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To better understand the long-term impact of Ophiostoma novo-ulmi Brasier on leaf physiology in 'Dodoens', a Dutch elm disease-tolerant hybrid, measurements of leaf area, leaf dry mass, petiole anatomy, petiole hydraulic conductivity, leaf and branch water potential, and branch sap flow were performed 3 years following an initial artificial inoculation. Although fungal hyphae were detected in fully expanded leaves, neither anatomical nor morphological traits were affected, indicating that there was no impact from the fungal hyphae on the leaves during leaf expansion. In contrast, however, infected trees showed both a lower transpiration rate of branches and a lower sap flow density. The long-term persistence of fungal hyphae inside vessels decreased the xylem hydraulic conductivity, but stomatal regulation of transpiration appeared to be unaffected as the leaf water potential in both infected and non-infected trees was similarly driven by the transpirational demands. Regardless of the fungal infection, leaves with a higher leaf mass per area ratio tended to have a higher leaf area-specific conductivity. Smaller leaves had an increased number of conduits with smaller diameters and thicker cell walls. Such a pattern could increase tolerance towards hydraulic dysfunction. Measurements of water potential and theoretical xylem conductivity revealed that petiole anatomy could predict the maximal transpiration rate. Three years following fungal inoculation, phenotypic expressions for the majority of the examined traits revealed a constitutive nature for their possible role in Dutch elm disease tolerance of 'Dodoens' trees.
- MeSH
- analýza hlavních komponent MeSH
- časové faktory MeSH
- hybridizace genetická MeSH
- kvantitativní znak dědičný * MeSH
- listy rostlin mikrobiologie fyziologie MeSH
- nemoci rostlin mikrobiologie MeSH
- Ophiostoma fyziologie MeSH
- stonky rostlin mikrobiologie fyziologie MeSH
- transpirace rostlin fyziologie MeSH
- Ulmus mikrobiologie fyziologie MeSH
- voda MeSH
- xylém mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Conifers and other trees are constantly adapting to changes in light conditions, water/nutrient supply and temperatures by physiological and morphological modifications of their foliage. However, the relationship between physiological processes and anatomical characteristics of foliage has been little explored in trees. In this study we evaluated needle structure and function in Norway spruce families exposed to different light conditions and transpiration regimes. We compared needle characteristics of sun-exposed and shaded current-year needles in a control plot and a thinned plot with 50% reduction in stand density. Whole-tree transpiration rates remained similar across plots, but increased transpiration of lower branches after thinning implies that sun-exposed needles in the thinned plot were subjected to higher water stress than sun-exposed needles in the control plot. In general, morphological and anatomical needle parameters increased with increasing tree height and light intensity. Needle width, needle cross-section area, needle stele area and needle flatness (the ratio of needle thickness to needle width) differed most between the upper and lower canopy. The parameters that were most sensitive to the altered needle water status of the upper canopy after thinning were needle thickness, needle flatness and percentage of stele area in needle area. These results show that studies comparing needle structure or function between tree species should consider not only tree height and light gradients, but also needle water status. Unaccounted for differences in needle water status may have contributed to the variable relationship between needle structure and irradiance that has been observed among conifers.
- MeSH
- aklimatizace MeSH
- dehydratace MeSH
- dusík metabolismus MeSH
- listy rostlin anatomie a histologie metabolismus fyziologie MeSH
- půda analýza MeSH
- sluneční záření MeSH
- smrk anatomie a histologie metabolismus fyziologie MeSH
- transpirace rostlin MeSH
- vlhkost MeSH
- voda analýza fyziologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remains elusive. With a progressively warming climate, atmospheric evaporative demand [i.e., vapor pressure deficit (VPD)] will be increasingly important for plant functioning, becoming the major control of plant water use in the twenty-first century. Using measurements in 34 tree species at seven sites across a precipitation gradient in the neotropics, we determined how the maximum sap flux velocity (vmax) and the VPD threshold at which vmax is reached (VPDmax) vary with precipitation regime [mean annual precipitation (MAP); seasonal drought intensity (PDRY)] and two functional traits related to foliar and wood economics spectra [leaf mass per area (LMA); wood specific gravity (WSG)]. We show that, even though vmax is highly variable within sites, it follows a negative trend in response to increasing MAP and PDRY across sites. LMA and WSG exerted little effect on vmax and VPDmax, suggesting that these widely used functional traits provide limited explanatory power of dynamic plant responses to environmental variation within hyper-diverse forests. This study demonstrates that long-term precipitation plays an important role in the sap flux response of humid tropical forests to VPD. Our findings suggest that under higher evaporative demand, trees growing in wetter environments in humid tropical regions may be subjected to reduced water exchange with the atmosphere relative to trees growing in drier climates.
