Evidence for tertiary buds within latent buds of Müller-Thurgau grapevines

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Grape berry splitting and some mechanical properties of the skin

Das Platzen von Weinbeeren und einige mechanische Eigenschaften der BeerenhautZur Messung von mechanischen Eigenschaften der Haut reifender Weinbeeren wurden Methoden entwickelt, bei denen definierte Wassermengen über feine, durch die Beerenstielchen eingeführte Injektionsnadeln in die Beeren injiziert wurden. Die Injektionen erhöhten den Turgor der Beeren; nach Erreichen eines Fließstillstands in der Nadel wurde dieser gemessen. Im Bereich niedriger Drücke war die Ausdehnung der Beerenhaut elastisch, bei höheren Drücken war sie plastisch, wobei irreversible Veränderungen der Beerenhaut erkennbar wurden. Bei sehr hohen Drücken platzten die Beeren in einer Weise, wie sie auch im Freiland zu beobachten ist. Messungen an Beeren von 9 Rebsorten bei konstanter Temperatur (15 °C) ergaben Unterschiede im Elastizitätsmodul (1700-5400 N m-1), in der Platzspannung (110-420 N m-1) und bei der linearen Ausdehnungsmeßzahl (0,027-0,112). Wie bei den meisten Materialien nahm die Starrheit und Härte der Beeren mit steigender Temperatur ab (10, 30, 50 °C). Veränderungen der Beerentemperatur verursachten Veränderungen im Druck (0,44 ± 0,1 kPa °C-1). Höhere Temperaturen und Drücke (50 °C, 40 kPa) hatten dauerhafte, plastische Deformationen zur Folge. Es kann angenommen werden, daß die sortenspezifische Neigung zum Platzen der Beeren mit den mechanischen Eigenschaften der Beerenhaut zu erklären ist

Weather effects of stalk necrosis in Vitis

A 5-step physiological explanation is offered for correlations found by THEILER and MÜLLER (1986) between aspects of the weather at flowering and the incidence of stalk necrosis in grape. Four of the steps are well supported in the literature and are discussed briefly. The other step proposes that the development of xylem in the peduncle is stimulated by floral evapotranspiration. This postulate is tested with measurements of xylem cross-sectional area in clusters taken from vineyards located in diverse regions of New Zealand for which meteorological data were available. Statistical analysis indicates a clear distinction between material from the climatic extremes and a significant (P = 0.05) correlation between calculated values of evapotranspiration during flowering and peduncular xylem area. The beginning of a physiological explanation for the seasonal effects on the incidence of stalk necrosis in grape has stimulated studies which may allow the selection of non-sensitive varieties

Developmental changes of primary processes of photosynthesis in sun- and shade-adapted berries of two grapevine cultivars

Light utilisation and thermal dissipation of field-grown sun- and shade-adapted berries of cvs Kerner (white) and Portugieser (red) were investigated during berry development by determining chlorophyll fluorescence parameters. In stages I and H of berry development for both cultivars the maximum quantum yield of photochemical energy conversion of dark-adapted berries (Fv/Fm) was close to the maximum (0.75-0.80). It decreased significantly in sun- and shade-adapted berries of cv. Kerner two weeks after veraison indicating damage of photosystem 11 (PSII) during ripening. When at veraison anthocyanins accumulated in the skin of berries chlorophyll fluorescence of cv. Portugieser berries could no longer be determined. In both cultivars the linear electron transport rate at light saturation (ETRmax) increased in stage I and reached maxima in stage 11, sun-adapted berries showing higher rates than shade-adapted. After high values in stage I non-photochemical quenching at light saturation (NPQmax) decreased in light- and shade-adapted Kerner berries in stage 11 indicating a lowering of the thermal dissipation efficiency. The pool size of the xanthophyll cycle pigments diverged significantly in sun- and shade-adapted berries during their development: under clear, warm and dry weather conditions in shade-adapted berries the xanthophyll pool size decreased to low levels, while in sun-adapted berries it increased to maximum values shortly before (cultivar Kerner) or at veraison (cultivar Portugieser) and subsequently declined. Unripe, sun-adapted berries of both cultivars showed a transient decline of the xanthophyll pool size during a rain period suggesting pool size adjustment to changes of ambient conditions in the longer term. It is concluded that unripe, sun-adapted berries are better adapted to high light than shade-adapted berries due to their higher capacity of photosynthetic energy consumption and thermal energy dissipation; at the onset of ripening these photoprotective mechanisms appear to loose importance.

