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Woody Stems (woody + stem)
Selected AbstractsTrade-off in oviposition strategy: choosing poor quality host plants reduces mortality from natural enemies for a salt marsh planthopperECOLOGICAL ENTOMOLOGY, Issue 3 2006DANIEL C. MOON Abstract 1.,Both host plant nutrition and mortality from natural enemies have been predicted to significantly impact host plant selection and oviposition behaviour of phytophagous insects. It is unclear, however, if oviposition decisions maximise fitness. 2.,This study examined whether the salt marsh planthopper Pissonotus quadripustulatus prefers higher quality host plants for oviposition, and if oviposition decisions are made so as to minimise mortality at the egg stage. 3.,A controlled laboratory experiment and 4 years of field data were used to assess the rates of planthopper oviposition on higher quality ,green' and lower quality ,woody' stems of the host plant Borrichia frutescens. The numbers and percentages of healthy eggs and eggs that were killed by parasitoids or the host plant were recorded. 4.,In all years, including the laboratory experiment, Pissonotus planthoppers laid more eggs on lower quality woody stems than on higher quality green stems. While host plant related egg mortality was higher in woody stems, the percentage of eggs parasitised was much greater in green stems. This resulted in a lower total mortality of eggs on woody stems. 5.,The results of this study demonstrate that, although Pissonotus prefers lower quality host plants for oviposition, this actually increases fitness. These data seem to support the enemy free space hypothesis, and suggest that for phytophagous insects that experience the majority of mortality in the egg stage, oviposition choices may be made such that mortality is minimised. [source] On the measurement of growth with applications to the modelling and analysis of plant growthFUNCTIONAL ECOLOGY, Issue 2 2000Roderick M. L. Abstract 1.,In this paper, a theoretical framework for the analysis of growth is described. Growth is equated with change in volume (V) and the growth rate is given by the equation; dV/dt = (dm/dt)(1/,) , (d,/dt)(m/,2) where m is the mass and , the density. The volume is inclusive of internal air spaces. 2.,The second term of the growth equation (see above) can be ignored if density is constant over time. Data for humans (and presumably other large animals) show that while composition changes over time, the density is approximately constant at about that of water. In that case, the growth rate can be estimated from measures of the rate of change of mass. However, the density of plants is variable (c. 0·4,1·2 g cm,3) and measures of mass and density are necessary to analyse plant growth. 3.,To use the theory as the basis of plant growth models, it is necessary to develop simple methods for estimating the surface area of roots, stems and leaves assuming that the mass and volume are known. A literature review found that the surface area to volume ratios of leaves and roots generally increase with the mass concentration of water. Theoretical arguments are used to predict that in woody stems, the situation should be reversed such that the surface area to volume ratio increases with the mass concentration of dry matter. Those relationships should be very useful in the development of plant growth models. 4.,Measures of plant dry mass and estimates of the rate of change in dry mass are shown to be very difficult to interpret because of differences in the mass concentration of dry matter between individuals and over time. 5.,It is concluded that measures of mass and density will be necessary before plant growth analysis can achieve its full potential. A framework for extending the theory to include the forces necessary for growth to occur is described. [source] Forest canopy and community dynamics in a temperate old-growth evergreen broad-leaved forest, south-western Japan: a 7-year study of a 4-ha plotJOURNAL OF ECOLOGY, Issue 5 2001Masahiro Miura Summary 1Forest canopy gap and community dynamics were studied in a 4-ha permanent plot of an old-growth evergreen broad-leaved forest dominated by Castanopsis cuspidata var. sieboldii and Distylium racemosum in the Tatera Forest Reserve, Tsushima Islands, south-western Japan. The forest was affected by a powerful typhoon in 1987 and was monitored from 1990 to 1997. 