- MeSH
- lesy MeSH
- období sucha MeSH
- stromy * MeSH
- tlak par MeSH
- transpirace rostlin * MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
Efficient water management is essential for the survival of vascular plants under drought stress. While interrelations among drought stress, plant anatomy and physiological functions have been described in woody dicots, similar research is very limited for non-palm arborescent and shrubby monocots despite their generally high drought tolerance. In this study, potted transplants of Dracaena marginata Lam. in primary growth stage were exposed to several short- and long-term drought periods. Continuous measurements of sap flow and stem diameter, the evaluation of capacitance and leaf conductance, the quantification of non-structural carbohydrates (NSC), and organ-specific anatomical analyses were performed to reveal the mechanisms promoting plant resistance to limited soil moisture. The plants showed sensitive stomata regulation in the face of drying soil, but only intermediate resistance to water loss through cuticular transpiration. The water losses were compensated by water release from stem characterized by densely interconnected, parenchyma-rich ground tissue and considerable hydraulic capacitance. Our results suggest that the high concentration of osmotically active NSC in aboveground organs combined with the production of root pressures supported water uptake and the restoration of depleted reserves after watering. The described anatomical features and physiological mechanisms impart D. marginata with high resistance to irregular watering and long-term water scarcity. These findings should help to improve predictions with respect to the impacts of droughts on this plant group.
BACKGROUND AND AIMS: Root hemiparasites from the rhinanthoid clade of Orobanchaceae possess metabolically active glandular trichomes that have been suggested to function as hydathode trichomes actively secreting water, a process that may facilitate resource acquisition from the host plant's root xylem. However, no direct evidence relating the trichomes to water secretion exists, and carbon budgets associated with this energy-demanding process have not been determined. METHODS: Macro- and microscopic observations of the leaves of hemiparasitic Rhinanthus alectorolophus were conducted and night-time gas exchange was measured. Correlations were examined among the intensity of guttation, respiration and transpiration, and analysis of these correlations allowed the carbon budget of the trichome activity to be quantified. We examined the intensity of guttation, respiration and transpiration, correlations among which indicate active water secretion. KEY RESULTS: Guttation was observed on the leaves of 50 % of the young, non-flowering plants that were examined, and microscopic observations revealed water secretion from the glandular trichomes present on the abaxial leaf side. Night-time rates of respiration and transpiration and the presence of guttation drops were positively correlated, which is a clear indicator of hydathode trichome activity. Subsequent physiological measurements on older, flowering plants indicated neither intense guttation nor the presence of correlations, which suggests that the peak activity of hydathodes is in the juvenile stage. CONCLUSIONS: This study provides the first unequivocal evidence for the physiological role of the hydathode trichomes in active water secretion in the rhinanthoid Orobanchaceae. Depending on the concentration of organic elements calculated to be in the host xylem sap, the direct effect of water secretion on carbon balance ranges from close to neutral to positive. However, it is likely to be positive in the xylem-only feeding holoparasites of the genus Lathraea, which is closely related to Rhinanthus. Thus, water secretion by the hydathodes might be viewed as a physiological pre-adaptation in the evolution of holoparasitism in the rhinanthoid lineage of Orobanchaceae.
