Investigation of grapevine root distribution by in situ minirhizotron observation

Root observations of Vitis berlandieri x Vitis riparia were conducted in two experimental sets using minirhizotron technique. Experiment 1 was a field experiment carried out on a 12 years old Riesling/5C vineyard. On six plants three minirhizotrons were installed at different angles (90°, 60°, 45°) and two directions per tube were used for observation. The maximum of root length density (RLD) was found in soil depths of 600-800 mm with high variation mainly due to plant x angle interaction. Observation direction did not influence the estimates of RLD. The installation angle of the tubes did not lead to any consistent effect on root observation. Experiment 2 was a pot trial of six pots with four vines each. Tubes were installed horizontally. RLD in the pot experiment according to the monolith method and the estimated RLD according to the minirhizotron method did not correlate, so the quantification of Vitis RLD distribution using minirhizotron is difficult.

Root dynamics and pattern of 'Riesling' on 5C rootstock using minirhizotrons

Root length density (RLD) in the years from 1994-1997 was estimated using minirhizotrons. The field experiment was conducted on six 'Riesling' vines in Rheingau (Germany). The majority of root distribution was found in soil depths of 60-100 cm with considerable variations between the plants. Roots dynamics showed a periodicity with one or two maxima, depending on year and vine plant. The first peak of RLD was observed around veraison, the second peak appeared after harvest. The rate of root length death was estimated. In the deeper layer the turnover of roots was 60% of the total RLD every year.

Is grape composition affected by current levels of UV-B radiation?

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Remote sensing of blood oxygenation using red-eye pupil reflection

To access publisher's full text version of this article click on the hyperlink belowObjective: To develop a technique for remote sensing of systemic blood oxygenation using red-eye pupil reflection. Approach: The ratio of the intensities of light from the bright pupil reflections at oxygen sensitive and isosbestic wavelengths is shown to be sensitive to the oxygenation of blood in the eye. A conventional retinal camera, fitted with an image-replicating imaging spectrometer, was used at standoff range to record snapshot spectral images of the face and eyes at eight different wavelengths. In our pilot study we measured optical-density ratios (ODRs) of pupil reflections at wavelengths of 780 nm and 800 nm, simultaneous with pulse oximetry, for ten healthy human subjects under conditions of normoxia and mild hypoxia (15% oxygen). The low absorption at these infrared wavelengths localises the sensing to the choroid. We propose that this can be used for as a proxy for systemic oximetry. Main results: A significant reduction (P < 0.001) in ODR of the pupil images was observed during hypoxia and returned to baseline on resumption of normoxia. We demonstrate that measurement of the choroidal ODR can be used to detect changes in blood oxygenation that correlate positively with pulse oximetry and with a noise-equivalent oximetry precision of 0.5%. Significance: We describe a new method to remotely and non-invasively sense the oxygen saturation of choroidal blood. The methodology provides a proxy for remote sensing of cerebral and systemic blood oxygenation. We demonstrate the technique at short range but it has potential for systemic oximetry at large standoff ranges

Fundamental differences in patterns of retinal ageing between primates and mice

Photoreceptors have high metabolic demands and age rapidly, undermining visual function. We base our understanding mainly on ageing mice where elevated inflammation, extracellular deposition, including that of amyloid beta, and rod and cone photoreceptor loss occur, but cones are not lost in ageing primate although their function declines, revealing that primate and mouse age differently. We examine ageing primate retinae and show elevated stress but low inflammation. However, aged primates have a >70% reduction in adenosine triphosphate (ATP) and a decrease in cytochrome c oxidase. There is a shift in cone mitochondrial positioning and glycolytic activity increases. Bruch’s membrane thickens but unlike in mice, amyloid beta is absent. Hence, reduced ATP may explain cone functional decline in ageing but their retained presence offers the possibility of functional restoration if they can be fuelled appropriately to restore cellular function. This is important because as humans we largely depend on cone function to see and are rarely fully dark adapted. Presence of limited aged inflammation and amyloid beta deposition question some of the therapeutic approaches taken to resolve problems of retinal ageing in humans and the possible lack of success in clinical trials in macular degeneration that have targeted inflammatory agents