2In 1990, all woody stems , 5 cm diameter at breast height (d.b.h.) in the plot were identified, mapped and marked, and the state of 1600 5 m × 5 m contiguous quadrats used to locate canopy gaps. Gaps occupied 17.1% of the plot, which contained 4494 tree and shrub stems (total basal area 63.48 m2 ha,1). Gaps were re-censused in 1997 and both marked and newly recruited (, 5 cm d.b.h.) stems were recorded in 1992 and 1997. 3Over 7 years the rates of canopy gap formation and closure were 0.72% year,1 and 1.61% year,1, respectively, mortality and recruitment rates were 0.97% year,1 and 0.99% year,1, and the rates of loss and gain in basal area were 0.95% year,1 and 0.83% year,1. 4The mortality of stems was size-dependent, with those in middle size classes having the lowest rates. Mortality of stems was lower in canopy and higher in the understorey, while the proportion of stems killed by disturbances increased with height. 5Stems that died during the 7 years were predominantly located in newly created gaps, whereas stems were recruited into both established and new gaps. Deciduous broad-leaved species were largely restricted to gaps that remained open throughout the study. 6Both composition and structure of the forest changed in response to disturbance-related effects on canopy dynamics. [source] Vegetation patterns and environmental gradients in tropical dry forests of the northern Yucatan PeninsulaJOURNAL OF VEGETATION SCIENCE, Issue 2 2004D.A. White Patterns of plant species composition and their relationships to soil and topographic variables were investigated in tropical dry forests across the north central Yucatan, Mexico. Seven sites were studied in the oldest accessible forests along a 200,km transect oriented northwest to southeast; an eighth site was located in a little-disturbed area located 75 km northeast of the transect. Two of the sites were on Mayan ruins. All sites were sampled using 9,24, 10m × 20m plots ( Phototropic bending of non-elongating and radially growing woody stems results from asymmetrical xylem formationPLANT CELL & ENVIRONMENT, Issue 5 2007JUN MATSUZAKI ABSTRACT Active phototropic bending of non-elongating and radially growing portion of stems (woody stems) has not been previously documented, whereas negative gravitropic bending is well known. We found phototropic bending in woody stems and searched for the underlying mechanism. We inclined 1-year-old Quercus crispula Blume seedlings and unilaterally illuminated them from a horizontal direction perpendicular to (,normal' illumination) or parallel to (,parallel' illumination) the inclination azimuth. With normal illumination, active phototropic bending and xylem formation could be evaluated separately from the negative gravitropic response and vertical deflection resulting from the weight of the seedlings. One-year-old stems with normal illumination bent significantly, with asymmetrical xylem formation towards the illuminated upper surface and side of the stem, whereas those with parallel illumination showed non-significant lateral bending, with asymmetrical xylem formation only on the upper side. A mechanical model was built on the assumption that a bending moment resulted from the asymmetrical xylem formation during phototropic bending of the woody stems. The model fitted the relationship between the observed spatial distributions of the xylem and the observed lateral bending, and thus supported the hypothesis that phototropic bending of woody stems results from asymmetrical xylem formation, as such occurs during gravitropism. [source] In vivo magnetic resonance imaging of xylem vessel contents in woody lianasPLANT CELL & ENVIRONMENT, Issue 8 2003M. J. CLEARWATER ABSTRACT Previous reports suggest that in some plant species the refilling of embolized xylem vessels can occur while negative pressure exists in the xylem. The aim of this experiment was to use non-destructive nuclear magnetic resonance imaging (MRI) to study the dynamics of xylem cavitation and embolism repair in-vivo. Serial 1H-MRI was used to monitor the contents of xylem vessels in stems of two dicotyledonous (Actinidia deliciosa and Actinidia chinensis, kiwifruit) and one monocotyledonous (Ripogonum scandens, supplejack) species of woody liana. The configuration of the horizontal wide bore magnet and probe allowed the imaging of woody stems up to 20 mm in diameter. Tests using excised stems confirmed that the image resolution of 78 µm and digital image subtraction could be used to detect the emptying and refilling of individual vessels. Imaging was conducted on both intact plants and excised shoots connected to a water supply. In the case of Ripogonum the excised shoots were long enough to allow