- MeSH
- biologická evoluce * MeSH
- buněčné dýchání MeSH
- interakce hostitele a parazita fyziologie MeSH
- kořeny rostlin parazitologie MeSH
- lineární modely MeSH
- listy rostlin metabolismus MeSH
- Orobanchaceae fyziologie MeSH
- plyny metabolismus MeSH
- transpirace rostlin MeSH
- trichomy fyziologie MeSH
- voda metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Since wetlands are ecosystems that have an ample supply of water, they play an important role in the energy budgets of their respective landscapes due to their capacity to shift energy fluxes in favor of latent heat. Rates of evapotranspiration in wetlands are commonly as high as 6-15 mm day⁻¹, testifying to the large amount of energy that is dissipated through this process. Emergent or semi-emergent wetland macrophytes substantially influence the solar energy distribution due to their high capacity for transpiration. Wetland ecosystems in eutrophic habitats show a high primary production of biomass because of the highly efficient use of solar energy in photosynthesis. In wetlands associated with the slow decomposition of dead organic matter, such as oligotrophic marshes or fens and bogs, the accumulation of biomass is also high, in spite of the rather low primary production of biomass. Most of the energy exchange in water-saturated wetlands is, however, linked with heat balance, whereby the largest proportion of the incoming energy is dissipated during the process of evapotranspiration. An example is shown of energy fluxes during the course of a day in the wetland ecosystem of Mokré Louky (Wet Meadows) near Třeboň. The negative consequences of the loss of wetlands for the local and regional climate are discussed.
The effectiveness of heavy metal uptake from contaminated nutrient solution by four aquatic macrophytes (Pistia stratiotes L., Salvinia auriculata AubL, Salvinia minima Baker, and Azolla filiculoides Lam) was estimated in this study. The influence of cadmium (3.5 mg L(-1) and 10.5 mg L(-1)) and lead (25 mg L(-1) and 125 mg L(-1)) on the stress symptoms was observed through the determination of chlorophyll content and transpiration rate over 14 days of the experiment. The results of the present study showed extreme reductions in Cd and Pb concentrations in solution during the first 4 days. The accumulation of Pb in plant tissues was the highest during the first 4 days and was more than 10 times higher in the roots (42,862 mg kg(-1)) than in the leaves (3867 mg kg(-1)). The accumulation of Cd slowly increased and was the highest at the end of the experiment. Concentrations in roots (3923 mg kg(-1)) were roughly 6 times higher than in the leaves (624 mg kg(-1)). Results showed significant decrease in the transpiration rate at Pb treatment and a significant increase at Cd treatment during 48 hours of exposition.
- MeSH
- Araceae chemie účinky léků metabolismus MeSH
- časové faktory MeSH
- chemické látky znečišťující vodu metabolismus MeSH
- chlorofyl metabolismus MeSH
- čištění vody metody MeSH
- kadmium metabolismus farmakologie MeSH
- kapradiny chemie účinky léků metabolismus MeSH
- kořeny rostlin chemie metabolismus MeSH
- listy rostlin chemie metabolismus MeSH
- olovo metabolismus farmakologie MeSH
- roztoky MeSH
- transpirace rostlin účinky léků MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
*Increasing evidence about hydraulic redistribution and its ecological consequences is emerging. Hydraulic redistribution results from an interplay between competing plant and soil water potential gradients. In this work, stem-mediated hydraulic redistribution was studied in a 53-year-old Douglas-fir tree during a period of drought. *Sap flux density measurements using the heat field deformation method were performed at four locations: in two large opposing roots and on two sides of the tree stem. Hydraulic redistribution was induced by localized irrigation on one of the measured roots, creating heterogeneous soil water conditions. *Stem-mediated hydraulic redistribution was detected during night-time conditions when water was redistributed from the wet side of the tree to the nonirrigated dry side. In addition to stem-mediated hydraulic redistribution, bidirectional flow in the dry root was observed, indicating radial sectoring in the xylem. *It was observed that, through stem-mediated hydraulic redistribution, Douglas-fir was unable to increase its transpiration despite the fact that sufficient water was available to one part of the root system. This resulted from the strong water potential gradient created by the dry soil in contact with the nonirrigated part of the root system. A mechanism of stem-mediated hydraulic redistribution is proposed and its possible implications are discussed.
