Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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QTL analysis for stomatal functioning in tetraploid Rosa x hybrida grown at high relative air humidity and its implications on postharvest longevity
Carvalho, D.R.A. ; Koning, C.F.S. ; Fanourakis, D. ; Vasconcelos, M.W. ; Carvalho, S.M.P. ; Heuvelink, E. ; Krens, F.A. ; Maliepaard, C.A. - \ 2015
Molecular Breeding 35 (2015). - ISSN 1380-3743 - 11 p.
marker-assisted selection - water relations - cut roses - in-vitro - traits - environments - conductance - sensitivity - improvement - resistance
High relative air humidity (RH = 85 %) during leaf development disturbs stomatal functioning leading to excessive water loss in conditions of high evaporative demand, resulting in severe reduction in postharvest longevity. In roses, this effect depends on the genotype, opening the possibility for breeding cultivars with more responsive stomata. In this study, we aim at identifying genomic regions associated with the control of water loss following growth at high RH. The F1 generation (108 offspring) and the two parents (P540 and P867) of a tetraploid cut rose population grown at high (85 %) RH were phenotyped for stomatal control to water loss by assessing the relative water content after 4 h of leaflet desiccation (RWC_4 h). The RWC_4 h varied between 7 and 62 % across the 110 studied individuals, with parents P540 and P867 showing 51 and 20 % RWC_4 h, respectively. Based on these data, a quantitative trait locus (QTL) analysis was performed. The impact of the identified QTLs on postharvest longevity of ten selected offspring was further evaluated. Three QTLs were identified: two major [positioned on linkage group 5 of the integrated consensus map (ICM 5) of both parents and on ICM 2 of the parent P867] and one putative minor (mapped to ICM 6 of both parents), explaining 32 % of the variability in the RWC_4 h. Low RWC_4 h was found to be a good proxy for eliminating the offspring with short vase life. This study constitutes a first step toward identifying the most likely regions for genes of interest controlling stomatal functioning in high RH-grown plants.
Diel growth dynamics in tree stems: linking anatomy and ecophysiology
Steppe, K. ; Sterck, F.J. ; Deslauriers, A. - \ 2015
Trends in Plant Science 20 (2015)6. - ISSN 1360-1385 - p. 335 - 343.
diameter variations - wood formation - sap-flow - water relations - hydraulic safety - phloem transport - munch hypothesis - turgor pressure - plant-responses - norway spruce
Impacts of climate on stem growth in trees are studied in anatomical, ecophysiological, and ecological disciplines, but an integrative framework to assess those impacts remains lacking. In this opinion article, we argue that three research efforts are required to provide that integration. First, we need to identify the missing links in diel patterns in stem diameter and stem growth and relate those patterns to the underlying mechanisms that control water and carbon balance. Second, we should focus on the understudied mechanisms responsible for seasonal impacts on such diel patterns. Third, information on stem anatomy and ecophysiology should be integrated in the same experiments and mechanistic plant growth models to capture both diel and seasonal scales.
