Discrimination of corn,grasses and dicot weeds by their UV-induced fluorescence spectral signature

Real-time spot spraying of weed patches requires the development of sensors for the automatic detection of weeds within a crop. In this context, the potential of UV-induced fluorescence of green plants for corn-weed discrimination was evaluated. A total of 1 440 spectral signatures of fluorescence were recorded in a greenhouse from three plant groups (four corn hybrids, four dicotyledonous weed species and four monocotyledonous weed species) grown in a growth chamber. With multi-variate analysis, the full information contained in each spectrum was first reduced to the scores calculated from five principal components. Then, a linear discriminant analysis was applied on these scores to classify spectra on a species/hybrids basis and, subsequently, the resulting classes were aggregated according to the three plant groups. This two-step process minimized the error generated by heterogeneous groups such as dicotyledonous weeds. The output of this classification shows the significant potential of UV-induced fluorescence for plant group discrimination as the success rate reached 91.8%. No error was observed between corn and dicot weeds and most of the errors between corn and grasses came from confusion between the hybrid Pioneer 39Y85 and Setaria glauca L. (Beauv.). Analysis also determined that the position of the fluorescence sensor on the leaf and the plant age had negligible effects on the efficiency of fluorescence to discriminate plant groups. The factors to consider for transferring the results about UV-induced fluoro-sensing from laboratory to the field are discussed.     

Winter variation in xylem sap pH of walnut trees: involvement of plasma membrane H+-ATPase of vessel-associated cells

We studied seasonal variation in xylem sap pH of Juglans regia L. Our main objectives were to (1) test the effect of temperature on seasonal changes in xylem sap pH and (2) study the involvement of plasma membrane H+-ATPase of vessel-associated cells in the control of sap pH. For this purpose, orchard-grown trees were compared with trees grown in a heated (> or = 15 degrees C) greenhouse. During autumn, sap pH was not directly influenced by temperature. A seasonal change in H+-ATPase activity resulting from seasonal variation in the amount of protein was measured in orchard-grown trees, whereas no significant seasonal changes were recorded in greenhouse-grown trees. Our data suggest that H+-ATPase does not regulate xylem sap pH directly by donating protons to the xylem, but by facilitating secondary active H+/sugar transport, among other mechanisms.     

Using a chain of models to simulate the distribution between quality clusters of a set of boards coming from a sessile oak (<Emphasis Type="Italic">Quercus petraea</Emphasis> Liebl.) resource. Validation of the simulations

Taking sessile oak as an example, this paper initially presents a method to predict the final production (quantity and quality) coming from a forest resource when two sets of data are available. The data sets are from two models: measured or simulated ring width profiles from pith to bark of the constituent trees as well as a mixed model for the basic wood properties which are used to grade the boards into quality clusters. The second part of the paper contains a validation for the proposed method. Simulations are used to predict two basic wood properties (volumetric swelling coefficient and wood density) in the trees of a forest resource in relation to the ring width profile of each tree. The simulations are used to compute a map of these two basic properties in each plank derived from the trees. A quality index derived from this map of basic wood properties in the boards is then used to allocate the planks to quality clusters. The basic wood properties considered in this paper are modelled with linear mixed models. Since computation of the plank properties or definition of the grading rule can use several properties simultaneously, the models used to simulate the basic properties are joint models. Modelling jointly several properties with a mixed model consists of defining a covariance structure between the random effects of the model. Such a model can be substantial in terms of parameters and computational resources required, thus we compared three kinds of joint models. The simplest one is not quite a joint model but is simply obtained from the juxtaposition of independent models, one for each of the two properties taken into consideration. We also defined a model with a moderate covariance structure between the two properties, and lastly, we used a third model with a full covariance structure. Simulations of volumetric swelling coefficient, wood density and the resulting board grading were carried out with each of these three models. All give results roughly in accordance with the observations, but the two truly joint models give better results than the simplest model.     

Spatial activity and expression of plasma membrane H+-ATPase in stem xylem of walnut during dormancy and growth resumption

Plasma membrane H+-ATPase (PM H+-ATPase) plays a key role in nutrient transport, stress responses and growth. To evaluate proton motive force differences between apical and basal parts of acrotonic 1-year-old shoots of walnut (Juglans regia L. cv 'Franquette') trees, spatial and seasonal changes in PM H+-ATPase were studied in mature xylem tissues. During both the dormancy and growth resumption periods, and in both the apical and basal parts of the stem, PM H+-ATPase activity showed positive correlations with the amount of immunodetectable protein. In spring, at the time of growth resumption, higher activities and immunoreactivities of PM H+-ATPase were found in the apical part of the stem than in the basal part of the stem. In spring, the decrease in xylem sugar concentration reflected the high sugar uptake rate. Our data suggest that PM H+-ATPase plays a major role in the uptake of carbohydrates from xylem vessels during growth resumption. These results are discussed in the context of the acrotonic tendency of walnut shoots.     

Hydrophobization of wood surfaces: covalent grafting of silicone polymers

 The hydrophilicity of Maritime pine wood surfaces was modified by silicone, an extremely hydrophobic material. A generic method for the introduction of a variety of silicones at the surface of pre-treated wood was developed. The initial treatment of wood with maleic anhydride and allyl glycidyl ether resulted in oligoesterified wood bearing terminal alkenes. The hydro- osilylation of these groups, performed with hydride-terminated silicones, led to very hydrophobic surfaces, even after extensive soxhlet extraction with good solvents for silicones. Thze presence of silicon, only at the surface of hydrosilylated wood, was confirmed by ESCA. The silicones appear to be attached to the wood by covalent bonds. Received 20 December 1998     

Rapid prediction of shrinkage and fibre saturation point on teak (Tectona grandis) wood based on near-infrared spectroscopy

? Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory.

? Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre saturation point of teak wood from Togo.

? The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre saturation point give R ² values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8.

? Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre saturation point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping.

     

Fagacées: a tree-centered growth and yield model for sessile oak (<Emphasis Type="Italic">Quercus petraea</Emphasis> L.) and common beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)

• Introduction  

Fagacées is a growth model that has been developed for pure Oak or Beech stand management in even-aged high forests and coppice with standards forests. It has been calibrated for the plain forests of northern France.