Xylem development and function in the grape peduncle: Relations to bunch stem necrosis

Using a simple flow test evidence is provided that in some grape varieties xylem development is suppressed just distal to each node of the peduncle system. A little further along, development is again normal giving a bottleneck appearance. The bottleneck would appear to offer a high resistance to xylem sap flow both because of its reduced area of cross-section and because of its having only small, primary vessels. The varieties exhibiting a distinct bottleneck tend to be those susceptible to bunch stem necrosis whereas the ones without it tend not to be susceptible

Susceptibility to bunch stem necrosis in grapes: A breeding screen

A breeding screen has been developed with which it is possible to predict the resistance of newbred grapevine varieties to bunch stem necrosis. The screen is based on a 5-year study of 17 commercial varieties in which it was noted that in those which are sensitive to the disorder, xylem development is relatively reduced just distal to each branch point in the peduncle so as to form a short ''bottleneck'' (DURING and LANG 1993). The procedure advocated, offers a probabilistic assessment of susceptibility to the disorder, calculated from simple light microscope measurements on a relatively small amount of material

Generating functional analysis of CDMA detection dynamics

We investigate the detection dynamics of the parallel interference canceller (PIC) for code-division multiple-access (CDMA) multiuser detection, applied to a randomly spread, fully syncronous base-band uncoded CDMA channel model with additive white Gaussian noise (AWGN) under perfect power control in the large-system limit. It is known that the predictions of the density evolution (DE) can fairly explain the detection dynamics only in the case where the detection dynamics converge. At transients, though, the predictions of DE systematically deviate from computer simulation results. Furthermore, when the detection dynamics fail to convergence, the deviation of the predictions of DE from the results of numerical experiments becomes large. As an alternative, generating functional analysis (GFA) can take into account the effect of the Onsager reaction term exactly and does not need the Gaussian assumption of the local field. We present GFA to evaluate the detection dynamics of PIC for CDMA multiuser detection. The predictions of GFA exhibits good consistency with the computer simulation result for any condition, even if the dynamics fail to convergence.Comment: 14 pages, 3 figure

Low-dimensional chaos induced by frustration in a non-monotonic system

We report a novel mechanism for the occurrence of chaos at the macroscopic level induced by the frustration of interaction, namely frustration-induced chaos, in a non-monotonic sequential associative memory model. We succeed in deriving exact macroscopic dynamical equations from the microscopic dynamics in the case of the thermodynamic limit and prove that two order parameters dominate this large-degree-of-freedom system. Two-parameter bifurcation diagrams are obtained from the order-parameter equations. Then we analytically show that the chaos is low-dimensional at the macroscopic level when the system has some degree of frustration, but that the chaos definitely does not occur without the frustration.Comment: 2 figure

Kinetic models for optimal control of wealth inequalities

We introduce and discuss optimal control strategies for kinetic models for wealth distribution in a simple market economy, acting to minimize the variance of the wealth density among the population. Our analysis is based on a finite time horizon approximation, or model predictive control, of the corresponding control problem for the microscopic agents' dynamic and results in an alternative theoretical approach to the taxation and redistribution policy at a global level. It is shown that in general the control is able to modify the Pareto index of the stationary solution of the corresponding Boltzmann kinetic equation, and that this modification can be exactly quantified. Connections between previous Fokker-Planck based models and taxation-redistribution policies and the present approach are also discussed