The effects of drought and shade on the performance, morphology and physiology of Ghanaian tree species
Amissah, L. ; Mohren, G.M.J. ; Kyereh, B. ; Poorter, L. - \ 2015
PLoS One 10 (2015)4. - ISSN 1932-6203
tropical forest - water relations - rain-forest - seedling establishment - desiccation-tolerance - carbon gain - trade-offs - photosynthetic acclimation - niche differentiation - relative importance
In tropical forests light and water availability are the most important factors for seedling growth and survival but an increasing frequency of drought may affect tree regeneration. One central question is whether drought and shade have interactive effects on seedling growth and survival. Here, we present results of a greenhouse experiment, in which seedlings of 10 Ghanaian tree species were exposed to combinations of strong seasonal drought (continuous watering versus withholding water for nine weeks) and shade (5% irradiance versus 20% irradiance). We evaluated the effects of drought and shade on seedling survival and growth and plasticity of 11 underlying traits related to biomass allocation, morphology and physiology. Seedling survival under dry conditions was higher in shade than in high light, thus providing support for the “facilitation hypothesis” that shade enhances plant performance through improved microclimatic conditions, and rejecting the trade-off hypothesis that drought should have stronger impact in shade because of reduced root investment. Shaded plants had low biomass fraction in roots, in line with the trade-off hypothesis, but they compensated for this with a higher specific root length (i.e., root length per unit root mass), resulting in a similar root length per plant mass and, hence, similar water uptake capacity as high-light plants. The majority (60%) of traits studied responded independently to drought and shade, indicating that within species shade- and drought tolerances are not in trade-off, but largely uncoupled. When individual species responses were analysed, then for most of the traits only one to three species showed significant interactive effects between drought and shade. The uncoupled response of most species to drought and shade should provide ample opportunity for niche differentiation and species coexistence under a range of water and light conditions. Overall our greenhouse results suggest that, in the absence of root competition shaded tropical forest tree seedlings may be able to survive prolonged drought.
Effects of Nutrient and NaCl Salinity on Growth, Yield, Quality and Composition of Pepper Grown in Soilless Closed System
Giuffrida, F. ; Graziani, G. ; Fogliano, V. ; Scuderia, D. ; Romano, D. ; Leonardi, C. - \ 2014
Journal of Plant Nutrition 37 (2014)9. - ISSN 0190-4167 - p. 1455 - 1474.
blossom-end rot - antioxidant activity - fruit-quality - sodium-chloride - water relations - sweet-pepper - horticultural crops - mineral-nutrition - salt tolerance - plants
The effects of nutrient or sodium chloride (NaCl) salinity on pepper grown in closed soilless culture systems were studied. A control (2 dS m-1) and two saline nutrient solutions (4 dS m-1) differing in the salt sources (fertilizers or NaCl) were studied. Shoot biomass production as well as total and marketable yield were more affected by NaCl than nutrient salinity. Fruit dry matter and total soluble solids increased in both salinity treatments compared to the control. Total phenol content rose slightly (10%) with NaCl salinity, while the concentration of carotenoids was enhanced by 40% with NaCl compared to the control and nutrient salinity. The results showed that the response of pepper to salinity is both osmotic and ion specific, but a more negative effect was recorded under NaCl stress. Moreover, the highest content of antioxidant compounds in NaCl treated fruits may indicate that NaCl caused more stressful conditions than nutrient salinity.
Fertilizer use should not be a fourth principle to define conservation. Response to the opinion paper of Vanlauwe et al. (2014)
Sommer, R. ; Thierfelder, C. ; Tittonell, P.A. ; Hove, L. ; Mureithi, J. ; Mkomwa, S. - \ 2014
Field Crops Research 169 (2014). - ISSN 0378-4290 - p. 145 - 148.
zea-mays l. - soil quality - residue management - southern africa - ecological intensification - water relations - systems - maize - tillage - yield
Source of vase life variation in cut roses: A review
Fanourakis, D. ; Pieruschka, R. ; Savvides, A. ; Macnish, A.J. ; Sarlikioti, V. ; Woltering, E.J. - \ 2013
Postharvest Biology and Technology 78 (2013). - ISSN 0925-5214 - p. 1 - 15.