the distal end of the shoot, including all leaves, to be exposed to ambient conditions outside the building while the proximal end was inside the MRI magnet. In total, six stems were monitored for 240 h while the shoots were subjected to treatments that included light and dark periods, water stress followed by re-watering, and the covering of all leaves to prevent transpiration. The sudden emptying of water-filled vessels occurred frequently while xylem water potential was low (below ,0.5 MPa for Actinidia, ,1.0 MPa for Ripogonum), and less frequently after xylem water potential approached zero at the end of water-stress treatments. No refilling of empty vessels was observed at any time in any of the species examined. It is concluded that embolism repair under negative pressure does not occur in the species examined here. Embolism repair may be more likely in species with narrower xylem vessels, but further experiments are required with other species before it can be concluded that repair during transpiration is a widespread phenomenon. [source] Trade-off in oviposition strategy: choosing poor quality host plants reduces mortality from natural enemies for a salt marsh planthopperECOLOGICAL ENTOMOLOGY, Issue 3 2006DANIEL C. MOON Abstract 1.,Both host plant nutrition and mortality from natural enemies have been predicted to significantly impact host plant selection and oviposition behaviour of phytophagous insects. It is unclear, however, if oviposition decisions maximise fitness. 2.,This study examined whether the salt marsh planthopper Pissonotus quadripustulatus prefers higher quality host plants for oviposition, and if oviposition decisions are made so as to minimise mortality at the egg stage. 3.,A controlled laboratory experiment and 4 years of field data were used to assess the rates of planthopper oviposition on higher quality ,green' and lower quality ,woody' stems of the host plant Borrichia frutescens. The numbers and percentages of healthy eggs and eggs that were killed by parasitoids or the host plant were recorded. 4.,In all years, including the laboratory experiment, Pissonotus planthoppers laid more eggs on lower quality woody stems than on higher quality green stems. While host plant related egg mortality was higher in woody stems, the percentage of eggs parasitised was much greater in green stems. This resulted in a lower total mortality of eggs on woody stems. 5.,The results of this study demonstrate that, although Pissonotus prefers lower quality host plants for oviposition, this actually increases fitness. These data seem to support the enemy free space hypothesis, and suggest that for phytophagous insects that experience the majority of mortality in the egg stage, oviposition choices may be made such that mortality is minimised. [source] Long-term acclimatization of hydraulic properties, xylem conduit size, wall strength and cavitation resistance in Phaseolus vulgaris in response to different environmental effectsPLANT CELL & ENVIRONMENT, Issue 5 2006ELLEN K. HOLSTE ABSTRACT Phaseolus vulgaris grown under various environmental conditions was used to assess long-term acclimatization of xylem structural characteristics and hydraulic properties. Conduit diameter tended to be reduced and ,wood' density (of ,woody' stems) increased under low moisture (,dry'), increased soil porosity (,porous soil') and low phosphorus (,low P') treatments. Dry and low P had the largest percentage of small vessels. Dry, low light (,shade') and porous soil treatments decreased P50 (50% loss in conductivity) by 0.15,0.25 MPa (greater cavitation resistance) compared with ,controls'. By contrast, low P increased P50 by 0.30 MPa (less cavitation resistance) compared with porous soil (the control for low P). Changes in cavitation resistance were independent of conduit diameter. By contrast, changes in cavitation resistance were correlated with wood density for the control, dry and porous soil treatments, but did not appear to be a function of wood density for the shade and low P treatments. In a separate experiment comparing control and porous soil plants, stem hydraulic conductivity (kh), specific conductivity (ks), leaf specific conductivity (LSC), total pot water loss, plant biomass and leaf area were all greater for control plants compared to porous soil plants. Porous soil plants, however, demonstrated higher midday stomatal conductance to water vapour (gs), apparently because they experienced proportionally less midday xylem cavitation. [source]
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