- MeSH
- fyziologická adaptace fyziologie MeSH
- kořeny rostlin fyziologie MeSH
- období sucha MeSH
- Pseudotsuga fyziologie MeSH
- půda MeSH
- stonky rostlin fyziologie MeSH
- stromy fyziologie MeSH
- transpirace rostlin fyziologie MeSH
- voda fyziologie MeSH
- xylém MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The Rhinanthoid clade of the family Orobanchaceae comprises plants displaying a hemiparasitic or holoparasitic strategy of resource acquisition. Some of its species (mainly Rhinanthus spp.) are often used as models for studies of hemiparasite physiology. Although there is a well-developed concept covering their physiological processes, most recent studies have neglected the existence of hydathode trichomes present on leaves of these hemiparasitic plants. As a first step for the proposed integration of these structures in the theory of physiological processes of the hemiparasites, we described the outer micromorphology and ultrastructure of the hydathode trichomes on leaves of hemiparasitic Rhinanthus alectorolophus and Odontites vernus with scanning and transmission electron microscopy (SEM and TEM, respectively). The TEM inspections of both types of trichome revealed typical ultrastructural features: labyrinthine cell wall, high content of cytoplasm in cells with numerous mitochondria and presence of plasmodesmata. All these features indicate high metabolic activity complying with their function as glandular trichomes actively secreting water. The active secretion of water by the hydathode trichomes (evidence for which is summarised here) also presents a possible mechanism explaining results of previous gas exchange measurements detecting high dark respiration and transpiration rates and a tight inter-correlation between them in hemiparasitic Orobanchaceae. In addition, this process is hypothesised to have allowed multiple evolutionary transitions from facultative to obligate hemiparasitism and unique xylem-feeding holoparasitism of Lathraea with a long-lived underground stage featuring a rhizome covered by scales of leaf origin.
- MeSH
- biologická evoluce MeSH
- buněčná stěna ultrastruktura MeSH
- buněčné dýchání MeSH
- epidermis rostlin genetika fyziologie ultrastruktura MeSH
- listy rostlin genetika fyziologie ultrastruktura MeSH
- mikroskopie elektronová rastrovací MeSH
- mitochondrie ultrastruktura MeSH
- Orobanchaceae genetika fyziologie ultrastruktura MeSH
- plazmodesmy ultrastruktura MeSH
- transmisní elektronová mikroskopie MeSH
- transpirace rostlin MeSH
- voda metabolismus MeSH
- xylém genetika fyziologie ultrastruktura MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Root-hemiparasitic plants of the genus Rhinanthus acquire resources through a water-wasting physiological strategy based on high transpiration rate mediated by the accumulation of osmotically active compounds and constantly open stomata. Interestingly, they were also documented to withstand moderate water stress which agrees with their common occurrence in rather dry habitats. Here, we focused on the water-stress physiology of Rhinanthus alectorolophus by examining gas exchange, water relations, stomatal density, and biomass production and its stable isotope composition in adult plants grown on wheat under contrasting (optimal and drought-inducing) water treatments. We also tested the effect of water stress on the survival of Rhinanthus seedlings, which were watered either once (after wheat sowing), twice (after wheat sowing and the hemiparasite planting) or continuously (twice and every sixth day after that). Water shortage significantly reduced seedling survival as well as the biomass production and gas exchange of adult hemiparasites. In spite of that drought-stressed and even wilted plants from both treatments still considerably photosynthesized and transpired. Strikingly, low-irrigated plants exhibited significantly elevated photosynthetic rate compared with high-irrigated plants of the same water status. This might relate to biochemical adjustments of these plants enhancing the resource uptake from the host. Moreover, low-irrigated plants did not acclimatize to water stress by lowering their osmotic potential, perhaps due to the capability to tolerate drought without such an adjustment, as their osmotic potential at full turgor was already low. Contrary to results of previous studies, hemiparasites seem to close their stomata in response to severe drought stress and this happens probably passively after turgor is lost in guard cells. The physiological traits of hemiparasites, namely the low osmotic potential associated with their parasitic lifestyle and the ability to withstand drought and recover from the wilting likely enable them to grow in dry habitats. However, the absence of osmotic adjustment of adults and sensitivity of seedlings to severe drought stress demonstrated here may result in a substantial decline of the hemiparasitic species with ongoing climate change.
- MeSH
- biomasa MeSH
- dehydratace MeSH
- fotosyntéza MeSH
- fyziologický stres fyziologie MeSH
- kořeny rostlin MeSH
- listy rostlin anatomie a histologie fyziologie MeSH
- Orobanchaceae anatomie a histologie fyziologie MeSH
- průduchy rostlin anatomie a histologie fyziologie MeSH
- semenáček anatomie a histologie fyziologie MeSH
- transpirace rostlin MeSH
- voda * metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