relative air humidity - acoustic-emission profiles - plant-population density - miniature potted roses - hybrida l. plants - botrytis-cinerea - water relations - keeping quality - postharvest performance - vascular occlusion
In determining vase life (VL), it is often not considered that the measured VL in a particular experiment may greatly depend on both the preharvest and evaluation environmental conditions. This makes the comparison between studies difficult and may lead to erroneous interpretation of results. In this review, we critically discuss the effect of the growth environment on the VL of cut roses. This effect is mainly related to changes in stomatal responsiveness, regulating water loss, whereas cut flower carbohydrate status appears less critical. When comparing cultivars, postharvest water loss and VL often show no correlation, indicating that components such as variation in the tissue resistance to cavitate and/or collapse at low water potential play an important role in the incidence of water stress symptoms. The effect of the growth environment on these components remains unknown. Botrytis cinerea sporulation and infection, as well as cut rose susceptibility to the pathogen are also affected by the growth environment, with the latter being largely unexplored. A huge variability in the choices made with respect to the experimental setup (harvest/conditioning methods, test room conditions and VL terminating symptoms) is reported. We highlight that these decisions, though frequently overlooked, influence the outcome of the study. Specifications for each of these factors are proposed as necessary to achieve a common VL protocol. Documentation of both preharvest conditions and a number of postharvest factors, including the test room conditions, is recommended not only for assisting comparisons between studies, but also to identify factors with major effects on VL.
Leaf adaptations of evergreen and deciduous trees of semi-arid and humid savannas on three continents
Tomlinson, K.W. ; Poorter, L. ; Sterck, F.J. ; Borghetti, M. ; Ward, D. ; Bie, S. de; Langevelde, F. van - \ 2013
Journal of Ecology 101 (2013)2. - ISSN 0022-0477 - p. 430 - 440.
carbon-isotope ratios - functional traits - tropical forest - water relations - life-span - growth-responses - seedling growth - atmospheric co2 - root morphology - high-rainfall
1. Drought stress selects for a suite of plant traits at root, stem and leaf level. Two strategies are proposed for trees growing in seasonally water-stressed environments: drought tolerance and drought avoidance. These are respectively associated with evergreen phenology, where plants retain their leaves throughout the year, and deciduous phenology, where plants drop their leaves during dry seasons. Evergreen species are thought to have leaf traits supporting lower photosynthesis and transpiration rates, in order to conserve water during dry periods. 2. We evaluated 18 morphological, chemical and physiological leaf traits of 51 abundant savanna tree species that differed in leaf habit (deciduous and evergreen), selected from two climate types (semi-arid and humid) in three continents (Australia, Africa and South America) (annual rainfall range: 500–1550 mm), and grown in a common garden experiment. We hypothesised that evergreen species have more conservative water use and differ more across climate types than deciduous species because evergreen species are forced to endure extended water deficits during dry seasons. 3. Trait shifts between semi-arid and humid savannas did not differ between evergreen and deciduous species. 4. Evergreen species had similar assimilation rates but lower photosynthetic water-use efficiency (PWUE) than deciduous species, possibly to extend their leaf lifespans by protecting their photosynthetic machinery from overheating through evaporative cooling. 5. Species of humid and semi-arid environments did not differ with respect to assimilation rate or PWUE, but semi-arid species did have smaller leaf sizes and greater leaf potassium and phosphorus concentrations. These traits may enable semi-arid species to maximize growth during episodes of favourable moisture availability. 6. Species from the three continents differed in their leaf traits. These probably reflect the greater proportion of evergreen species in Australia as compared to the other continents and generally infertile soils in the South American sampling sites compared to the wider fertility range in the African sites. 7. Synthesis: Water stress in savannas does not select for more conservative water use, but may select for rapid adjustment to prevailing water conditions and for heat avoidance mechanisms.
Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests
Rigling, A. ; Bigler, C. ; Eilmann, B. ; Feldmeyer-Christe, E. ; Gimmi, U. ; Ginzler, C. - \ 2013
Global Change Biology 19 (2013)1. - ISSN 1354-1013 - p. 229 - 240.
long-term consequences - global climate-change - album ssp austriacum - swiss rhone valley - tree-ring width - sylvestris l. - drought stress - quercus-pubescens - water relations - radial growth
An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low elevation forests is changing: The sub-boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub-Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services.
