due to the particular co-evolutionary dynamics between these plants and their pollinators. We suggest that the pollination by sexual swindle used by Ophrys orchids is the main driver of this coevolution. Flowers of each Ophrys species mimic sexually receptive females of one particular insect species, mainly bees. Male bees are attracted by pseudo-pheromones emitted by Ophrys flowers that are similar to the sexual pheromones of their females. Males lured by the flower shape, color and hairiness attempt to copulate with the flower, which glues pollen on their bodies. Pollen is eventually transferred to the stigma of another flower of the same Ophrys species during similar copulation attempts. Three observations led us to propose the scenario of an asymmetric co-evolutionary relationship between Ophrys and their pollinators. Firstly, there is a strong intra-specific competition among Ophrys individuals for the attraction of their species-specific pollinators, which is due to the high learning and memorization abilities of bees that record the pheromone signatures of kin or of previously courted partner to avoid (further) copulation attempts. Mnemonic pollinators induce thus a strong selective pressure for variation in the pseudo-pheromones emitted by individual flowers, which will potentially generate shifts in pollinator species, and hence Ophrys speciation. These pollinator shifts are adaptive for new Ophrys species because they may benefit from a competitor-free space. Secondly, such shifts in pollinator species are due to the random crossing of peaks in the olfactory landscape of the pollinator guild that is syntopic to each particular Ophrys population. This selective process on individual, random variation in pseudo-pheromone bouquets is followed by directional selection on flower phenotypes that will reinforce the attraction of the new pollinator. Thirdly, pollinators use the pseudo-pheromones emitted by Ophrys to locate suitable habitats from a distance within complex landscapes. Pollinators stay fixed for a while in these habitats by the local diversity of pseudo-pheromones, which increases their probability of encounter with a receptive female and hence the reproduction probability of both sexes. Conversely, pollinators disperse out of small suitable habitats once they have memorized the local diversity of sexual pseudo-pheromone bouquet or if fecundated Ophrys flowers repel pollinators, which decreases the probability of geitonogamy (plant advantage) but limit pollinator mating with locally emergent insect females, thus limiting inbreeding and favoring gene flow (pollinator advantage). Finally, we propose several research avenues that emerged according to this scenario of adaptive radiation by assymetric coevolution between Ophrys species and their pollinators.

scholarly journals Deciphering bacterial and fungal endophyte communities in leaves of two maple trees with green islands

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Franziska Wemheuer ◽  
Bernd Wemheuer ◽  
Rolf Daniel ◽  
Stefan Vidal
Keyword(s):  
Fungal Pathogens ◽  
Fungal Endophytes ◽  
Fungal Endophyte ◽  
Fungal Community Composition ◽  
Senescent Leaf ◽  
Acer Campestre ◽  
Main Driver ◽  
Leaf Tissues ◽  
Species Specific ◽  
Green Island

Abstract Green islands (the re-greening of senescent leaf tissues) are particularly evident on leaves infected with fungal pathogens. To date, there is only a limited number of studies investigating foliar endophytic microorganisms in phytopathogen-infected leaves. Here, we analysed bacterial and fungal endophyte communities in leaves without green islands (control leaves; CL), within green island areas (GLA) and the surrounding yellow leaf areas (YLA) of leaves with green islands of Acer campestre and A. platanoides. GLA samples of A. campestre and A. platanoides were dominated by Sawadaea polyfida and S. bicornis, respectively, suggesting that these fungi might be responsible for the green islands. We detected a higher fungal richness and diversity in CL compared to GLA samples of A. campestre. Leaf status (CL, GLA, YLA) significantly altered the composition of fungal communities of A. campestre. This was related to differences in fungal community composition between YLA and GLA samples. Site was the main driver of bacterial communities, suggesting that bacterial and fungal endophytes are shaped by different factors. Overall, we observed Acer species-specific responses of endophyte communities towards the presence of green islands and/or leaf type, which might be attributed to several fungi and bacteria specifically associated with one Acer species.

Differences in Water Relations Parameters for the Chlorenchyma and the Parenchyma of Opuntia ficus-indica Under Wet Versus Dry Conditions

1991 ◽  
Vol 18 (2) ◽  
pp. 95 ◽  
Author(s):  
G Goldstein ◽  
JL Andrade ◽  
PS Nobel
Keyword(s):  
Osmotic Pressure ◽  
Water Relations ◽  
Water Storage ◽  
Dry Weight ◽  
High Water ◽  
Opuntia Ficus Indica ◽  
Large Numbers ◽  
Parenchyma Cells ◽  
Storage Parenchyma ◽  
Dry Conditions

Water relations of the photosynthetic tissue (chlorenchyma) and of the water-storage parenchyma were studied for well watered and droughted Opuntia ficus-indica, a crassulacean acid metabolism plant cultivated worldwide for its fruits and cladodes. For well watered plants, die1 changes in osmotic pressure were evident in the chlorenchyma. Droughting the plants for 4 months resulted in a massive loss of water from the cladodes, particularly from the water-storage parenchyma, which could lose up to 82% of the water present at full turgor without irreversible tissue damage. Pressure-volume curves indicated a decrease in the osmotic pressure at full turgor of about 0.1 MPa for the water-storage parenchyma cells during drought; such a decrease of osmotically active solutes was consistent with the appearance of large numbers of starch grains. The bulk modulus of elasticity was 0.36 MPa for the water-storage parenchyma cells and 2.5-fold higher for the chlorenchyma cells, which were smaller with thicker cell walls than the former cells. Mucilage, a polysaccharide occurring extracellularly, constituted about 14% of the cladode dry weight; it could hold more than 30% of the total water content of the water-storage parenchyma. Polymerisation of sugars, large elastic cells in the water-storage parenchyma and mucilage with its high water-holding capacity helped maintain a positive turgor in the photosynthetic tissue, even after 4 months of drought.

Sign in / Sign up

Export Citation Format

Share Document