The application of Magnetic Resonance Imaging (mri) to the examination of plant tissues and water barriers.

The aim of the present study is to extend the applicability of MRI measurements similar to those used in human diagnostics to the examination of water barriers in living plants, thus broadening their use in natural sciences. The cucumber, Cucumis sativus, and Phillyrea angustifolia, or false olive, were chosen as test plants. The MRI measurements were carried out on three samples of each plant in the same position vis-a-vis the MRI apparatus using a Siemens Avanto MRI scanner. Two different relaxation times were employed, T1, capable of histological mapping, and T2, used for the examination of water content. In the course of the analysis, it was found that certain histological formations and branching cause modifications to the intensity detected with relaxation time T2. Furthermore, these positions can also be found in T1 measurements. A monotonic correlation (cucumber: ρ = 0.829; false olive: ρ = -0.84) was observed between the T1 and T2 measurements. In the course of the statistical analysis of the signal intensities of the xylems it was concluded that they cannot be regarded as independent in a statistical sense; these changes rather depend on the anatomic structure of the plant, as the intensity profile is modified by nodes, leaves and branches. This serves as a demonstration of the applicability of MRI to the measurement of well know plant physiological processes. The special parametrization required for this equipment, which is usually used in human diagnostics, is also documented in the present study.

Comparative study of inflorescence development in Oleaceae.

PREMISE OF THE STUDY: Investigations of inflorescence architecture offer insight into the evolution of an astounding array of reproductive shoot systems in the angiosperms, as well as the potential to genetically manipulate these branching patterns to improve crop yield and enhance the aesthetics of horticultural species. The diversity of inflorescences in the economically important family Oleaceae was studied from a comparative developmental point of view for the first time, based on species of seven genera (Chionanthus, Fontanesia, Fraxinus, Jasminum, Ligustrum, Olea, Syringa). METHODS: Series of developmental stages of chemically fixed inflorescences were studied with epi-illumination light microscopy. KEY RESULTS: All taxa studied have inflorescences with terminal flowers. The inflorescences are mostly panicles, but in some cases thyrsoids or compound botryoids. Phyllotaxis of the flower-subtending bracts is mostly decussate, rarely tricussate (Fraxinus) or spiral (Jasminum). Accessory flowers or accessory inflorescences, almost unknown in Oleaceae as yet, were found in two genera. In Syringa, common bract-flower primordia are formed by a delay in early bract development compared to flower development. Such a delay is also expressed by the loss of bracts in the distal part of inflorescence branches in Syringa and Chionanthus. CONCLUSIONS: Significant variation in branching pattern and phyllotaxy was observed among the studied species of Oleaceae. The suppression of bracts and formation of accessory flowers were found as special features of inflorescence ontogeny. The occurrence of accessory flowers and accessory partial inflorescences is interesting from the point of view of dense and flower-rich inflorescences in ornamental species.

Xylem vulnerability to cavitation can be accurately characterised in species with long vessels using a centrifuge method.

Vulnerability to cavitation curves describe the decrease in xylem hydraulic conductivity as xylem pressure declines. Several techniques for constructing vulnerability curves use centrifugal force to induce negative xylem pressure in stem or root segments. Centrifuge vulnerability curves constructed for long-vesselled species have been hypothesised to overestimate xylem vulnerability to cavitation due to increased vulnerability of vessels cut open at stem ends that extend to the middle or entirely through segments. We tested two key predictions of this hypothesis: (i) centrifugation induces greater embolism than dehydration in long-vesselled species, and (ii) the proportion of open vessels changes centrifuge vulnerability curves. Centrifuge and dehydration vulnerability curves were compared for a long- and short-vesselled species. The effect of open vessels was tested in four species by comparing centrifuge vulnerability curves for stems of two lengths. Centrifuge and dehydration vulnerability curves agreed well for the long- and short-vesselled species. Centrifuge vulnerability curves constructed using two stem lengths were similar. Also, the distribution of embolism along the length of centrifuged stems matched the theoretical pressure profile induced by centrifugation. We conclude that vulnerability to cavitation can be accurately characterised with vulnerability curves constructed using a centrifuge technique, even in long-vesselled species.

Effects of fruit collection date on Phillyrea latifolia L. seed germination.

This study was conducted to determine the effects of date of fruit collection on the germination of Phillyrea latifolia L. Fruits were collected between September and December of 2007, in Egirdir, Turkey. It was found that the one thousand seed weight for the species seeds was 400 g, with significant differences among dates of fruit collection. The highest germination percentage of 58% was obtained from the seeds collected on the ground from previous years on the 1st of September 2007. The seeds from crown on the 1st of September 2007 had a germination percentage of 42%. Moreover, seeds from crown on the 1st of November and December 2007 and 15th of October and November 2007 did not germinate. In conclusion, P. latifolia seeds collected on the ground from previous years could be sown in early autumn to obtain a high germination rate.

On the role of flavonoids in the integrated mechanisms of response of Ligustrum vulgare and Phillyrea latifolia to high solar radiation.

The role of flavonoids in mechanisms of acclimation to high solar radiation was analysed in Ligustrum vulgare and Phillyrea latifolia, two Mediterranean shrubs that have the same flavonoid composition but differ strikingly in their leaf morpho-anatomical traits. In plants exposed to 12 or 100% solar radiation, measurements were made for surface morphology and leaf anatomy; optical properties, photosynthetic pigments, and photosystem II efficiency; antioxidant enzymes, lipid peroxidation and phenylalanine ammonia lyase; synthesis of hydroxycinnamates and flavonoids; and the tissue-specific distribution of flavonoid aglycones and ortho-dihydroxylated B-ring flavonoid glycosides. A denser indumentum of glandular trichomes, coupled with both a thicker cuticle and a larger amount of cuticular flavonoids, allowed P. latifolia to prevent highly damaging solar wavelengths from reaching sensitive targets to a greater degree than L. vulgare. Antioxidant enzymes in P. latifolia were also more effective in countering light-induced oxidative load than those in L. vulgare. Consistently, light-induced accumulation of flavonoids in L. vulgare, particularly ortho-dihydroxylated flavonoids in the leaf mesophyll, greatly exceeded that in P. latifolia. We conclude that the accumulation of flavonoid glycosides associated with high solar radiation-induced oxidative stress and, hence, biosynthesis of flavonoids appear to be unrelated to 'tolerance' to high solar radiation in the species examined.