A lifetime perspective of biomass allocation in Quercus pubescens trees in a dry, alpine valley
Slot, M. ; Janse-ten Klooster, S.H. ; Sterck, F.J. ; Sass-Klaassen, U. ; Zweifel, R. - \ 2012
Trees-Structure and Function 26 (2012)5. - ISSN 0931-1890 - p. 1661 - 1668.
carbon allocation - pinus-sylvestris - water relations - hydraulic conductance - summer drought - radial growth - scots pine - plants - responses - roots
Plasticity of biomass allocation is a key to growth and survival of trees exposed to variable levels of stress in their lifetime. Most of our understanding of dynamic biomass allocation comes from seedling studies, but plasticity may be different in mature trees. We used stem analysis to reconstruct whole-tree growth and biomass allocation patterns in Quercus pubescens trees harvested from a dry woodland in Valais, Switzerland. We identified three distinct growth phases. In phase I, a primary root developed but the aboveground structure did not persist. In phase II, height growth occurred and secondary roots developed. In phase III, height growth ceased and stems and roots only grew radially. Reference trees harvested from a less dry site nearby only showed phase II-type growth. In line with our hypothesis, drought-stressed trees maintained more biomass in roots and less in aboveground woody parts than reference trees. Contrary to our expectation, stressed trees allocated proportionally more resources to leaves and less to roots in the growing season before harvest than reference trees. It appears that sub-seasonal wood anatomical adjustments to water availability minimize hydraulic failure, thus enabling these dry woodland trees to invest preferentially in leaves. Wet years did not see preferential investment in aboveground tissues, suggesting more restricted plasticity in biomass allocation in these mature trees than in seedlings. It is concluded that trees beyond seedling stage show different responses to variation in drought than the better-studied seedlings.
How to deal with visco-elastic properties of cellular tissues during osmotic dehydration
Oliver, L. ; Betoret, N. ; Fito, P. ; Meinders, M.B.J. - \ 2012
Journal of Food Engineering 110 (2012)2. - ISSN 0260-8774 - p. 278 - 288.
var. granny-smith - mass-transfer - apple slices - compositional profiles - vacuum impregnation - structural-changes - water relations - food - kinetics - permeability
In this work, vacuum impregnated apple discs with different isotonic solutions (sucrose and trehalose) were equilibrated during osmotic dehydration (55°Brix glucose at 40 °C). Changes in sample composition (water and soluble solid contents), weight and volume are analysed. A mathematical model is proposed to describe and quantify the outflow of water from the protoplast as well as the visco-elastic behaviour of the cell. Good correspondence between simulated and measured data of non impregnated samples and samples impregnated with isotonic solutions of sucrose or trehalose during long term osmotic dehydration is obtained. Fitted values of the cell permeability correspond well with tabulated values. Furthermore, also the obtained values of the parameters describing the mechanical properties of the cell wall and Hectian strands seem to reflect the observed structural development of these structures for the different treated samples well.
Non-linear effects of drought under shade: reconciling physiological and ecological models in plant communities
Holmgren, M. ; Gomez-Aparicio, L. ; Quero, J.L. ; Valladares, F. - \ 2012
Oecologia 169 (2012)2. - ISSN 0029-8549 - p. 293 - 305.
stress-gradient hypothesis - oak quercus-suber - seedling establishment - positive interactions - biomass allocation - semiarid woodland - woody seedlings - water relations - summer drought - abiotic stress
The combined effects of shade and drought on plant performance and the implications for species interactions are highly debated in plant ecology. Empirical evidence for positive and negative effects of shade on the performance of plants under dry conditions supports two contrasting theoretical models about the role of shade under dry conditions: the trade-off and the facilitation hypotheses. We performed a meta-analysis of field and greenhouse studies evaluating the effects of drought at two or more irradiance levels on nine response variables describing plant physiological condition, growth, and survival. We explored differences in plant response across plant functional types, ecosystem types and methodological approaches. The data were best fit using quadratic models indicating a humped-back shape response to drought along an irradiance gradient for survival, whole plant biomass, maximum photosynthetic capacity, stomatal conductance and maximal photochemical efficiency. Drought effects were ameliorated at intermediate irradiance, becoming more severe at higher or lower light levels. This general pattern was maintained when controlling for potential variations in the strength of the drought treatment among light levels. Our quantitative meta-analysis indicates that dense shade ameliorates drought especially among drought-intolerant and shade-tolerant species. Wet tropical species showed larger negative effects of drought with increasing irradiance than semiarid and cold temperate species. Non-linear responses to irradiance were stronger under field conditions than under controlled greenhouse conditions. Non-linear responses to drought along the irradiance gradient reconciliate opposing views in plant ecology, indicating that facilitation is more likely within certain range of environmental conditions, fading under deep shade, especially for drought-tolerant species.
