Shoot weight

A number of issues influenced the selection of the dose-response model form and the treatment of the data prior to fitting the model. First, shoot weight and shoot length are continuous response measurements therefore, use of a standardized logistic model form is not appropriate. Second, the natural variation in plant growth often resulted in apparent increased shoot weight and shoot length measurements relative to the control at low herbicide application rates. A dose-response model needs to perform well even when some measurements in treatment levels exceed the controls. 

A standard approach was used to model the data after normalization relative to the appropriate control. The raw shoot weight or shoot length data were normalized by dividing by the control mean for each test to transform the endpoint to the fraction of the control (which was used as the response endpoint in the model). This transformation is presented as ... 

Examples of the model fit for shoot weight and shoot length are shown in Figures 7.5 and 7.6, respectively. The models fit the data well, particularly at the low concentrations where risk-based decisions are typically focused. The benefit of the additional model parameter, Wq i, is evident by the floor effect seen in the raw data at higher concentrations. Both data-rich and relatively data-poor data sets followed the shape of the model curve. 

Figures 7.7 and 7.8 show the dose-response curves generated at the species level for shoot weight and shoot length, respectively. Each dotted curve on the plot is species specific. For many species, multiple toxicity tests are available. The random...

FIGURE 7.5 Cucumber shoot weight dose-response data and model. 

FIGURE 7.7 Integrated Bayesian effects for shoot weight. 

Fig. 6. Comparison of the responses of two grasses of contrasted growth rate and morphology to five intensities of shoot impedance, (a) Lolium perenne b) Festuca ovina. Each curve records the mean progress of shoot expansion in five replicate plants subjected to standardised resistances (indicated on each curve as the force in newtons required for initial deflection of weighted windows). Plants were grown individually within a transparent cone, from which the shoots, in order to escape, must deflect windows of standard dimensions and angle of inclination.

Fig. 7. Root and shoot dry weight of wheat after 22 days of growth (5-leaf Stage) at various soil penetrometer resistances. Variations in penetrometer resistance were obtained by varying soil bulk density and water content. Symbols are as follows. Shape refers to bulk density (g cm ) 0,1.17 A, 1.29 , 1.37 <0, 1.41 V, 1.45. Shade refers to water content (g g dry soil) open symbols, 0.22 or 0.23 half-shaded, 0.25 closed, 0.27. Points are means s.E. (n = 6). Modified from Masle Passioura (1988).

TABLE VI. Residues (ppm on Fresh Weight Basis) of Glyphosate and N-Nitrosoglyphosate in Roots and Shoots of Oat Plants Grown in the Treated Soil ... 

Other than a nutritional role linked to mineralization processes, humic compounds have been hypothesized to directly affect plant nutrition, since it has been suggested that roots may take up low-molecular-weight humic molecules (21). Interestingly, plants have been ob.served to express carriers for amino acids (22) and small peptides (23) at the root level. Certain components of the humic fraction have been found inside root cells and were, moreover, translocated to the shoots (24,25). Recent experiments performed on rice cells in suspension culture seem to suggest that they may use carbon skeletons from humic molecules to synthesize proteins and DNA (26). 

Dry weights of birdsfoot trefoil roots and shoots were retarded by the 10 g concentration of genotypes 360 and 698 as compared with the control (Table VII). Other treatments had no significant effect on root weight. 

Table Vll. Dry weights of roots and shoots of birdsfoot trefoil and red clover seedlings grown in water extracts of leaves and of tall fescue genotypes...

For Newtonian dynamics and a canonical distributions of initial conditions one can reject or accept the new path before even generating the trajectory. This can be done because Newtonian dynamics conserves the energy and the canonical phase-space distribution is a function of the energy only. Therefore, the ratio plz ]/p z at time 0 is equal to the ratio p[.tj,n ]/p z ° at the shooting time and the new trajectory needs to be calculated only if accepted. For a microcanonical distribution of initial conditions all phase-space points on the energy shell have the same weight and therefore all new pathways are accepted. The same is true for Langevin dynamics with a canonical distribution of initial conditions. 

Production of poly(3HB) in the chloroplast of A. thaliana has also been independently demonstrated with similar experiments by the group of Monsanto. They have reported that by using the phaA, phaB, and phaC genes modified for plastid targeting and expressed under the CaMV35S promoter, poly(3HB) levels up to 12-13% dry weight were obtained in A. thaliana shoots. 

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