Leaf gas exchange in the frankincense tree (Boswellia papyrifera) of African dry woodlands
Mengistu, T. ; Sterck, F.J. ; Fetene, M. ; Tadesse, W. ; Bongers, F. - \ 2011
Tree Physiology 31 (2011)7. - ISSN 0829-318X - p. 740 - 750.
vapor-pressure deficit - water relations - stomatal conductance - forest tree - seasonal-changes - photosynthesis - traits - transpiration - australia - ethiopia
A conceptual model was tested for explaining environmental and physiological effects on leaf gas exchange in the deciduous dry tropical woodland tree Boswellia papyrifera (Del.) Hochst. For this species we aimed at (i) understanding diurnal patterns in leaf gas exchange, (ii) exploring cause–effect relationships among external environment, internal physiology and leaf gas exchange, and (iii) exploring site differences in leaf gas exchange in response to environmental variables. Diurnal courses in gas exchange, underlying physiological traits and environmental variables were measured for 90 trees on consecutive days at two contrasting areas, one at high and the other at low altitude. Assimilation was highest in the morning and slightly decreased during the day. In contrast, transpiration increased from early morning to midday, mainly in response to an increasing vapor pressure deficit (VPD) and gradual stomatal closure. The leaf water potential varied relatively little and did not influence gas exchange during the measurement period. Our results suggest that the same cause–effect relationships function at contrasting areas. However, leaves at the higher altitude had higher photosynthetic capacity, reflecting acclimation to higher light levels. Trees at both areas nevertheless achieved similar leaf assimilation rates since assimilation was down-regulated by stomatal closure due to the higher VPD at the higher altitude, while it became more light limited at the lower altitude. Gas exchange was thus limited by a high VPD or low light levels during the wet season, despite the ability of the species to acclimate to different conditions
Species-specific growth responses to climate variations in understory trees of a Central African rain forest
Couralet, C. ; Sterck, F.J. ; Sass-Klaassen, U. ; Acker, J. Van; Beekman, H. - \ 2010
Biotropica 42 (2010)4. - ISSN 0006-3606 - p. 503 - 511.
semi-deciduous forest - northern thailand - dendroecological analysis - drought sensitivity - tropical forests - water relations - pinus-merkusii - ring formation - radial growth - phenology
Basic knowledge of the relationships between tree growth and environmental variables is crucial for understanding forest dynamics and predicting vegetation responses to climate variations. Trees growing in tropical areas with a clear seasonality in rainfall often form annual growth rings. In the understory, however, tree growth is supposed to be mainly affected by interference for access to light and other resources. In the semi-deciduous Mayombe forest of the Democratic Republic of Congo, the evergreen species Aidia ochroleuca, Corynanthe paniculata and Xylopia wilwerthii dominate the understory. We studied their wood to determine whether they form annual growth rings in response to changing climate conditions. Distinct growth rings were proved to be annual and triggered by a common external factor for the three species. Species-specific site chronologies were thus constructed from the cross-dated individual growth-ring series. Correlation analysis with climatic variables revealed that annual radial stem growth is positively related to precipitation during the rainy season but at different months. The growth was found to associate with precipitation during the early rainy season for Aidia but at the end of the rainy season for Corynanthe and Xylopia. Our results suggest that a dendrochronological approach allows the understanding of climate–growth relationships in tropical forests, not only for canopy trees but also for evergreen understory species and thus arguably for the whole tree community. Global climate change influences climatic seasonality in tropical forest areas, which is likely to result in differential responses across species with a possible effect on forest composition over time
Persisting soil drought reduces leaf specific conductivity in Scots pine (Pinus sylvestris) and pubescent oak (Quercus pubescens)
Sterck, F.J. ; Zweifel, R. ; Sass-Klaassen, U. ; Qumruzzaman, C. - \ 2008
Tree Physiology 28 (2008)4. - ISSN 0829-318X - p. 529 - 536.
hydraulic architecture - water relations - radial growth - sessile oak - stem wood - tree - xylem - transpiration - resistance - stand
Summary Leaf specific conductivity (LSC; the ratio of stem conductivity (KP) to leaf area (AL)), a measure of the hydraulic capacity of the stem to supply leaves with water, varies with soil water content. Empirical evidence for LSC responses to drought is ambiguous, because previously published results were subject to many confounding factors.We tested howLSC of similar-sized trees of the same population, under similar climatic conditions, responds to persistently wet or dry soil. Scots pine (Pinus sylvestris L.) and pubescent oak (Quercus pubescensWilld.) trees were compared between a dry site and a wet site in theValais, an inner alpine valley in Switzerland. Soilwater strongly influenced AL and KP and the plant components affecting KP, such as conduit radius, conduit density and functional sapwood area. Trees at the dry site had lower LSC than trees with the same stem diameter at the wet site. Low LSC in trees at the dry site was associated with a smaller functional sapwood area and narrower conduits, resulting in a stronger reduction in KP than in AL. These observations support the hypothesis that trees maintain a homeostatic water pressure gradient. An alternative hypothesis is that relatively high investments in leaves compared with sapwood contribute to carbon gain over an entire season by enabling rapid whole-plant photosynthesis during periods of high water availability (e.g., in spring, after rain events and during morning hours when leafto- air vapor pressure deficit is small). Dynamic data and a hydraulic plant growth model are needed to test how investments in leaves versus sapwood and roots contribute to transpiration and to maximizing carbon gain throughout entire growth seasons. Keywords: Huber value, leaf area, soil water potential, stem conductivity.
Tree establishment along an ENSO experimental gradient in the Atacama desert
Squeo, F.A. ; Holmgren, M. ; Jimenez, L. ; Alban, L. ; Reyes, J. ; Gutierrez, J.R. - \ 2007
Journal of Vegetation Science 18 (2007)2. - ISSN 1100-9233 - p. 195 - 202.
el-nino - prosopis-chilensis - water relations - arid ecosystem - climate-change - south-america - soil texture - growth - oscillation - variability
Questions: (1) What are the roles of regional climate and plant growth rate for seedling establishment during ENSO rainy pulses along the western coast of South America? (2) What is the water threshold for tree seedling establishment in these arid ecosystems? Location: Atacama Desert, western South America: Piura (5°10' S, 80°37' W), Mejia (17°00' S, 71°59' W), Fray Jorge (30°41' S, 71°37' W). Methods: We experimentally simulated a gradient of ENSO rainfall in three locations encompassing the total extent of the Atacama Desert to test the relative importance of regional climate for seedling establishment during rainy pulses. We also carried out a common garden experiment to test the role of potential interspecific differences in growth rate among two Prosopis tree species. Results: Water threshold for seedling survival increased towards the south with less than 27 mm required in Piura, 100 mm in Mejia and 450 mm in Fray Jorge. We found that seedling survival and growth rate (shoots and roots) were much higher in Piura than in the other two sites for both Prosopis species. Conclusions: Our results indicate that tree establishment during rainy pulses is more likely to be successful in regions where rain falls during warm months and stimulates fast plant growth, and where loose soil texture facilitates deep root growth and therefore access to more stable water sources.
Long-term effects of elevated atmospheric CO2 on species composition and productivity of a southern African C4 dominated grassland in the vicinity of a CO2 exhalation.
Stock, W.D. ; Ludwig, F. ; Morrow, C. ; Midgley, G.F. ; Wand, S.J.E. ; Allsopp, N. ; Bell, T.L. - \ 2005
Plant Ecology 178 (2005)2. - ISSN 1385-0237 - p. 211 - 224.
tallgrass prairie ecosystem - soil carbon - biomass production - plant-communities - water relations - gas-exchange - growth - enrichment - responses - dynamics
We describe the long-term effects of a CO2 exhalation, created more than 70 years ago, on a natural C4 dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO2 enrichment changes the competitive balance between plants with C3 and C4 photosynthetic pathways and how CO2 enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO2 on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO2 alone. Species compositional data and soil ¿13C isotopic evidence suggest no detectable effect of CO2 enrichment on C3:C4 plant mixtures and individual species dominance. Contrary to many general predictions C3 grasses did not become more abundant and C3 shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO2 concentrations averaging 610 ¿mol mol-1. Leaf properties such as total N decreased in the C 3 but not C4 grass under elevated CO2 while total non-structural carbohydrate accumulation was not affected. Elevated CO2 possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO2 enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO2 source. The conservative response of this grassland suggests that many of the reported effects of elevated CO2 on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO2 conditions
Abscisic acid controls embryo growth potential and endosperm cap weakening during coffee (Coffea arabica cv. Rubi) seed germination
Silva, E.A.A. da; Toorop, P.E. ; Aelst, A.C. van; Hilhorst, H.W.M. - \ 2004
Planta 220 (2004)2. - ISSN 0032-0935 - p. 251 - 261.
endo-beta-mannanase - celery apium-graveolens - tomato seeds - radicle protrusion - water relations - cell-walls - beta-1,3-glucanases - imbibition - dormancy - expression
The mechanism and regulation of coffee seed germination were studied in Coffea arabica L. cv. Rubi. The coffee embryo grew inside the endosperm prior to radicle protrusion and abscisic acid (ABA) inhibited the increase in its pressure potential. There were two steps of endosperm cap weakening. An increase in cellulase activity coincided with the first step and an increase in endo-beta-mannanase (EBM) activity with the second step. ABA inhibited the second step of endosperm cap weakening, presumably by inhibiting the activities of at least two EBM isoforms and/or, indirectly, by inhibiting the pressure force of the radicle. The increase in the activities of EBM and cellulase coincided with the decrease in the force required to puncture the endosperm and with the appearance of porosity in the cell walls as observed by low-temperature scanning electronic microscopy. Tissue printing showed that EBM activity was spatially regulated in the endosperm. Activity was initiated in the endosperm cap whereas later during germination it could also be detected in the remainder of the endosperm. Tissue printing revealed that ABA inhibited most of the EBM activity in the endosperm cap, but not in the remainder of the endosperm. ABA did not inhibit cellulase activity. There was a transient rise in ABA content in the embryo during imbibition, which was likely to be responsible for slow germination, suggesting that endogenous ABA also may control embryo growth potential and the second step of endosperm cap weakening during coffee seed germination.
Flower opening and closure: a review
Doorn, W.G. van; Meeteren, U. van - \ 2003
Journal of Experimental Botany 54 (2003). - ISSN 0022-0957 - p. 1801 - 1812.
ipomoea-nil convolvulaceae - a/b binding-protein - kalanchoe-blossfeldiana - pharbitis-nil - circadian-rhythms - photoperiodic control - ethylene production - silver thiosulfate - water relations - petal movement
Flower opening and closure are traits of a reproductive syndrome, as it allows pollen removal and/or pollination. Various types of opening can be distinguished such as nocturnal and diurnal and single or repetitive. Opening is generally due to cell expansion. Osmotic solute levels increase by the conversion of polysaccharides (starch or fructan) to monosaccharides, and/or the uptake of sugars from the apoplast. Repeated opening and closure movements are often brought about by differential elongation. In tulip petals, for example, the upper and lower sides of the mesophyll exhibit a 10degreesC difference in optimum temperature for elongation growth, resulting in opening in the morning and closure in the evening. Opening and closure in several other species is regulated by changes in light intensity and, in some species with nocturnal opening, by an increase in relative humidity. A minimum duration of darkness and light are usually required for opening and closure, respectively, in flowers that open during the day. Both phytochrome and a blue light receptor seem involved in light perception. In some species, opening and closure are regulated by an endogenous rhythm, which, in all cases investigated, can be reset by changes from dark to light and/or light to dark. So far, Arabidopsis mutants have not been used to investigate the timing of flower opening and closure. As its flowers open and close in a circadian fashion, several mutants that are involved in the circadian clock and its light input may help to provide an insight into this type of flower opening. The co-ordination of processes culminating in synchronized flower opening is, in many species, highly intricate. The complex control by endogenous and exogenous factors sets flower opening and closure apart from most other growth processes.
Hoogwaterreductie vanuit regionale stroomgebieden: samenhang of tegenstellingen?
Bakel, P.J.T. van; Hoogendoorn, J. ; Luijendijk, J. ; Peerboom, J.M.P.M. - \ 2001
H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 34 (2001)3. - ISSN 0166-8439 - p. 27 - 29.
wateropslag - water - opslag - retentie - waterbeheer - drainage - neerslag - stroomgebieden - hydrologie van stroomgebieden - beheer van waterbekkens - hoogwaterbeheersing - stroming - waterrelaties - hydrologie - reservoirs - waterstand - hoogwater - ruimtelijke ordening - stroomgebied - waterberging - water storage - storage - retention - water management - precipitation - watersheds - catchment hydrology - watershed management - flood control - flow - water relations - hydrology - water level
In het kader van hoogwatermanagement spelen berging en veerkracht van watersystemen een steeds grotere rol. In dit artikel een afvoerhydrologische analyse op stroomgebied-niveau: de complexe relaties tussen neerslagpieken, berging in verschillende reservoirs (bodem, maaivelddepressies, oppervlaktewater), ontwatering/afwatering, en resulterende afvoerpieken
Gebruikershandleiding houtbijgroeigrafieken (HBGG) versie 1.00; een raadpleeg- en kennissysteem over houtbijgroeigrafieken
Boogaard, H.L. ; Bron, W.A. - \ 2001
Wageningen : Alterra (Alterra-rapport 324) - 27
opbrengsttabellen - opbrengsten - bosbomen - grondwaterspiegel - grondwaterwinning - bosschade - waterrelaties - grondwaterstand - databanken - nederland - bosbouw - bosverjonging - houtproductie - verdroging - vernatting - yield tables - yields - forest trees - water table - groundwater extraction - forest damage - water relations - groundwater level - databases - netherlands
Voor het berekenen van verminderde houtbijgroei als gevolg van grondwateronttrekking heeft de Commissie van Deskundigen Grondwaterwet in samenwerking met Alterra een methodiek ontwikkeld waarmee een groeigrafiek voor een bepaalde boomsoort kan worden geconstrueerd. Deze groeigrafieken zijn opgeslagen in een database waarin de bijgroei is vermeld in afhankelijkheid van parameters zoals boomsoort, voedingstoestand en vocht. Onderliggende gebruikershandleiding beschrijft het raadpleeg- en kennissysteem houtbijgroeigrafieken (HBGG), waarmee op inzichtelijke en eenvoudige wijze houtbijgroeigrafieken kunnen worden gepresenteerd en veldgegevens kunnen worden doorgerekend.
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